{"id":100217,"date":"2026-02-15T20:27:54","date_gmt":"2026-02-15T20:27:54","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100217"},"modified":"2026-07-15T00:13:54","modified_gmt":"2026-07-15T00:13:54","slug":"safety-valve-sizing","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/az\/calculators\/safety-valve-sizing\/","title":{"rendered":"Documented Pressure-Relief Area Comparison Worksheet"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Documented Pressure-Relief Area Comparison Worksheet\",\"description\":\"Compare one controlled required effective discharge area with one compatible certified candidate area. 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th{background:var(--soft)}.vbm217-limit{padding:14px;border-left:4px solid var(--warn);background:var(--warnbg)}.vbm217-footer{margin-top:24px;padding:16px;border-top:1px solid var(--line);color:var(--muted);font-size:13px}\n@media(max-width:720px){.vbm217-grid,.vbm217-result-grid{grid-template-columns:1fr}.vbm217-result.primary,.vbm217-field.full,.vbm217-fieldset{grid-column:1}.vbm217-body,.vbm217-section,.vbm217-hero{padding:16px}.vbm217-actions .vbm217-btn{flex:1 1 140px}}\n<\/style>\n\n<main class=\"vbm217\" aria-labelledby=\"vbm217-title\">\n  <header class=\"vbm217-hero\">\n    <div class=\"vbm217-kicker\">Controlled area record \u00b7 non-normative arithmetic<\/div>\n    <h1 id=\"vbm217-title\">Documented Pressure-Relief Area Comparison Worksheet<\/h1>\n    <p class=\"vbm217-lead\">Compare one required effective discharge area from an approved governing calculation with one compatible certified candidate area. The two values must describe the same relief case, fluid regime, coefficient basis and unit.<\/p>\n    <div class=\"vbm217-badges\"><span class=\"vbm217-badge\">no sizing formula<\/span><span class=\"vbm217-badge\">no default coefficients<\/span><span class=\"vbm217-badge\">no API letter table<\/span><span class=\"vbm217-badge\">no compliance verdict<\/span><\/div>\n    <div class=\"vbm217-alert\"><strong>This worksheet does not size or select a pressure-relief device.<\/strong> It does not establish the relieving load, choose an API\/ISO\/ASME equation, determine allowable overpressure, calculate back-pressure or viscosity corrections, certify capacity, or verify inlet\/outlet installation.<\/div>\n  <\/header>\n\n  <section class=\"vbm217-card\" aria-labelledby=\"vbm217-input-title\">\n    <div class=\"vbm217-card-h\"><h2 id=\"vbm217-input-title\">Controlled comparison record<\/h2><p>Enter areas only after a competent calculation and a certified manufacturer record have established a compatible basis.<\/p><\/div>\n    <div class=\"vbm217-body\">\n      <form id=\"vbm217-form\" novalidate>\n        <div class=\"vbm217-grid\">\n          <div class=\"vbm217-field full\"><label for=\"vbm217-unit\">Shared effective-area unit<\/label><select id=\"vbm217-unit\"><option value=\"\">Select the controlled unit<\/option><option value=\"mm2\">square millimetres (mm\u00b2)<\/option><option value=\"in2\">square inches (in\u00b2)<\/option><\/select><span class=\"vbm217-hint\">Changing the unit clears both areas and the result; this worksheet performs no hidden unit conversion.<\/span><\/div>\n          <div class=\"vbm217-field\"><label for=\"vbm217-required\">Required effective discharge area Areq<\/label><input id=\"vbm217-required\" inputmode=\"decimal\" autocomplete=\"off\" placeholder=\"blank\"><span class=\"vbm217-hint\">Positive area copied from the approved governing calculation.<\/span><\/div>\n          <div class=\"vbm217-field\"><label for=\"vbm217-certified\">Certified candidate effective area Acert<\/label><input id=\"vbm217-certified\" inputmode=\"decimal\" autocomplete=\"off\" placeholder=\"blank\"><span class=\"vbm217-hint\">Positive compatible area from the controlled valve certificate\/catalog\/type-test record.