{"id":100288,"date":"2026-02-15T20:32:00","date_gmt":"2026-02-15T20:32:00","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100288"},"modified":"2026-02-15T20:32:00","modified_gmt":"2026-02-15T20:32:00","slug":"vibration-iso20816-4-gas-turbines","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/nb\/calculators\/vibration-iso20816-4-gas-turbines\/","title":{"rendered":"Vibrasjonsgrenser \u2013 Gassturbiner | ISO 20816-4"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Vibration Limits Calculator \u2014 ISO 20816-4 Gas Turbines\",\"alternateName\":[\"ISO 20816-4 Calculator\",\"Gas Turbine Vibration Limits\",\"Gas Turbine Vibration Evaluation\"],\"description\":\"Free online vibration zone evaluation calculator per ISO 20816-4 for gas turbines including industrial heavy, aero-derivative, and small units.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/vibration-iso20816-4-gas-turbines\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2025-01-01\",\"dateModified\":\"2025-02-14\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true,\"featureList\":[\"ISO 20816-4 zone evaluation\",\"Bearing housing velocity\",\"Shaft relative displacement\",\"Industrial and aero-derivative types\",\"Color-coded zone display\"],\"keywords\":\"vibration limits, ISO 20816-4, gas turbine, aero-derivative, zone A B C D\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What types of gas turbines does ISO 20816-4 cover?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"ISO 20816-4 covers all types of gas turbines used in power generation and mechanical drive applications, including industrial heavy-duty gas turbines (typically >40 MW), aero-derivative gas turbines (typically 20\u201360 MW), and small gas turbines (<3 MW). It applies to both single-shaft and multi-shaft configurations.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the difference between bearing housing and shaft measurement?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Bearing housing vibration is measured with sensors on the bearing pedestal in mm\/s RMS velocity. Shaft relative displacement is measured with proximity probes inside the bearing in \u03bcm peak-to-peak. Gas turbines typically require both measurements for comprehensive evaluation, especially those with fluid-film bearings.\"}},\n{\"@type\":\"Question\",\"name\":\"Why do gas turbines have higher vibration limits than steam turbines?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Gas turbines generally operate at higher speeds (up to 15,000+ RPM for aero-derivatives) and have different rotor dynamics compared to steam turbines. The combustion process also introduces additional vibration sources. The zone boundaries in ISO 20816-4 reflect these operational characteristics.\"}},\n{\"@type\":\"Question\",\"name\":\"How do aero-derivative limits differ from industrial gas turbines?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Aero-derivative gas turbines typically operate at higher speeds with lighter, stiffer rotors and rolling element bearings (rather than fluid-film). They generally have tighter vibration tolerances for shaft measurements but may show different spectral characteristics due to their multi-spool design.\"}},\n{\"@type\":\"Question\",\"name\":\"What action should I take when vibration increases suddenly?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"A sudden increase in gas turbine vibration requires immediate investigation regardless of the absolute zone. Check for combustion dynamics issues, foreign object damage, bearing deterioration, coupling problems, or thermal transient effects. Many gas turbines have automatic trip systems that activate at Zone D levels.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Vibration Limits ISO 20816-4\",\"item\":\"https:\/\/vibromera.eu\/calculators\/vibration-iso20816-4-gas-turbines\/\"}\n]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;0,9..40,700;1,9..40,400&#038;family=JetBrains+Mono:wght@400;500;600&#038;family=Fraunces:opsz,wght@9..144,700;9..144,800&#038;display=swap\" rel=\"stylesheet\">\n\n<link rel=\"stylesheet\" href=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.css\">\n\n<style>\n:root {\n    --vc-bg: #f4f1ec;\n    --vc-surface: #ffffff;\n    --vc-surface-alt: #f8f6f2;\n    --vc-ink: #1a1a1a;\n    --vc-ink-secondary: #5a5650;\n    --vc-ink-muted: #8a857e;\n    --vc-accent: #c85a2a;\n    --vc-accent-hover: #b04d22;\n    --vc-accent-light: #fdf0ea;\n    --vc-blue: #2a5c8c;\n    --vc-blue-light: #eaf1f8;\n    --vc-green: #2a7a4b;\n    --vc-green-light: #eaf8ef;\n    --vc-yellow: #a67c00;\n    --vc-yellow-light: #fef9e8;\n    --vc-red: #b91c1c;\n    --vc-red-light: #fef2f2;\n    --vc-border: #d9d4cc;\n    --vc-border-light: #e8e4dd;\n    --vc-shadow: 0 1px 3px rgba(26,26,26,0.06), 0 4px 12px rgba(26,26,26,0.04);\n    --vc-shadow-lg: 0 4px 12px rgba(26,26,26,0.08), 0 16px 40px rgba(26,26,26,0.06);\n    --vc-radius: 8px;\n    --vc-radius-lg: 12px;\n    --vc-font: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;\n    --vc-mono: 'JetBrains Mono', 'Consolas', 'Monaco', monospace;\n    --vc-display: 'Fraunces', Georgia, serif;\n\n    --zone-a: #16a34a;\n    --zone-a-light: #dcfce7;\n    --zone-b: #ca8a04;\n    --zone-b-light: #fef9c3;\n    --zone-c: #ea580c;\n    --zone-c-light: #fff7ed;\n    --zone-d: #dc2626;\n    --zone-d-light: #fef2f2;\n}\n\n.vc-calculator {\n    font-family: var(--vc-font);\n    font-size: 15px;\n    line-height: 1.65;\n    color: var(--vc-ink);\n    max-width: 960px;\n    margin: 0 auto;\n    padding: 20px 16px 40px;\n    -webkit-font-smoothing: antialiased;\n}\n.vc-calculator *, .vc-calculator *::before, .vc-calculator *::after { box-sizing: border-box; }\n\n.vc-header { text-align: center; padding: 48px 24px 40px; position: relative; }\n.vc-header::after { content:''; position:absolute; bottom:0; left:50%; transform:translateX(-50%); width:80px; height:3px; background:var(--vc-accent); border-radius:2px; }\n.vc-header-eyebrow { font-family:var(--vc-mono); font-size:11px; font-weight:500; letter-spacing:0.15em; text-transform:uppercase; color:var(--vc-accent); margin:0 0 12px; }\n.vc-header-title { font-family:var(--vc-display); font-size:clamp(24px,4vw,36px); font-weight:800; line-height:1.15; color:var(--vc-ink); margin:0 0 16px; letter-spacing:-0.02em; }\n.vc-header-subtitle { font-size:15px; color:var(--vc-ink-secondary); margin:0 auto 20px; max-width:600px; }\n.vc-badges { display:inline-flex; gap:8px; flex-wrap:wrap; justify-content:center; }\n.vc-badge { font-family:var(--vc-mono); font-size:11px; font-weight:500; padding:4px 10px; border-radius:4px; background:var(--vc-surface); border:1px solid var(--vc-border); color:var(--vc-ink-secondary); }\n\n.vc-card { background:var(--vc-surface); border:1px solid var(--vc-border); border-radius:var(--vc-radius-lg); box-shadow:var(--vc-shadow); overflow:hidden; margin-top:32px; }\n\n.vc-form { padding:24px; }\n.vc-form-grid { display:grid; grid-template-columns:1fr 1fr; gap:18px; }\n@media(max-width:600px) { .vc-form-grid { grid-template-columns:1fr; } }\n.vc-field { display:flex; flex-direction:column; }\n.vc-field-full { grid-column: 1 \/ -1; }\n.vc-label { font-size:12px; font-weight:600; letter-spacing:0.04em; text-transform:uppercase; color:var(--vc-ink-secondary); margin-bottom:6px; }\n.vc-label-hint { font-weight:400; text-transform:none; letter-spacing:0; color:var(--vc-ink-muted); font-size:11px; }\n.vc-select, .vc-input { width:100%; padding:10px 12px; border:1.5px solid var(--vc-border); border-radius:6px; font-family:var(--vc-font); font-size:14px; color:var(--vc-ink); background:var(--vc-surface); transition:border-color 0.15s, box-shadow 0.15s; }\n.vc-select { padding-right:36px; appearance:none; -webkit-appearance:none; cursor:pointer; background-image:url(\"data:image\/svg+xml,%3Csvg xmlns='http:\/\/www.w3.org\/2000\/svg' width='16' height='16' fill='none' stroke='%235a5650' stroke-width='2'%3E%3Cpath d='M4 6l4 4 4-4'\/%3E%3C\/svg%3E\"); background-repeat:no-repeat; background-position:right 10px center; }\n.vc-select:focus, .vc-input:focus { outline:none; border-color:var(--vc-accent); box-shadow:0 0 0 3px rgba(200,90,42,0.12); }\n.vc-select:hover, .vc-input:hover { border-color:var(--vc-ink-muted); }\n\n.vc-presets { display:flex; flex-wrap:wrap; gap:8px; margin-top:18px; padding-top:18px; border-top:1px solid var(--vc-border-light); }\n.vc-presets-label { font-family:var(--vc-mono); font-size:11px; font-weight:500; letter-spacing:0.1em; text-transform:uppercase; color:var(--vc-ink-muted); width:100%; margin-bottom:2px; }\n.vc-preset-btn { padding:5px 12px; font-family:var(--vc-font); font-size:12px; font-weight:500; border:1px solid var(--vc-border); border-radius:6px; background:var(--vc-surface-alt); color:var(--vc-ink-secondary); cursor:pointer; transition:all 0.15s; }\n.vc-preset-btn:hover { border-color:var(--vc-accent); color:var(--vc-accent); background:var(--vc-accent-light); }\n\n.vc-results { border-top:1px solid var(--vc-border-light); background:var(--vc-surface-alt); padding:0; max-height:0; overflow:hidden; transition:max-height 0.5s cubic-bezier(0.4,0,0.2,1), padding 0.3s; }\n.vc-results.vc-visible { max-height:2000px; padding:24px; }\n.vc-results-head { display:flex; align-items:center; justify-content:space-between; margin-bottom:18px; }\n.vc-results-title { font-family:var(--vc-display); font-size:20px; font-weight:700; color:var(--vc-ink); margin:0; }\n.vc-copy-btn { display:inline-flex; align-items:center; gap:5px; padding:6px 12px; border:1px solid var(--vc-border); border-radius:6px; background:var(--vc-surface); font-family:var(--vc-font); font-size:12px; font-weight:500; color:var(--vc-ink-secondary); cursor:pointer; transition:all 0.15s; }\n.vc-copy-btn:hover { border-color:var(--vc-accent); color:var(--vc-accent); }\n.vc-copy-btn.vc-copied { background:var(--vc-green-light); border-color:var(--vc-green); color:var(--vc-green); }\n\n.vc-result-grid { display:grid; grid-template-columns:1fr 