{"id":100303,"date":"2026-02-15T20:45:00","date_gmt":"2026-02-15T20:45:00","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100303"},"modified":"2026-03-05T15:33:54","modified_gmt":"2026-03-05T15:33:54","slug":"vibration-zones-iso20816-1","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/bn\/calculators\/vibration-zones-iso20816-1\/","title":{"rendered":"ISO 20816-1 \u0995\u09ae\u09cd\u09aa\u09a8 \u0985\u099e\u09cd\u099a\u09b2 A\/B\/C\/D \u09ae\u09c2\u09b2\u09cd\u09af\u09be\u09af\u09bc\u09a8 \u09b8\u09b0\u099e\u09cd\u099c\u09be\u09ae"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Vibration Zone Evaluation Calculator \u2014 ISO 20816-1\",\"alternateName\":[\"ISO 20816-1 Calculator\",\"Vibration Zone Calculator\",\"Machine Vibration Evaluation\"],\"description\":\"Free online vibration zone evaluation calculator per ISO 20816-1. Enter machine group and measured vibration to determine zone A\/B\/C\/D.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/vibration-zones-iso20816-1\/\",\"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 20816-1 zone evaluation\",\"Machine groups 1\u20134\",\"Velocity and displacement input\",\"Color-coded zone display\",\"Visual zone bar\",\"URL parameter sharing\"],\"keywords\":\"vibration zones, ISO 20816-1, zone A B C D, vibration evaluation\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What are vibration zones A, B, C, and D?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"ISO 20816-1 defines four evaluation zones: Zone A \u2014 newly commissioned machines in excellent condition; Zone B \u2014 acceptable for long-term unrestricted operation; Zone C \u2014 not suitable for long-term operation, remedial action needed; Zone D \u2014 dangerous vibration levels, damage may occur, immediate shutdown recommended.\"}},\n{\"@type\":\"Question\",\"name\":\"How do I select the correct machine group?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Group 1: Large machines >300 kW on rigid foundations. Group 2: Medium machines 15\u2013300 kW on rigid foundations. Group 3: Pumps (multistage, vertical, etc.). Group 4: Large machines >300 kW on flexible foundations. If unsure, consult the machine manufacturer or use Group 2 as a conservative default.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the difference between velocity and displacement?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Vibration velocity (mm\/s RMS) is the standard measurement for evaluating machine condition per ISO 20816-1 and is preferred for most rotating machinery in the 10\u20131000 Hz range. Displacement (\u03bcm peak-to-peak) is useful for low-speed machines (<600 RPM) where velocity readings may be very small.\"}},\n{\"@type\":\"Question\",\"name\":\"What action should I take for Zone C?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Zone C indicates the machine is not suitable for long-term continuous operation. 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}\n.vc-related-link:hover { border-color:var(--vc-accent); color:var(--vc-accent); background:var(--vc-accent-light); }\n\n\/* \u2500\u2500 PROMO \u2500\u2500 *\/\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\/* \u2500\u2500 FOOTER \u2500\u2500 *\/\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\/* \u2500\u2500 PRINT \u2500\u2500 *\/\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-iso20816-1\">\n\n<!-- Header -->\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool #019<\/p>\n    <h1 class=\"vc-header-title\">Vibration Evaluation Zones A\/B\/C\/D<\/h1>\n    <p class=\"vc-header-subtitle\">Evaluate machine vibration severity per ISO 20816-1. Select machine group, enter measured vibration, and get the zone classification with recommended actions.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">ISO 20816-1<\/span>\n        <span class=\"vc-badge\">Zones A\/B\/C\/D<\/span>\n        <span class=\"vc-badge\">General Guidelines<\/span>\n    <\/div>\n<\/header>\n\n<!-- Calculator Card -->\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-group\">Machine Group<\/label>\n                <select class=\"vc-select\" id=\"vc-group\">\n                    <option value=\"1\">Group 1 \u2014 Large machines &gt;300 kW, rigid foundation<\/option>\n                    <option value=\"2\" selected>Group 2 \u2014 Medium machines 15\u2013300 kW, rigid foundation<\/option>\n                    <option value=\"3\">Group 3 \u2014 Pumps (multistage, vertical, etc.)