ISO 14694 \u2014 Balance Quality & Vibration Limits for Industrial Fans \u2014 Vibromera<\/title>\n<meta name=\"description\" content=\"Complete guide to ISO 14694: fan balance quality (BV-1 to BV-5) and vibration limits (FV-1 to FV-5). Interactive BV tolerance calculator, FV acceptance tables, BV-to-G-grade mapping, field balancing procedures for centrifugal and axial fans.\">\n<meta name=\"keywords\" content=\"ISO 14694, industrial fan balancing, fan vibration limits, BV category, FV category, fan balance quality, impeller balancing, fan vibration standard, G-grade fans, centrifugal fan, axial fan, Balanset, fan acceptance testing\">\n<meta name=\"author\" content=\"Vibromera\">\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large\">\n\n\n\n\n\n\n\n\n\n\n\n<meta property=\"og:type\" content=\"article\">\n<meta property=\"og:title\" content=\"ISO 14694 \u2014 Balance Quality & Vibration Limits for Industrial Fans\">\n<meta property=\"og:description\" content=\"BV balance grades (BV-1\u2192BV-5) and FV vibration categories (FV-1\u2192FV-5) for centrifugal, axial, and mixed-flow fans. Interactive calculators, tables, worked examples.\">\n<meta property=\"og:url\" content=\"https:\/\/vibromera.eu\/glossary\/iso-14694\/\">\n<meta property=\"og:site_name\" content=\"Vibromera \u2014 Vibration Analysis & Balancing Equipment\">\n<meta property=\"og:locale\" content=\"en_US\">\n<meta property=\"og:image\" content=\"https:\/\/vibromera.eu\/wp-content\/uploads\/iso-14694-og.jpg\">\n<meta property=\"article:publisher\" content=\"https:\/\/vibromera.eu\/\">\n<meta property=\"article:section\" content=\"Glossary\">\n<meta property=\"article:tag\" content=\"ISO 14694\">\n<meta property=\"article:tag\" content=\"Fan Balancing\">\n<meta property=\"article:tag\" content=\"Fan Vibration\">\n\n\n<meta name=\"twitter:card\" content=\"summary_large_image\">\n<meta name=\"twitter:title\" content=\"ISO 14694 \u2014 Industrial Fan Vibration & Balance Quality Standard\">\n<meta name=\"twitter:description\" content=\"BV impeller balance grades, FV vibration limits, calculators for fan balancing tolerance per ISO 14694.\">\n\n\n<meta name=\"geo.region\" content=\"EU\">\n<meta name=\"geo.placename\" content=\"Porto, Portugal\">\n<meta name=\"geo.position\" content=\"41.1579;-8.6291\">\n<meta name=\"ICBM\" content=\"41.1579, -8.6291\">\n\n\n<script type=\"application\/ld+json\">\n{\n \"@context\": \"https:\/\/schema.org\",\n \"@graph\": [\n {\n \"@type\": \"TechArticle\",\n \"@id\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/#article\",\n \"headline\": \"ISO 14694: Industrial Fans \u2014 Specifications for Balance Quality and Vibration Levels\",\n \"description\": \"Comprehensive guide to ISO 14694 covering BV impeller balance categories, FV operational vibration limits, acceptance testing, and practical fan field balancing with worked examples.\",\n \"author\": {\"@type\": \"Organization\", \"name\": \"Vibromera\", \"url\": \"https:\/\/vibromera.eu\/\"},\n \"publisher\": {\"@type\": \"Organization\", \"name\": \"Vibromera\", \"url\": \"https:\/\/vibromera.eu\/\", \"logo\": {\"@type\": \"ImageObject\", \"url\": \"https:\/\/vibromera.eu\/wp-content\/uploads\/vibromera-logo.png\"}},\n \"mainEntityOfPage\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/\",\n \"datePublished\": \"2024-06-15\",\n \"dateModified\": \"2026-02-07\",\n \"inLanguage\": \"en\",\n \"about\": [\n {\"@type\": \"Thing\", \"name\": \"ISO 14694\"},\n {\"@type\": \"Thing\", \"name\": \"Industrial Fan Balancing\"},\n {\"@type\": \"Thing\", \"name\": \"Fan Vibration Limits\"},\n {\"@type\": \"Thing\", \"name\": \"Balance Quality Grade\"}\n ],\n \"isPartOf\": {\"@type\": \"WebPage\", \"url\": \"https:\/\/vibromera.eu\/glossary\/\"}\n },\n {\n \"@type\": \"FAQPage\",\n \"@id\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/#faq\",\n \"mainEntity\": [\n {\n \"@type\": \"Question\",\n \"name\": \"What is ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 is an international standard that specifies balance quality requirements and acceptable vibration levels for industrial fans (centrifugal, axial, and mixed-flow). It defines BV categories (BV-1 to BV-5) for impeller balance quality corresponding to ISO 1940 G-grades, and FV categories (FV-1 to FV-5) for operational vibration limits of the assembled fan. It applies to all industrial fans except those for aircraft or air-cushion vehicles.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What is the difference between BV and FV categories in ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"BV (Balance Vibration) categories define the balance quality of the impeller as a standalone component, measured on a balancing machine before assembly. FV (Fan Vibration) categories define the acceptable operational vibration of the complete assembled fan, measured on bearing housings during operation. Good impeller balance (BV) is necessary but not sufficient for low operational vibration (FV), which also depends on alignment, foundation, aerodynamic forces, and bearing condition.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What G-Grade does ISO 14694 require for fan impellers?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 maps BV categories to ISO 1940 G-grades: BV-1 = G 1.0 (precision fans), BV-2 = G 2.5 (critical fans), BV-3 = G 6.3 (standard industrial \u2014 the most common), BV-4 = G 16 (general purpose), BV-5 = G 40 (non-critical). The majority of industrial fans are specified as BV-3 (G 6.3).\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What are the vibration limits for industrial fans per ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 FV categories define max RMS velocity on bearing housings: FV-1 \u2264 1.8 mm\/s (precision), FV-2 \u2264 2.8 mm\/s (high-quality), FV-3 \u2264 4.5 mm\/s (standard \u2014 most common), FV-4 \u2264 7.1 mm\/s (general purpose), FV-5 \u2264 11.2 mm\/s (non-critical). These are broadband 10\u20131000 Hz measurements.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"Can I balance a fan impeller in the field to ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. Portable instruments like the Balanset-1A can balance fan impellers in-situ without removal. The device measures vibration and phase, calculates correction weights, and includes a built-in ISO 1940 tolerance calculator for BV category verification. Field balancing is standard practice for large fans where impeller removal is impractical.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"How does ISO 14694 relate to ISO 10816?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 FV vibration limits are derived from the same methodology as ISO 10816 but tailored specifically for fans. FV limit values correspond closely to ISO 10816-1 zone boundaries. ISO 14694 provides clearer, more direct guidance than interpreting the broader machine groups in ISO 10816-3 for fans.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What BV category should I specify for an HVAC fan?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Most general-purpose HVAC fans require BV-3 (G 6.3). For noise-sensitive installations such as hospitals, recording studios, or laboratories, specify BV-2 (G 2.5). Large critical air-handling units above 300 kW also typically use BV-2. Always state the BV category explicitly in the purchase specification.\"}\n }\n ]\n },\n {\n \"@type\": \"BreadcrumbList\",\n \"itemListElement\": [\n {\"@type\": \"ListItem\", \"position\": 1, \"name\": \"Home\", \"item\": \"https:\/\/vibromera.eu\/\"},\n {\"@type\": \"ListItem\", \"position\": 2, \"name\": \"Glossary\", \"item\": \"https:\/\/vibromera.eu\/glossary\/\"},\n {\"@type\": \"ListItem\", \"position\": 3, \"name\": \"ISO 14694\"}\n ]\n }\n ]\n}\n<\/script>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Serif+Display&family=Source+Sans+3:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap\" rel=\"stylesheet\">\n<style>\n:root {\n --navy:#0a2540;--navy-light:#1a3a5c;--blue:#2563eb;--blue-light:#3b82f6;--blue-pale:#dbeafe;--blue-ghost:#eff6ff;\n --beige:#f5f0e8;--beige-dark:#e8dfd3;--beige-light:#faf7f2;--white:#ffffff;--text:#1e293b;--text-secondary:#475569;\n --text-muted:#94a3b8;--border:#cbd5e1;--border-light:#e2e8f0;--success:#059669;--success-light:#d1fae5;\n --warning:#d97706;--warning-light:#fef3c7;--danger:#dc2626;--danger-light:#fee2e2;\n --shadow-sm:0 1px 3px rgba(10,37,64,0.08);--shadow-md:0 4px 12px rgba(10,37,64,0.1);--shadow-lg:0 8px 30px rgba(10,37,64,0.12);\n --radius:12px;--radius-sm:8px;--radius-lg:16px;\n}\n*{margin:0;padding:0;box-sizing:border-box;}\nbody{font-family:'Source Sans 3',sans-serif;color:var(--text);background:var(--beige-light);min-width:1200px;line-height:1.7;font-size:16px;-webkit-font-smoothing:antialiased;}\n\n\/* HERO *\/\n.hero{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 50%,#234e7a 100%);color:var(--white);padding:56px 0 48px;position:relative;overflow:hidden;}\n.hero::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 25% 75%,rgba(37,99,235,0.15) 0%,transparent 50%),radial-gradient(circle at 75% 25%,rgba(37,99,235,0.1) 0%,transparent 50%);pointer-events:none;}\n.hero-inner{max-width:1280px;margin:0 auto;padding:0 48px;position:relative;z-index:1;}\n.hero h1{font-family:'DM Serif Display',serif;font-size:42px;font-weight:400;line-height:1.15;margin-bottom:8px;letter-spacing:-0.5px;}\n.hero h1 span{color:var(--blue-light);}\n.hero .subtitle{font-size:19px;font-weight:300;color:rgba(255,255,255,0.78);max-width:840px;line-height:1.6;}\n.breadcrumb{margin-bottom:20px;font-size:14px;color:rgba(255,255,255,0.5);}\n.breadcrumb a{color:rgba(255,255,255,0.6);text-decoration:none;}\n.breadcrumb a:hover{color:rgba(255,255,255,0.9);}\n.canon-badge{display:inline-flex;align-items:center;gap:6px;padding:4px 12px;background:rgba(37,99,235,0.2);border:1px solid rgba(37,99,235,0.3);border-radius:20px;font-size:12px;font-weight:600;letter-spacing:0.5px;color:rgba(255,255,255,0.85);margin-bottom:12px;text-transform:uppercase;}\n\n\/* QUICK NAV *\/\n.quick-nav{background:var(--white);border-bottom:1px solid var(--border-light);position:sticky;top:0;z-index:100;box-shadow:var(--shadow-sm);}\n.quick-nav-inner{max-width:1280px;margin:0 auto;padding:0 48px;display:flex;gap:0;overflow-x:auto;}\n.quick-nav a{display:flex;align-items:center;gap:6px;padding:14px 16px;font-size:14px;font-weight:500;color:var(--text-secondary);text-decoration:none;white-space:nowrap;border-bottom:2px solid transparent;transition:all 0.2s;}\n.quick-nav a:hover{color:var(--blue);border-bottom-color:var(--blue);background:var(--blue-ghost);}\n\n.container{max-width:1280px;margin:0 auto;padding:0 48px;}\n\n\/* DASHBOARD *\/\n.summary-dashboard{padding:40px 0;background:var(--white);border-bottom:1px solid var(--border-light);}\n.dashboard-grid{display:grid;grid-template-columns:1fr 1fr;gap:32px;}\n.calc-panel{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-lg);padding:32px;position:relative;overflow:hidden;}\n.calc-panel::before{content:'';position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--blue),var(--blue-light));}\n.panel-title{font-family:'DM Serif Display',serif;font-size:22px;margin-bottom:6px;color:var(--navy);}\n.panel-subtitle{font-size:14px;color:var(--text-muted);margin-bottom:24px;}\n.calc-form{display:grid;grid-template-columns:1fr 1fr;gap:16px;}\n.form-group{display:flex;flex-direction:column;gap:5px;}\n.form-group.full-width{grid-column:1\/-1;}\n.form-group label{font-size:13px;font-weight:600;color:var(--text-secondary);text-transform:uppercase;letter-spacing:0.5px;}\n.form-group label .unit{font-weight:400;text-transform:none;color:var(--text-muted);}\n.form-group input,.form-group select{padding:10px 14px;border:1px solid var(--border);border-radius:var(--radius-sm);font-size:15px;font-family:'JetBrains Mono',monospace;background:var(--white);color:var(--text);transition:border-color 0.2s,box-shadow 0.2s;}\n.form-group input:focus,.form-group select:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px rgba(37,99,235,0.12);}\n.calc-btn{grid-column:1\/-1;padding:13px;background:var(--blue);color:var(--white);border:none;border-radius:var(--radius-sm);font-size:15px;font-weight:600;font-family:'Source Sans 3',sans-serif;cursor:pointer;transition:all 0.2s;margin-top:4px;}\n.calc-btn:hover{background:var(--navy);transform:translateY(-1px);box-shadow:var(--shadow-md);}\n\n.results-panel{background:var(--navy);border-radius:var(--radius-lg);padding:32px;color:var(--white);position:relative;overflow:hidden;}\n.results-panel::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 100% 0%,rgba(37,99,235,0.2) 0%,transparent 60%);pointer-events:none;}\n.results-panel .panel-title{color:var(--white);}\n.results-panel .panel-subtitle{color:rgba(255,255,255,0.5);}\n.result-primary{background:rgba(255,255,255,0.07);border:1px solid rgba(255,255,255,0.1);border-radius:var(--radius);padding:22px;text-align:center;margin-bottom:14px;position:relative;z-index:1;}\n.result-primary .res-label{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:1px;color:var(--blue-light);margin-bottom:6px;}\n.result-primary .res-value{font-family:'JetBrains Mono',monospace;font-size:36px;font-weight:700;line-height:1;margin-bottom:4px;}\n.result-primary .res-unit{font-size:15px;color:rgba(255,255,255,0.5);}\n.results-secondary{display:grid;grid-template-columns:1fr 1fr;gap:12px;position:relative;z-index:1;}\n.res-card{background:rgba(255,255,255,0.06);border:1px solid rgba(255,255,255,0.08);border-radius:var(--radius-sm);padding:14px;}\n.res-card .rc-label{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.5px;color:rgba(255,255,255,0.45);margin-bottom:4px;}\n.res-card .rc-value{font-family:'JetBrains Mono',monospace;font-size:20px;font-weight:600;}\n.res-card .rc-unit{font-size:12px;color:rgba(255,255,255,0.4);}\n.results-empty{text-align:center;padding:80px 20px;color:rgba(255,255,255,0.35);font-size:15px;position:relative;z-index:1;}\n.results-empty .icon{font-size:36px;margin-bottom:12px;display:block;}\n.plane-note{margin-top:14px;padding:14px;border-radius:var(--radius-sm);position:relative;z-index:1;background:rgba(37,99,235,0.1);border:1px solid rgba(37,99,235,0.2);text-align:center;}\n.plane-note .pn-label{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:0.5px;color:var(--blue-light);margin-bottom:4px;}\n.plane-note .pn-value{font-family:'JetBrains Mono',monospace;font-size:18px;font-weight:600;}\n.plane-note .pn-unit{font-size:12px;color:rgba(255,255,255,0.4);}\n\n\/* SECTIONS *\/\n.section-bg{padding:40px 0 48px;}\n.section-bg.alt{background:var(--beige-light);}\n.section-header{margin-bottom:28px;}\n.section-header h2{font-family:'DM Serif Display',serif;font-size:30px;color:var(--navy);margin-bottom:6px;}\n.section-header p{font-size:16px;color:var(--text-secondary);}\n\n\/* BV CARDS *\/\n.cat-cards{display:grid;grid-template-columns:repeat(5,1fr);gap:16px;margin-bottom:36px;}\n.cat-card{background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow-sm);transition:all 0.3s;position:relative;overflow:hidden;text-align:center;}\n.cat-card:hover{box-shadow:var(--shadow-lg);transform:translateY(-3px);}\n.cat-card::before{content:'';position:absolute;top:0;left:0;right:0;height:3px;}\n.cat-card.c1::before{background:#7c3aed;}.cat-card.c2::before{background:var(--blue);}\n.cat-card.c3::before{background:var(--success);}.cat-card.c4::before{background:var(--warning);}\n.cat-card.c5::before{background:var(--text-muted);}\n.cc-grade{font-family:'JetBrains Mono',monospace;font-size:24px;font-weight:700;color:var(--navy);margin-bottom:2px;}\n.cc-sub{font-family:'JetBrains Mono',monospace;font-size:13px;color:var(--blue);margin-bottom:8px;font-weight:600;}\n.cc-desc{font-size:12px;color:var(--text-secondary);line-height:1.4;}\n\n\/* TABLES *\/\n.table-wrap{background:var(--white);border-radius:var(--radius);border:1px solid var(--border-light);overflow:hidden;box-shadow:var(--shadow-sm);margin-bottom:32px;}\n.table-wrap .table-title{padding:16px 