{"id":100065,"date":"2026-02-15T20:14:37","date_gmt":"2026-02-15T20:14:37","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100065"},"modified":"2026-07-12T00:00:38","modified_gmt":"2026-07-12T00:00:38","slug":"cooling-tower-fan-vibration","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/hr\/calculators\/cooling-tower-fan-vibration\/","title":{"rendered":"Cooling Tower Fan Kinematics &#038; Unbalance Force Calculator"},"content":{"rendered":"\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Cooling Tower Fan Kinematics and Unbalance Force Calculator\",\"description\":\"Calculate shaft and blade-pass frequencies, blade-tip speed, force from a supplied residual unbalance, tip-clearance ratio and descriptive separation from a measured structural natural frequency.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/cooling-tower-fan-vibration\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"dateModified\":\"2026-07-12\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true}<\/script>\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Does this page set vibration alarm or trip limits?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. Limits depend on the applicable fan standard, category, power, installation, measurement quantity\/location and contractual or manufacturer criteria.\"}},{\"@type\":\"Question\",\"name\":\"Does frequency proximity prove resonance?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. The page reports arithmetic separation from a supplied measured natural frequency. Mode shape, damping, excitation orders and operating response require test and engineering review.\"}},{\"@type\":\"Question\",\"name\":\"Where does residual unbalance come from?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Enter an actual measured or specified residual unbalance in gram millimetres with traceable rotor scope and tolerance source. This page does not select a balance grade.\"}}]}<\/script>\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Cooling Tower Fan Kinematics\",\"item\":\"https:\/\/vibromera.eu\/calculators\/cooling-tower-fan-vibration\/\"}]}<\/script>\r\n<link rel=\"preconnect\" 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16px;font-size:13px;color:var(--vc-ink-muted)}.vc-footer a{color:var(--vc-accent);text-decoration:none}.vc-footer a:hover{text-decoration:underline}.vc-footer-links{margin-top:8px;font-size:12px}.vc-footer-links a{margin:0 8px}\r\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}\r\n.vc-faq-item{border:1px solid var(--vc-border-light);border-radius:var(--vc-radius);margin-bottom:8px;overflow:hidden}\r\n.vc-faq-q{width:100%;display:flex;align-items:center;justify-content:space-between;padding:14px 16px;border:none;background:transparent;cursor:pointer;font-family:var(--vc-font);font-size:14px;font-weight:600;text-align:left;color:var(--vc-ink);transition:background 0.15s}\r\n.vc-faq-q:hover{background:var(--vc-surface-alt)}\r\n.vc-faq-chevron{width:16px;height:16px;color:var(--vc-ink-muted);transition:transform 0.3s;flex-shrink:0}\r\n.vc-faq-item.vc-open .vc-faq-chevron{transform:rotate(180deg)}\r\n.vc-faq-a{max-height:0;overflow:hidden;transition:max-height 0.3s ease}\r\n.vc-faq-item.vc-open .vc-faq-a{max-height:2000px}\r\n.vc-faq-a-inner{padding:0 16px 14px;font-size:14px;color:var(--vc-ink-secondary);line-height:1.65}\r\n.vc-faq-a-inner p{margin:0 0 8px}\r\n@media print{.vc-section-body{max-height:none!important}.vc-results{max-height:none!important;padding:24px!important}.vc-promo{display:none!important}}\r\n<\/style>\r\n<div class=\"vc-calculator\" id=\"vc-ct-fan\"><header class=\"vc-header\"><p class=\"vc-header-eyebrow\">General kinematics and force arithmetic<\/p><h1 class=\"vc-header-title\">Cooling Tower Fan Kinematics Calculator<\/h1><p class=\"vc-header-subtitle\">Calculate shaft frequency, blade-pass frequency and blade-tip speed. Optional inputs add force from a supplied residual unbalance, tip-clearance ratio and descriptive frequency separation.