<\/option>\n                    <option value=\"4\">Group 4 \u2014 Large machines &gt;300 kW, flexible foundation<\/option>\n                <\/select>\n            <\/div>\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=\"velocity\" selected>Velocity (mm\/s RMS)<\/option>\n                    <option value=\"displacement\">Displacement (\u03bcm p-p)<\/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. 3.5\" value=\"3.5\">\n            <\/div>\n        <\/div>\n\n        <!-- Presets -->\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-g=\"2\" data-t=\"velocity\" data-v=\"3.5\">Group 2, 3.5 mm\/s<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-g=\"1\" data-t=\"velocity\" data-v=\"5.0\">Group 1, 5.0 mm\/s<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-g=\"4\" data-t=\"velocity\" data-v=\"8.0\">Group 4, 8.0 mm\/s<\/button>\n        <\/div>\n    <\/form>\n\n    <!-- Results -->\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        <!-- Zone bar -->\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\">Machine Group<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-group\">\u2014<\/div>\n            <\/div>\n        <\/div>\n\n        <!-- Boundaries table -->\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 & Reference -->\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>Zone Evaluation Concept<\/h3>\n            <p>ISO 20816-1 provides general guidelines for evaluating machine vibration by comparing measured vibration values against zone boundaries. The standard defines four zones:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n            <ul>\n                <li><strong>Zone A<\/strong> \u2014 Vibration of newly commissioned machines typically falls within this zone<\/li>\n                <li><strong>Zone B<\/strong> \u2014 Machines with vibration in this zone are normally considered acceptable for unrestricted long-term operation<\/li>\n                <li><strong>Zone C<\/strong> \u2014 Machines with vibration in this zone are normally considered unsatisfactory for long-term continuous operation; remedial action should be taken at the next convenient opportunity<\/li>\n                <li><strong>Zone D<\/strong> \u2014 Vibration values within this zone are normally considered severe enough to cause damage to the machine<\/li>\n            <\/ul>\n\n            <h3>Vibration Measurement<\/h3>\n            <p>The primary measurement parameter is vibration velocity in mm\/s RMS (root mean square), measured on the bearing housing in the frequency range 10\u20131000 Hz. This parameter has been shown to correlate well with machine condition for most rotating machinery.<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n\n            <h3>Zone Boundaries by Machine Group<\/h3>\n            <table class=\"vc-table\">\n                <thead><tr><th>Zone Boundary<\/th><th>Group 1<br><small>Large rigid<\/small><\/th><th>Group 2<br><small>Medium rigid<\/small><\/th><th>Group 3<br><small>Pumps<\/small><\/th><th>Group 4<br><small>Large flexible<\/small><\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>A\/B<\/td><td>2.3 mm\/s<\/td><td>1.4 mm\/s<\/td><td>2.3 mm\/s<\/td><td>3.5 mm\/s<\/td><\/tr>\n                    <tr><td>B\/C<\/td><td>4.5 mm\/s<\/td><td>2.8 mm\/s<\/td><td>4.5 mm\/s<\/td><td>7.1 mm\/s<\/td><\/tr>\n                    <tr><td>C\/D<\/td><td>7.1 mm\/s<\/td><td>4.5 mm\/s<\/td><td>7.1 mm\/s<\/td><td>11.0 mm\/s<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <div class=\"vc-info-box\">\n                <p><strong>\u2139\ufe0f Note:<\/strong> ISO 20816-1 provides general guidelines. For specific machine types, refer to the dedicated parts: ISO 20816-2 (steam turbines &gt;40 MW), ISO 20816-3 (industrial machines 15 kW\u201350 MW), ISO 20816-4 (gas turbines).<\/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> Zone boundaries are guideline values. Machine-specific acceptance criteria may be defined by the manufacturer. Always consider trending \u2014 a significant increase in vibration may warrant investigation even if the absolute level is within Zone B.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related Calculators -->\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-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\/vibration-iso20816-4-gas-turbines\/\">ISO 20816-4 \u2014 Gas Turbines<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-velocity\/\">Vibration Velocity (ISO 10816)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 21940)<\/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<!