1fr; gap:12px; margin-bottom:20px; }\n@media(max-width:500px) { .vc-result-grid { grid-template-columns:1fr; } }\n.vc-rcard { background:var(--vc-surface); border:1px solid var(--vc-border-light); border-radius:var(--vc-radius); padding:16px; transition:transform 0.2s; }\n.vc-rcard:hover { transform:translateY(-1px); }\n.vc-rcard-primary { border-width:2px; grid-column:1 \/ -1; }\n.vc-rcard-label { font-family:var(--vc-mono); font-size:10px; font-weight:500; letter-spacing:0.1em; text-transform:uppercase; color:var(--vc-ink-muted); margin-bottom:4px; }\n.vc-rcard-value { font-family:var(--vc-mono); font-size:22px; font-weight:600; color:var(--vc-ink); line-height:1.2; }\n.vc-rcard-primary .vc-rcard-value { font-size:30px; }\n.vc-rcard-unit { font-size:14px; font-weight:400; color:var(--vc-ink-secondary); }\n.vc-rcard-desc { font-size:13px; color:var(--vc-ink-secondary); margin-top:6px; line-height:1.5; }\n\n.vc-zone-a { border-color:var(--zone-a); background:linear-gradient(135deg, var(--zone-a-light) 0%, var(--vc-surface) 100%); }\n.vc-zone-a .vc-rcard-value { color:var(--zone-a); }\n.vc-zone-b { border-color:var(--zone-b); background:linear-gradient(135deg, var(--zone-b-light) 0%, var(--vc-surface) 100%); }\n.vc-zone-b .vc-rcard-value { color:var(--zone-b); }\n.vc-zone-c { border-color:var(--zone-c); background:linear-gradient(135deg, var(--zone-c-light) 0%, var(--vc-surface) 100%); }\n.vc-zone-c .vc-rcard-value { color:var(--zone-c); }\n.vc-zone-d { border-color:var(--zone-d); background:linear-gradient(135deg, var(--zone-d-light) 0%, var(--vc-surface) 100%); }\n.vc-zone-d .vc-rcard-value { color:var(--zone-d); }\n\n.vc-zone-bar { display:flex; height:36px; border-radius:6px; overflow:hidden; margin-bottom:16px; border:1px solid var(--vc-border-light); }\n.vc-zone-bar-seg { flex:1; display:flex; align-items:center; justify-content:center; font-family:var(--vc-mono); font-size:11px; font-weight:600; color:#fff; position:relative; transition:opacity 0.3s; }\n.vc-zone-bar-seg.zb-a { background:var(--zone-a); }\n.vc-zone-bar-seg.zb-b { background:var(--zone-b); }\n.vc-zone-bar-seg.zb-c { background:var(--zone-c); }\n.vc-zone-bar-seg.zb-d { background:var(--zone-d); }\n.vc-zone-bar-seg.zb-dim { opacity:0.35; }\n.vc-zone-bar-seg.zb-active { opacity:1; box-shadow:inset 0 0 0 2px rgba(255,255,255,0.5); }\n.vc-zone-bar-labels { display:flex; margin-top:4px; font-family:var(--vc-mono); font-size:10px; color:var(--vc-ink-muted); }\n.vc-zone-bar-labels span { flex:1; text-align:center; }\n\n.vc-zone-table { width:100%; border-collapse:collapse; margin:12px 0; font-size:13px; }\n.vc-zone-table th, .vc-zone-table td { padding:8px 12px; border:1px solid var(--vc-border-light); text-align:center; }\n.vc-zone-table th { background:var(--vc-surface-alt); font-size:11px; font-weight:600; text-transform:uppercase; letter-spacing:0.05em; color:var(--vc-ink-secondary); }\n.vc-zone-table .zt-a { background:var(--zone-a-light); }\n.vc-zone-table .zt-b { background:var(--zone-b-light); }\n.vc-zone-table .zt-c { background:var(--zone-c-light); }\n.vc-zone-table .zt-d { background:var(--zone-d-light); }\n\n.vc-section { margin-top:24px; border:1px solid var(--vc-border); border-radius:var(--vc-radius-lg); background:var(--vc-surface); box-shadow:var(--vc-shadow); overflow:hidden; }\n.vc-section-toggle { width:100%; display:flex; align-items:center; justify-content:space-between; padding:18px 24px; border:none; background:transparent; cursor:pointer; font-family:var(--vc-font); text-align:left; transition:background 0.15s; }\n.vc-section-toggle:hover { background:var(--vc-surface-alt); }\n.vc-section-toggle-text { display:flex; align-items:center; gap:10px; }\n.vc-section-icon { font-size:20px; line-height:1; }\n.vc-section-title { font-family:var(--vc-display); font-size:18px; font-weight:700; color:var(--vc-ink); margin:0; }\n.vc-section-chevron { width:20px; height:20px; color:var(--vc-ink-muted); transition:transform 0.3s; flex-shrink:0; }\n.vc-section.vc-open .vc-section-chevron { transform:rotate(180deg); }\n.vc-section-body { max-height:0; overflow:hidden; transition:max-height 0.4s cubic-bezier(0.4,0,0.2,1); }\n.vc-section.vc-open .vc-section-body { max-height:20000px; }\n.vc-section-inner { padding:0 24px 24px; border-top:1px solid var(--vc-border-light); }\n\n.vc-theory h3 { font-family:var(--vc-display); font-size:17px; font-weight:700; color:var(--vc-ink); margin:28px 0 10px; }\n.vc-theory h3:first-child { margin-top:20px; }\n.vc-theory p { font-size:14px; color:var(--vc-ink-secondary); margin:0 0 10px; }\n.vc-theory ul, .vc-theory ol { font-size:14px; color:var(--vc-ink-secondary); margin:0 0 12px 18px; padding:0; }\n.vc-theory li { margin-bottom:5px; }\n.vc-formula-box { background:var(--vc-surface-alt); border:2px solid var(--vc-border); border-radius:6px; padding:14px 20px; font-family:var(--vc-mono); font-size:16px; font-weight:500; text-align:center; margin:14px 0; color:var(--vc-ink); overflow-x:auto; }\n.vc-info-box { background:var(--vc-blue-light); border-left:3px solid