<\/span><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-designation\">Manufacturer, model and orifice\/designation<\/label><input id=\"vbm217-designation\" autocomplete=\"off\" placeholder=\"manufacturer; series\/model; exact designation\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-calc-source\">Required-area calculation report, ID and revision<\/label><input id=\"vbm217-calc-source\" autocomplete=\"off\" placeholder=\"approved calculation\/report identifier and revision\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-code\">Governing code\/standard, exact edition, addenda and jurisdiction<\/label><input id=\"vbm217-code\" autocomplete=\"off\" placeholder=\"exact controlled document set; do not enter only API 520 or ISO 4126\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-clause\">Sizing equation, clause\/table and licensed-source reference<\/label><input id=\"vbm217-clause\" autocomplete=\"off\" placeholder=\"equation and clause actually used; licensed document\/control reference\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-load\">Relieving scenario, required load and load-derivation revision<\/label><input id=\"vbm217-load\" autocomplete=\"off\" placeholder=\"credible case; mass\/volumetric load; source model and revision\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-fluid\">Fluid composition, phase and flow model<\/label><input id=\"vbm217-fluid\" autocomplete=\"off\" placeholder=\"gas\/vapour, steam, liquid, flashing\/two-phase\/reacting; composition and property source\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-state\">Relieving inlet state and upstream-loss record<\/label><input id=\"vbm217-state\" autocomplete=\"off\" placeholder=\"flowing absolute pressure, temperature, density\/M\/Z\/k or other required properties; inlet loss basis\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-backpressure\">Back-pressure, discharge configuration and correction record<\/label><input id=\"vbm217-backpressure\" autocomplete=\"off\" placeholder=\"superimposed\/built-up back pressure; conventional\/balanced\/pilot; certified correction source\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-coefficients\">Discharge\/capacity and combination-correction coefficients<\/label><input id=\"vbm217-coefficients\" autocomplete=\"off\" placeholder=\"every coefficient, value, basis, source and applicability\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-cert-source\">Certified area\/capacity source and revision<\/label><input id=\"vbm217-cert-source\" autocomplete=\"off\" placeholder=\"manufacturer certificate, datasheet, catalog or type-test record and revision\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-installation\">Installation, inlet\/outlet and certification boundary<\/label><input id=\"vbm217-installation\" autocomplete=\"off\" placeholder=\"line losses, discharge system, stability, materials, temperature, certification and set-pressure limits\"><\/div>\n          <div class=\"vbm217-field full\"><label for=\"vbm217-record-id\">Comparison record ID and intended decision boundary<\/label><input id=\"vbm217-record-id\" autocomplete=\"off\" placeholder=\"record ID; comparison purpose; reviewer boundary\"><\/div>\n          <fieldset class=\"vbm217-fieldset\">\n            <legend>Required compatibility confirmation<\/legend>\n            <label class=\"vbm217-check\"><input type=\"checkbox\" id=\"vbm217-c1\"><span>Areq came from the approved governing method for the recorded credible scenario and required relieving load; it was not calculated by this page.<\/span><\/label>\n            <label class=\"vbm217-check\"><input type=\"checkbox\" id=\"vbm217-c2\"><span>Acert is a certified effective discharge area or capacity-derived area on the same basis, not merely a nominal bore, seat diameter or geometric opening.