-- Promo -->\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>\n        Professional field balancing instruments and vibration analyzers. Evaluate machine condition on-site per ISO 20816. 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 -->\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 20816-1. 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-zones-iso20816-1';\n\n    \/* Zone boundaries: [A\/B, B\/C, C\/D] in mm\/s RMS *\/\n    var ZONES = {\n        '1': { name: 'Group 1 \u2014 Large rigid (>300 kW)', ab: 2.3, bc: 4.5, cd: 7.1 },\n        '2': { name: 'Group 2 \u2014 Medium rigid (15\u2013300 kW)', ab: 1.4, bc: 2.8, cd: 4.5 },\n        '3': { name: 'Group 3 \u2014 Pumps', ab: 2.3, bc: 4.5, cd: 7.1 },\n        '4': { name: 'Group 4 \u2014 Large flexible (>300 kW)', ab: 3.5, bc: 7.1, cd: 11.0 }\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, z) {\n        if (val <= z.ab) return 'A';\n        if (val <= z.bc) return 'B';\n        if (val <= z.cd) return 'C';\n        return 'D';\n    }\n\n    function calculate() {\n        var group = $('vc-group').value;\n        var measType = $('vc-meastype').value;\n        var val = parseFloat($('vc-value').value);\n\n        if (isNaN(val) || val < 0) {\n            $('vc-results').classList.remove('vc-visible');\n            return;\n        }\n\n        var z = ZONES[group];\n        var zone = getZone(val, z);\n        var unit = measType === 'velocity' ? 'mm\/s RMS' : '\u03bcm p-p';\n\n        \/\/ Update zone bar\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        \/\/ Zone bar labels\n        $('zl-a').textContent = '\u2264' + z.ab;\n        $('zl-b').textContent = z.ab + '\u2013' + z.bc;\n        $('zl-c').textContent = z.bc + '\u2013' + z.cd;\n        $('zl-d').textContent = '>' + z.cd;\n\n        \/\/ Primary zone result\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, 2) + ' <span class=\"vc-rcard-unit\">' + unit + '<\/span>';\n        $('vc-r-group').textContent = z.name;\n\n        \/\/ Boundary table\n        var tbody = $('vc-boundary-body');\n        tbody.innerHTML =\n            '<tr class=\"zt-a\"><td><strong>Zone A<\/strong><\/td><td>\u2264 ' + z.ab + ' ' + unit + '<\/td><td>' + ZONE_DESC.A + '<\/td><\/tr>' +\n            '<tr class=\"zt-b\"><td><strong>Zone B<\/strong><\/td><td>' + z.ab + ' \u2013 ' + z.bc + ' ' + unit + '<\/td><td>' + ZONE_DESC.B + '<\/td><\/tr>' +\n            '<tr class=\"zt-c\"><td><strong>Zone C<\/strong><\/td><td>' + z.bc + ' \u2013 ' + z.cd + ' ' + unit + '<\/td><td>' + ZONE_DESC.C + '<\/td><\/tr>' +\n            '<tr class=\"zt-d\"><td><strong>Zone D<\/strong><\/td><td>&gt; ' + z.cd + ' ' + unit + '<\/td><td>' + ZONE_DESC.D + '<\/td><\/tr>';\n\n        $('vc-results').classList.add('vc-visible');\n\n        \/\/ URL params\n        var u = new URL(window.location);\n        u.searchParams.set('group', group);\n        u.searchParams.set('type', measType);\n        u.searchParams.set('value', val);\n        history.replaceState(null, '', u.toString());\n\n        saveHistory({ group: group, type: measType, value: val, zone: zone, _summary: z.name + ', ' + val + ' ' + unit + ' \u2192 Zone ' + zone });\n    }\n\n    \/* Measurement type change *\/\n    $('vc-meastype').addEventListener('change', function() {\n        $('vc-value-hint').textContent = this.value === 'velocity' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n        calculate();\n    });\n\n    \/* Presets *\/\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-group').value = this.getAttribute('data-g');\n            $('vc-meastype').value = this.getAttribute('data-t');\n            $('vc-value').value = this.getAttribute('data-v');\n            $('vc-value-hint').textContent = this.getAttribute('data-t') === 'velocity' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n            calculate();\n        });\n    });\n\n    \/* Auto-calculate *\/\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    \/* Copy *\/\n    $('vc-copy-btn').addEventListener('click', function() {\n        var text = 'Vibration Zone Evaluation \u2014 ISO 20816-1\\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            'Machine Group: ' + $('vc-r-group').textContent + '\\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-zones-iso20816-1\/';\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    \/* Collapsible sections *\/\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    \/* FAQ *\/\n    var faqData = [\n        { q: 'What are vibration zones A, B, C, and D?', a: '<p>ISO 20816-1 defines four evaluation zones for assessing machine vibration:<\/p><ul><li><strong>Zone A<\/strong> \u2014 Vibration of newly commissioned machines. Excellent condition.