{"id":100201,"date":"2026-02-15T20:26:27","date_gmt":"2026-02-15T20:26:27","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100201"},"modified":"2026-02-15T20:26:27","modified_gmt":"2026-02-15T20:26:27","slug":"pump-cavitation-frequency","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/bn\/calculators\/pump-cavitation-frequency\/","title":{"rendered":"\u09aa\u09be\u09ae\u09cd\u09aa \u0995\u09cd\u09af\u09be\u09ad\u09bf\u099f\u09c7\u09b6\u09a8 \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf \u0985\u09a8\u09c1\u09ae\u09be\u09a8\u0995\u09be\u09b0\u09c0"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Pump Cavitation Frequency Estimator\",\"alternateName\":[\"Vane Pass Frequency Calculator\",\"Blade Pass Frequency Calculator\",\"BPF Calculator\",\"Pump Vibration Calculator\"],\"description\":\"Free online engineering calculator for pump cavitation frequency estimation. Calculate vane pass frequency (BPF), shaft frequency, expected cavitation frequency range, and NPSH margin with risk indicator.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/pump-cavitation-frequency\/\",\"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\":\"2025-02-15\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true,\"featureList\":[\"Vane pass frequency (BPF)\",\"Shaft frequency\",\"Cavitation frequency range\",\"NPSH margin calculation\",\"Risk level indicator\",\"Auto-calculation on input change\",\"URL parameter sharing\",\"Calculation history\"],\"keywords\":\"pump cavitation, vane pass frequency, blade pass frequency, BPF, NPSH, centrifugal pump, cavitation indicator\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What is vane pass frequency (BPF)?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Vane pass frequency (VPF), also called blade pass frequency (BPF), is the rate at which impeller blades pass a fixed point such as the volute cutwater. It equals the number of impeller vanes multiplied by shaft rotational frequency: BPF = Z \u00d7 RPM \/ 60. Elevated BPF amplitude indicates flow disturbances, recirculation, or cavitation.\"}},\n{\"@type\":\"Question\",\"name\":\"What frequencies indicate pump cavitation?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Cavitation produces broadband high-frequency noise typically in the 1\u2013100 kHz range due to the collapse of vapor bubbles. In addition, vane pass frequency (BPF) and its harmonics often increase in amplitude during cavitation. The combination of elevated broadband noise and increased BPF is a strong indicator of cavitation.\"}},\n{\"@type\":\"Question\",\"name\":\"What is NPSH margin and why does it matter?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"NPSH margin is the difference between NPSH available (NPSHa) and NPSH required (NPSHr). A positive margin means sufficient suction pressure to prevent cavitation. Industry guidelines typically recommend NPSHa \u2265 1.3\u00d7 NPSHr for general service, and NPSHa \u2265 2\u00d7 NPSHr for high-energy or critical pumps.\"}},\n{\"@type\":\"Question\",\"name\":\"How do I detect cavitation using vibration analysis?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Cavitation detection via vibration: (1) High-frequency broadband noise (ultrasonic range 20\u2013100 kHz), (2) Increased BPF harmonics amplitude, (3) Raised overall vibration levels, (4) Acoustic emission monitoring. Enveloping or demodulation techniques on acceleration data are effective for early cavitation detection.\"}},\n{\"@type\":\"Question\",\"name\":\"What causes pump cavitation?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Common causes include: insufficient suction head (NPSHa < NPSHr), high fluid temperature reducing vapor pressure, excessive flow rate, suction line restrictions (clogged strainer, partially closed valve), excessive suction lift, air entrainment, and operating far from best efficiency point (BEP). Recirculation cavitation occurs at very low flows.