<\/span><\/label>\n            <label class=\"vbm217-check\"><input type=\"checkbox\" id=\"vbm217-c3\"><span>The unit, fluid regime, inlet state, pressure convention, coefficient set, corrections, valve configuration and certification basis are compatible and no factor is missing or applied twice.<\/span><\/label>\n            <label class=\"vbm217-check\"><input type=\"checkbox\" id=\"vbm217-c4\"><span>I will not use this arithmetic comparison as a sizing, selection, installation, certification, PASS\/FAIL or code-compliance decision without independent competent review.<\/span><\/label>\n          <\/fieldset>\n        <\/div>\n        <div class=\"vbm217-actions\"><button class=\"vbm217-btn\" type=\"submit\">Calculate documented area comparison<\/button><button class=\"vbm217-btn secondary\" type=\"button\" id=\"vbm217-reset\">Clear<\/button><\/div>\n        <div class=\"vbm217-error\" id=\"vbm217-error\" role=\"alert\"><\/div>\n      <\/form>\n    <\/div>\n  <\/section>\n\n  <section class=\"vbm217-card vbm217-results\" id=\"vbm217-results\" aria-live=\"polite\" aria-labelledby=\"vbm217-results-title\">\n    <div class=\"vbm217-card-h\"><h2 id=\"vbm217-results-title\">Arithmetic comparison result<\/h2><p id=\"vbm217-result-context\"><\/p><\/div>\n    <div class=\"vbm217-body\">\n      <div class=\"vbm217-result-grid\">\n        <div class=\"vbm217-result primary\"><div class=\"vbm217-result-label\">Candidate-to-required area ratio Q = Acert\/Areq<\/div><div class=\"vbm217-result-value\" id=\"vbm217-r-ratio\">\u2014<\/div><div class=\"vbm217-result-note\">Dimensionless arithmetic only; not a code acceptance ratio.<\/div><\/div>\n        <div class=\"vbm217-result\"><div class=\"vbm217-result-label\">Arithmetic area utilization U = Areq\/Acert<\/div><div class=\"vbm217-result-value\" id=\"vbm217-r-util\">\u2014<\/div><div class=\"vbm217-result-note\">Not a certified capacity utilization or compliance value.<\/div><\/div>\n        <div class=\"vbm217-result\"><div class=\"vbm217-result-label\">Signed area difference Acert \u2212 Areq<\/div><div class=\"vbm217-result-value\" id=\"vbm217-r-difference\">\u2014<\/div><div class=\"vbm217-result-note\" id=\"vbm217-r-values\"><\/div><\/div>\n        <div class=\"vbm217-result\"><div class=\"vbm217-result-label\">Relative area difference (Acert \u2212 Areq)\/Areq<\/div><div class=\"vbm217-result-value\" id=\"vbm217-r-relative\">\u2014<\/div><div class=\"vbm217-result-note\">Pure arithmetic; no allowance,capacity margin or certified tolerance is inferred.<\/div><\/div>\n      <\/div>\n      <div class=\"vbm217-boundary\"><strong>No selection verdict is produced.<\/strong> A larger recorded area does not prove adequate certified capacity,stable operation,acceptable blowdown,compatible valve construction or compliant installation.<\/div>\n    <\/div>\n  <\/section>\n\n  <section class=\"vbm217-section\" aria-labelledby=\"vbm217-model-title\">\n    <h2 id=\"vbm217-model-title\">Formula and model boundary<\/h2>\n    <p>For positive compatible effective areas expressed in one shared unit:<\/p>\n    <div class=\"vbm217-equation\">Q = Acert\/Areq \u00b7 U = Areq\/Acert = 1\/Q \u00b7 \u0394A = Acert\u2212Areq \u00b7 \u03b4 = (Acert\u2212Areq)\/Areq<\/div>\n    <p>Q, U and \u03b4 are dimensionless; \u0394A retains the selected area unit. These identities do not establish a relief load, discharge capacity or regulatory acceptance criterion.<\/p>\n    <h3>Why the former sizing formulas and presets were removed<\/h3>\n    <p>The previous page combined gas\/vapour and steam, assumed fixed discharge coefficients, invented a generic back-pressure factor, used a fixed 10% overpressure and treated water density as universal. It did not control critical versus subcritical flow, phase behaviour, certified coefficient basis, inlet losses, built-up and superimposed back pressure, viscosity\/two-phase behaviour, installation or jurisdiction. Those omissions can change a required area materially and cannot be repaired by relabelling one simplified equation.