24px;font-weight:600;font-size:15px;background:var(--beige);border-bottom:1px solid var(--border-light);color:var(--navy);}\ntable{width:100%;border-collapse:collapse;}\ntable th{background:var(--navy);color:var(--white);padding:12px 16px;font-size:13px;font-weight:600;text-transform:uppercase;letter-spacing:0.5px;text-align:left;}\ntable td{padding:11px 16px;font-size:14px;border-bottom:1px solid var(--border-light);color:var(--text);}\ntable tr:last-child td{border-bottom:none;}\ntable tr:hover td{background:var(--blue-ghost);}\ntable td:first-child{font-weight:600;}\n.mono{font-family:'JetBrains Mono',monospace;font-size:13px;}\n.tag{display:inline-block;padding:2px 8px;border-radius:4px;font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.3px;}\n.tag.ultra{background:#ede9fe;color:#5b21b6;}\n.tag.precision{background:var(--blue-pale);color:var(--navy);}\n.tag.standard{background:var(--success-light);color:#065f46;}\n.tag.general{background:var(--warning-light);color:#92400e;}\n.tag.coarse{background:var(--danger-light);color:#991b1b;}\n\n\/* MAIN CONTENT *\/\n.main-content{padding:48px 0 64px;background:var(--white);}\n.content-layout{display:grid;grid-template-columns:1fr 300px;gap:48px;}\n.toc-sidebar{position:sticky;top:80px;align-self:start;}\n.toc-box{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius);padding:24px;}\n.toc-box h3{font-size:14px;font-weight:700;text-transform:uppercase;letter-spacing:0.5px;color:var(--navy);margin-bottom:16px;}\n.toc-box a{display:block;padding:6px 0;font-size:14px;color:var(--text-secondary);text-decoration:none;border-left:2px solid transparent;padding-left:12px;transition:all 0.2s;}\n.toc-box a:hover{color:var(--blue);border-left-color:var(--blue);}\n.toc-box a.sub{padding-left:28px;font-size:13px;color:var(--text-muted);}\n\n.article-content h2{font-family:'DM Serif Display',serif;font-size:28px;color:var(--navy);margin:48px 0 16px;padding-top:20px;}\n.article-content h2:first-child{margin-top:0;}\n.article-content h3{font-size:20px;font-weight:700;color:var(--navy-light);margin:32px 0 12px;}\n.article-content p{margin-bottom:16px;color:var(--text);line-height:1.8;}\n.article-content ul,.article-content ol{margin:0 0 16px 24px;line-height:1.8;}\n.article-content li{margin-bottom:6px;}\n.article-content li strong{color:var(--navy);}\n.article-content a{color:var(--blue);text-decoration:none;border-bottom:1px solid transparent;transition:border-color 0.2s;}\n.article-content a:hover{border-bottom-color:var(--blue);}\n\n.info-box{background:var(--blue-ghost);border-left:4px solid var(--blue);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:20px 24px;margin:24px 0;}\n.info-box.warning{background:#fffbeb;border-left-color:var(--warning);}\n.info-box.success{background:#ecfdf5;border-left-color:var(--success);}\n.info-box.danger{background:#fef2f2;border-left-color:var(--danger);}\n.info-box .box-title{font-weight:700;font-size:15px;margin-bottom:6px;color:var(--navy);}\n.info-box p{margin-bottom:8px;font-size:14px;}\n.info-box p:last-child{margin-bottom:0;}\n\n.example-block{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius);padding:28px;margin:24px 0;}\n.example-block .example-title{font-family:'DM Serif Display',serif;font-size:18px;color:var(--navy);margin-bottom:16px;}\n\n.formula-box{background:var(--navy);color:var(--white);border-radius:var(--radius);padding:24px 32px;margin:24px 0;text-align:center;position:relative;overflow:hidden;}\n.formula-box::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 80% 50%,rgba(37,99,235,0.15) 0%,transparent 60%);pointer-events:none;}\n.formula-box .formula-label{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:1px;color:var(--blue-light);margin-bottom:10px;position:relative;}\n.formula-box .formula-main{font-family:'JetBrains Mono',monospace;font-size:22px;font-weight:600;position:relative;line-height:1.4;}\n.formula-box .formula-note{font-size:13px;color:rgba(255,255,255,0.5);margin-top:10px;position:relative;}\n\n.shop-cta{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 100%);padding:48px 0;color:var(--white);text-align:center;position:relative;overflow:hidden;}\n.shop-cta::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 50% 50%,rgba(37,99,235,0.15) 0%,transparent 60%);pointer-events:none;}\n.shop-cta h2{font-family:'DM Serif Display',serif;font-size:32px;margin-bottom:12px;position:relative;}\n.shop-cta p{font-size:17px;color:rgba(255,255,255,0.7);margin-bottom:28px;max-width:640px;margin-left:auto;margin-right:auto;position:relative;}\n.shop-cta .cta-btn{display:inline-flex;align-items:center;gap:8px;padding:14px 36px;background:var(--blue);color:var(--white);text-decoration:none;border-radius:var(--radius-sm);font-weight:600;font-size:16px;transition:all 0.2s;position:relative;}\n.shop-cta .cta-btn:hover{background:var(--blue-light);transform:translateY(-2px);box-shadow:0 8px 24px rgba(37,99,235,0.3);}\n.page-footer{background:var(--beige);border-top:1px solid var(--beige-dark);padding:32px 0;text-align:center;}\n.page-footer a{color:var(--blue);text-decoration:none;font-weight:500;}\n.page-footer p{font-size:14px;color:var(--text-muted);}\n@media print{.quick-nav,.shop-cta{display:none;}body{min-width:auto;}}\n<\/style>\n<\/head>\n<body>\n\n\n<header class=\"hero\">\n <div class=\"hero-inner\">\n <div class=\"breadcrumb\"><a href=\"https:\/\/vibromera.eu\/\">Home<\/a> \u2192 <a href=\"https:\/\/vibromera.eu\/glossary\/\">Glossary<\/a> \u2192 ISO 14694<\/div>\n <h1>ISO 14694 \u2014 <span>Balance Quality & Vibration<\/span> for Industrial Fans<\/h1>\n <div class=\"canon-badge\"><span style=\"font-size:14px;\">\ud83d\udccc<\/span> Canonical Reference Article \u2014 vibromera.eu<\/div>\n <p class=\"subtitle\">The dedicated standard for industrial fan impeller balancing (BV categories) and operational vibration acceptance limits (FV categories) \u2014 tailoring ISO 1940 and ISO 10816 specifically to centrifugal, axial, and mixed-flow fans.<\/p>\n <\/div>\n<\/header>\n\n\n<nav class=\"quick-nav\">\n <div class=\"quick-nav-inner\">\n <a href=\"#calculator\">\u2699 BV Calculator<\/a>\n <a href=\"#bv-cards\">\u2696 BV Categories<\/a>\n <a href=\"#fv-table\">\ud83d\udcca FV Limits<\/a>\n <a href=\"#definition\">\ud83d\udcd0 Overview<\/a>\n <a href=\"#bv-section\">\ud83d\udd22 Balance Quality<\/a>\n <a href=\"#fv-section\">\ud83d\udcc8 Vibration Limits<\/a>\n <a href=\"#testing\">\ud83d\udee0 Testing<\/a>\n <a href=\"#field-balancing\">\ud83d\udd27 Field Balancing<\/a>\n <a href=\"#case-studies\">\ud83d\udcdd Cases<\/a>\n <a href=\"#faq\">\u2753 FAQ<\/a>\n <\/div>\n<\/nav>\n\n\n<section class=\"summary-dashboard\" id=\"calculator\">\n <div class=\"container\">\n <div class=\"dashboard-grid\">\n <div class=\"calc-panel\">\n <h2 class=\"panel-title\">Fan Impeller Balance Tolerance (BV)<\/h2>\n <p class=\"panel-subtitle\">Calculate permissible residual unbalance per ISO 14694 BV category<\/p>\n <div class=\"calc-form\">\n <div class=\"form-group full-width\">\n <label>BV Category (Balance Quality)<\/label>\n <select id=\"bvCat\">\n <option value=\"1.0\" data-bv=\"BV-1\">BV-1 \u2192 G 1.0 \u2014 Precision fans<\/option>\n <option value=\"2.5\" data-bv=\"BV-2\">BV-2 \u2192 G 2.5 \u2014 Critical service<\/option>\n <option value=\"6.3\" data-bv=\"BV-3\" selected>BV-3 \u2192 G 6.3 \u2014 Standard industrial (most common)<\/option>\n <option value=\"16\" data-bv=\"BV-4\">BV-4 \u2192 G 16 \u2014 General purpose<\/option>\n <option value=\"40\" data-bv=\"BV-5\">BV-5 \u2192 G 40 \u2014 Non-critical<\/option>\n <\/select>\n <\/div>\n <div class=\"form-group\"><label>Impeller Mass <span class=\"unit\">(kg)<\/span><\/label><input type=\"number\" id=\"impMass\" value=\"45\" min=\"0.01\" step=\"0.1\"><\/div>\n <div class=\"form-group\"><label>Max Speed <span class=\"unit\">(RPM)<\/span><\/label><input type=\"number\" id=\"impRPM\" value=\"1480\" min=\"1\" step=\"1\"><\/div>\n <div class=\"form-group\"><label>Correction Planes<\/label><select id=\"impPlanes\"><option value=\"1\">1 plane (narrow impeller)<\/option><option value=\"2\" selected>2 planes (wide impeller)<\/option><\/select><\/div>\n <div class=\"form-group\"><label>Correction Radius <span class=\"unit\">(mm, optional)<\/span><\/label><input type=\"number\" id=\"impRadius\" value=\"\" min=\"0.1\" step=\"0.1\" placeholder=\"e.g. 350\"><\/div>\n <button class=\"calc-btn\" onclick=\"calcBV()\">Calculate BV Tolerance \u2192<\/button>\n <\/div>\n <\/div>\n <div class=\"results-panel\">\n <h2 class=\"panel-title\">Results \u2014 ISO 14694<\/h2>\n <p class=\"panel-subtitle\">Impeller balance tolerance and per-plane values<\/p>\n <div id=\"resultsArea\"><div class=\"results-empty\"><span class=\"icon\">\u2696\ufe0f<\/span>Enter impeller parameters<br>to see balancing tolerance<\/div><\/div>\n <\/div>\n <\/div>\n <\/div>\n<\/section>\n\n\n<section class=\"section-bg alt\" id=\"bv-cards\">\n <div class=\"container\">\n <div class=\"section-header\">\n <h2>BV Categories \u2014 Impeller Balance Quality<\/h2>\n <p>ISO 14694 maps fan applications to ISO 1940 G-grades through five BV (Balance Vibration) categories<\/p>\n <\/div>\n\n <div class=\"cat-cards\">\n <div class=\"cat-card c1\"><div class=\"cc-grade\">BV-1<\/div><div class=\"cc-sub\">G 1.0<\/div><div class=\"cc-desc\">Ultra-high-speed precision fans, turbo-blowers, clean-room<\/div><\/div>\n <div class=\"cat-card c2\"><div class=\"cc-grade\">BV-2<\/div><div class=\"cc-sub\">G 2.5<\/div><div class=\"cc-desc\">Critical process fans, high-speed centrifugal, noise-sensitive HVAC<\/div><\/div>\n <div class=\"cat-card c3\"><div class=\"cc-grade\">BV-3<\/div><div class=\"cc-sub\">G 6.3<\/div><div class=\"cc-desc\"><strong>Standard<\/strong> \u2014 most industrial centrifugal & axial fans, HVAC, process<\/div><\/div>\n <div class=\"cat-card c4\"><div class=\"cc-grade\">BV-4<\/div><div class=\"cc-sub\">G 16<\/div><div class=\"cc-desc\">General-purpose low-speed, belt-driven, material handling fans<\/div><\/div>\n <div class=\"cat-card c5\"><div class=\"cc-grade\">BV-5<\/div><div class=\"cc-sub\">G 40<\/div><div class=\"cc-desc\">Non-critical, very slow, agricultural or temporary fans<\/div><\/div>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udccb Complete BV Category \u2192 G-Grade Mapping with Application Guide<\/div>\n <table>\n <thead><tr><th>BV<\/th><th>G-Grade<\/th><th>e\u00b7\u03c9 (mm\/s)<\/th><th>Typical Fan Types<\/th><th>Speed Range<\/th><\/tr><\/thead>\n <tbody>\n <tr><td class=\"mono\">BV-1<\/td><td class=\"mono\">G 1.0<\/td><td class=\"mono\">1.0<\/td><td>High-speed precision fans; turbocharger fans; semiconductor clean-room supply fans<\/td><td>> 6 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-2<\/td><td class=\"mono\">G 2.5<\/td><td class=\"mono\">2.5<\/td><td>Critical process fans; hospital \/ laboratory HVAC; direct-drive high-speed centrifugal; power-plant ID fans<\/td><td>3 000\u20136 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-3<\/td><td class=\"mono\">G 6.3<\/td><td class=\"mono\">6.3<\/td><td><strong>Standard industrial<\/strong>: centrifugal, axial, mixed-flow; HVAC supply \/ return; process ventilation; boiler fans<\/td><td>750\u20133 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-4<\/td><td class=\"mono\">G 16<\/td><td class=\"mono\">16<\/td><td>General-purpose low-speed; belt-driven; dust extraction; material handling; mine ventilation<\/td><td>300\u2013750 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-5<\/td><td class=\"mono\">G 40<\/td><td class=\"mono\">40<\/td><td>Non-critical very slow; agricultural barn fans; temporary or disposable fan assemblies<\/td><td>< 300 RPM<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\" id=\"fv-table\">\n <div class=\"table-title\">\ud83d\udcca FV Categories \u2014 Operational Vibration Limits for Assembled Fans (RMS Velocity, mm\/s)<\/div>\n <table>\n <thead><tr><th>FV<\/th><th>Max RMS Velocity<\/th><th>\u2248 ISO 10816 Zone<\/th><th>Application Level<\/th><th>Typical Installation<\/th><\/tr><\/thead>\n <tbody>\n <tr><td class=\"mono\">FV-1<\/td><td class=\"mono\">\u2264 1.8 mm\/s<\/td><td><span class=\"tag ultra\">Zone A<\/span><\/td><td>Precision \/ vibration-critical<\/td><td>Hospital AHU, laboratory, semiconductor fab<\/td><\/tr>\n <tr><td class=\"mono\">FV-2<\/td><td class=\"mono\">\u2264 2.8 mm\/s<\/td><td><span class=\"tag precision\">A\/B boundary<\/span><\/td><td>High-quality<\/td><td>Critical process fans, data centre cooling<\/td><\/tr>\n <tr><td class=\"mono\">FV-3<\/td><td class=\"mono\">\u2264 4.5 mm\/s<\/td><td><span class=\"tag standard\">Zone B<\/span><\/td><td><strong>Standard industrial<\/strong><\/td><td>General HVAC, boiler fans \u2014 most common<\/td><\/tr>\n <tr><td class=\"mono\">FV-4<\/td><td class=\"mono\">\u2264 7.1 mm\/s<\/td><td><span class=\"tag general\">B\/C boundary<\/span><\/td><td>General purpose<\/td><td>Dust extraction, material handling, outdoor<\/td><\/tr>\n <tr><td class=\"mono\">FV-5<\/td><td class=\"mono\">\u2264 11.2 mm\/s<\/td><td><span class=\"tag coarse\">Zone C<\/span><\/td><td>Non-critical<\/td><td>Agricultural, temporary, non-critical exhaust<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udcca Pre-Calculated BV Tolerances for Common Fan Configurations<\/div>\n <table>\n <thead><tr><th>Fan Type<\/th><th>Mass (kg)<\/th><th>Speed (RPM)<\/th><th>BV<\/th><th>U<sub>per<\/sub> Total (g\u00b7mm)<\/th><th>U<sub>per<\/sub> \/ Plane<\/th><th>e<sub>per<\/sub> (\u00b5m)<\/th><\/tr><\/thead>\n <tbody>\n <tr><td>Small HVAC centrifugal<\/td><td class=\"mono\">8<\/td><td class=\"mono\">2 900<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">166<\/td><td class=\"mono\">83<\/td><td class=\"mono\">20.7<\/td><\/tr>\n <tr><td>Medium roof exhaust<\/td><td class=\"mono\">25<\/td><td class=\"mono\">1 450<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">1 039<\/td><td class=\"mono\">520<\/td><td class=\"mono\">41.6<\/td><\/tr>\n <tr><td>Large AHU centrifugal<\/td><td class=\"mono\">85<\/td><td class=\"mono\">1 480<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">3 459<\/td><td class=\"mono\">1 730<\/td><td class=\"mono\">40.7<\/td><\/tr>\n <tr><td>Power-plant ID fan<\/td><td class=\"mono\">350<\/td><td class=\"mono\">990<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">8 468<\/td><td class=\"mono\">4 234<\/td><td class=\"mono\">24.2<\/td><\/tr>\n <tr><td>Tunnel ventilation axial<\/td><td class=\"mono\">120<\/td><td class=\"mono\">980<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">7 380<\/td><td class=\"mono\">3 690<\/td><td class=\"mono\">61.5<\/td><\/tr>\n <tr><td>Dust collector fan<\/td><td class=\"mono\">65<\/td><td class=\"mono\">1 750<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">5 700<\/td><td class=\"mono\">2 850<\/td><td class=\"mono\">87.7<\/td><\/tr>\n <tr><td>Mine ventilation fan<\/td><td class=\"mono\">500<\/td><td class=\"mono\">590<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">129 600<\/td><td class=\"mono\">64 800<\/td><td class=\"mono\">259<\/td><\/tr>\n <tr><td>Clean-room FFU fan<\/td><td class=\"mono\">3<\/td><td class=\"mono\">3 500<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">20.4<\/td><td class=\"mono\">10.2<\/td><td class=\"mono\">6.8<\/td><\/tr>\n <tr><td>Cooling tower fan<\/td><td class=\"mono\">200<\/td><td class=\"mono\">320<\/td><td class=\"mono\">BV-5<\/td><td class=\"mono\">238 500<\/td><td class=\"mono\">119 250<\/td><td class=\"mono\">1 193<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udd17 Typical BV \/ FV Combinations by Application<\/div>\n <table>\n <thead><tr><th>Application<\/th><th>Fan Type<\/th><th>BV<\/th><th>FV<\/th><th>Foundation<\/th><th>Notes<\/th><\/tr><\/thead>\n <tbody>\n <tr><td>Office HVAC<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-2 \/ FV-3<\/td><td>Flexible<\/td><td>Noise-sensitive; rubber isolators<\/td><\/tr>\n <tr><td>Hospital AHU<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-2<\/td><td>Flexible<\/td><td>Strict noise; premium balance<\/td><\/tr>\n <tr><td>Process exhaust<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-3<\/td><td>Rigid<\/td><td>Concrete base; standard<\/td><\/tr>\n <tr><td>Power-plant ID\/FD<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-1 \/ FV-2<\/td><td>Rigid<\/td><td>Critical; high power > 300 kW<\/td><\/tr>\n <tr><td>Tunnel ventilation<\/td><td>Axial<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-3<\/td><td>Rigid<\/td><td>Concrete duct mounts<\/td><\/tr>\n <tr><td>Dust collection<\/td><td>Radial blade<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">FV-3 \/ FV-4<\/td><td>Rigid<\/td><td>Material buildup \u2192 frequent rebalancing<\/td><\/tr>\n <tr><td>Cooling tower<\/td><td>Axial (large)<\/td><td class=\"mono\">BV-5<\/td><td class=\"mono\">FV-4 \/ FV-5<\/td><td>Flexible<\/td><td>Very low speed<\/td><\/tr>\n <tr><td>Data centre<\/td><td>EC \/ plug fan<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-2<\/td><td>Flexible<\/td><td>Vibration & noise critical<\/td><\/tr>\n <tr><td>Agricultural drying<\/td><td>Axial<\/td><td class=\"mono\">BV-4 \/ BV-5<\/td><td class=\"mono\">FV-4 \/ FV-5<\/td><td>Rigid<\/td><td>Seasonal; minimal requirements<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n <\/div>\n<\/section>\n\n\n<main class=\"main-content\" id=\"definition\">\n <div class=\"container\">\n <div class=\"content-layout\">\n <article class=\"article-content\">\n\n <h2>What is ISO 14694?