var(--vc-blue); padding:14px 16px; border-radius:0 6px 6px 0; margin:14px 0; }\n.vc-info-box p { margin:0; font-size:14px; color:var(--vc-ink-secondary); }\n.vc-warning-box { background:var(--vc-yellow-light); border-left:3px solid var(--vc-yellow); padding:14px 16px; border-radius:0 6px 6px 0; margin:14px 0; }\n.vc-table { width:100%; border-collapse:collapse; margin:14px 0; font-size:13px; }\n.vc-table th, .vc-table td { padding:10px 12px; border:1px solid var(--vc-border-light); text-align:left; }\n.vc-table th { background:var(--vc-surface-alt); font-size:11px; font-weight:600; text-transform:uppercase; letter-spacing:0.05em; color:var(--vc-ink-secondary); }\n.vc-table tr:nth-child(even) { background:var(--vc-surface-alt); }\n@media(max-width:600px) { .vc-table { font-size:12px; } .vc-table th, .vc-table td { padding:8px; } }\n\n.vc-faq-list { display:flex; flex-direction:column; gap:8px; margin-top:20px; }\n.vc-faq-item { border:1px solid var(--vc-border-light); border-radius:6px; overflow:hidden; }\n.vc-faq-q { width:100%; display:flex; align-items:center; justify-content:space-between; gap:12px; padding:14px 16px; border:none; background:var(--vc-surface-alt); cursor:pointer; font-family:var(--vc-font); font-size:15px; font-weight:600; color:var(--vc-ink); text-align:left; transition:background 0.15s; }\n.vc-faq-q:hover { background:#ede9e3; }\n.vc-faq-chevron { width:16px; height:16px; color:var(--vc-ink-muted); flex-shrink:0; transition:transform 0.25s; }\n.vc-faq-item.vc-open .vc-faq-chevron { transform:rotate(180deg); }\n.vc-faq-a { max-height:0; overflow:hidden; transition:max-height 0.35s; }\n.vc-faq-item.vc-open .vc-faq-a { max-height:1200px; }\n.vc-faq-a-inner { padding:14px 16px; border-top:1px solid var(--vc-border-light); font-size:14px; color:var(--vc-ink-secondary); }\n.vc-faq-a-inner p { margin:0 0 8px; }\n.vc-faq-a-inner p:last-child { margin-bottom:0; }\n.vc-faq-a-inner ul { margin:4px 0 8px 16px; padding:0; }\n.vc-faq-a-inner li { margin-bottom:3px; }\n\n.vc-related { display:flex; flex-wrap:wrap; gap:10px; margin-top:16px; }\n.vc-related-link { display:inline-block; padding:8px 16px; font-family:var(--vc-font); font-size:13px; font-weight:600; background:var(--vc-surface-alt); color:var(--vc-ink-secondary); border:1px solid var(--vc-border); border-radius:var(--vc-radius); text-decoration:none; transition:all 0.15s; }\n.vc-related-link:hover { border-color:var(--vc-accent); color:var(--vc-accent); background:var(--vc-accent-light); }\n\n.vc-promo { margin-top:24px; padding:20px; background:linear-gradient(135deg, var(--vc-accent-light), var(--vc-surface)); border:1px solid var(--vc-border); border-radius:var(--vc-radius-lg); display:flex; align-items:center; gap:16px; }\n.vc-promo-text { flex:1; font-size:14px; color:var(--vc-ink-secondary); }\n.vc-promo-text strong { color:var(--vc-ink); }\n.vc-promo-link { padding:8px 20px; font-size:13px; font-weight:700; color:#fff; background:var(--vc-accent); border-radius:var(--vc-radius); text-decoration:none; white-space:nowrap; transition:background 0.15s; }\n.vc-promo-link:hover { background:var(--vc-accent-hover); }\n\n.vc-footer { text-align:center; padding:32px 16px; font-size:13px; color:var(--vc-ink-muted); }\n.vc-footer a { color:var(--vc-accent); text-decoration:none; }\n.vc-footer a:hover { text-decoration:underline; }\n.vc-footer-links { margin-top:8px; font-size:12px; }\n.vc-footer-links a { margin:0 8px; }\n\n@media print {\n    .vc-section-body { max-height:none!important; }\n    .vc-faq-a { max-height:none!important; }\n    .vc-results { max-height:none!important; padding:24px!important; }\n    .vc-copy-btn, .vc-section-chevron, .vc-faq-chevron, .vc-presets, .vc-promo { display:none!important; }\n}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-iso20816-4\">\n\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool #022<\/p>\n    <h1 class=\"vc-header-title\">Vibration Limits \u2014 Gas Turbines<\/h1>\n    <p class=\"vc-header-subtitle\">Evaluate vibration severity for gas turbines per ISO 20816-4. Supports bearing housing velocity and shaft relative displacement for industrial, aero-derivative, and small gas turbines.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">ISO 20816-4<\/span>\n        <span class=\"vc-badge\">Zones A\/B\/C\/D<\/span>\n        <span class=\"vc-badge\">Gas Turbines<\/span>\n    <\/div>\n<\/header>\n\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-meastype\">Measurement Type<\/label>\n                <select class=\"vc-select\" id=\"vc-meastype\">\n                    <option value=\"bearing\" selected>Bearing Housing Velocity (mm\/s RMS)<\/option>\n                    <option value=\"shaft\">Shaft Relative Displacement (\u03bcm p-p)<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-turbine\">Gas Turbine Type<\/label>\n                <select class=\"vc-select\" id=\"vc-turbine\">\n                    <option value=\"industrial\" selected>Industrial Heavy-Duty<\/option>\n                    <option