<\/p><div class=\"vc-badges\"><span class=\"vc-badge\">No automatic balance grade<\/span><span class=\"vc-badge\">No generic alarm limits<\/span><span class=\"vc-badge\">SI units<\/span><\/div><\/header>\r\n<div class=\"vc-card\"><form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\"><div class=\"vc-form-grid\">\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-diam\">Fan diameter D <span class=\"vc-label-hint\">(m)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-diam\" inputmode=\"decimal\"><\/div>\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-blades\">Number of blades z <span class=\"vc-label-hint\">(positive integer)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-blades\" inputmode=\"numeric\"><\/div>\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-rpm\">Rotational speed n <span class=\"vc-label-hint\">(r\/min)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-rpm\" inputmode=\"decimal\"><\/div>\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-u\">Residual unbalance U <span class=\"vc-label-hint\">(g\u00b7mm; optional; \u22650)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-u\" inputmode=\"decimal\"><\/div>\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-fn\">Measured structural natural frequency f<sub>n<\/sub> <span class=\"vc-label-hint\">(Hz; optional)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-fn\" inputmode=\"decimal\"><\/div>\r\n<div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-clearance\">Measured radial tip clearance c <span class=\"vc-label-hint\">(mm; optional; \u22650)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-clearance\" inputmode=\"decimal\"><\/div>\r\n<\/div><p id=\"vc-error\" role=\"alert\" style=\"margin:.75rem 0 0;color:#b42318\"><\/p><div class=\"vc-warning-box\"><p style=\"margin:0\"><strong>Input boundary:<\/strong> U must represent the intended rotating assembly and reference axis. Natural frequency must be measured for the relevant structural mode. Clearance ratio is descriptive; the acceptable clearance comes from the fan manufacturer and verified operating deflection\/thermal envelope.<\/p><\/div><\/form>\r\n<div class=\"vc-results\" id=\"vc-results\"><div class=\"vc-results-head\"><h2 class=\"vc-results-title\">Calculated quantities<\/h2><button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">Copy<\/button><\/div><div class=\"vc-result-grid\">\r\n<div class=\"vc-rcard vc-rcard-primary\"><div class=\"vc-rcard-label\">Blade-pass frequency<\/div><div class=\"vc-rcard-value\" id=\"vc-r-bpf\">\u2014<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Shaft 1\u00d7 frequency<\/div><div class=\"vc-rcard-value\" id=\"vc-r-1x\">\u2014<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Blade-tip speed<\/div><div class=\"vc-rcard-value\" id=\"vc-r-tip\">\u2014<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Force amplitude from supplied U<\/div><div class=\"vc-rcard-value\" id=\"vc-r-force\">Not calculated<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Tip-clearance \/ diameter ratio<\/div><div class=\"vc-rcard-value\" id=\"vc-r-clearance\">Not calculated<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Separation: f<sub>n<\/sub> versus 1\u00d7<\/div><div class=\"vc-rcard-value\" id=\"vc-r-sep1\">Not calculated<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Separation: f<sub>n<\/sub> versus BPF<\/div><div class=\"vc-rcard-value\" id=\"vc-r-sepb\">Not calculated<\/div><\/div><\/div><p id=\"vc-r-note\" style=\"margin:0;color:var(--vc-ink-secondary)\"><\/p><\/div><\/div>\r\n<div class=\"vc-section