<\/h2>\n <div class=\"info-box\" style=\"border-left-color:var(--navy);background:var(--beige-light);\">\n <div class=\"box-title\" style=\"font-size:16px;\">Quick Answer<\/div>\n <p style=\"font-size:15px;\"><strong>ISO 14694<\/strong> (<em>Industrial fans \u2014 Specifications for balance quality and vibration levels<\/em>) is the standard that tailors <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940 G-grades<\/a> and <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816 vibration zones<\/a> specifically for industrial fans. It defines <strong>BV categories<\/strong> (BV-1 to BV-5) for impeller balance quality and <strong>FV categories<\/strong> (FV-1 to FV-5) for maximum operational vibration. The standard default is <strong>BV-3 (G 6.3)<\/strong> for balance and <strong>FV-3 (\u2264 4.5 mm\/s RMS)<\/strong> for vibration acceptance.<\/p>\n <\/div>\n\n <p>Fans are the most common rotating machine in industry, yet they have unique characteristics \u2014 large-diameter impellers, significant aerodynamic forces, often cantilevered rotor arrangements, and highly variable operating environments \u2014 that justify a dedicated standard. ISO 14694 removes the ambiguity of interpreting general-purpose standards for fans by providing application-specific BV and FV categories that are clear, unambiguous, and directly usable in purchase specifications and acceptance testing.<\/p>\n\n <p>The standard covers all types: centrifugal (radial), axial, mixed-flow, and cross-flow fans of all sizes for stationary, terrestrial use. It excludes aircraft, air-cushion vehicles, and similar specialized applications.<\/p>\n\n <h3>Two-Part Structure<\/h3>\n <p>ISO 14694 is logically divided into two complementary parts that mirror its two category systems:<\/p>\n <ul>\n <li><strong>Part 1 \u2014 BV (Balance Quality):<\/strong> Specifies the permissible residual unbalance for the <em>fan impeller alone<\/em>, before assembly. Verified on a <a href=\"https:\/\/vibromera.eu\/glossary\/balancing-machine\/\">balancing machine<\/a>.<\/li>\n <li><strong>Part 2 \u2014 FV (Vibration Limits):<\/strong> Specifies the maximum operational vibration for the <em>complete assembled fan<\/em>. Verified by measurement on bearing housings during operation per <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816<\/a> methodology.<\/li>\n <\/ul>\n\n <h2 id=\"bv-section\">Balance Quality Requirements (BV Categories)<\/h2>\n <p>BV categories specify the maximum permissible residual <a href=\"https:\/\/vibromera.eu\/glossary\/unbalance\/\">unbalance<\/a> for the fan impeller as a standalone component. Each BV category maps directly to an <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940-1 G-grade<\/a>. This mapping is the key contribution of ISO 14694: it eliminates the guesswork of selecting the correct G-grade by providing fan-specific guidance.<\/p>\n\n <div class=\"formula-box\">\n <div class=\"formula-label\">Permissible Residual Unbalance (ISO 14694 \/ ISO 1940)<\/div>\n <div class=\"formula-main\">U<sub>per<\/sub> = (9 549 \u00d7 G \u00d7 m) \/ n<\/div>\n <div class=\"formula-note\">U<sub>per<\/sub> in g\u00b7mm | G = BV grade value in mm\/s | m = impeller mass in kg | n = max service speed in RPM<\/div>\n <\/div>\n\n <h3>Selecting the Right BV Category<\/h3>\n <ul>\n <li><strong>BV-1 (G 1.0):<\/strong> Ultra-precision \u2014 turbo-fans with small, very high-speed impellers. Requires specialized high-speed balancing machines with sub-milligram resolution. Rarely specified outside turbo-blowers and semiconductor equipment.<\/li>\n <li><strong>BV-2 (G 2.5):<\/strong> Critical-service fans (power-plant ID\/FD), noise-sensitive HVAC (hospitals, recording studios, clean rooms), and high-speed centrifugal fans above 3 000 RPM. Often paired with FV-1 or FV-2 acceptance.<\/li>\n <li><strong>BV-3 (G 6.3):<\/strong> The standard for the <strong>vast majority<\/strong> of industrial fans \u2014 centrifugal and axial, HVAC supply\/return, process ventilation. This is the assumed default if no BV category is specified contractually.<\/li>\n <li><strong>BV-4 (G 16):<\/strong> Heavy-duty fans handling particulate-laden or corrosive air: dust collectors, material handling, mine ventilation. Looser tolerance acknowledges that these fans need frequent rebalancing due to buildup and erosion.<\/li>\n <li><strong>BV-5 (G 40):<\/strong> Non-critical, very slow impellers: cooling-tower fans, agricultural ventilation, temporary systems.<\/li>\n <\/ul>\n\n <div class=\"info-box\">\n <div class=\"box-title\">Use Service Speed, Not Balancing-Machine Speed<\/div>\n <p>The tolerance must be calculated at the <em>maximum operating speed<\/em>. Many impellers are balanced on low-speed machines at 300\u2013600 RPM, but the tolerance calculation must use the actual operating speed (e.g., 1 480 RPM). Using balancing-machine speed produces a tolerance that is dangerously loose.<\/p>\n <\/div>\n\n <h3>Single-Plane vs. Two-Plane Balancing<\/h3>\n <p>ISO 14694 follows ISO 21940-12 guidance: narrow impellers (width\/diameter L\/D < 0.5, typical for most centrifugal fans) need <strong>single-plane<\/strong> balancing \u2014 full U<sub>per<\/sub> applies to one plane. Wide impellers or long axial fan rotors (L\/D \u2265 0.5) need <strong>two-plane dynamic balancing<\/strong> \u2014 U<sub>per<\/sub> is divided between planes (equally for symmetric rotors, proportionally for asymmetric ones).<\/p>\n\n <h2 id=\"fv-section\">Operational Vibration Limits (FV Categories)<\/h2>\n <p>FV categories define the maximum allowable broadband <strong><a href=\"https:\/\/vibromera.eu\/glossary\/rms\/\">RMS vibration velocity<\/a><\/strong> (mm\/s) measured on bearing housings of the complete fan at design speed and load, in the 10\u20131 000 Hz range per <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816-1<\/a> methodology.<\/p>\n\n <h3>Rigid vs. Flexible Foundation<\/h3>\n <p>Like ISO 10816, ISO 14694 recognizes that the support structure critically affects measured vibration:<\/p>\n <ul>\n <li><strong>Rigid:<\/strong> Fan on massive concrete or heavy steel. First <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\">natural frequency<\/a> of the fan-foundation system above 1\u00d7 RPM. Lower vibration readings.<\/li>\n <li><strong>Flexible:<\/strong> Fan on spring isolators, rubber pads, or light steel platform. First natural frequency below 1\u00d7 RPM. Higher vibration readings \u2014 but lower force transmission to the building.<\/li>\n <\/ul>\n <p>Some specifications allow one FV category higher for flexibly mounted fans (e.g., FV-3 rigid \u2192 FV-4 flexible for the same application).<\/p>\n\n <div class=\"info-box warning\">\n <div class=\"box-title\">BV Compliance \u2260 FV Compliance<\/div>\n <p>A perfectly balanced impeller (meeting BV-3) does <strong>not<\/strong> guarantee the assembled fan meets FV-3. Operational vibration depends on many factors beyond impeller balance: shaft <a href=\"https:\/\/vibromera.eu\/glossary\/misalignment\/\">misalignment<\/a>, <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-fault-frequencies\/\">bearing condition<\/a>, foundation <a href=\"https:\/\/vibromera.eu\/glossary\/resonance\/\">resonance<\/a>, aerodynamic forces (inlet distortion, damper position), belt tension, and coupling condition. BV is necessary but not sufficient for FV.<\/p>\n <\/div>\n\n <h3>Aerodynamic Sources of Fan Vibration<\/h3>\n <p>Unlike most rotating machines, fans interact dynamically with the airstream, creating vibration sources unique to fans:<\/p>\n <ul>\n <li><strong>Blade pass frequency (BPF):<\/strong> Every fan produces vibration at BPF = blades \u00d7 RPM \u00f7 60. Excessive BPF amplitude indicates clearance issues, inlet distortion, or guide-vane interaction.<\/li>\n <li><strong>Inlet distortion:<\/strong> Elbows, dampers, or obstructions close to the inlet create non-uniform flow \u2192 periodic blade loading \u2192 <a href=\"https:\/\/vibromera.eu\/glossary\/harmonics-vibration\/\">harmonics<\/a> of shaft speed.<\/li>\n <li><strong>Stall and surge:<\/strong> Operating far from the design point causes aerodynamic instability \u2014 blade stall or system surge, producing broadband vibration and noise.<\/li>\n <li><strong>Material buildup:<\/strong> In dust collectors and cement plants, uneven deposits on blades create progressive unbalance. A fan that met BV-3 at commissioning may exceed FV limits within weeks.<\/li>\n <\/ul>\n\n <h2 id=\"testing\">Acceptance Testing \u2014 Two-Stage Verification<\/h2>\n\n <h3>Stage 1: Impeller Balance Verification (BV)<\/h3>\n <p>The impeller is balanced on a calibrated balancing machine <em>before assembly<\/em>. The procedure:<\/p>\n <ol>\n <li>Mount impeller on balancing machine mandrel or in its own bearings<\/li>\n <li>Perform single-plane or two-plane balancing (depending on L\/D ratio)<\/li>\n <li>Reduce residual unbalance below U<sub>per<\/sub> for the specified BV category<\/li>\n <li>Document: initial unbalance, correction masses placed, final residual unbalance<\/li>\n <li><strong>Pass criterion:<\/strong> final residual \u2264 U<sub>per<\/sub> for specified BV<\/li>\n <\/ol>\n\n <h3>Stage 2: Operational Vibration Test (FV)<\/h3>\n <p>After assembly and installation, the fan is tested under operational conditions:<\/p>\n <ol>\n <li>Install vibration sensors on bearing housings \u2014 three orthogonal directions (V, H, A) at each bearing<\/li>\n <li>Run fan at design speed and operating point; allow thermal stabilisation (15\u201330 min)<\/li>\n <li>Record broadband RMS velocity (mm\/s) in 10\u20131 000 Hz range<\/li>\n <li><strong>Pass criterion:<\/strong> the highest single reading from any bearing in any direction \u2264 FV category limit<\/li>\n <\/ol>\n\n <div class=\"info-box success\">\n <div class=\"box-title\">Always Record the Full Spectrum<\/div>\n <p>While acceptance is based on overall RMS, always record the <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum<\/a> during commissioning. If the fan later develops problems, comparison with the baseline spectrum is invaluable for diagnosis. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> records both overall RMS and full frequency spectrum automatically.<\/p>\n <\/div>\n\n <h2 id=\"field-balancing\">Field Balancing of Fan Impellers<\/h2>\n <p>Many industrial fans must be balanced in-situ \u2014 either because the impeller is too large to remove, or because balance was lost during operation due to material buildup, erosion, or blade damage. ISO 14694 implicitly supports field balancing as the practical way to maintain BV and FV compliance throughout the fan's operating life.<\/p>\n\n <h3>When Field Balancing Is Needed<\/h3>\n <ul>\n <li>Fan vibration exceeds FV limit and FFT spectrum shows dominant 1\u00d7 (unbalance) component<\/li>\n <li>Material buildup has changed impeller balance since commissioning<\/li>\n <li>Blade repair, blade replacement, or erosion shield replacement performed<\/li>\n <li>Impeller cannot be removed without major disassembly (centrifugal fans in scroll housings)<\/li>\n <li>Production schedule cannot accommodate a long shutdown for shop balancing<\/li>\n <\/ul>\n\n <h3>Procedure with Balanset-1A<\/h3>\n <ol>\n <li><strong>Setup:<\/strong> Mount vibration sensor on bearing housing (radial direction), laser tachometer aimed at shaft. Select single-plane (F2) or two-plane (F3) mode.<\/li>\n <li><strong>Initial run:<\/strong> Record baseline vibration \u2014 amplitude and phase at 1\u00d7 shaft speed. Example: 8.2 mm\/s at 135\u00b0.<\/li>\n <li><strong>Trial weight:<\/strong> Mount known mass (e.g., 20 g) on accessible blade or hub. Run again, record new vector. Example: 5.5 mm\/s at 210\u00b0.<\/li>\n <li><strong>Correction:<\/strong> Software calculates required mass and angle. Example: \"Add 35 g at 285\u00b0.\" Weight splitting available for blade mounting.<\/li>\n <li><strong>Verify:<\/strong> Final run confirms residual vibration below FV limit. Typical result: 1.0\u20132.0 mm\/s after one correction cycle.<\/li>\n <\/ol>\n\n <div class=\"info-box\">\n <div class=\"box-title\">Single-Plane vs. Two-Plane in the Field<\/div>\n <p>Most centrifugal fan impellers are narrow enough for <strong>single-plane<\/strong> balancing (Balanset F2 mode). Wide impellers, multi-stage fans, and long axial fans need <strong>two-plane<\/strong> (Balanset F3 with two sensors). Quick test: measure both bearings \u2014 if there is a significant amplitude or phase difference, use two-plane.<\/p>\n <\/div>\n\n <h2 id=\"case-studies\">Case Studies \u2014 ISO 14694 in Practice<\/h2>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 1: HVAC Supply Fan \u2014 Acceptance Testing<\/div>\n <p><strong>Fan:<\/strong> Centrifugal HVAC supply, 22 kW, 1 460 RPM, impeller mass 38 kg, direct-drive on rigid concrete base.<\/p>\n <p><strong>Spec:<\/strong> BV-3 (G 6.3), FV-3 (\u2264 4.5 mm\/s).<\/p>\n <p><strong>BV tolerance:<\/strong> U<sub>per<\/sub> = 9 549 \u00d7 6.3 \u00d7 38 \/ 1 460 = <strong>1 566 g\u00b7mm<\/strong> total \u2192 783 g\u00b7mm per plane.<\/p>\n <p><strong>Balance check:<\/strong> Factory certificate: 420 g\u00b7mm residual \u2014 well within 1 566 g\u00b7mm limit. \u2705<\/p>\n <p><strong>FV test:<\/strong> Highest reading: 3.8 mm\/s (horizontal, drive-end bearing). Within FV-3 limit of 4.5 mm\/s. \u2705<\/p>\n <p><strong>Baseline spectrum:<\/strong> Clean 1\u00d7 at 24.3 Hz, small BPF at 170 Hz (7 blades). Healthy fan.<\/p>\n <\/div>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 2: Dust Collector Fan \u2014 Progressive Unbalance from Buildup<\/div>\n <p><strong>Fan:<\/strong> Radial-blade dust collector, 30 kW, 1 750 RPM, impeller 40 kg, rigid base.<\/p>\n <p><strong>Problem:<\/strong> Vibration grew from 3.5 mm\/s at commissioning to 9.8 mm\/s after 6 months. FV-3 rigid limit = 4.5 mm\/s \u2192 <strong>EXCEEDS<\/strong>.<\/p>\n <p><strong>Diagnosis:<\/strong> Balanset-1A FFT: dominant 1\u00d7 peak at 29.2 Hz = shaft speed. Minimal 2\u00d7 or other harmonics. Root cause: non-uniform dust buildup on blades.<\/p>\n <p><strong>Action:<\/strong> Blades cleaned, field balanced with <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a>. Trial weight 15 g, calculated correction 28 g at 195\u00b0. Post-balance: <strong>1.3 mm\/s<\/strong>. \u2705<\/p>\n <p><strong>Recommendation:<\/strong> Schedule quarterly cleaning + rebalancing for material-handling fans.<\/p>\n <\/div>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 3: Roof Exhaust Fan \u2014 Blade-Pass Resonance Problem<\/div>\n <p><strong>Fan:<\/strong> Centrifugal roof exhaust, 15 kW, 2 940 RPM, impeller 8 kg, spring isolators (flexible).