value=\"aero\">Aero-Derivative<\/option>\n                    <option value=\"small\">Small (&lt;3 MW)<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field vc-field-full\">\n                <label class=\"vc-label\" for=\"vc-value\">Measured Value <span class=\"vc-label-hint\" id=\"vc-value-hint\">(mm\/s RMS)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-value\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 5.5\" value=\"5.5\">\n            <\/div>\n        <\/div>\n\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-t=\"bearing\" data-gt=\"industrial\" data-v=\"5.5\">Industrial GT bearing 5.5 mm\/s<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-t=\"shaft\" data-gt=\"aero\" data-v=\"90\">Aero-derivative shaft 90 \u03bcm<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-t=\"bearing\" data-gt=\"small\" data-v=\"4.0\">Small GT 4.0 mm\/s<\/button>\n        <\/div>\n    <\/form>\n\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Results<\/h2>\n            <button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">\n                <svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg>\n                Copy\n            <\/button>\n        <\/div>\n\n        <div class=\"vc-zone-bar\" id=\"vc-zone-bar\">\n            <div class=\"vc-zone-bar-seg zb-a\" id=\"zb-a\">A<\/div>\n            <div class=\"vc-zone-bar-seg zb-b\" id=\"zb-b\">B<\/div>\n            <div class=\"vc-zone-bar-seg zb-c\" id=\"zb-c\">C<\/div>\n            <div class=\"vc-zone-bar-seg zb-d\" id=\"zb-d\">D<\/div>\n        <\/div>\n        <div class=\"vc-zone-bar-labels\" id=\"vc-zone-labels\">\n            <span id=\"zl-a\"><\/span><span id=\"zl-b\"><\/span><span id=\"zl-c\"><\/span><span id=\"zl-d\"><\/span>\n        <\/div>\n\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\" id=\"vc-r-zone-card\">\n                <div class=\"vc-rcard-label\">Vibration Zone<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-zone\">\u2014<\/div>\n                <div class=\"vc-rcard-desc\" id=\"vc-r-zone-desc\"><\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Measured Value<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-measured\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Turbine Type<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-type\" style=\"font-size:18px;\">\u2014<\/div>\n            <\/div>\n        <\/div>\n\n        <table class=\"vc-zone-table\" id=\"vc-boundary-table\">\n            <thead><tr><th>Zone<\/th><th>Boundary<\/th><th>Description<\/th><\/tr><\/thead>\n            <tbody id=\"vc-boundary-body\"><\/tbody>\n        <\/table>\n    <\/div>\n<\/div>\n\n<!-- Theory -->\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcd8<\/span>\n            <span class=\"vc-section-title\">Theory &amp; Formulas<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>ISO 20816-4 Scope<\/h3>\n            <p>ISO 20816-4 specifies vibration evaluation criteria for gas turbines used in power generation and mechanical drive applications. It covers industrial heavy-duty gas turbines, aero-derivative gas turbines, and small gas turbines below 3 MW.<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n\n            <h3>Bearing Housing Vibration (Industrial Heavy-Duty)<\/h3>\n            <p>Broadband vibration velocity measured on the bearing housing in mm\/s RMS, frequency range 10\u20131000 Hz.<\/p>\n            <table class=\"vc-table\">\n                <thead><tr><th>Zone Boundary<\/th><th>Velocity (mm\/s RMS)<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>A\/B<\/td><td>3.5<\/td><\/tr>\n                    <tr><td>B\/C<\/td><td>7.1<\/td><\/tr>\n                    <tr><td>C\/D<\/td><td>11.2<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <h3>Shaft Relative Displacement (Industrial)<\/h3>\n            <p>Shaft vibration measured with proximity probes, expressed as peak-to-peak displacement in \u03bcm.<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n            <table class=\"vc-table\">\n                <thead><tr><th>Zone Boundary<\/th><th>Displacement (\u03bcm p-p)<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>A\/B<\/td><td>65<\/td><\/tr>\n                    <tr><td>B\/C<\/td><td>130<\/td><\/tr>\n                    <tr><td>C\/D<\/td><td>200<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <h3>Gas Turbine Types<\/h3>\n            <table class=\"vc-table\">\n                <thead><tr><th>Type<\/th><th>Power Range<\/th><th>Typical Speed<\/th><th>Characteristics<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>Industrial heavy-duty<\/td><td>&gt;40 MW<\/td><td>3000\u20133600 RPM<\/td><td>Single-shaft, journal bearings, heavy rotor<\/td><\/tr>\n                    <tr><td>Aero-derivative<\/td><td>20\u201360 MW<\/td><td>3600\u201315000+ RPM<\/td><td>Multi-spool, lighter rotors, may use rolling element bearings<\/td><\/tr>\n                    <tr><td>Small (&lt;3 MW)<\/td><td>&lt;3 MW<\/td><td>Variable<\/td><td>Package units, microturbines, industrial drives<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <div class=\"vc-info-box\">\n                <p><strong>\u2139\ufe0f Note:<\/strong> For aero-derivative and small gas turbines, the zone boundaries shown are based on the industrial heavy-duty values as a general guideline. Manufacturer-specific limits may differ. Always consult the OEM vibration specifications for your specific machine.