<\/li><li><strong>Zone B<\/strong> \u2014 Acceptable for unrestricted long-term operation.<\/li><li><strong>Zone C<\/strong> \u2014 Not suitable for long-term operation. Plan remedial action at the next convenient opportunity.<\/li><li><strong>Zone D<\/strong> \u2014 Dangerous vibration levels that may cause damage. Immediate shutdown or corrective action required.<\/li><\/ul>' },\n        { q: 'How do I select the correct machine group?', a: '<p>Machine groups are defined by power rating and foundation type:<\/p><ul><li><strong>Group 1<\/strong> \u2014 Large machines over 300 kW on rigid foundations (e.g., large motors, generators)<\/li><li><strong>Group 2<\/strong> \u2014 Medium machines 15\u2013300 kW on rigid foundations (most common industrial motors and pumps)<\/li><li><strong>Group 3<\/strong> \u2014 Pumps including multistage, vertical, and special-purpose pumps<\/li><li><strong>Group 4<\/strong> \u2014 Large machines over 300 kW on flexible (soft) foundations<\/li><\/ul><p>If unsure, Group 2 is a conservative default for most medium-sized industrial machinery.<\/p>' },\n        { q: 'Should I use velocity or displacement measurement?', a: '<p><strong>Velocity (mm\/s RMS)<\/strong> is the standard and preferred parameter for vibration evaluation per ISO 20816-1. It correlates well with vibration severity across the typical frequency range of 10\u20131000 Hz.<\/p><p><strong>Displacement (\u03bcm peak-to-peak)<\/strong> is more useful for low-speed machines (&lt;600 RPM) where velocity values may be very small but displacement is significant. It is also used for shaft relative measurements on machines with fluid-film bearings.<\/p>' },\n        { q: 'What action should I take for Zone C?', a: '<p>Zone C means the machine is <strong>not suitable for long-term continuous operation<\/strong>. Recommended actions:<\/p><ul><li>Investigate root cause \u2014 check for unbalance, misalignment, bearing wear, looseness, resonance<\/li><li>Increase monitoring frequency (daily or continuous)<\/li><li>Schedule corrective maintenance at the next planned opportunity<\/li><li>The machine may continue operating for a limited period while preparing for repair<\/li><li>If vibration is trending upward toward Zone D, consider immediate action<\/li><\/ul>' },\n        { q: 'What is the difference between ISO 20816 and ISO 10816?', a: '<p>ISO 20816 is the modern replacement for ISO 10816. Key differences:<\/p><ul><li>ISO 20816-1 replaces ISO 10816-1 with the same zone boundaries and methodology<\/li><li>The new numbering reflects consolidation of the ISO 20816 series<\/li><li>ISO 20816 includes updated guidance on shaft vibration measurement alongside bearing housing vibration<\/li><li>The evaluation zone concept (A\/B\/C\/D) remains identical<\/li><\/ul><p>For practical purposes, the zone limits are the same and both standards can be used interchangeably.<\/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    \/* History *\/\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    \/* URL Params *\/\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        if (p.has('group')) $('vc-group').value = p.get('group');\n        if (p.has('type')) {\n            $('vc-meastype').value = p.get('type');\n            $('vc-value-hint').textContent = p.get('type') === 'velocity' ? '(mm\/s RMS)' : '(\u03bcm p-p)';\n        }\n        if (p.has('value')) $('vc-value').value = p.get('value');\n    }\n\n    \/* KaTeX *\/\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('v_{\\\\text{RMS}} = \\\\sqrt{\\\\frac{1}{T}\\\\int_0^T v(t)^2 \\\\, dt} \\\\quad [\\\\text{mm\/s}]', $('vc-katex-2'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    \/* Init *\/\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>Free online vibration zone evaluation calculator per ISO 20816-1. 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