<\/p>\n <p><strong>Problem:<\/strong> Overall vibration 12.5 mm\/s. Field balancing reduced 1\u00d7 from 7.0 to 1.5 mm\/s, but overall only dropped to 10.8 mm\/s.<\/p>\n <p><strong>Diagnosis:<\/strong> FFT shows strong 7\u00d7 peak at 343 Hz = 8.5 mm\/s (BPF, 7 blades \u00d7 49 Hz). Fan housing <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\">natural frequency<\/a> at ~340 Hz \u2014 resonance.<\/p>\n <p><strong>Root cause:<\/strong> 90\u00b0 elbow immediately before inlet \u2192 non-uniform inlet velocity \u2192 BPF excitation \u2192 housing resonance amplification.<\/p>\n <p><strong>Solution:<\/strong> Inlet guide vanes installed + elbow relocated further upstream. BPF dropped to 2.1 mm\/s. Overall: <strong>3.2 mm\/s<\/strong>. \u2705<\/p>\n <p>This case illustrates why BV compliance alone does not guarantee FV compliance \u2014 aerodynamic factors produce vibration independently of balance quality.<\/p>\n <\/div>\n\n <h2 id=\"standards-context\">Relationship to Other Standards<\/h2>\n <p>ISO 14694 does not exist in isolation \u2014 it references and builds upon several international standards:<\/p>\n <ul>\n <li><strong><a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940-1 \/ ISO 21940-11<\/a>:<\/strong> The G-grade system that BV categories reference. ISO 14694 selects appropriate G-grades for each fan type.<\/li>\n <li><strong><a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816-1 \/ ISO 20816-1<\/a>:<\/strong> General vibration measurement methodology. FV categories are derived from and compatible with ISO 10816 zones.<\/li>\n <li><strong>ISO 10816-3:<\/strong> Industrial machines 15\u2013300 kW. Fans in this range could use either standard, but ISO 14694 provides more specific fan guidance.<\/li>\n <li><strong>ISO 5801:<\/strong> Fan performance testing. FV tests reference operating conditions from this standard.<\/li>\n <li><strong>ISO 13347:<\/strong> Fan acoustics (noise). Related but separate \u2014 reducing vibration often reduces noise transmission.<\/li>\n <li><strong>AMCA 204:<\/strong> North American fan vibration standard. Similar scope; fans meeting one generally meet the other.<\/li>\n <\/ul>\n\n <div class=\"info-box success\">\n <div class=\"box-title\">Vibromera Equipment for ISO 14694 Compliance<\/div>\n <p>The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> portable balancer provides: two-channel vibration measurement (both bearings simultaneously), built-in ISO 1940 \/ ISO 14694 tolerance calculator, single-plane and two-plane <a href=\"https:\/\/vibromera.eu\/glossary\/rotor-balancing\/\">balancing<\/a> modes, correction weight splitting for blade-mounted weights, <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum analysis<\/a> for fault diagnostics, and vibrometer mode for FV acceptance measurement. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-4\/\">Balanset-4<\/a> extends this to four channels for complex multi-bearing fan assemblies.<\/p>\n <\/div>\n\n <hr style=\"margin:48px 0 24px;border:none;border-top:1px solid var(--border-light);\">\n <p><strong>Official standard:<\/strong> <a href=\"https:\/\/www.iso.org\/standard\/37371.html\" rel=\"nofollow noopener\" target=\"_blank\">ISO 14694 on ISO Store \u2192<\/a><\/p>\n <p><a href=\"https:\/\/vibromera.eu\/glossary\/\">\u2190 Back to Glossary Index<\/a><\/p>\n\n <\/article>\n\n \n <aside class=\"toc-sidebar\">\n <div class=\"toc-box\">\n <h3>On This Page<\/h3>\n <a href=\"#calculator\">BV Tolerance Calculator<\/a>\n <a href=\"#bv-cards\">BV Category Cards<\/a>\n <a href=\"#fv-table\">FV Vibration Limits<\/a>\n <a href=\"#definition\">What is ISO 14694?<\/a>\n <a href=\"#bv-section\">Balance Quality (BV)<\/a>\n <a class=\"sub\" href=\"#bv-section\">BV selection guide<\/a>\n <a class=\"sub\" href=\"#bv-section\">Tolerance formula<\/a>\n <a class=\"sub\" href=\"#bv-section\">Single vs. two-plane<\/a>\n <a href=\"#fv-section\">Vibration Limits (FV)<\/a>\n <a class=\"sub\" href=\"#fv-section\">FV categories<\/a>\n <a class=\"sub\" href=\"#fv-section\">Aerodynamic sources<\/a>\n <a href=\"#testing\">Test Procedures<\/a>\n <a href=\"#field-balancing\">Field Balancing<\/a>\n <a href=\"#case-studies\">Case Studies (3)<\/a>\n <a href=\"#standards-context\">Related Standards<\/a>\n <a href=\"#faq\">FAQ (7 Questions)<\/a>\n <\/div>\n <div class=\"toc-box\" style=\"margin-top:24px;background:var(--navy);border-color:var(--navy);\">\n <h3 style=\"color:var(--white);\">Fan Balancing Equipment<\/h3>\n <p style=\"color:rgba(255,255,255,0.6);font-size:13px;margin-bottom:12px;\">Portable field balancing with built-in ISO 14694 \/ ISO 1940 tolerance calculator.<\/p>\n <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\" style=\"display:block;padding:8px 14px;background:var(--blue);color:white;border-radius:6px;text-align:center;font-weight:600;font-size:14px;text-decoration:none;margin-bottom:8px;border-left:none;\">Balanset-1A \u2192<\/a>\n <a href=\"https:\/\/vibromera.eu\/product\/balanset-4\/\" style=\"display:block;padding:8px 14px;background:rgba(255,255,255,0.1);color:white;border-radius:6px;text-align:center;font-weight:600;font-size:14px;text-decoration:none;border:1px solid rgba(255,255,255,0.2);border-left:none;\">Balanset-4 \u2192<\/a>\n <\/div>\n <\/aside>\n <\/div>\n <\/div>\n<\/main>\n\n\n<section class=\"section-bg alt\" id=\"faq\">\n <div class=\"container\" style=\"max-width:900px;\">\n <div class=\"section-header\"><h2>Frequently Asked Questions \u2014 ISO 14694<\/h2><p>Common questions about fan balance quality (BV) and vibration acceptance (FV)<\/p><\/div>\n <div style=\"display:flex;flex-direction:column;gap:16px;\">\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What is the difference between BV and FV categories?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>BV<\/strong> defines the balance quality of the <em>impeller alone<\/em> \u2014 measured on a balancing machine before assembly. <strong>FV<\/strong> defines the acceptable vibration of the <em>complete assembled fan<\/em> \u2014 measured on bearing housings during operation. An impeller can pass BV but the fan may fail FV if there are alignment, resonance, or aerodynamic issues. Conversely, a well-installed fan with moderate impeller balance may still meet FV if other factors are favourable.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What BV category for standard industrial fans?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>BV-3 (G 6.3)<\/strong> \u2014 the standard for most centrifugal and axial fans at 750\u20133 000 RPM. Covers HVAC, process ventilation, and general industrial applications. Only specify BV-2 for critical\/high-speed fans or BV-4 for slow\/non-critical fans. BV-3 is the assumed default when no BV category is stated in the specification.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What BV category should I specify for HVAC fans in a hospital?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n For noise-sensitive HVAC installations such as hospitals, recording studios, and laboratories, specify <strong>BV-2 (G 2.5)<\/strong> combined with <strong>FV-2 (\u2264 2.8 mm\/s)<\/strong>. This provides premium impeller balance and strict operational vibration limits. Large critical AHU fans above 300 kW in these environments also typically require BV-2.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> Can I balance a fan in-situ to ISO 14694?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n Yes. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> portable balancer enables field balancing of installed fans \u2014 single-plane or two-plane \u2014 with built-in ISO tolerance calculation. The instrument measures vibration amplitude and phase, calculates correction weights, and verifies that the final balance meets the BV category tolerance. This is standard practice for large fans where impeller removal is impractical.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> Fan passes BV but fails FV \u2014 why?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n Good impeller balance is necessary but not sufficient. Common causes of FV failure despite good BV: shaft <a href=\"https:\/\/vibromera.eu\/glossary\/misalignment\/\">alignment<\/a> problems (coupling or belt), structural <a href=\"https:\/\/vibromera.eu\/glossary\/resonance\/\">resonance<\/a> of the fan frame or ductwork, aerodynamic imbalance (blade pitch variation, inlet obstruction, stall), <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-fault-frequencies\/\">bearing defects<\/a>, soft foot, and pipe\/duct strain. Use <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum analysis<\/a> to identify the dominant frequency.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> How does ISO 14694 relate to ISO 10816?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n ISO 14694 FV limits are derived from the same velocity-based methodology as ISO 10816 but are tailored specifically for fans. FV-3 = 4.5 mm\/s corresponds to the ISO 10816-1 Class I C\/D boundary and the ISO 10816-3 Group 2 Rigid C\/D boundary. ISO 14694 provides more direct and unambiguous guidance than interpreting the broader machine groups in ISO 10816-3 for fans.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What vibration level is acceptable for a typical industrial fan?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>FV-3 (\u2264 4.5 mm\/s RMS)<\/strong> is the standard acceptance criterion. Newly installed fans should ideally be below 2.8 mm\/s. Above 7.1 mm\/s (FV-4 exceeded) requires investigation. Above 11.2 mm\/s indicates potential damage risk and requires immediate attention. For condition monitoring, trending vibration over time is more valuable than any single reading.\n <\/div>\n <\/details>\n\n <\/div>\n <\/div>\n<\/section>\n\n\n<section style=\"padding:32px 0;background:var(--white);border-top:1px solid var(--border-light);\">\n <div class=\"container\" style=\"max-width:900px;\">\n <h3 style=\"font-family:'DM Serif Display',serif;font-size:22px;color:var(--navy);margin-bottom:20px;\">Related Glossary Articles<\/h3>\n <div style=\"display:grid;grid-template-columns:repeat(3,1fr);gap:16px;\">\n <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Balance Quality Grade<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">ISO 1940 \/ 21940-11 G-grades \u2014 the system BV categories reference<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">ISO 10816-1<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">General vibration evaluation \u2014 the methodology behind FV categories<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/rotor-balancing\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Rotor Balancing<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">Single-plane and two-plane balancing procedures for fan impellers<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/unbalance\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Unbalance<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">The primary controllable source of fan vibration<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/harmonics-vibration\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Harmonics in Vibration<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">Blade pass frequency, 1\u00d7, 2\u00d7 \u2014 diagnosing fan vibration spectra<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Natural Frequency<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">When fan frame resonance causes high vibration despite good balance<\/div>\n <\/a>\n <\/div>\n <\/div>\n<\/section>\n\n\n<section class=\"shop-cta\">\n <div class=\"container\">\n <h2>Balance Fans to ISO 14694 \u2014 In the Field<\/h2>\n <p>Vibromera portable balancing devices calculate BV tolerances automatically and guide correction weight placement \u2014 single-plane or two-plane, no impeller removal required.<\/p>\n <a href=\"https:\/\/vibromera.eu\/shop\/\" class=\"cta-btn\">Browse Fan Balancing Equipment \u2192<\/a>\n <\/div>\n<\/section>\n\n<footer class=\"page-footer\">\n <div class=\"container\"><p><a href=\"https:\/\/vibromera.eu\/glossary\/\">\u2190 Back to Glossary<\/a> | <a href=\"https:\/\/vibromera.eu\/\">vibromera.eu<\/a><\/p><\/div>\n<\/footer>\n\n\n<script>\nfunction calcBV(){\n const G=parseFloat(document.getElementById('bvCat').value);\n const bv=document.getElementById('bvCat').selectedOptions[0].getAttribute('data-bv');\n const m=parseFloat(document.getElementById('impMass').value);\n const n=parseFloat(document.getElementById('impRPM').value);\n const p=parseInt(document.getElementById('impPlanes').value);\n const R=parseFloat(document.getElementById('impRadius').value)||0;\n if(!m||!n||m<=0||n<=0)return;\n const e=(9549*G)\/n, U=e*m, Up=U\/p, w=2*Math.PI*n\/60, F=(U\/1e6)*w*w;\n let cw=R>0?Up\/R:0;\n const f=v=>v>=100?v.toFixed(0):v>=1?v.toFixed(1):v.toFixed(3);\n document.getElementById('resultsArea').innerHTML=`\n <div class=\"result-primary\">\n <div class=\"res-label\">Total Permissible Unbalance (${bv})<\/div>\n <div class=\"res-value\">${f(U)}<\/div>\n <div class=\"res-unit\">g\u00b7mm \u2014 ISO 14694 \/ ISO 1940<\/div>\n <\/div>\n <div class=\"results-secondary\">\n <div class=\"res-card\"><div class=\"rc-label\">Specific Eccentricity<\/div><div class=\"rc-value\">${e>=10?e.toFixed(1):e>=0.1?e.toFixed(2):e.toFixed(3)}<\/div><div class=\"rc-unit\">\u00b5m (e<sub>per<\/sub>)<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">Centrifugal Force<\/div><div class=\"rc-value\">${F>=10?F.toFixed(1):F>=0.1?F.toFixed(2):F.toFixed(3)}<\/div><div class=\"rc-unit\">N at ${n} RPM<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">BV \/ G-Grade<\/div><div class=\"rc-value\" style=\"font-size:16px\">${bv} (G ${G})<\/div><div class=\"rc-unit\">ISO 14694<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">Impeller<\/div><div class=\"rc-value\" style=\"font-size:14px;font-family:'Source Sans 3',sans-serif\">${m} kg @ ${n} RPM<\/div><div class=\"rc-unit\">${p} plane${p>1?'s':''}<\/div><\/div>\n <\/div>\n <div class=\"plane-note\">\n <div class=\"pn-label\">Per Plane (${p===1?'single plane':'each of '+p+' planes'})<\/div>\n <div class=\"pn-value\">${f(Up)}<\/div>\n <div class=\"pn-unit\">g\u00b7mm${cw>0?' = '+(cw>=0.1?cw.toFixed(2):cw.toFixed(3))+' g at R = '+R+' mm':''}<\/div>\n <\/div>`;\n}\n\/\/ Auto-calculate on input\n['bvCat','impMass','impRPM','impPlanes','impRadius'].forEach(id=>{\n const el=document.getElementById(id);\n el.addEventListener(el.tagName==='SELECT'?'change':'input',calcBV);\n});\ncalcBV();\n<\/script>\n\n<\/body>\n<\/html><\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>En oversikt over ISO 14694, standarden som spesifiserer krav til balansekvalitet og vibrasjonsgrenser spesielt for industrivifter.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[109,112],"tags":[],"class_list":["post-20603","glossary","type-glossary","status-publish","hentry","category-glossary","category-iso-standards"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/glossary"}],"version-history":[{"count":4,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603\/revisions"}],"predecessor-version":[{"id":101499,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603\/revisions\/101499"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=20603"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=20603"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=20603"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