\"}}\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\":\"Pump Cavitation Frequency\",\"item\":\"https:\/\/vibromera.eu\/calculators\/pump-cavitation-frequency\/\"}\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 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}\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-pump-cavitation\">\n\n<!-- Header -->\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p>\n    <h1 class=\"vc-header-title\">Pump Cavitation Frequency Estimator<\/h1>\n    <p class=\"vc-header-subtitle\">Calculate vane pass frequency (BPF), shaft frequency, expected cavitation frequency range, and NPSH margin with risk level indicator for centrifugal pumps.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">Vane Pass \/ BPF<\/span>\n        <span class=\"vc-badge\">Cavitation<\/span>\n        <span class=\"vc-badge\">NPSH Margin<\/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-rpm\">Pump Speed <span class=\"vc-label-hint\">(RPM)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-rpm\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 2950\" value=\"2950\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-vanes\">Number of Vanes \/ Impeller Blades <span class=\"vc-label-hint\">(Z)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-vanes\" inputmode=\"numeric\" step=\"1\" min=\"1\" placeholder=\"e.g. 6\" value=\"6\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-npsha\">NPSH Available <span class=\"vc-label-hint\">(m, optional)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-npsha\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 8\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-npshr\">NPSH Required <span class=\"vc-label-hint\">(m, optional)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-npshr\" inputmode=\"decimal\" step=\"any\" min=\"0\" placeholder=\"e.g. 3\">\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-rpm=\"2950\" data-vanes=\"6\" data-npsha=\"8\" data-npshr=\"3\">Centrifugal 6 vanes 2950 RPM NPSHa=8 NPSHr=3<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-rpm=\"1475\" data-vanes=\"5\" data-npsha=\"\" data-npshr=\"\">Pump 5 vanes 1475 RPM<\/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        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Vane Pass Frequency (BPF)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-bpf\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Shaft Frequency (1\u00d7)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-fshaft\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Expected Cavitation Range<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-cavrange\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Number of Vanes<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-vanes\">\u2014<\/div>\n            <\/div>\n        <\/div>\n\n        <!-- NPSH Indicator -->\n        <div class=\"vc-npsh-indicator\" id=\"vc-npsh-box\" style=\"display:none;\">\n            <div class=\"vc-npsh-label\">NPSH Margin Analysis<\/div>\n            <div class=\"vc-npsh-value\" id=\"vc-npsh-value\">\u2014<\/div>\n            <div class=\"vc-npsh-risk\" id=\"vc-npsh-risk\">\u2014<\/div>\n        <\/div>\n\n        <!-- BPF Harmonics Table -->\n        <h3 style=\"font-family:var(--vc-display);font-size:17px;font-weight:700;margin:20px 0 10px;\">BPF Harmonics<\/h3>\n        <table class=\"vc-table\" id=\"vc-harmonics-table\">\n            <thead><tr><th>Harmonic<\/th><th>Frequency (Hz)<\/th><th>CPM<\/th><th>Note<\/th><\/tr><\/thead>\n            <tbody id=\"vc-harmonics-body\"><\/tbody>\n        <\/table>\n\n        <div class=\"vc-info-box\" style=\"margin-top:14px;\">\n            <p><strong>Cavitation signature:<\/strong> Broadband high-frequency noise (typically 1\u2013100 kHz) combined with elevated BPF harmonics. Use ultrasonic or high-frequency acceleration measurements for early detection.