vc-open\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udcd8<\/span><span class=\"vc-section-title\">Equations and standards boundary<\/span><\/span><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner vc-theory\"><div class=\"vc-formula-box\">f<sub>1\u00d7<\/sub>=n\/60; &nbsp; f<sub>BPF<\/sub>=zn\/60; &nbsp; v<sub>tip<\/sub>=\u03c0Dn\/60<\/div><div class=\"vc-formula-box\">\u03c9=2\u03c0n\/60; &nbsp; F=U\u00b710<sup>\u22126<\/sup>\u00b7\u03c9\u00b2<\/div><div class=\"vc-formula-box\">clearance ratio=100c\/(1000D); &nbsp; separation=100|f<sub>exc<\/sub>\u2212f<sub>n<\/sub>|\/f<sub>n<\/sub><\/div><p>These are general kinematic, geometric and rotating-force equations; they are not formulas mandated by ISO. With U in g\u00b7mm, 1 g\u00b7mm=10<sup>\u22126<\/sup> kg\u00b7m, so the force result is in newtons.<\/p><p><a href=\"https:\/\/www.iso.org\/standard\/37371.html\" target=\"_blank\" rel=\"noopener\">ISO 14694:2003\/Amd 1:2010<\/a> covers industrial-fan balance\/vibration specifications within stated power\/application limits and excludes foundation\/installation effects and effects on personnel, equipment or processes. It is under revision. <a href=\"https:\/\/www.iso.org\/standard\/37370.html\" target=\"_blank\" rel=\"noopener\">ISO 14695:2003\/Cor 1:2009<\/a> describes fan-vibration measurement and does not itself give interpretation criteria.<\/p><p><a href=\"https:\/\/www.iso.org\/standard\/54074.html\" target=\"_blank\" rel=\"noopener\">ISO 21940-11:2016<\/a> with <a href=\"https:\/\/www.iso.org\/standard\/78116.html\" target=\"_blank\" rel=\"noopener\">Amd 1:2022<\/a> establishes procedures\/tolerances for rotors with rigid behaviour and excludes flexible rotors. This page therefore does not choose G6.3, allocate permissible unbalance to planes or assert that a cooling-tower fan is rigid.<\/p><div class=\"vc-warning-box\"><p style=\"margin:0\"><strong>No risk classification:<\/strong> frequency proximity alone is not proof of resonance, and tip speed or clearance ratio alone is not proof of safe blade stress\/contact margin. Use manufacturer limits, modal\/operational testing, damping and operating-envelope review.<\/p><\/div><\/div><\/div><\/div>\r\n<div class=\"vc-section\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\u2753<\/span><span class=\"vc-section-title\">Frequently Asked Questions<\/span><\/span><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div><\/div><\/div><\/div><footer class=\"vc-footer\"><p>\u00a9 2024\u20132026 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a><\/p><p>General arithmetic only; no vibration, balance, stress, clearance or trip acceptance decision. Scientific review: July 2026.<\/p><\/footer><\/div>\r\n<script>(function(){'use strict';function $(i){return document.getElementById(i)}function num(v,zero){var s=String(v).trim().replace(\/\\s+\/g,'');if(!\/^[+]?(?:\\d+(?:[.,]\\d*)?|[.,]\\d+)$\/.test(s))return NaN;var x=Number(s.replace(',','.'));return Number.isFinite(x)&&(zero?x>=0:x>0)?x:NaN}function f(x){return x.toFixed(9).replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,'')}function calc(){var D=num($('vc-diam').value,false),zr=$('vc-blades').value.trim(),z=num(zr,false),n=num($('vc-rpm').value,false),ur=$('vc-u').value.trim(),U=ur===''?null:num(ur,true),fr=$('vc-fn').value.trim(),fn=fr===''?null:num(fr,false),cr=$('vc-clearance').value.trim(),c=cr===''?null:num(cr,true),any=[$('vc-diam').value,zr,$('vc-rpm').value,ur,fr,cr].some(function(v){return String(v).trim()});if(![D,z,n].every(Number.isFinite)||!Number.isInteger(z)||(ur!==''&&!Number.isFinite(U))||(fr!==''&&!Number.isFinite(fn))||(cr!