\n\n\n\n\nISO 14694 \u2014 Balance Quality & Vibration Limits for Industrial Fans \u2014 Vibromera<\/title>\n<meta name=\"description\" content=\"Complete guide to ISO 14694: fan balance quality (BV-1 to BV-5) and vibration limits (FV-1 to FV-5). Interactive BV tolerance calculator, FV acceptance tables, BV-to-G-grade mapping, field balancing procedures for centrifugal and axial fans.\">\n<meta name=\"keywords\" content=\"ISO 14694, industrial fan balancing, fan vibration limits, BV category, FV category, fan balance quality, impeller balancing, fan vibration standard, G-grade fans, centrifugal fan, axial fan, Balanset, fan acceptance testing\">\n<meta name=\"author\" content=\"Vibromera\">\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large\">\n\n\n\n\n\n\n\n\n\n\n\n<meta property=\"og:type\" content=\"article\">\n<meta property=\"og:title\" content=\"ISO 14694 \u2014 Balance Quality & Vibration Limits for Industrial Fans\">\n<meta property=\"og:description\" content=\"BV balance grades (BV-1\u2192BV-5) and FV vibration categories (FV-1\u2192FV-5) for centrifugal, axial, and mixed-flow fans. Interactive calculators, tables, worked examples.\">\n<meta property=\"og:url\" content=\"https:\/\/vibromera.eu\/glossary\/iso-14694\/\">\n<meta property=\"og:site_name\" content=\"Vibromera \u2014 Vibration Analysis & Balancing Equipment\">\n<meta property=\"og:locale\" content=\"en_US\">\n<meta property=\"og:image\" content=\"https:\/\/vibromera.eu\/wp-content\/uploads\/iso-14694-og.jpg\">\n<meta property=\"article:publisher\" content=\"https:\/\/vibromera.eu\/\">\n<meta property=\"article:section\" content=\"Glossary\">\n<meta property=\"article:tag\" content=\"ISO 14694\">\n<meta property=\"article:tag\" content=\"Fan Balancing\">\n<meta property=\"article:tag\" content=\"Fan Vibration\">\n\n\n<meta name=\"twitter:card\" content=\"summary_large_image\">\n<meta name=\"twitter:title\" content=\"ISO 14694 \u2014 Industrial Fan Vibration & Balance Quality Standard\">\n<meta name=\"twitter:description\" content=\"BV impeller balance grades, FV vibration limits, calculators for fan balancing tolerance per ISO 14694.\">\n\n\n<meta name=\"geo.region\" content=\"EU\">\n<meta name=\"geo.placename\" content=\"Porto, Portugal\">\n<meta name=\"geo.position\" content=\"41.1579;-8.6291\">\n<meta name=\"ICBM\" content=\"41.1579, -8.6291\">\n\n\n<script type=\"application\/ld+json\">\n{\n \"@context\": \"https:\/\/schema.org\",\n \"@graph\": [\n {\n \"@type\": \"TechArticle\",\n \"@id\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/#article\",\n \"headline\": \"ISO 14694: Industrial Fans \u2014 Specifications for Balance Quality and Vibration Levels\",\n \"description\": \"Comprehensive guide to ISO 14694 covering BV impeller balance categories, FV operational vibration limits, acceptance testing, and practical fan field balancing with worked examples.\",\n \"author\": {\"@type\": \"Organization\", \"name\": \"Vibromera\", \"url\": \"https:\/\/vibromera.eu\/\"},\n \"publisher\": {\"@type\": \"Organization\", \"name\": \"Vibromera\", \"url\": \"https:\/\/vibromera.eu\/\", \"logo\": {\"@type\": \"ImageObject\", \"url\": \"https:\/\/vibromera.eu\/wp-content\/uploads\/vibromera-logo.png\"}},\n \"mainEntityOfPage\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/\",\n \"datePublished\": \"2024-06-15\",\n \"dateModified\": \"2026-02-07\",\n \"inLanguage\": \"en\",\n \"about\": [\n {\"@type\": \"Thing\", \"name\": \"ISO 14694\"},\n {\"@type\": \"Thing\", \"name\": \"Industrial Fan Balancing\"},\n {\"@type\": \"Thing\", \"name\": \"Fan Vibration Limits\"},\n {\"@type\": \"Thing\", \"name\": \"Balance Quality Grade\"}\n ],\n \"isPartOf\": {\"@type\": \"WebPage\", \"url\": \"https:\/\/vibromera.eu\/glossary\/\"}\n },\n {\n \"@type\": \"FAQPage\",\n \"@id\": \"https:\/\/vibromera.eu\/glossary\/iso-14694\/#faq\",\n \"mainEntity\": [\n {\n \"@type\": \"Question\",\n \"name\": \"What is ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 is an international standard that specifies balance quality requirements and acceptable vibration levels for industrial fans (centrifugal, axial, and mixed-flow). It defines BV categories (BV-1 to BV-5) for impeller balance quality corresponding to ISO 1940 G-grades, and FV categories (FV-1 to FV-5) for operational vibration limits of the assembled fan. It applies to all industrial fans except those for aircraft or air-cushion vehicles.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What is the difference between BV and FV categories in ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"BV (Balance Vibration) categories define the balance quality of the impeller as a standalone component, measured on a balancing machine before assembly. FV (Fan Vibration) categories define the acceptable operational vibration of the complete assembled fan, measured on bearing housings during operation. Good impeller balance (BV) is necessary but not sufficient for low operational vibration (FV), which also depends on alignment, foundation, aerodynamic forces, and bearing condition.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What G-Grade does ISO 14694 require for fan impellers?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 maps BV categories to ISO 1940 G-grades: BV-1 = G 1.0 (precision fans), BV-2 = G 2.5 (critical fans), BV-3 = G 6.3 (standard industrial \u2014 the most common), BV-4 = G 16 (general purpose), BV-5 = G 40 (non-critical). The majority of industrial fans are specified as BV-3 (G 6.3).\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What are the vibration limits for industrial fans per ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 FV categories define max RMS velocity on bearing housings: FV-1 \u2264 1.8 mm\/s (precision), FV-2 \u2264 2.8 mm\/s (high-quality), FV-3 \u2264 4.5 mm\/s (standard \u2014 most common), FV-4 \u2264 7.1 mm\/s (general purpose), FV-5 \u2264 11.2 mm\/s (non-critical). These are broadband 10\u20131000 Hz measurements.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"Can I balance a fan impeller in the field to ISO 14694?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. Portable instruments like the Balanset-1A can balance fan impellers in-situ without removal. The device measures vibration and phase, calculates correction weights, and includes a built-in ISO 1940 tolerance calculator for BV category verification. Field balancing is standard practice for large fans where impeller removal is impractical.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"How does ISO 14694 relate to ISO 10816?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"ISO 14694 FV vibration limits are derived from the same methodology as ISO 10816 but tailored specifically for fans. FV limit values correspond closely to ISO 10816-1 zone boundaries. ISO 14694 provides clearer, more direct guidance than interpreting the broader machine groups in ISO 10816-3 for fans.\"}\n },\n {\n \"@type\": \"Question\",\n \"name\": \"What BV category should I specify for an HVAC fan?\",\n \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Most general-purpose HVAC fans require BV-3 (G 6.3). For noise-sensitive installations such as hospitals, recording studios, or laboratories, specify BV-2 (G 2.5). Large critical air-handling units above 300 kW also typically use BV-2. Always state the BV category explicitly in the purchase specification.\"}\n }\n ]\n },\n {\n \"@type\": \"BreadcrumbList\",\n \"itemListElement\": [\n {\"@type\": \"ListItem\", \"position\": 1, \"name\": \"Home\", \"item\": \"https:\/\/vibromera.eu\/\"},\n {\"@type\": \"ListItem\", \"position\": 2, \"name\": \"Glossary\", \"item\": \"https:\/\/vibromera.eu\/glossary\/\"},\n {\"@type\": \"ListItem\", \"position\": 3, \"name\": \"ISO 14694\"}\n ]\n }\n ]\n}\n<\/script>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Serif+Display&family=Source+Sans+3:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap\" rel=\"stylesheet\">\n<style>\n:root {\n --navy:#0a2540;--navy-light:#1a3a5c;--blue:#2563eb;--blue-light:#3b82f6;--blue-pale:#dbeafe;--blue-ghost:#eff6ff;\n --beige:#f5f0e8;--beige-dark:#e8dfd3;--beige-light:#faf7f2;--white:#ffffff;--text:#1e293b;--text-secondary:#475569;\n --text-muted:#94a3b8;--border:#cbd5e1;--border-light:#e2e8f0;--success:#059669;--success-light:#d1fae5;\n --warning:#d97706;--warning-light:#fef3c7;--danger:#dc2626;--danger-light:#fee2e2;\n --shadow-sm:0 1px 3px rgba(10,37,64,0.08);--shadow-md:0 4px 12px rgba(10,37,64,0.1);--shadow-lg:0 8px 30px rgba(10,37,64,0.12);\n --radius:12px;--radius-sm:8px;--radius-lg:16px;\n}\n*{margin:0;padding:0;box-sizing:border-box;}\nbody{font-family:'Source Sans 3',sans-serif;color:var(--text);background:var(--beige-light);min-width:1200px;line-height:1.7;font-size:16px;-webkit-font-smoothing:antialiased;}\n\n\/* HERO *\/\n.hero{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 50%,#234e7a 100%);color:var(--white);padding:56px 0 48px;position:relative;overflow:hidden;}\n.hero::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 25% 75%,rgba(37,99,235,0.15) 0%,transparent 50%),radial-gradient(circle at 75% 25%,rgba(37,99,235,0.1) 0%,transparent 50%);pointer-events:none;}\n.hero-inner{max-width:1280px;margin:0 auto;padding:0 48px;position:relative;z-index:1;}\n.hero h1{font-family:'DM Serif Display',serif;font-size:42px;font-weight:400;line-height:1.15;margin-bottom:8px;letter-spacing:-0.5px;}\n.hero h1 span{color:var(--blue-light);}\n.hero .subtitle{font-size:19px;font-weight:300;color:rgba(255,255,255,0.78);max-width:840px;line-height:1.6;}\n.breadcrumb{margin-bottom:20px;font-size:14px;color:rgba(255,255,255,0.5);}\n.breadcrumb a{color:rgba(255,255,255,0.6);text-decoration:none;}\n.breadcrumb a:hover{color:rgba(255,255,255,0.9);}\n.canon-badge{display:inline-flex;align-items:center;gap:6px;padding:4px 12px;background:rgba(37,99,235,0.2);border:1px solid rgba(37,99,235,0.3);border-radius:20px;font-size:12px;font-weight:600;letter-spacing:0.5px;color:rgba(255,255,255,0.85);margin-bottom:12px;text-transform:uppercase;}\n\n\/* QUICK NAV *\/\n.quick-nav{background:var(--white);border-bottom:1px solid var(--border-light);position:sticky;top:0;z-index:100;box-shadow:var(--shadow-sm);}\n.quick-nav-inner{max-width:1280px;margin:0 auto;padding:0 48px;display:flex;gap:0;overflow-x:auto;}\n.quick-nav a{display:flex;align-items:center;gap:6px;padding:14px 16px;font-size:14px;font-weight:500;color:var(--text-secondary);text-decoration:none;white-space:nowrap;border-bottom:2px solid transparent;transition:all 0.2s;}\n.quick-nav a:hover{color:var(--blue);border-bottom-color:var(--blue);background:var(--blue-ghost);}\n\n.container{max-width:1280px;margin:0 auto;padding:0 48px;}\n\n\/* DASHBOARD *\/\n.summary-dashboard{padding:40px 0;background:var(--white);border-bottom:1px solid var(--border-light);}\n.dashboard-grid{display:grid;grid-template-columns:1fr 1fr;gap:32px;}\n.calc-panel{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-lg);padding:32px;position:relative;overflow:hidden;}\n.calc-panel::before{content:'';position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--blue),var(--blue-light));}\n.panel-title{font-family:'DM Serif Display',serif;font-size:22px;margin-bottom:6px;color:var(--navy);}\n.panel-subtitle{font-size:14px;color:var(--text-muted);margin-bottom:24px;}\n.calc-form{display:grid;grid-template-columns:1fr 1fr;gap:16px;}\n.form-group{display:flex;flex-direction:column;gap:5px;}\n.form-group.full-width{grid-column:1\/-1;}\n.form-group label{font-size:13px;font-weight:600;color:var(--text-secondary);text-transform:uppercase;letter-spacing:0.5px;}\n.form-group label .unit{font-weight:400;text-transform:none;color:var(--text-muted);}\n.form-group input,.form-group select{padding:10px 14px;border:1px solid var(--border);border-radius:var(--radius-sm);font-size:15px;font-family:'JetBrains Mono',monospace;background:var(--white);color:var(--text);transition:border-color 0.2s,box-shadow 0.2s;}\n.form-group input:focus,.form-group select:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px rgba(37,99,235,0.12);}\n.calc-btn{grid-column:1\/-1;padding:13px;background:var(--blue);color:var(--white);border:none;border-radius:var(--radius-sm);font-size:15px;font-weight:600;font-family:'Source Sans 3',sans-serif;cursor:pointer;transition:all 0.2s;margin-top:4px;}\n.calc-btn:hover{background:var(--navy);transform:translateY(-1px);box-shadow:var(--shadow-md);}\n\n.results-panel{background:var(--navy);border-radius:var(--radius-lg);padding:32px;color:var(--white);position:relative;overflow:hidden;}\n.results-panel::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 100% 0%,rgba(37,99,235,0.2) 0%,transparent 60%);pointer-events:none;}\n.results-panel .panel-title{color:var(--white);}\n.results-panel .panel-subtitle{color:rgba(255,255,255,0.5);}\n.result-primary{background:rgba(255,255,255,0.07);border:1px solid rgba(255,255,255,0.1);border-radius:var(--radius);padding:22px;text-align:center;margin-bottom:14px;position:relative;z-index:1;}\n.result-primary .res-label{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:1px;color:var(--blue-light);margin-bottom:6px;}\n.result-primary .res-value{font-family:'JetBrains Mono',monospace;font-size:36px;font-weight:700;line-height:1;margin-bottom:4px;}\n.result-primary .res-unit{font-size:15px;color:rgba(255,255,255,0.5);}\n.results-secondary{display:grid;grid-template-columns:1fr 1fr;gap:12px;position:relative;z-index:1;}\n.res-card{background:rgba(255,255,255,0.06);border:1px solid rgba(255,255,255,0.08);border-radius:var(--radius-sm);padding:14px;}\n.res-card .rc-label{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.5px;color:rgba(255,255,255,0.45);margin-bottom:4px;}\n.res-card .rc-value{font-family:'JetBrains Mono',monospace;font-size:20px;font-weight:600;}\n.res-card .rc-unit{font-size:12px;color:rgba(255,255,255,0.4);}\n.results-empty{text-align:center;padding:80px 20px;color:rgba(255,255,255,0.35);font-size:15px;position:relative;z-index:1;}\n.results-empty .icon{font-size:36px;margin-bottom:12px;display:block;}\n.plane-note{margin-top:14px;padding:14px;border-radius:var(--radius-sm);position:relative;z-index:1;background:rgba(37,99,235,0.1);border:1px solid rgba(37,99,235,0.2);text-align:center;}\n.plane-note .pn-label{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:0.5px;color:var(--blue-light);margin-bottom:4px;}\n.plane-note .pn-value{font-family:'JetBrains Mono',monospace;font-size:18px;font-weight:600;}\n.plane-note .pn-unit{font-size:12px;color:rgba(255,255,255,0.4);}\n\n\/* SECTIONS *\/\n.section-bg{padding:40px 0 48px;}\n.section-bg.alt{background:var(--beige-light);}\n.section-header{margin-bottom:28px;}\n.section-header h2{font-family:'DM Serif Display',serif;font-size:30px;color:var(--navy);margin-bottom:6px;}\n.section-header p{font-size:16px;color:var(--text-secondary);}\n\n\/* BV CARDS *\/\n.cat-cards{display:grid;grid-template-columns:repeat(5,1fr);gap:16px;margin-bottom:36px;}\n.cat-card{background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow-sm);transition:all 0.3s;position:relative;overflow:hidden;text-align:center;}\n.cat-card:hover{box-shadow:var(--shadow-lg);transform:translateY(-3px);}\n.cat-card::before{content:'';position:absolute;top:0;left:0;right:0;height:3px;}\n.cat-card.c1::before{background:#7c3aed;}.cat-card.c2::before{background:var(--blue);}\n.cat-card.c3::before{background:var(--success);}.cat-card.c4::before{background:var(--warning);}\n.cat-card.c5::before{background:var(--text-muted);}\n.cc-grade{font-family:'JetBrains Mono',monospace;font-size:24px;font-weight:700;color:var(--navy);margin-bottom:2px;}\n.cc-sub{font-family:'JetBrains Mono',monospace;font-size:13px;color:var(--blue);margin-bottom:8px;font-weight:600;}\n.cc-desc{font-size:12px;color:var(--text-secondary);line-height:1.4;}\n\n\/* TABLES *\/\n.table-wrap{background:var(--white);border-radius:var(--radius);border:1px solid var(--border-light);overflow:hidden;box-shadow:var(--shadow-sm);margin-bottom:32px;}\n.table-wrap .table-title{padding:16px 24px;font-weight:600;font-size:15px;background:var(--beige);border-bottom:1px solid var(--border-light);color:var(--navy);}\ntable{width:100%;border-collapse:collapse;}\ntable th{background:var(--navy);color:var(--white);padding:12px 16px;font-size:13px;font-weight:600;text-transform:uppercase;letter-spacing:0.5px;text-align:left;}\ntable td{padding:11px 16px;font-size:14px;border-bottom:1px solid var(--border-light);color:var(--text);}\ntable tr:last-child td{border-bottom:none;}\ntable