<\/p>\n        <\/div>\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>Vane Pass Frequency (BPF)<\/h3>\n            <p>The vane pass frequency (also called blade pass frequency, BPF) is the rate at which impeller blades pass a fixed point (such as the volute cutwater):<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n            <ul>\n                <li><strong>Z<\/strong> \u2014 number of impeller vanes (blades)<\/li>\n                <li><strong>n<\/strong> \u2014 pump shaft speed (RPM)<\/li>\n            <\/ul>\n\n            <h3>Cavitation Frequency Characteristics<\/h3>\n            <p>Cavitation in centrifugal pumps produces a characteristic broadband high-frequency noise due to the implosion of vapor bubbles:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n            <p>In addition to broadband noise, cavitation typically causes an increase in BPF amplitude and its harmonics (2\u00d7BPF, 3\u00d7BPF).<\/p>\n\n            <h3>NPSH Margin<\/h3>\n            <p>The NPSH (Net Positive Suction Head) margin indicates the safety factor against cavitation:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-3\"><\/div>\n\n            <table class=\"vc-table\">\n                <thead><tr><th>NPSH Ratio (NPSHa\/NPSHr)<\/th><th>Risk Level<\/th><th>Recommendation<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>&gt; 2.0<\/td><td style=\"color:var(--vc-green);font-weight:600;\">Low<\/td><td>Adequate margin \u2014 no cavitation expected<\/td><\/tr>\n                    <tr><td>1.3 \u2013 2.0<\/td><td style=\"color:var(--vc-yellow);font-weight:600;\">Moderate<\/td><td>Acceptable for general service, monitor<\/td><\/tr>\n                    <tr><td>1.0 \u2013 1.3<\/td><td style=\"color:var(--vc-red);font-weight:600;\">High<\/td><td>Insufficient margin \u2014 cavitation likely<\/td><\/tr>\n                    <tr><td>&lt; 1.0<\/td><td style=\"color:var(--vc-red);font-weight:600;\">Critical<\/td><td>NPSHa below NPSHr \u2014 cavitation certain<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <div class=\"vc-example-box\">\n                <div class=\"vc-example-title\">Example \u2014 Centrifugal Pump 6 Vanes at 2950 RPM<\/div>\n                <p><strong>Given:<\/strong> Z = 6, n = 2950 RPM, NPSHa = 8 m, NPSHr = 3 m<\/p>\n                <p>Shaft freq = 2950 \/ 60 = <strong>49.17 Hz<\/strong><\/p>\n                <p>BPF = 6 \u00d7 2950 \/ 60 = <strong>295.0 Hz<\/strong><\/p>\n                <p>NPSH margin = 8 \u2212 3 = <strong>5.0 m<\/strong><\/p>\n                <p>NPSH ratio = 8 \/ 3 = <strong>2.67<\/strong> \u2014 Low risk<\/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 Note:<\/strong> Cavitation noise is broadband and primarily in the ultrasonic range (>20 kHz). Standard vibration sensors (accelerometers up to 10\u201315 kHz) may not capture it. Use high-frequency accelerometers, ultrasonic sensors, or acoustic emission transducers for reliable cavitation detection.<\/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\/bearing-defect-frequencies\/\">Bearing Defect Frequencies<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/journal-bearing-frequencies\/\">Journal Bearing Frequencies<\/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 1940)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/belt-defect-frequencies\/\">Belt Defect Frequencies<\/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 vibration analysis instruments for pump diagnostics. Detect cavitation, unbalance, and bearing defects 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 -->\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;\">Pump cavitation frequency reference. 