<\/p>\n            <\/div>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Important:<\/strong> Gas turbines typically have automatic vibration trip systems. Ensure that protection system setpoints are aligned with the ISO 20816-4 zone boundaries or OEM specifications. Never disable vibration protection systems.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related -->\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udd17<\/span>\n            <span class=\"vc-section-title\">Related Calculators<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-related\">\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-zones-iso20816-1\/\">ISO 20816-1 \u2014 General Guidelines<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-iso20816-2-turbines\/\">ISO 20816-2 \u2014 Steam Turbines<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-iso20816-3-industrial\/\">ISO 20816-3 \u2014 Industrial Machines<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 21940)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-velocity\/\">Vibration Velocity (ISO 10816)<\/a>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- FAQ -->\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\u2753<\/span>\n            <span class=\"vc-section-title\">Frequently Asked Questions<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>\n        Professional vibration analyzers and field balancing systems for turbomachinery. Evaluate gas turbine condition per ISO 20816-4 on-site. Used in 50+ countries.\n    <\/div>\n    <a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a>\n<\/div>\n\n<footer class=\"vc-footer\">\n    <p>\u00a9 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Based on ISO 20816-4. Last updated: February 2025<\/p>\n    <div class=\"vc-footer-links\">\n        <a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a>\n        <a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a>\n    <\/div>\n<\/footer>\n\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function() {\n    'use strict';\n\n    var SLUG = 'vibration-iso20816-4-gas-turbines';\n\n    \/* Zone limits per measurement type and turbine type *\/\n    var LIMITS = {\n        bearing: {\n            industrial: { ab: 3.5, bc: 7.1, cd: 11.2, unit: 'mm\/s RMS', label: 'Industrial Heavy-Duty' },\n            aero:       { ab: 3.5, bc: 7.1, cd: 11.2, unit: 'mm\/s RMS', label: 'Aero-Derivative' },\n            small:      { ab: 3.5, bc: 7.1, cd: 11.2, unit: 'mm\/s RMS', label: 'Small (<3 MW)' }\n        },\n        shaft: {\n            industrial: { ab: 65, bc: 130, cd: 200, unit: '\u03bcm p-p', label: 'Industrial Heavy-Duty' },\n            aero:       { ab: 65, bc: 130, cd: 200, unit: '\u03bcm p-p', label: 'Aero-Derivative' },\n            small:      { ab: 65, bc: 130, cd: 200, unit: '\u03bcm p-p', label: 'Small (<3 MW)' }\n        }\n    };\n\n    var ZONE_DESC = {\n        A: 'Newly commissioned machines \u2014 excellent condition',\n        B: 'Acceptable for unrestricted long-term operation',\n        C: 'Not suitable for long-term operation \u2014 plan remedial action',\n        D: 'Dangerous vibration level \u2014 risk of damage, immediate action required'\n    };\n\n    function $(id) { return document.getElementById(id); }\n    function fmt(n, d) { if(isNaN(n)) return '\u2014'; var f=n.toFixed(d===undefined?2:d); return f.replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,''); }\n\n    function getZone(val, lim) {\n        if (val <= lim.ab) return 'A';\n        if (val <= lim.bc) return 'B';\n        if (val <= lim.cd) return 'C';\n        return 'D';\n    }\n\n    function calculate() {\n        var measType = $('vc-meastype').value;\n        var turbine = $('vc-turbine').value;\n        var val = parseFloat($('vc-value').value);\n\n        if (isNaN(val) || val < 0) {\n            $('vc-results').classList.remove('vc-visible');\n            return;\n        }\n\n        var lim = LIMITS[measType][turbine];\n        var zone = getZone(val, lim);\n\n        ['a','b','c','d'].forEach(function(letter) {\n            var seg = $('zb-' + letter);\n            seg.className = 'vc-zone-bar-seg zb-' + letter + (letter.toUpperCase() === zone ? ' zb-active' : ' zb-dim');\n        });\n\n        $('zl-a').textContent = '\u2264' + lim.ab;\n        $('zl-b').textContent = lim.ab + '\u2013' + lim.bc;\n        $('zl-c').textContent = lim.bc + '\u2013' + lim.cd;\n        $('zl-d').textContent = '>' + lim.cd;\n\n        var zoneCard = $('vc-r-zone-card');\n        zoneCard.className = 'vc-rcard vc-rcard-primary vc-zone-' + zone.toLowerCase();\n        $('vc-r-zone').textContent = 'Zone ' + zone;\n        $('vc-r-zone-desc').textContent = ZONE_DESC[zone];\n\n        $('vc-r-measured').innerHTML = fmt(val, measType === 'shaft' ? 