==''&&!Number.isFinite(c))){$('vc-error').textContent=any?'Enter D>0,positive integer z,n>0; optional U\/c\u22650 and optional fn>0.':'';$('vc-results').classList.remove('vc-visible');return}var f1=n\/60,bpf=z*f1,tip=Math.PI*D*f1,w=2*Math.PI*f1;$('vc-error').textContent='';$('vc-r-1x').textContent=f(f1)+' Hz';$('vc-r-bpf').textContent=f(bpf)+' Hz';$('vc-r-tip').textContent=f(tip)+' m\/s';$('vc-r-force').textContent=U===null?'Not calculated':f(U*1e-6*w*w)+' N';$('vc-r-clearance').textContent=c===null?'Not calculated':f(100*c\/(1000*D))+' %';if(fn===null){$('vc-r-sep1').textContent='Not calculated';$('vc-r-sepb').textContent='Not calculated'}else{$('vc-r-sep1').textContent=f(Math.abs(f1-fn))+' Hz; '+f(100*Math.abs(f1-fn)\/fn)+' % of fn';$('vc-r-sepb').textContent=f(Math.abs(bpf-fn))+' Hz; '+f(100*Math.abs(bpf-fn)\/fn)+' % of fn'}$('vc-r-note').textContent='Separation is descriptive and normalized by supplied fn; no acceptance threshold is applied.';$('vc-results').classList.add('vc-visible');var u=new URL(location),v={fan_diameter_m:D,blade_count:z,rotational_speed_rpm:n};if(U===null)u.searchParams.delete('residual_unbalance_g_mm');else v.residual_unbalance_g_mm=U;if(fn===null)u.searchParams.delete('measured_structural_natural_frequency_hz');else v.measured_structural_natural_frequency_hz=fn;if(c===null)u.searchParams.delete('measured_radial_tip_clearance_mm');else v.measured_radial_tip_clearance_mm=c;Object.keys(v).forEach(function(k){u.searchParams.set(k,v[k])});history.replaceState(null,'',u.toString())}$('vc-form').addEventListener('input',calc);$('vc-copy-btn').addEventListener('click',function(){if(navigator.clipboard)navigator.clipboard.writeText($('vc-results').innerText)});document.querySelectorAll('.vc-section-toggle').forEach(function(b){b.addEventListener('click',function(){var s=this.closest('.vc-section');s.classList.toggle('vc-open');this.setAttribute('aria-expanded',s.classList.contains('vc-open'))})});var qa=[['Does this set alarm or trip limits?','No. Use the applicable fan category,measurement method,manufacturer and site criteria.'],['Does close frequency separation prove resonance?','No. Confirm relevant mode shape,damping and forced response by test and engineering review.'],['Why enter U directly?','It prevents an unverified balance-grade\/category choice. U must be measured or specified for the actual rotor scope.']];var l=$('vc-faq-list');qa.forEach(function(v){l.innerHTML+='<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\">'+v[0]+'<\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\"><p>'+v[1]+'<\/p><\/div><\/div><\/div>'});l.addEventListener('click',function(e){var b=e.target.closest('.vc-faq-q');if(b)b.closest('.vc-faq-item').classList.toggle('vc-open')});var p=new URLSearchParams(location.search),map={fan_diameter_m:'vc-diam',blade_count:'vc-blades',rotational_speed_rpm:'vc-rpm',residual_unbalance_g_mm:'vc-u',measured_structural_natural_frequency_hz:'vc-fn',measured_radial_tip_clearance_mm:'vc-clearance'};Object.keys(map).forEach(function(k){if(p.has(k))$(map[k]).value=p.get(k)});calc()})();<\/script>\r\n","protected":false},"excerpt":{"rendered":"<p>Calculate 1\u00d7 and blade-pass frequencies, tip speed, force from supplied residual unbalance, clearance ratio and separation from a measured natural frequency\u2014without generic alarm limits.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100065","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100065","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":2,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100065\/revisions"}],"predecessor-version":[{"id":102355,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100065\/revisions\/102355"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/media?parent=100065"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/categories?post=100065"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/tags?post=100065"}],"curies":[{"name":"radni list","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}