tr:hover td{background:var(--blue-ghost);}\ntable td:first-child{font-weight:600;}\n.mono{font-family:'JetBrains Mono',monospace;font-size:13px;}\n.tag{display:inline-block;padding:2px 8px;border-radius:4px;font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.3px;}\n.tag.ultra{background:#ede9fe;color:#5b21b6;}\n.tag.precision{background:var(--blue-pale);color:var(--navy);}\n.tag.standard{background:var(--success-light);color:#065f46;}\n.tag.general{background:var(--warning-light);color:#92400e;}\n.tag.coarse{background:var(--danger-light);color:#991b1b;}\n\n\/* MAIN CONTENT *\/\n.main-content{padding:48px 0 64px;background:var(--white);}\n.content-layout{display:grid;grid-template-columns:1fr 300px;gap:48px;}\n.toc-sidebar{position:sticky;top:80px;align-self:start;}\n.toc-box{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius);padding:24px;}\n.toc-box h3{font-size:14px;font-weight:700;text-transform:uppercase;letter-spacing:0.5px;color:var(--navy);margin-bottom:16px;}\n.toc-box a{display:block;padding:6px 0;font-size:14px;color:var(--text-secondary);text-decoration:none;border-left:2px solid transparent;padding-left:12px;transition:all 0.2s;}\n.toc-box a:hover{color:var(--blue);border-left-color:var(--blue);}\n.toc-box a.sub{padding-left:28px;font-size:13px;color:var(--text-muted);}\n\n.article-content h2{font-family:'DM Serif Display',serif;font-size:28px;color:var(--navy);margin:48px 0 16px;padding-top:20px;}\n.article-content h2:first-child{margin-top:0;}\n.article-content h3{font-size:20px;font-weight:700;color:var(--navy-light);margin:32px 0 12px;}\n.article-content p{margin-bottom:16px;color:var(--text);line-height:1.8;}\n.article-content ul,.article-content ol{margin:0 0 16px 24px;line-height:1.8;}\n.article-content li{margin-bottom:6px;}\n.article-content li strong{color:var(--navy);}\n.article-content a{color:var(--blue);text-decoration:none;border-bottom:1px solid transparent;transition:border-color 0.2s;}\n.article-content a:hover{border-bottom-color:var(--blue);}\n\n.info-box{background:var(--blue-ghost);border-left:4px solid var(--blue);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:20px 24px;margin:24px 0;}\n.info-box.warning{background:#fffbeb;border-left-color:var(--warning);}\n.info-box.success{background:#ecfdf5;border-left-color:var(--success);}\n.info-box.danger{background:#fef2f2;border-left-color:var(--danger);}\n.info-box .box-title{font-weight:700;font-size:15px;margin-bottom:6px;color:var(--navy);}\n.info-box p{margin-bottom:8px;font-size:14px;}\n.info-box p:last-child{margin-bottom:0;}\n\n.example-block{background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius);padding:28px;margin:24px 0;}\n.example-block .example-title{font-family:'DM Serif Display',serif;font-size:18px;color:var(--navy);margin-bottom:16px;}\n\n.formula-box{background:var(--navy);color:var(--white);border-radius:var(--radius);padding:24px 32px;margin:24px 0;text-align:center;position:relative;overflow:hidden;}\n.formula-box::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 80% 50%,rgba(37,99,235,0.15) 0%,transparent 60%);pointer-events:none;}\n.formula-box .formula-label{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:1px;color:var(--blue-light);margin-bottom:10px;position:relative;}\n.formula-box .formula-main{font-family:'JetBrains Mono',monospace;font-size:22px;font-weight:600;position:relative;line-height:1.4;}\n.formula-box .formula-note{font-size:13px;color:rgba(255,255,255,0.5);margin-top:10px;position:relative;}\n\n.shop-cta{background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 100%);padding:48px 0;color:var(--white);text-align:center;position:relative;overflow:hidden;}\n.shop-cta::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 50% 50%,rgba(37,99,235,0.15) 0%,transparent 60%);pointer-events:none;}\n.shop-cta h2{font-family:'DM Serif Display',serif;font-size:32px;margin-bottom:12px;position:relative;}\n.shop-cta p{font-size:17px;color:rgba(255,255,255,0.7);margin-bottom:28px;max-width:640px;margin-left:auto;margin-right:auto;position:relative;}\n.shop-cta .cta-btn{display:inline-flex;align-items:center;gap:8px;padding:14px 36px;background:var(--blue);color:var(--white);text-decoration:none;border-radius:var(--radius-sm);font-weight:600;font-size:16px;transition:all 0.2s;position:relative;}\n.shop-cta .cta-btn:hover{background:var(--blue-light);transform:translateY(-2px);box-shadow:0 8px 24px rgba(37,99,235,0.3);}\n.page-footer{background:var(--beige);border-top:1px solid var(--beige-dark);padding:32px 0;text-align:center;}\n.page-footer a{color:var(--blue);text-decoration:none;font-weight:500;}\n.page-footer p{font-size:14px;color:var(--text-muted);}\n@media print{.quick-nav,.shop-cta{display:none;}body{min-width:auto;}}\n<\/style>\n<\/head>\n<body>\n\n\n<header class=\"hero\">\n <div class=\"hero-inner\">\n <div class=\"breadcrumb\"><a href=\"https:\/\/vibromera.eu\/\">Home<\/a> \u2192 <a href=\"https:\/\/vibromera.eu\/glossary\/\">Glossary<\/a> \u2192 ISO 14694<\/div>\n <h1>ISO 14694 \u2014 <span>Balance Quality & Vibration<\/span> for Industrial Fans<\/h1>\n <div class=\"canon-badge\"><span style=\"font-size:14px;\">\ud83d\udccc<\/span> Canonical Reference Article \u2014 vibromera.eu<\/div>\n <p class=\"subtitle\">The dedicated standard for industrial fan impeller balancing (BV categories) and operational vibration acceptance limits (FV categories) \u2014 tailoring ISO 1940 and ISO 10816 specifically to centrifugal, axial, and mixed-flow fans.<\/p>\n <\/div>\n<\/header>\n\n\n<nav class=\"quick-nav\">\n <div class=\"quick-nav-inner\">\n <a href=\"#calculator\">\u2699 BV Calculator<\/a>\n <a href=\"#bv-cards\">\u2696 BV Categories<\/a>\n <a href=\"#fv-table\">\ud83d\udcca FV Limits<\/a>\n <a href=\"#definition\">\ud83d\udcd0 Overview<\/a>\n <a href=\"#bv-section\">\ud83d\udd22 Balance Quality<\/a>\n <a href=\"#fv-section\">\ud83d\udcc8 Vibration Limits<\/a>\n <a href=\"#testing\">\ud83d\udee0 Testing<\/a>\n <a href=\"#field-balancing\">\ud83d\udd27 Field Balancing<\/a>\n <a href=\"#case-studies\">\ud83d\udcdd Cases<\/a>\n <a href=\"#faq\">\u2753 FAQ<\/a>\n <\/div>\n<\/nav>\n\n\n<section class=\"summary-dashboard\" id=\"calculator\">\n <div class=\"container\">\n <div class=\"dashboard-grid\">\n <div class=\"calc-panel\">\n <h2 class=\"panel-title\">Fan Impeller Balance Tolerance (BV)<\/h2>\n <p class=\"panel-subtitle\">Calculate permissible residual unbalance per ISO 14694 BV category<\/p>\n <div class=\"calc-form\">\n <div class=\"form-group full-width\">\n <label>BV Category (Balance Quality)<\/label>\n <select id=\"bvCat\">\n <option value=\"1.0\" data-bv=\"BV-1\">BV-1 \u2192 G 1.0 \u2014 Precision fans<\/option>\n <option value=\"2.5\" data-bv=\"BV-2\">BV-2 \u2192 G 2.5 \u2014 Critical service<\/option>\n <option value=\"6.3\" data-bv=\"BV-3\" selected>BV-3 \u2192 G 6.3 \u2014 Standard industrial (most common)<\/option>\n <option value=\"16\" data-bv=\"BV-4\">BV-4 \u2192 G 16 \u2014 General purpose<\/option>\n <option value=\"40\" data-bv=\"BV-5\">BV-5 \u2192 G 40 \u2014 Non-critical<\/option>\n <\/select>\n <\/div>\n <div class=\"form-group\"><label>Impeller Mass <span class=\"unit\">(kg)<\/span><\/label><input type=\"number\" id=\"impMass\" value=\"45\" min=\"0.01\" step=\"0.1\"><\/div>\n <div class=\"form-group\"><label>Max Speed <span class=\"unit\">(RPM)<\/span><\/label><input type=\"number\" id=\"impRPM\" value=\"1480\" min=\"1\" step=\"1\"><\/div>\n <div class=\"form-group\"><label>Correction Planes<\/label><select id=\"impPlanes\"><option value=\"1\">1 plane (narrow impeller)<\/option><option value=\"2\" selected>2 planes (wide impeller)<\/option><\/select><\/div>\n <div class=\"form-group\"><label>Correction Radius <span class=\"unit\">(mm, optional)<\/span><\/label><input type=\"number\" id=\"impRadius\" value=\"\" min=\"0.1\" step=\"0.1\" placeholder=\"e.g. 350\"><\/div>\n <button class=\"calc-btn\" onclick=\"calcBV()\">Calculate BV Tolerance \u2192<\/button>\n <\/div>\n <\/div>\n <div class=\"results-panel\">\n <h2 class=\"panel-title\">Results \u2014 ISO 14694<\/h2>\n <p class=\"panel-subtitle\">Impeller balance tolerance and per-plane values<\/p>\n <div id=\"resultsArea\"><div class=\"results-empty\"><span class=\"icon\">\u2696\ufe0f<\/span>Enter impeller parameters<br>to see balancing tolerance<\/div><\/div>\n <\/div>\n <\/div>\n <\/div>\n<\/section>\n\n\n<section class=\"section-bg alt\" id=\"bv-cards\">\n <div class=\"container\">\n <div class=\"section-header\">\n <h2>BV Categories \u2014 Impeller Balance Quality<\/h2>\n <p>ISO 14694 maps fan applications to ISO 1940 G-grades through five BV (Balance Vibration) categories<\/p>\n <\/div>\n\n <div class=\"cat-cards\">\n <div class=\"cat-card c1\"><div class=\"cc-grade\">BV-1<\/div><div class=\"cc-sub\">G 1.0<\/div><div class=\"cc-desc\">Ultra-high-speed precision fans, turbo-blowers, clean-room<\/div><\/div>\n <div class=\"cat-card c2\"><div class=\"cc-grade\">BV-2<\/div><div class=\"cc-sub\">G 2.5<\/div><div class=\"cc-desc\">Critical process fans, high-speed centrifugal, noise-sensitive HVAC<\/div><\/div>\n <div class=\"cat-card c3\"><div class=\"cc-grade\">BV-3<\/div><div class=\"cc-sub\">G 6.3<\/div><div class=\"cc-desc\"><strong>Standard<\/strong> \u2014 most industrial centrifugal & axial fans, HVAC, process<\/div><\/div>\n <div class=\"cat-card c4\"><div class=\"cc-grade\">BV-4<\/div><div class=\"cc-sub\">G 16<\/div><div class=\"cc-desc\">General-purpose low-speed, belt-driven, material handling fans<\/div><\/div>\n <div class=\"cat-card c5\"><div class=\"cc-grade\">BV-5<\/div><div class=\"cc-sub\">G 40<\/div><div class=\"cc-desc\">Non-critical, very slow, agricultural or temporary fans<\/div><\/div>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udccb Complete BV Category \u2192 G-Grade Mapping with Application Guide<\/div>\n <table>\n <thead><tr><th>BV<\/th><th>G-Grade<\/th><th>e\u00b7\u03c9 (mm\/s)<\/th><th>Typical Fan Types<\/th><th>Speed Range<\/th><\/tr><\/thead>\n <tbody>\n <tr><td class=\"mono\">BV-1<\/td><td class=\"mono\">G 1.0<\/td><td class=\"mono\">1.0<\/td><td>High-speed precision fans; turbocharger fans; semiconductor clean-room supply fans<\/td><td>> 6 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-2<\/td><td class=\"mono\">G 2.5<\/td><td class=\"mono\">2.5<\/td><td>Critical process fans; hospital \/ laboratory HVAC; direct-drive high-speed centrifugal; power-plant ID fans<\/td><td>3 000\u20136 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-3<\/td><td class=\"mono\">G 6.3<\/td><td class=\"mono\">6.3<\/td><td><strong>Standard industrial<\/strong>: centrifugal, axial, mixed-flow; HVAC supply \/ return; process ventilation; boiler fans<\/td><td>750\u20133 000 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-4<\/td><td class=\"mono\">G 16<\/td><td class=\"mono\">16<\/td><td>General-purpose low-speed; belt-driven; dust extraction; material handling; mine ventilation<\/td><td>300\u2013750 RPM<\/td><\/tr>\n <tr><td class=\"mono\">BV-5<\/td><td class=\"mono\">G 40<\/td><td class=\"mono\">40<\/td><td>Non-critical very slow; agricultural barn fans; temporary or disposable fan assemblies<\/td><td>< 300 RPM<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\" id=\"fv-table\">\n <div class=\"table-title\">\ud83d\udcca FV Categories \u2014 Operational Vibration Limits for Assembled Fans (RMS Velocity, mm\/s)<\/div>\n <table>\n <thead><tr><th>FV<\/th><th>Max RMS Velocity<\/th><th>\u2248 ISO 10816 Zone<\/th><th>Application Level<\/th><th>Typical Installation<\/th><\/tr><\/thead>\n <tbody>\n <tr><td class=\"mono\">FV-1<\/td><td class=\"mono\">\u2264 1.8 mm\/s<\/td><td><span class=\"tag ultra\">Zone A<\/span><\/td><td>Precision \/ vibration-critical<\/td><td>Hospital AHU, laboratory, semiconductor fab<\/td><\/tr>\n <tr><td class=\"mono\">FV-2<\/td><td class=\"mono\">\u2264 2.8 mm\/s<\/td><td><span class=\"tag precision\">A\/B boundary<\/span><\/td><td>High-quality<\/td><td>Critical process fans, data centre cooling<\/td><\/tr>\n <tr><td class=\"mono\">FV-3<\/td><td class=\"mono\">\u2264 4.5 mm\/s<\/td><td><span class=\"tag standard\">Zone B<\/span><\/td><td><strong>Standard industrial<\/strong><\/td><td>General HVAC, boiler fans \u2014 most common<\/td><\/tr>\n <tr><td class=\"mono\">FV-4<\/td><td class=\"mono\">\u2264 7.1 mm\/s<\/td><td><span class=\"tag general\">B\/C boundary<\/span><\/td><td>General purpose<\/td><td>Dust extraction, material handling, outdoor<\/td><\/tr>\n <tr><td class=\"mono\">FV-5<\/td><td class=\"mono\">\u2264 11.2 mm\/s<\/td><td><span class=\"tag coarse\">Zone C<\/span><\/td><td>Non-critical<\/td><td>Agricultural, temporary, non-critical exhaust<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udcca Pre-Calculated BV Tolerances for Common Fan Configurations<\/div>\n <table>\n <thead><tr><th>Fan Type<\/th><th>Mass (kg)<\/th><th>Speed (RPM)<\/th><th>BV<\/th><th>U<sub>per<\/sub> Total (g\u00b7mm)<\/th><th>U<sub>per<\/sub> \/ Plane<\/th><th>e<sub>per<\/sub> (\u00b5m)<\/th><\/tr><\/thead>\n <tbody>\n <tr><td>Small HVAC centrifugal<\/td><td class=\"mono\">8<\/td><td class=\"mono\">2 900<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">166<\/td><td class=\"mono\">83<\/td><td class=\"mono\">20.7<\/td><\/tr>\n <tr><td>Medium roof exhaust<\/td><td class=\"mono\">25<\/td><td class=\"mono\">1 450<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">1 039<\/td><td class=\"mono\">520<\/td><td class=\"mono\">41.6<\/td><\/tr>\n <tr><td>Large AHU centrifugal<\/td><td class=\"mono\">85<\/td><td class=\"mono\">1 480<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">3 459<\/td><td class=\"mono\">1 730<\/td><td class=\"mono\">40.7<\/td><\/tr>\n <tr><td>Power-plant ID fan<\/td><td class=\"mono\">350<\/td><td class=\"mono\">990<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">8 468<\/td><td class=\"mono\">4 234<\/td><td class=\"mono\">24.2<\/td><\/tr>\n <tr><td>Tunnel ventilation axial<\/td><td class=\"mono\">120<\/td><td class=\"mono\">980<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">7 380<\/td><td class=\"mono\">3 690<\/td><td class=\"mono\">61.5<\/td><\/tr>\n <tr><td>Dust collector fan<\/td><td class=\"mono\">65<\/td><td class=\"mono\">1 750<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">5 700<\/td><td class=\"mono\">2 850<\/td><td class=\"mono\">87.7<\/td><\/tr>\n <tr><td>Mine ventilation fan<\/td><td class=\"mono\">500<\/td><td class=\"mono\">590<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">129 600<\/td><td class=\"mono\">64 800<\/td><td class=\"mono\">259<\/td><\/tr>\n <tr><td>Clean-room FFU fan<\/td><td class=\"mono\">3<\/td><td class=\"mono\">3 500<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">20.4<\/td><td class=\"mono\">10.2<\/td><td class=\"mono\">6.8<\/td><\/tr>\n <tr><td>Cooling tower fan<\/td><td class=\"mono\">200<\/td><td class=\"mono\">320<\/td><td class=\"mono\">BV-5<\/td><td class=\"mono\">238 500<\/td><td class=\"mono\">119 250<\/td><td class=\"mono\">1 193<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n\n \n <div class=\"table-wrap\">\n <div class=\"table-title\">\ud83d\udd17 Typical BV \/ FV Combinations by Application<\/div>\n <table>\n <thead><tr><th>Application<\/th><th>Fan Type<\/th><th>BV<\/th><th>FV<\/th><th>Foundation<\/th><th>Notes<\/th><\/tr><\/thead>\n <tbody>\n <tr><td>Office HVAC<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-2 \/ FV-3<\/td><td>Flexible<\/td><td>Noise-sensitive; rubber isolators<\/td><\/tr>\n <tr><td>Hospital AHU<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-2<\/td><td>Flexible<\/td><td>Strict noise; premium balance<\/td><\/tr>\n <tr><td>Process exhaust<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-3<\/td><td>Rigid<\/td><td>Concrete base; standard<\/td><\/tr>\n <tr><td>Power-plant ID\/FD<\/td><td>Centrifugal<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-1 \/ FV-2<\/td><td>Rigid<\/td><td>Critical; high power > 300 kW<\/td><\/tr>\n <tr><td>Tunnel ventilation<\/td><td>Axial<\/td><td class=\"mono\">BV-3<\/td><td class=\"mono\">FV-3<\/td><td>Rigid<\/td><td>Concrete duct mounts<\/td><\/tr>\n <tr><td>Dust collection<\/td><td>Radial blade<\/td><td class=\"mono\">BV-4<\/td><td class=\"mono\">FV-3 \/ FV-4<\/td><td>Rigid<\/td><td>Material buildup \u2192 frequent rebalancing<\/td><\/tr>\n <tr><td>Cooling tower<\/td><td>Axial (large)<\/td><td class=\"mono\">BV-5<\/td><td class=\"mono\">FV-4 \/ FV-5<\/td><td>Flexible<\/td><td>Very low speed<\/td><\/tr>\n <tr><td>Data centre<\/td><td>EC \/ plug fan<\/td><td class=\"mono\">BV-2<\/td><td class=\"mono\">FV-2<\/td><td>Flexible<\/td><td>Vibration & noise critical<\/td><\/tr>\n <tr><td>Agricultural drying<\/td><td>Axial<\/td><td class=\"mono\">BV-4 \/ BV-5<\/td><td class=\"mono\">FV-4 \/ FV-5<\/td><td>Rigid<\/td><td>Seasonal; minimal requirements<\/td><\/tr>\n <\/tbody>\n <\/table>\n <\/div>\n <\/div>\n<\/section>\n\n\n<main class=\"main-content\" id=\"definition\">\n <div class=\"container\">\n <div class=\"content-layout\">\n <article class=\"article-content\">\n\n <h2>What is ISO 14694?