0 : 1) + ' <span class=\"vc-rcard-unit\">' + lim.unit + '<\/span>';\n        $('vc-r-type').textContent = lim.label;\n\n        var tbody = $('vc-boundary-body');\n        tbody.innerHTML =\n            '<tr class=\"zt-a\"><td><strong>Zone A<\/strong><\/td><td>\u2264 ' + lim.ab + ' ' + lim.unit + '<\/td><td>' + ZONE_DESC.A + '<\/td><\/tr>' +\n            '<tr class=\"zt-b\"><td><strong>Zone B<\/strong><\/td><td>' + lim.ab + ' \u2013 ' + lim.bc + ' ' + lim.unit + '<\/td><td>' + ZONE_DESC.B + '<\/td><\/tr>' +\n            '<tr class=\"zt-c\"><td><strong>Zone C<\/strong><\/td><td>' + lim.bc + ' \u2013 ' + lim.cd + ' ' + lim.unit + '<\/td><td>' + ZONE_DESC.C + '<\/td><\/tr>' +\n            '<tr class=\"zt-d\"><td><strong>Zone D<\/strong><\/td><td>&gt; ' + lim.cd + ' ' + lim.unit + '<\/td><td>' + ZONE_DESC.D + '<\/td><\/tr>';\n\n        $('vc-results').classList.add('vc-visible');\n\n        var u = new URL(window.location);\n        u.searchParams.set('type', measType);\n        u.searchParams.set('turbine', turbine);\n        u.searchParams.set('value', val);\n        history.replaceState(null, '', u.toString());\n\n        var measNames = { bearing: 'Bearing housing', shaft: 'Shaft relative' };\n        saveHistory({ type: measType, turbine: turbine, value: val, zone: zone, _summary: lim.label + ', ' + measNames[measType] + ' ' + val + ' ' + lim.unit + ' \u2192 Zone ' + zone });\n    }\n\n    $('vc-meastype').addEventListener('change', function() {\n        $('vc-value-hint').textContent = this.value === 'bearing' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n        calculate();\n    });\n\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-meastype').value = this.getAttribute('data-t');\n            $('vc-turbine').value = this.getAttribute('data-gt');\n            $('vc-value').value = this.getAttribute('data-v');\n            $('vc-value-hint').textContent = this.getAttribute('data-t') === 'bearing' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n            calculate();\n        });\n    });\n\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    $('vc-copy-btn').addEventListener('click', function() {\n        var lim = LIMITS[$('vc-meastype').value][$('vc-turbine').value];\n        var text = 'Vibration Zone Evaluation \u2014 ISO 20816-4\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'Gas Turbine: ' + lim.label + '\\n' +\n            'Measurement: ' + $('vc-meastype').options[$('vc-meastype').selectedIndex].text + '\\n' +\n            'Measured: ' + $('vc-r-measured').textContent + '\\n' +\n            'Zone: ' + $('vc-r-zone').textContent + '\\n' +\n            'Assessment: ' + $('vc-r-zone-desc').textContent + '\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'vibromera.eu\/calculators\/vibration-iso20816-4-gas-turbines\/';\n\n        if (navigator.clipboard) {\n            navigator.clipboard.writeText(text).then(function() {\n                var btn = $('vc-copy-btn');\n                btn.classList.add('vc-copied');\n                btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';\n                setTimeout(function() {\n                    btn.classList.remove('vc-copied');\n                    btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';\n                }, 2000);\n            });\n        }\n    });\n\n    document.querySelectorAll('.vc-section-toggle').forEach(function(btn) {\n        btn.addEventListener('click', function() {\n            var section = this.closest('.vc-section');\n            var isOpen = section.classList.contains('vc-open');\n            section.classList.toggle('vc-open');\n            this.setAttribute('aria-expanded', !isOpen);\n        });\n    });\n\n    var faqData = [\n        { q: 'What types of gas turbines does ISO 20816-4 cover?', a: '<p>ISO 20816-4 covers all types of gas turbines used in power generation and mechanical drive:<\/p><ul><li><strong>Industrial heavy-duty<\/strong> \u2014 Large frame machines typically &gt;40 MW (e.g., GE Frame 7\/9, Siemens SGT-800\/2000)<\/li><li><strong>Aero-derivative<\/strong> \u2014 Derived from aircraft engines, typically 20\u201360 MW (e.g., GE LM2500\/LM6000, Rolls-Royce Trent)<\/li><li><strong>Small gas turbines<\/strong> \u2014 Units below 3 MW including microturbines and small industrial drives<\/li><\/ul>' },\n        { q: 'What is the difference between bearing housing and shaft measurement?', a: '<p><strong>Bearing housing vibration<\/strong> is measured with sensors (accelerometers or velocimeters) mounted on the bearing pedestal. It provides overall machine vibration in mm\/s RMS and is the most common measurement for protection and monitoring.<\/p><p><strong>Shaft relative displacement<\/strong> is measured with proximity (eddy current) probes installed inside the bearing clearance. It measures the actual shaft orbit in \u03bcm peak-to-peak and is essential for detecting rotor dynamic issues that may not be visible on the bearing housing.