<\/p>\n    <p>API 520 Part I and the relevant ISO 4126 parts are controlled standards with application-specific procedures and data. Their closed equations, coefficients and tables are not reproduced or inferred here. A competent engineer with the licensed governing documents and manufacturer data must produce Areq and verify Acert.<\/p>\n    <h3>Exact numerical checks<\/h3>\n    <div class=\"vbm217-table-wrap\"><table><thead><tr><th>Inputs<\/th><th>Q<\/th><th>U<\/th><th>\u0394A<\/th><th>\u03b4<\/th><\/tr><\/thead><tbody><tr><td>Areq=100 mm\u00b2; Acert=120 mm\u00b2<\/td><td>1.2<\/td><td>83.3333333333%<\/td><td>20 mm\u00b2<\/td><td>20%<\/td><\/tr><tr><td>Areq=0.5 in\u00b2; Acert=0.75 in\u00b2<\/td><td>1.5<\/td><td>66.6666666667%<\/td><td>0.25 in\u00b2<\/td><td>50%<\/td><\/tr><\/tbody><\/table><\/div>\n\n    <h3>Official source status and classification<\/h3>\n    <div class=\"vbm217-table-wrap\"><table><thead><tr><th>Source<\/th><th>Current public status inspected<\/th><th>Use on this page<\/th><\/tr><\/thead><tbody>\n      <tr><td>API Standard 520 Part I<\/td><td>10th edition, published 2020-10-28; official API title is sizing and selection of pressure-relieving devices in refineries<\/td><td>Scope\/lifecycle only. No formula or coefficient is copied.<\/td><\/tr>\n      <tr><td>API Standard 526<\/td><td>8th edition, published 2023-08-14; flanged steel pressure-relief valves<\/td><td>No built-in orifice-letter table. Use the controlled current standard and manufacturer record.<\/td><\/tr>\n      <tr><td>ISO 4126-1:2013 + Amd 1:2016<\/td><td>Edition 3, published and confirmed in 2025<\/td><td>The official abstract calls Part 1 a product standard and says it is not applicable to applications of safety valves.<\/td><\/tr>\n      <tr><td>ISO 4126-7:2013 + Amd 1:2016<\/td><td>Edition 2, published and confirmed in 2025<\/td><td>Common data for Parts 1\u20136; licensed content is required for technical use.<\/td><\/tr>\n      <tr><td>ISO 4126-9:2008<\/td><td>Edition 1, published and confirmed in 2026<\/td><td>Application\/installation of safety devices for static pressure equipment; its public scope assumes single-phase discharge and points two-phase conditions to ISO 4126-10.<\/td><\/tr>\n    <\/tbody><\/table><\/div>\n    <p><a href=\"https:\/\/www.api.org\/products-and-services\/standards\/important-standards-announcements\/520parti\" target=\"_blank\" rel=\"noopener\">API 520 Part I official announcement<\/a> \u00b7 <a href=\"https:\/\/www.api.org\/products-and-services\/standards\/standards-plan\" target=\"_blank\" rel=\"noopener\">API official standards plan<\/a> \u00b7 <a href=\"https:\/\/www.iso.org\/standard\/50826.html\" target=\"_blank\" rel=\"noopener\">ISO 4126-1 official card<\/a> \u00b7 <a href=\"https:\/\/www.iso.org\/standard\/50829.html\" target=\"_blank\" rel=\"noopener\">ISO 4126-7 official card<\/a> \u00b7 <a href=\"https:\/\/www.iso.org\/standard\/35393.html\" target=\"_blank\" rel=\"noopener\">ISO 4126-9 official card<\/a><\/p>\n    <p><strong>Accessed:<\/strong> 15 July 2026. <strong>Licensed-source boundary:<\/strong> NEEDS_LICENSED_SOURCE for every sizing equation, coefficient, correction, allowable-overpressure rule, standardized orifice table and acceptance criterion. None was guessed from a search snippet or another online calculator.<\/p>\n    <div class=\"vbm217-limit\"><strong>Independent engineering and manufacturer review required.