<\/h2>\n <div class=\"info-box\" style=\"border-left-color:var(--navy);background:var(--beige-light);\">\n <div class=\"box-title\" style=\"font-size:16px;\">Quick Answer<\/div>\n <p style=\"font-size:15px;\"><strong>ISO 14694<\/strong> (<em>Industrial fans \u2014 Specifications for balance quality and vibration levels<\/em>) is the standard that tailors <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940 G-grades<\/a> and <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816 vibration zones<\/a> specifically for industrial fans. It defines <strong>BV categories<\/strong> (BV-1 to BV-5) for impeller balance quality and <strong>FV categories<\/strong> (FV-1 to FV-5) for maximum operational vibration. The standard default is <strong>BV-3 (G 6.3)<\/strong> for balance and <strong>FV-3 (\u2264 4.5 mm\/s RMS)<\/strong> for vibration acceptance.<\/p>\n <\/div>\n\n <p>Fans are the most common rotating machine in industry, yet they have unique characteristics \u2014 large-diameter impellers, significant aerodynamic forces, often cantilevered rotor arrangements, and highly variable operating environments \u2014 that justify a dedicated standard. ISO 14694 removes the ambiguity of interpreting general-purpose standards for fans by providing application-specific BV and FV categories that are clear, unambiguous, and directly usable in purchase specifications and acceptance testing.<\/p>\n\n <p>The standard covers all types: centrifugal (radial), axial, mixed-flow, and cross-flow fans of all sizes for stationary, terrestrial use. It excludes aircraft, air-cushion vehicles, and similar specialized applications.<\/p>\n\n <h3>Two-Part Structure<\/h3>\n <p>ISO 14694 is logically divided into two complementary parts that mirror its two category systems:<\/p>\n <ul>\n <li><strong>Part 1 \u2014 BV (Balance Quality):<\/strong> Specifies the permissible residual unbalance for the <em>fan impeller alone<\/em>, before assembly. Verified on a <a href=\"https:\/\/vibromera.eu\/glossary\/balancing-machine\/\">balancing machine<\/a>.<\/li>\n <li><strong>Part 2 \u2014 FV (Vibration Limits):<\/strong> Specifies the maximum operational vibration for the <em>complete assembled fan<\/em>. Verified by measurement on bearing housings during operation per <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816<\/a> methodology.<\/li>\n <\/ul>\n\n <h2 id=\"bv-section\">Balance Quality Requirements (BV Categories)<\/h2>\n <p>BV categories specify the maximum permissible residual <a href=\"https:\/\/vibromera.eu\/glossary\/unbalance\/\">unbalance<\/a> for the fan impeller as a standalone component. Each BV category maps directly to an <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940-1 G-grade<\/a>. This mapping is the key contribution of ISO 14694: it eliminates the guesswork of selecting the correct G-grade by providing fan-specific guidance.<\/p>\n\n <div class=\"formula-box\">\n <div class=\"formula-label\">Permissible Residual Unbalance (ISO 14694 \/ ISO 1940)<\/div>\n <div class=\"formula-main\">U<sub>per<\/sub> = (9 549 \u00d7 G \u00d7 m) \/ n<\/div>\n <div class=\"formula-note\">U<sub>per<\/sub> in g\u00b7mm | G = BV grade value in mm\/s | m = impeller mass in kg | n = max service speed in RPM<\/div>\n <\/div>\n\n <h3>Selecting the Right BV Category<\/h3>\n <ul>\n <li><strong>BV-1 (G 1.0):<\/strong> Ultra-precision \u2014 turbo-fans with small, very high-speed impellers. Requires specialized high-speed balancing machines with sub-milligram resolution. Rarely specified outside turbo-blowers and semiconductor equipment.<\/li>\n <li><strong>BV-2 (G 2.5):<\/strong> Critical-service fans (power-plant ID\/FD), noise-sensitive HVAC (hospitals, recording studios, clean rooms), and high-speed centrifugal fans above 3 000 RPM. Often paired with FV-1 or FV-2 acceptance.<\/li>\n <li><strong>BV-3 (G 6.3):<\/strong> The standard for the <strong>vast majority<\/strong> of industrial fans \u2014 centrifugal and axial, HVAC supply\/return, process ventilation. This is the assumed default if no BV category is specified contractually.<\/li>\n <li><strong>BV-4 (G 16):<\/strong> Heavy-duty fans handling particulate-laden or corrosive air: dust collectors, material handling, mine ventilation. Looser tolerance acknowledges that these fans need frequent rebalancing due to buildup and erosion.<\/li>\n <li><strong>BV-5 (G 40):<\/strong> Non-critical, very slow impellers: cooling-tower fans, agricultural ventilation, temporary systems.<\/li>\n <\/ul>\n\n <div class=\"info-box\">\n <div class=\"box-title\">Use Service Speed, Not Balancing-Machine Speed<\/div>\n <p>The tolerance must be calculated at the <em>maximum operating speed<\/em>. Many impellers are balanced on low-speed machines at 300\u2013600 RPM, but the tolerance calculation must use the actual operating speed (e.g., 1 480 RPM). Using balancing-machine speed produces a tolerance that is dangerously loose.<\/p>\n <\/div>\n\n <h3>Single-Plane vs. Two-Plane Balancing<\/h3>\n <p>ISO 14694 follows ISO 21940-12 guidance: narrow impellers (width\/diameter L\/D < 0.5, typical for most centrifugal fans) need <strong>single-plane<\/strong> balancing \u2014 full U<sub>per<\/sub> applies to one plane. Wide impellers or long axial fan rotors (L\/D \u2265 0.5) need <strong>two-plane dynamic balancing<\/strong> \u2014 U<sub>per<\/sub> is divided between planes (equally for symmetric rotors, proportionally for asymmetric ones).<\/p>\n\n <h2 id=\"fv-section\">Operational Vibration Limits (FV Categories)<\/h2>\n <p>FV categories define the maximum allowable broadband <strong><a href=\"https:\/\/vibromera.eu\/glossary\/rms\/\">RMS vibration velocity<\/a><\/strong> (mm\/s) measured on bearing housings of the complete fan at design speed and load, in the 10\u20131 000 Hz range per <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816-1<\/a> methodology.<\/p>\n\n <h3>Rigid vs. Flexible Foundation<\/h3>\n <p>Like ISO 10816, ISO 14694 recognizes that the support structure critically affects measured vibration:<\/p>\n <ul>\n <li><strong>Rigid:<\/strong> Fan on massive concrete or heavy steel. First <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\">natural frequency<\/a> of the fan-foundation system above 1\u00d7 RPM. Lower vibration readings.<\/li>\n <li><strong>Flexible:<\/strong> Fan on spring isolators, rubber pads, or light steel platform. First natural frequency below 1\u00d7 RPM. Higher vibration readings \u2014 but lower force transmission to the building.<\/li>\n <\/ul>\n <p>Some specifications allow one FV category higher for flexibly mounted fans (e.g., FV-3 rigid \u2192 FV-4 flexible for the same application).<\/p>\n\n <div class=\"info-box warning\">\n <div class=\"box-title\">BV Compliance \u2260 FV Compliance<\/div>\n <p>A perfectly balanced impeller (meeting BV-3) does <strong>not<\/strong> guarantee the assembled fan meets FV-3. Operational vibration depends on many factors beyond impeller balance: shaft <a href=\"https:\/\/vibromera.eu\/glossary\/misalignment\/\">misalignment<\/a>, <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-fault-frequencies\/\">bearing condition<\/a>, foundation <a href=\"https:\/\/vibromera.eu\/glossary\/resonance\/\">resonance<\/a>, aerodynamic forces (inlet distortion, damper position), belt tension, and coupling condition. BV is necessary but not sufficient for FV.<\/p>\n <\/div>\n\n <h3>Aerodynamic Sources of Fan Vibration<\/h3>\n <p>Unlike most rotating machines, fans interact dynamically with the airstream, creating vibration sources unique to fans:<\/p>\n <ul>\n <li><strong>Blade pass frequency (BPF):<\/strong> Every fan produces vibration at BPF = blades \u00d7 RPM \u00f7 60. Excessive BPF amplitude indicates clearance issues, inlet distortion, or guide-vane interaction.<\/li>\n <li><strong>Inlet distortion:<\/strong> Elbows, dampers, or obstructions close to the inlet create non-uniform flow \u2192 periodic blade loading \u2192 <a href=\"https:\/\/vibromera.eu\/glossary\/harmonics-vibration\/\">harmonics<\/a> of shaft speed.<\/li>\n <li><strong>Stall and surge:<\/strong> Operating far from the design point causes aerodynamic instability \u2014 blade stall or system surge, producing broadband vibration and noise.<\/li>\n <li><strong>Material buildup:<\/strong> In dust collectors and cement plants, uneven deposits on blades create progressive unbalance. A fan that met BV-3 at commissioning may exceed FV limits within weeks.<\/li>\n <\/ul>\n\n <h2 id=\"testing\">Acceptance Testing \u2014 Two-Stage Verification<\/h2>\n\n <h3>Stage 1: Impeller Balance Verification (BV)<\/h3>\n <p>The impeller is balanced on a calibrated balancing machine <em>before assembly<\/em>. The procedure:<\/p>\n <ol>\n <li>Mount impeller on balancing machine mandrel or in its own bearings<\/li>\n <li>Perform single-plane or two-plane balancing (depending on L\/D ratio)<\/li>\n <li>Reduce residual unbalance below U<sub>per<\/sub> for the specified BV category<\/li>\n <li>Document: initial unbalance, correction masses placed, final residual unbalance<\/li>\n <li><strong>Pass criterion:<\/strong> final residual \u2264 U<sub>per<\/sub> for specified BV<\/li>\n <\/ol>\n\n <h3>Stage 2: Operational Vibration Test (FV)<\/h3>\n <p>After assembly and installation, the fan is tested under operational conditions:<\/p>\n <ol>\n <li>Install vibration sensors on bearing housings \u2014 three orthogonal directions (V, H, A) at each bearing<\/li>\n <li>Run fan at design speed and operating point; allow thermal stabilisation (15\u201330 min)<\/li>\n <li>Record broadband RMS velocity (mm\/s) in 10\u20131 000 Hz range<\/li>\n <li><strong>Pass criterion:<\/strong> the highest single reading from any bearing in any direction \u2264 FV category limit<\/li>\n <\/ol>\n\n <div class=\"info-box success\">\n <div class=\"box-title\">Always Record the Full Spectrum<\/div>\n <p>While acceptance is based on overall RMS, always record the <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum<\/a> during commissioning. If the fan later develops problems, comparison with the baseline spectrum is invaluable for diagnosis. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> records both overall RMS and full frequency spectrum automatically.<\/p>\n <\/div>\n\n <h2 id=\"field-balancing\">Field Balancing of Fan Impellers<\/h2>\n <p>Many industrial fans must be balanced in-situ \u2014 either because the impeller is too large to remove, or because balance was lost during operation due to material buildup, erosion, or blade damage. ISO 14694 implicitly supports field balancing as the practical way to maintain BV and FV compliance throughout the fan's operating life.<\/p>\n\n <h3>When Field Balancing Is Needed<\/h3>\n <ul>\n <li>Fan vibration exceeds FV limit and FFT spectrum shows dominant 1\u00d7 (unbalance) component<\/li>\n <li>Material buildup has changed impeller balance since commissioning<\/li>\n <li>Blade repair, blade replacement, or erosion shield replacement performed<\/li>\n <li>Impeller cannot be removed without major disassembly (centrifugal fans in scroll housings)<\/li>\n <li>Production schedule cannot accommodate a long shutdown for shop balancing<\/li>\n <\/ul>\n\n <h3>Procedure with Balanset-1A<\/h3>\n <ol>\n <li><strong>Setup:<\/strong> Mount vibration sensor on bearing housing (radial direction), laser tachometer aimed at shaft. Select single-plane (F2) or two-plane (F3) mode.<\/li>\n <li><strong>Initial run:<\/strong> Record baseline vibration \u2014 amplitude and phase at 1\u00d7 shaft speed. Example: 8.2 mm\/s at 135\u00b0.<\/li>\n <li><strong>Trial weight:<\/strong> Mount known mass (e.g., 20 g) on accessible blade or hub. Run again, record new vector. Example: 5.5 mm\/s at 210\u00b0.<\/li>\n <li><strong>Correction:<\/strong> Software calculates required mass and angle. Example: \"Add 35 g at 285\u00b0.\" Weight splitting available for blade mounting.<\/li>\n <li><strong>Verify:<\/strong> Final run confirms residual vibration below FV limit. Typical result: 1.0\u20132.0 mm\/s after one correction cycle.<\/li>\n <\/ol>\n\n <div class=\"info-box\">\n <div class=\"box-title\">Single-Plane vs. Two-Plane in the Field<\/div>\n <p>Most centrifugal fan impellers are narrow enough for <strong>single-plane<\/strong> balancing (Balanset F2 mode). Wide impellers, multi-stage fans, and long axial fans need <strong>two-plane<\/strong> (Balanset F3 with two sensors). Quick test: measure both bearings \u2014 if there is a significant amplitude or phase difference, use two-plane.<\/p>\n <\/div>\n\n <h2 id=\"case-studies\">Case Studies \u2014 ISO 14694 in Practice<\/h2>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 1: HVAC Supply Fan \u2014 Acceptance Testing<\/div>\n <p><strong>Fan:<\/strong> Centrifugal HVAC supply, 22 kW, 1 460 RPM, impeller mass 38 kg, direct-drive on rigid concrete base.<\/p>\n <p><strong>Spec:<\/strong> BV-3 (G 6.3), FV-3 (\u2264 4.5 mm\/s).<\/p>\n <p><strong>BV tolerance:<\/strong> U<sub>per<\/sub> = 9 549 \u00d7 6.3 \u00d7 38 \/ 1 460 = <strong>1 566 g\u00b7mm<\/strong> total \u2192 783 g\u00b7mm per plane.<\/p>\n <p><strong>Balance check:<\/strong> Factory certificate: 420 g\u00b7mm residual \u2014 well within 1 566 g\u00b7mm limit. \u2705<\/p>\n <p><strong>FV test:<\/strong> Highest reading: 3.8 mm\/s (horizontal, drive-end bearing). Within FV-3 limit of 4.5 mm\/s. \u2705<\/p>\n <p><strong>Baseline spectrum:<\/strong> Clean 1\u00d7 at 24.3 Hz, small BPF at 170 Hz (7 blades). Healthy fan.<\/p>\n <\/div>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 2: Dust Collector Fan \u2014 Progressive Unbalance from Buildup<\/div>\n <p><strong>Fan:<\/strong> Radial-blade dust collector, 30 kW, 1 750 RPM, impeller 40 kg, rigid base.<\/p>\n <p><strong>Problem:<\/strong> Vibration grew from 3.5 mm\/s at commissioning to 9.8 mm\/s after 6 months. FV-3 rigid limit = 4.5 mm\/s \u2192 <strong>EXCEEDS<\/strong>.<\/p>\n <p><strong>Diagnosis:<\/strong> Balanset-1A FFT: dominant 1\u00d7 peak at 29.2 Hz = shaft speed. Minimal 2\u00d7 or other harmonics. Root cause: non-uniform dust buildup on blades.<\/p>\n <p><strong>Action:<\/strong> Blades cleaned, field balanced with <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a>. Trial weight 15 g, calculated correction 28 g at 195\u00b0. Post-balance: <strong>1.3 mm\/s<\/strong>. \u2705<\/p>\n <p><strong>Recommendation:<\/strong> Schedule quarterly cleaning + rebalancing for material-handling fans.<\/p>\n <\/div>\n\n <div class=\"example-block\">\n <div class=\"example-title\">Case 3: Roof Exhaust Fan \u2014 Blade-Pass Resonance Problem<\/div>\n <p><strong>Fan:<\/strong> Centrifugal roof exhaust, 15 kW, 2 940 RPM, impeller 8 kg, spring isolators (flexible).<\/p>\n <p><strong>Problem:<\/strong> Overall vibration 12.5 mm\/s. Field balancing reduced 1\u00d7 from 7.0 to 1.5 mm\/s, but overall only dropped to 10.8 mm\/s.<\/p>\n <p><strong>Diagnosis:<\/strong> FFT shows strong 7\u00d7 peak at 343 Hz = 8.5 mm\/s (BPF, 7 blades \u00d7 49 Hz). Fan housing <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\">natural frequency<\/a> at ~340 Hz \u2014 resonance.