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 = 'pump-cavitation-frequency';\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    \/* \u2500\u2500 CALCULATION \u2500\u2500 *\/\n    function calculate() {\n        var rpm = parseFloat($('vc-rpm').value);\n        var vanes = parseInt($('vc-vanes').value);\n        var npsha = parseFloat($('vc-npsha').value);\n        var npshr = parseFloat($('vc-npshr').value);\n\n        if (!rpm || rpm <= 0 || !vanes || vanes <= 0) {\n            $('vc-results').classList.remove('vc-visible');\n            return;\n        }\n\n        \/\/ Shaft frequency\n        var fShaft = rpm \/ 60;\n        \/\/ BPF = Z \u00d7 RPM \/ 60\n        var bpf = vanes * rpm \/ 60;\n\n        \/\/ Display\n        $('vc-r-bpf').innerHTML = fmt(bpf, 2) + ' <span class=\"vc-rcard-unit\">Hz<\/span> <span class=\"vc-rcard-unit\">(' + fmt(bpf * 60, 0) + ' CPM)<\/span>';\n        $('vc-r-fshaft').innerHTML = fmt(fShaft, 3) + ' <span class=\"vc-rcard-unit\">Hz<\/span> <span class=\"vc-rcard-unit\">(' + fmt(rpm, 0) + ' CPM)<\/span>';\n        $('vc-r-cavrange').innerHTML = '1 \u2013 100 <span class=\"vc-rcard-unit\">kHz<\/span> <span class=\"vc-rcard-unit\">(broadband)<\/span>';\n        $('vc-r-vanes').innerHTML = vanes + ' <span class=\"vc-rcard-unit\">blades<\/span>';\n\n        \/\/ NPSH indicator\n        var npshBox = $('vc-npsh-box');\n        if (!isNaN(npsha) && npsha > 0 && !isNaN(npshr) && npshr > 0) {\n            var margin = npsha - npshr;\n            var ratio = npsha \/ npshr;\n            var riskClass, riskText;\n\n            if (ratio < 1.0) {\n                riskClass = 'vc-risk-high';\n                riskText = 'CRITICAL \u2014 NPSHa is below NPSHr. Cavitation is certain. Immediate action required.';\n            } else if (ratio < 1.3) {\n                riskClass = 'vc-risk-high';\n                riskText = 'HIGH RISK \u2014 Insufficient NPSH margin. Cavitation is likely under varying conditions.';\n            } else if (ratio <= 2.0) {\n                riskClass = 'vc-risk-moderate';\n                riskText = 'MODERATE \u2014 Acceptable for general service. Monitor for cavitation indicators. Consider increasing margin for critical applications.';\n            } else {\n                riskClass = 'vc-risk-low';\n                riskText = 'LOW RISK \u2014 Adequate NPSH margin. No cavitation expected under normal conditions.';\n            }\n\n            npshBox.className = 'vc-npsh-indicator ' + riskClass;\n            $('vc-npsh-value').innerHTML = 'Margin: ' + fmt(margin, 2) + ' m &nbsp;|&nbsp; Ratio: ' + fmt(ratio, 2) + ' (NPSHa\/NPSHr)';\n            $('vc-npsh-risk').textContent = riskText;\n            npshBox.style.display = '';\n        } else {\n            npshBox.style.display = 'none';\n        }\n\n        \/\/ Harmonics table\n        var tbody = $('vc-harmonics-body');\n        tbody.innerHTML = '';\n        \/\/ Shaft frequency\n        tbody.innerHTML += '<tr><td><strong>1\u00d7 Shaft<\/strong><\/td><td>' + fmt(fShaft, 3) + ' Hz<\/td><td>' + fmt(rpm, 0) + '<\/td><td>Shaft rotational frequency<\/td><\/tr>';\n        var bpfNotes = [\n            'Fundamental BPF \u2014 blade\/cutwater interaction',\n            '2nd BPF harmonic \u2014 flow recirculation',\n            '3rd BPF harmonic \u2014 elevated = cavitation indicator',\n            '4th BPF harmonic'\n        ];\n        for (var i = 1; i <= 4; i++) {\n            var f = bpf * i;\n            tbody.innerHTML += '<tr><td><strong>' + i + '\u00d7 BPF<\/strong><\/td><td>' + fmt(f, 2) + ' Hz<\/td><td>' + fmt(f * 60, 0) + '<\/td><td>' + bpfNotes[i - 1] + '<\/td><\/tr>';\n        }\n\n        $('vc-results').classList.add('vc-visible');\n\n        \/\/ URL params\n        var u = new URL(window.location);\n        u.searchParams.set('rpm', rpm);\n        u.searchParams.set('vanes', vanes);\n        if (!isNaN(npsha) && npsha > 0) u.searchParams.set('npsha', npsha);\n        