<\/strong> Verify the credible overpressure scenarios and required load, governing code and jurisdiction, fluid phase\/properties, relieving pressure and temperature, inlet loss, back pressure, reaction forces, discharge disposal, valve stability, materials, certification, set-pressure tolerances, capacity certification and installation before any safety decision.<\/div>\n    <div class=\"vbm217-footer\">Revision: scientific audit 2026-07-15 \u00b7 English source page \u00b7 Arithmetic comparison only \u00b7 Preserve the complete controlled calculation and certificate with every result.<\/div>\n  <\/section>\n<\/main>\n\n<script id=\"vbm-c100217-logic\">\n(function(){\n  'use strict';\n  function el(id){return document.getElementById(id)}\n  function value(id){return el(id).value}\n  function setText(id,text){el(id).textContent=text}\n  function clearError(){var box=el('vbm217-error');box.textContent='';box.classList.remove('show')}\n  function invalidate(){clearError();el('vbm217-results').classList.remove('show')}\n  function showError(err){invalidate();var box=el('vbm217-error');box.textContent=err.message||String(err);box.classList.add('show');box.focus()}\n  function strictPositive(raw,name){var s=String(raw==null?'':raw).trim();if(!\/^(?:\\d+(?:[.,]\\d*)?|[.,]\\d+)$\/.test(s))throw new Error(name+' must be one complete positive decimal number.');var n=Number(s.replace(',','.'));if(!Number.isFinite(n)||n<=0)throw new Error(name+' must be finite and greater than zero.');return n}\n  function finite(n,name){if(!Number.isFinite(n))throw new Error(name+' is outside the finite numerical range.');return n}\n  function finitePositive(n,name){if(!Number.isFinite(n)||n<=0)throw new Error(name+' must be positive and finite.');return n}\n  function calculate(x){\n    if(!x||!['mm2','in2'].includes(x.unit))throw new Error('Select the shared effective-area unit.');\n    var required=strictPositive(x.required,'Required effective discharge area Areq');\n    var certified=strictPositive(x.certified,'Certified candidate effective area Acert');\n    var ratio=finitePositive(certified\/required,'Candidate-to-required area ratio');\n    var utilization=finitePositive(required\/certified,'Arithmetic area utilization');\n    var difference=finite(certified-required,'Signed area difference');\n    var relative=finite(difference\/required,'Relative area difference');\n    return {unit:x.unit,required:required,certified:certified,ratio:ratio,utilization:utilization,difference:difference,relative:relative};\n  }\n  function format(n){if(Object.is(n,-0))n=0;if(n===0)return'0';var a=Math.abs(n);if(a>=1e12||a<1e-9)return n.toExponential(8).replace(\/\\.0+e\/,'e').replace(\/(\\.\\d*?)0+e\/,'$1e');return Number(n.toPrecision(12)).toString()}\n  function read(){\n    var requiredIds=['vbm217-designation','vbm217-calc-source','vbm217-code','vbm217-clause','vbm217-load','vbm217-fluid','vbm217-state','vbm217-backpressure','vbm217-coefficients','vbm217-cert-source','vbm217-installation','vbm217-record-id'];\n    requiredIds.forEach(function(id){if(!value(id).trim())throw new Error(el(id).previousElementSibling.textContent.trim()+' is required.')});\n    ['vbm217-c1','vbm217-c2','vbm217-c3','vbm217-c4'].forEach(function(id){if(!el(id).checked)throw new Error('Complete all compatibility confirmations before calculating.')});\n    return calculate({unit:value('vbm217-unit'),required:value('vbm217-required'),certified:value('vbm217-certified')});\n  }\n  function render(r){\n    var unit=r.unit==='mm2'?'mm\u00b2':'in\u00b2';\n    setText('vbm217-result-context',value('vbm217-designation').trim()+' \u00b7 '+value('vbm217-record-id').trim());\n    setText('vbm217-r-ratio',format(r.ratio));\n    setText('vbm217-r-util',format(r.utilization*100)+'%');\n    setText('vbm217-r-difference',format(r.difference)+' '+unit);\n    setText('vbm217-r-values','Areq = '+format(r.required)+' '+unit+'; 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