<\/p>\n <p><strong>Root cause:<\/strong> 90\u00b0 elbow immediately before inlet \u2192 non-uniform inlet velocity \u2192 BPF excitation \u2192 housing resonance amplification.<\/p>\n <p><strong>Solution:<\/strong> Inlet guide vanes installed + elbow relocated further upstream. BPF dropped to 2.1 mm\/s. Overall: <strong>3.2 mm\/s<\/strong>. \u2705<\/p>\n <p>This case illustrates why BV compliance alone does not guarantee FV compliance \u2014 aerodynamic factors produce vibration independently of balance quality.<\/p>\n <\/div>\n\n <h2 id=\"standards-context\">Relationship to Other Standards<\/h2>\n <p>ISO 14694 does not exist in isolation \u2014 it references and builds upon several international standards:<\/p>\n <ul>\n <li><strong><a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\">ISO 1940-1 \/ ISO 21940-11<\/a>:<\/strong> The G-grade system that BV categories reference. ISO 14694 selects appropriate G-grades for each fan type.<\/li>\n <li><strong><a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\">ISO 10816-1 \/ ISO 20816-1<\/a>:<\/strong> General vibration measurement methodology. FV categories are derived from and compatible with ISO 10816 zones.<\/li>\n <li><strong>ISO 10816-3:<\/strong> Industrial machines 15\u2013300 kW. Fans in this range could use either standard, but ISO 14694 provides more specific fan guidance.<\/li>\n <li><strong>ISO 5801:<\/strong> Fan performance testing. FV tests reference operating conditions from this standard.<\/li>\n <li><strong>ISO 13347:<\/strong> Fan acoustics (noise). Related but separate \u2014 reducing vibration often reduces noise transmission.<\/li>\n <li><strong>AMCA 204:<\/strong> North American fan vibration standard. Similar scope; fans meeting one generally meet the other.<\/li>\n <\/ul>\n\n <div class=\"info-box success\">\n <div class=\"box-title\">Vibromera Equipment for ISO 14694 Compliance<\/div>\n <p>The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> portable balancer provides: two-channel vibration measurement (both bearings simultaneously), built-in ISO 1940 \/ ISO 14694 tolerance calculator, single-plane and two-plane <a href=\"https:\/\/vibromera.eu\/glossary\/rotor-balancing\/\">balancing<\/a> modes, correction weight splitting for blade-mounted weights, <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum analysis<\/a> for fault diagnostics, and vibrometer mode for FV acceptance measurement. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-4\/\">Balanset-4<\/a> extends this to four channels for complex multi-bearing fan assemblies.<\/p>\n <\/div>\n\n <hr style=\"margin:48px 0 24px;border:none;border-top:1px solid var(--border-light);\">\n <p><strong>Official standard:<\/strong> <a href=\"https:\/\/www.iso.org\/standard\/37371.html\" rel=\"nofollow noopener\" target=\"_blank\">ISO 14694 on ISO Store \u2192<\/a><\/p>\n <p><a href=\"https:\/\/vibromera.eu\/glossary\/\">\u2190 Back to Glossary Index<\/a><\/p>\n\n <\/article>\n\n \n <aside class=\"toc-sidebar\">\n <div class=\"toc-box\">\n <h3>On This Page<\/h3>\n <a href=\"#calculator\">BV Tolerance Calculator<\/a>\n <a href=\"#bv-cards\">BV Category Cards<\/a>\n <a href=\"#fv-table\">FV Vibration Limits<\/a>\n <a href=\"#definition\">What is ISO 14694?<\/a>\n <a href=\"#bv-section\">Balance Quality (BV)<\/a>\n <a class=\"sub\" href=\"#bv-section\">BV selection guide<\/a>\n <a class=\"sub\" href=\"#bv-section\">Tolerance formula<\/a>\n <a class=\"sub\" href=\"#bv-section\">Single vs. two-plane<\/a>\n <a href=\"#fv-section\">Vibration Limits (FV)<\/a>\n <a class=\"sub\" href=\"#fv-section\">FV categories<\/a>\n <a class=\"sub\" href=\"#fv-section\">Aerodynamic sources<\/a>\n <a href=\"#testing\">Test Procedures<\/a>\n <a href=\"#field-balancing\">Field Balancing<\/a>\n <a href=\"#case-studies\">Case Studies (3)<\/a>\n <a href=\"#standards-context\">Related Standards<\/a>\n <a href=\"#faq\">FAQ (7 Questions)<\/a>\n <\/div>\n <div class=\"toc-box\" style=\"margin-top:24px;background:var(--navy);border-color:var(--navy);\">\n <h3 style=\"color:var(--white);\">Fan Balancing Equipment<\/h3>\n <p style=\"color:rgba(255,255,255,0.6);font-size:13px;margin-bottom:12px;\">Portable field balancing with built-in ISO 14694 \/ ISO 1940 tolerance calculator.<\/p>\n <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\" style=\"display:block;padding:8px 14px;background:var(--blue);color:white;border-radius:6px;text-align:center;font-weight:600;font-size:14px;text-decoration:none;margin-bottom:8px;border-left:none;\">Balanset-1A \u2192<\/a>\n <a href=\"https:\/\/vibromera.eu\/product\/balanset-4\/\" style=\"display:block;padding:8px 14px;background:rgba(255,255,255,0.1);color:white;border-radius:6px;text-align:center;font-weight:600;font-size:14px;text-decoration:none;border:1px solid rgba(255,255,255,0.2);border-left:none;\">Balanset-4 \u2192<\/a>\n <\/div>\n <\/aside>\n <\/div>\n <\/div>\n<\/main>\n\n\n<section class=\"section-bg alt\" id=\"faq\">\n <div class=\"container\" style=\"max-width:900px;\">\n <div class=\"section-header\"><h2>Frequently Asked Questions \u2014 ISO 14694<\/h2><p>Common questions about fan balance quality (BV) and vibration acceptance (FV)<\/p><\/div>\n <div style=\"display:flex;flex-direction:column;gap:16px;\">\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What is the difference between BV and FV categories?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>BV<\/strong> defines the balance quality of the <em>impeller alone<\/em> \u2014 measured on a balancing machine before assembly. <strong>FV<\/strong> defines the acceptable vibration of the <em>complete assembled fan<\/em> \u2014 measured on bearing housings during operation. An impeller can pass BV but the fan may fail FV if there are alignment, resonance, or aerodynamic issues. Conversely, a well-installed fan with moderate impeller balance may still meet FV if other factors are favourable.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What BV category for standard industrial fans?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>BV-3 (G 6.3)<\/strong> \u2014 the standard for most centrifugal and axial fans at 750\u20133 000 RPM. Covers HVAC, process ventilation, and general industrial applications. Only specify BV-2 for critical\/high-speed fans or BV-4 for slow\/non-critical fans. BV-3 is the assumed default when no BV category is stated in the specification.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What BV category should I specify for HVAC fans in a hospital?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n For noise-sensitive HVAC installations such as hospitals, recording studios, and laboratories, specify <strong>BV-2 (G 2.5)<\/strong> combined with <strong>FV-2 (\u2264 2.8 mm\/s)<\/strong>. This provides premium impeller balance and strict operational vibration limits. Large critical AHU fans above 300 kW in these environments also typically require BV-2.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> Can I balance a fan in-situ to ISO 14694?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n Yes. The <a href=\"https:\/\/vibromera.eu\/product\/balanset-1\/\">Balanset-1A<\/a> portable balancer enables field balancing of installed fans \u2014 single-plane or two-plane \u2014 with built-in ISO tolerance calculation. The instrument measures vibration amplitude and phase, calculates correction weights, and verifies that the final balance meets the BV category tolerance. This is standard practice for large fans where impeller removal is impractical.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> Fan passes BV but fails FV \u2014 why?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n Good impeller balance is necessary but not sufficient. Common causes of FV failure despite good BV: shaft <a href=\"https:\/\/vibromera.eu\/glossary\/misalignment\/\">alignment<\/a> problems (coupling or belt), structural <a href=\"https:\/\/vibromera.eu\/glossary\/resonance\/\">resonance<\/a> of the fan frame or ductwork, aerodynamic imbalance (blade pitch variation, inlet obstruction, stall), <a href=\"https:\/\/vibromera.eu\/glossary\/bearing-fault-frequencies\/\">bearing defects<\/a>, soft foot, and pipe\/duct strain. Use <a href=\"https:\/\/vibromera.eu\/glossary\/fft\/\">FFT spectrum analysis<\/a> to identify the dominant frequency.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> How does ISO 14694 relate to ISO 10816?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n ISO 14694 FV limits are derived from the same velocity-based methodology as ISO 10816 but are tailored specifically for fans. FV-3 = 4.5 mm\/s corresponds to the ISO 10816-1 Class I C\/D boundary and the ISO 10816-3 Group 2 Rigid C\/D boundary. ISO 14694 provides more direct and unambiguous guidance than interpreting the broader machine groups in ISO 10816-3 for fans.\n <\/div>\n <\/details>\n\n <details style=\"background:var(--white);border:1px solid var(--border-light);border-radius:var(--radius);overflow:hidden;\">\n <summary style=\"padding:18px 24px;font-weight:700;font-size:16px;cursor:pointer;color:var(--navy);list-style:none;display:flex;align-items:center;gap:10px;\"><span style=\"color:var(--blue);font-size:18px;\">\u25b8<\/span> What vibration level is acceptable for a typical industrial fan?<\/summary>\n <div style=\"padding:0 24px 18px 52px;font-size:15px;line-height:1.7;color:var(--text);\">\n <strong>FV-3 (\u2264 4.5 mm\/s RMS)<\/strong> is the standard acceptance criterion. Newly installed fans should ideally be below 2.8 mm\/s. Above 7.1 mm\/s (FV-4 exceeded) requires investigation. Above 11.2 mm\/s indicates potential damage risk and requires immediate attention. For condition monitoring, trending vibration over time is more valuable than any single reading.\n <\/div>\n <\/details>\n\n <\/div>\n <\/div>\n<\/section>\n\n\n<section style=\"padding:32px 0;background:var(--white);border-top:1px solid var(--border-light);\">\n <div class=\"container\" style=\"max-width:900px;\">\n <h3 style=\"font-family:'DM Serif Display',serif;font-size:22px;color:var(--navy);margin-bottom:20px;\">Related Glossary Articles<\/h3>\n <div style=\"display:grid;grid-template-columns:repeat(3,1fr);gap:16px;\">\n <a href=\"https:\/\/vibromera.eu\/glossary\/balance-quality-grade\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Balance Quality Grade<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">ISO 1940 \/ 21940-11 G-grades \u2014 the system BV categories reference<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/iso-10816-1\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">ISO 10816-1<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">General vibration evaluation \u2014 the methodology behind FV categories<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/rotor-balancing\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Rotor Balancing<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">Single-plane and two-plane balancing procedures for fan impellers<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/unbalance\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Unbalance<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">The primary controllable source of fan vibration<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/harmonics-vibration\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Harmonics in Vibration<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">Blade pass frequency, 1\u00d7, 2\u00d7 \u2014 diagnosing fan vibration spectra<\/div>\n <\/a>\n <a href=\"https:\/\/vibromera.eu\/glossary\/natural-frequency\/\" style=\"display:block;padding:18px;background:var(--beige-light);border:1px solid var(--beige-dark);border-radius:var(--radius-sm);text-decoration:none;box-shadow:var(--shadow-sm);\">\n <div style=\"font-weight:700;color:var(--navy);font-size:15px;margin-bottom:4px;\">Natural Frequency<\/div>\n <div style=\"font-size:13px;color:var(--text-secondary);\">When fan frame resonance causes high vibration despite good balance<\/div>\n <\/a>\n <\/div>\n <\/div>\n<\/section>\n\n\n<section class=\"shop-cta\">\n <div class=\"container\">\n <h2>Balance Fans to ISO 14694 \u2014 In the Field<\/h2>\n <p>Vibromera portable balancing devices calculate BV tolerances automatically and guide correction weight placement \u2014 single-plane or two-plane, no impeller removal required.<\/p>\n <a href=\"https:\/\/vibromera.eu\/shop\/\" class=\"cta-btn\">Browse Fan Balancing Equipment \u2192<\/a>\n <\/div>\n<\/section>\n\n<footer class=\"page-footer\">\n <div class=\"container\"><p><a href=\"https:\/\/vibromera.eu\/glossary\/\">\u2190 Back to Glossary<\/a> | <a href=\"https:\/\/vibromera.eu\/\">vibromera.eu<\/a><\/p><\/div>\n<\/footer>\n\n\n<script>\nfunction calcBV(){\n const G=parseFloat(document.getElementById('bvCat').value);\n const bv=document.getElementById('bvCat').selectedOptions[0].getAttribute('data-bv');\n const m=parseFloat(document.getElementById('impMass').value);\n const n=parseFloat(document.getElementById('impRPM').value);\n const p=parseInt(document.getElementById('impPlanes').value);\n const R=parseFloat(document.getElementById('impRadius').value)||0;\n if(!m||!n||m<=0||n<=0)return;\n const e=(9549*G)\/n, U=e*m, Up=U\/p, w=2*Math.PI*n\/60, F=(U\/1e6)*w*w;\n let cw=R>0?Up\/R:0;\n const f=v=>v>=100?v.toFixed(0):v>=1?v.toFixed(1):v.toFixed(3);\n document.getElementById('resultsArea').innerHTML=`\n <div class=\"result-primary\">\n <div class=\"res-label\">Total Permissible Unbalance (${bv})<\/div>\n <div class=\"res-value\">${f(U)}<\/div>\n <div class=\"res-unit\">g\u00b7mm \u2014 ISO 14694 \/ ISO 1940<\/div>\n <\/div>\n <div class=\"results-secondary\">\n <div class=\"res-card\"><div class=\"rc-label\">Specific Eccentricity<\/div><div class=\"rc-value\">${e>=10?e.toFixed(1):e>=0.1?e.toFixed(2):e.toFixed(3)}<\/div><div class=\"rc-unit\">\u00b5m (e<sub>per<\/sub>)<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">Centrifugal Force<\/div><div class=\"rc-value\">${F>=10?F.toFixed(1):F>=0.1?F.toFixed(2):F.toFixed(3)}<\/div><div class=\"rc-unit\">N at ${n} RPM<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">BV \/ G-Grade<\/div><div class=\"rc-value\" style=\"font-size:16px\">${bv} (G ${G})<\/div><div class=\"rc-unit\">ISO 14694<\/div><\/div>\n <div class=\"res-card\"><div class=\"rc-label\">Impeller<\/div><div class=\"rc-value\" style=\"font-size:14px;font-family:'Source Sans 3',sans-serif\">${m} kg @ ${n} RPM<\/div><div class=\"rc-unit\">${p} plane${p>1?'s':''}<\/div><\/div>\n <\/div>\n <div class=\"plane-note\">\n <div class=\"pn-label\">Per Plane (${p===1?'single plane':'each of '+p+' planes'})<\/div>\n <div class=\"pn-value\">${f(Up)}<\/div>\n <div class=\"pn-unit\">g\u00b7mm${cw>0?' = '+(cw>=0.1?cw.toFixed(2):cw.toFixed(3))+' g at R = '+R+' mm':''}<\/div>\n <\/div>`;\n}\n\/\/ Auto-calculate on input\n['bvCat','impMass','impRPM','impPlanes','impRadius'].forEach(id=>{\n const el=document.getElementById(id);\n el.addEventListener(el.tagName==='SELECT'?'change':'input',calcBV);\n});\ncalcBV();\n<\/script>\n\n<\/body>\n<\/html><\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>En oversikt over ISO 14694, standarden som spesifiserer krav til balansekvalitet og vibrasjonsgrenser spesielt for industrivifter.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[109,112],"tags":[],"class_list":["post-20603","glossary","type-glossary","status-publish","hentry","category-glossary","category-iso-standards"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/glossary"}],"version-history":[{"count":4,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603\/revisions"}],"predecessor-version":[{"id":101499,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/glossary\/20603\/revisions\/101499"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=20603"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=20603"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=20603"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}