if (!isNaN(npshr) && npshr > 0) u.searchParams.set('npshr', npshr);\n        history.replaceState(null, '', u.toString());\n\n        \/\/ History\n        var summary = vanes + ' vanes, ' + rpm + ' RPM';\n        if (!isNaN(npsha) && npsha > 0) summary += ', NPSHa=' + npsha;\n        if (!isNaN(npshr) && npshr > 0) summary += ', NPSHr=' + npshr;\n        saveHistory({ rpm: rpm, vanes: vanes, npsha: npsha || '', npshr: npshr || '', _summary: summary });\n    }\n\n    \/* \u2500\u2500 PRESETS \u2500\u2500 *\/\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-rpm').value = this.getAttribute('data-rpm');\n            $('vc-vanes').value = this.getAttribute('data-vanes');\n            $('vc-npsha').value = this.getAttribute('data-npsha') || '';\n            $('vc-npshr').value = this.getAttribute('data-npshr') || '';\n            calculate();\n        });\n    });\n\n    \/* \u2500\u2500 AUTO-CALCULATE \u2500\u2500 *\/\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    \/* \u2500\u2500 COPY \u2500\u2500 *\/\n    $('vc-copy-btn').addEventListener('click', function() {\n        var text = 'Pump Cavitation Frequency Estimation\\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            'Pump Speed: ' + $('vc-rpm').value + ' RPM\\n' +\n            'Vanes: ' + $('vc-vanes').value + '\\n' +\n            'Vane Pass Freq (BPF): ' + $('vc-r-bpf').textContent + '\\n' +\n            'Shaft Freq: ' + $('vc-r-fshaft').textContent + '\\n' +\n            'Cavitation Range: ' + $('vc-r-cavrange').textContent + '\\n';\n\n        var npshVal = $('vc-npsh-value');\n        if ($('vc-npsh-box').style.display !== 'none') {\n            text += 'NPSH: ' + npshVal.textContent + '\\n';\n        }\n\n        text += '\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\/pump-cavitation-frequency\/';\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    \/* \u2500\u2500 COLLAPSIBLE SECTIONS \u2500\u2500 *\/\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    \/* \u2500\u2500 FAQ \u2500\u2500 *\/\n    var faqData = [\n        { q: 'What is vane pass frequency (BPF)?', a: '<p>Vane pass frequency (VPF), also called blade pass frequency (BPF), is the rate at which impeller blades pass a fixed point such as the volute cutwater or diffuser vane. It equals the number of impeller blades multiplied by the shaft rotational frequency:<\/p><p>BPF = Z \u00d7 RPM \/ 60<\/p><p>Elevated BPF amplitude indicates flow disturbances, recirculation, cavitation, or excessive gap between impeller and cutwater.<\/p>' },\n        { q: 'What frequencies indicate pump cavitation?', a: '<p>Cavitation produces a characteristic broadband high-frequency noise typically in the 1\u2013100 kHz range due to the collapse of vapor bubbles. Key indicators:<\/p><ul><li>Broadband noise increase in the ultrasonic range<\/li><li>Elevated BPF amplitude and harmonics<\/li><li>Random, crackling noise (audible in severe cases)<\/li><li>Increased overall acceleration levels (gE or HFD)<\/li><\/ul><p>The combination of elevated broadband noise and increased BPF harmonics is a strong indicator of active cavitation.<\/p>' },\n        { q: 'What is NPSH margin and why does it matter?', a: '<p>NPSH margin is the difference between NPSH available (NPSHa) and NPSH required (NPSHr). A positive margin means sufficient suction pressure to prevent cavitation.