<\/p>' },\n        { q: 'Why do gas turbines have higher vibration limits than steam turbines?', a: '<p>Gas turbines generally have higher allowable vibration limits due to:<\/p><ul><li>Combustion-induced vibration \u2014 a source not present in steam turbines<\/li><li>Higher power density and different rotor dynamics<\/li><li>Operating environment factors (thermal gradients, fuel variations)<\/li><li>Different bearing and support configurations<\/li><\/ul><p>For example, bearing housing velocity Zone A\/B boundary is 3.5 mm\/s for gas turbines (ISO 20816-4) vs. 2.8 mm\/s for steam turbines (ISO 20816-2).<\/p>' },\n        { q: 'How do aero-derivative limits differ from industrial gas turbines?', a: '<p>Aero-derivative gas turbines have unique characteristics:<\/p><ul><li><strong>Multi-spool design<\/strong> \u2014 gas generator and power turbine rotate at different speeds<\/li><li><strong>Higher speeds<\/strong> \u2014 gas generator may run at 8000\u201315000+ RPM<\/li><li><strong>Rolling element bearings<\/strong> \u2014 some aero-derivatives use ball\/roller bearings instead of journal bearings<\/li><li><strong>Lighter rotors<\/strong> \u2014 more responsive to unbalance and thermal effects<\/li><\/ul><p>The zone boundaries in this calculator apply as general guidelines; always check OEM specifications for your specific machine.<\/p>' },\n        { q: 'What action should I take when gas turbine vibration increases suddenly?', a: '<p>A sudden vibration increase on a gas turbine requires immediate investigation:<\/p><ul><li><strong>Check combustion dynamics<\/strong> \u2014 combustor issues can cause sudden vibration spikes<\/li><li><strong>Foreign object damage (FOD)<\/strong> \u2014 blade loss causes immediate unbalance<\/li><li><strong>Bearing deterioration<\/strong> \u2014 sudden change may indicate bearing failure<\/li><li><strong>Coupling problems<\/strong> \u2014 misalignment or coupling component failure<\/li><li><strong>Thermal transients<\/strong> \u2014 rapid load changes can cause temporary rotor bowing<\/li><\/ul><p>Most gas turbines have automatic vibration trip systems. Never override or bypass vibration protection.<\/p>' }\n    ];\n\n    var faqList = $('vc-faq-list');\n    faqData.forEach(function(faq) {\n        faqList.innerHTML += '<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>' + faq.q + '<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">' + faq.a + '<\/div><\/div><\/div>';\n    });\n    faqList.addEventListener('click', function(e) {\n        var btn = e.target.closest('.vc-faq-q');\n        if (!btn) return;\n        btn.closest('.vc-faq-item').classList.toggle('vc-open');\n    });\n\n    function saveHistory(entry) {\n        var key = 'vc_history_' + SLUG;\n        var arr = [];\n        try { arr = JSON.parse(localStorage.getItem(key)) || []; } catch(e) {}\n        entry._ts = new Date().toISOString();\n        arr.unshift(entry);\n        if (arr.length > 10) arr = arr.slice(0, 10);\n        try { localStorage.setItem(key, JSON.stringify(arr)); } catch(e) {}\n    }\n\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        if (p.has('type')) {\n            $('vc-meastype').value = p.get('type');\n            $('vc-value-hint').textContent = p.get('type') === 'bearing' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n        }\n        if (p.has('turbine')) $('vc-turbine').value = p.get('turbine');\n        if (p.has('value')) $('vc-value').value = p.get('value');\n    }\n\n    function renderFormulas() {\n        try {\n            katex.render('\\\\text{Zone} = \\\\begin{cases} A & v_{\\\\text{meas}} \\\\leq v_{A\/B} \\\\\\\\ B & v_{A\/B} < v_{\\\\text{meas}} \\\\leq v_{B\/C} \\\\\\\\ C & v_{B\/C} < v_{\\\\text{meas}} \\\\leq v_{C\/D} \\\\\\\\ D & v_{\\\\text{meas}} > v_{C\/D} \\\\end{cases}', $('vc-katex-1'), { displayMode: true, throwOnError: false });\n            katex.render('s_{\\\\text{p-p}} = \\\\max\\\\bigl(r(\\\\theta)\\\\bigr) - \\\\min\\\\bigl(r(\\\\theta)\\\\bigr) \\\\quad [\\\\mu m]', $('vc-katex-2'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    function init() {\n        loadParams();\n        renderFormulas();\n        calculate();\n    }\n\n    if (document.readyState === 'loading') {\n        document.addEventListener('DOMContentLoaded', init);\n    } else {\n        init();\n    }\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Gratis online kalkulator for evaluering av vibrasjonssoner i henhold til ISO 20816-4 for gassturbiner. Evaluer lagerhusets hastighet og akselforskyvning mot sone A\/B\/C\/D-grenser for industrielle, aeroderivative og sm\u00e5 gassturbiner.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100288","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100288","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100288\/revisions"}],"predecessor-version":[{"id":100596,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100288\/revisions\/100596"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}