<\/p><p>Industry guidelines:<\/p><ul><li><strong>NPSHa \u2265 2\u00d7 NPSHr<\/strong> \u2014 recommended for critical or high-energy pumps<\/li><li><strong>NPSHa \u2265 1.3\u00d7 NPSHr<\/strong> \u2014 minimum for general service<\/li><li><strong>NPSHa < NPSHr<\/strong> \u2014 cavitation is certain<\/li><\/ul>' },\n        { q: 'How do I detect cavitation using vibration analysis?', a: '<p>Cavitation detection methods:<\/p><ul><li><strong>High-frequency acceleration<\/strong> \u2014 use accelerometers with >10 kHz range, look for broadband noise increase<\/li><li><strong>Ultrasonic sensors<\/strong> \u2014 20\u2013100 kHz range, most sensitive to cavitation onset<\/li><li><strong>Envelope\/demodulation analysis<\/strong> \u2014 reveals cavitation impacts modulating BPF<\/li><li><strong>Acoustic emission<\/strong> \u2014 detects stress waves from bubble collapse<\/li><li><strong>Audible noise<\/strong> \u2014 severe cavitation sounds like gravel or marbles<\/li><\/ul>' },\n        { q: 'What causes pump cavitation?', a: '<p>Common causes include:<\/p><ul><li>Insufficient suction head (NPSHa < NPSHr)<\/li><li>High fluid temperature reducing vapor pressure<\/li><li>Excessive flow rate (operating far right of BEP)<\/li><li>Suction line restrictions (clogged strainer, partially closed valve)<\/li><li>Excessive suction lift<\/li><li>Air entrainment or vortexing at suction<\/li><li>Operating far from best efficiency point (BEP)<\/li><li>Recirculation cavitation at very low flows<\/li><\/ul>' }\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    \/* \u2500\u2500 HISTORY \u2500\u2500 *\/\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    \/* \u2500\u2500 URL PARAMS \u2500\u2500 *\/\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        if (p.get('rpm')) $('vc-rpm').value = p.get('rpm');\n        if (p.get('vanes')) $('vc-vanes').value = p.get('vanes');\n        if (p.get('npsha')) $('vc-npsha').value = p.get('npsha');\n        if (p.get('npshr')) $('vc-npshr').value = p.get('npshr');\n    }\n\n    \/* \u2500\u2500 KATEX \u2500\u2500 *\/\n    function renderFormulas() {\n        try {\n            katex.render('f_{BPF} = \\\\frac{Z \\\\times n}{60} \\\\quad [\\\\text{Hz}]', $('vc-katex-1'), { displayMode: true, throwOnError: false });\n            katex.render('f_{cavitation} \\\\approx 1 \\\\ldots 100 \\\\text{ kHz} \\\\quad \\\\text{(broadband random noise)}', $('vc-katex-2'), { displayMode: true, throwOnError: false });\n            katex.render('\\\\text{NPSH margin} = \\\\text{NPSH}_a - \\\\text{NPSH}_r \\\\quad [\\\\text{m}]', $('vc-katex-3'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    \/* \u2500\u2500 INIT \u2500\u2500 *\/\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>\u09aa\u09be\u09ae\u09cd\u09aa \u0995\u09cd\u09af\u09be\u09ad\u09bf\u099f\u09c7\u09b6\u09a8 \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf \u0985\u09a8\u09c1\u09ae\u09be\u09a8 \u0995\u09b0\u09be\u09b0 \u099c\u09a8\u09cd\u09af \u09ac\u09bf\u09a8\u09be\u09ae\u09c2\u09b2\u09cd\u09af\u09c7 \u0985\u09a8\u09b2\u09be\u0987\u09a8 \u0995\u09cd\u09af\u09be\u09b2\u0995\u09c1\u09b2\u09c7\u099f\u09b0\u0964 \u09ad\u09c7\u09a8 \u09aa\u09cd\u09af\u09be\u09b8 \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf (BPF), \u09b6\u09cd\u09af\u09be\u09ab\u099f \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf, \u09aa\u09cd\u09b0\u09a4\u09cd\u09af\u09be\u09b6\u09bf\u09a4 \u0995\u09cd\u09af\u09be\u09ad\u09bf\u099f\u09c7\u09b6\u09a8 \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf \u09aa\u09b0\u09bf\u09b8\u09c0\u09ae\u09be \u098f\u09ac\u0982 \u099d\u09c1\u0981\u0995\u09bf \u09b8\u09c2\u099a\u0995 \u09b8\u09b9 NPSH \u09ae\u09be\u09b0\u09cd\u099c\u09bf\u09a8 \u0997\u09a3\u09a8\u09be \u0995\u09b0\u09c1\u09a8\u0964<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100201","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100201","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100201\/revisions"}],"predecessor-version":[{"id":100516,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100201\/revisions\/100516"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/media?parent=100201"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/categories?post=100201"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/tags?post=100201"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}