{"id":56790,"date":"2026-09-07T11:18:57","date_gmt":"2026-09-07T11:18:57","guid":{"rendered":"https:\/\/zobai.com\/?p=56790"},"modified":"2026-09-07T11:26:26","modified_gmt":"2026-09-07T11:26:26","slug":"heat-exchanger-tube-rupture-relief","status":"publish","type":"post","link":"https:\/\/zobai.com\/ru\/blog\/heat-exchanger-tube-rupture-relief\/","title":{"rendered":"\u0421\u0431\u0440\u043e\u0441 \u0434\u0430\u0432\u043b\u0435\u043d\u0438\u044f \u043f\u0440\u0438 \u0440\u0430\u0437\u0440\u044b\u0432\u0435 \u0442\u0440\u0443\u0431 \u0432 \u0442\u0435\u043f\u043b\u043e\u043e\u0431\u043c\u0435\u043d\u043d\u0438\u043a\u0435: \u043d\u0430 \u0447\u0442\u043e \u0434\u043e\u043b\u0436\u0435\u043d \u0431\u044b\u0442\u044c \u0440\u0430\u0441\u0441\u0447\u0438\u0442\u0430\u043d \u043f\u0440\u0435\u0434\u043e\u0445\u0440\u0430\u043d\u0438\u0442\u0435\u043b\u044c\u043d\u044b\u0439 \u043a\u043b\u0430\u043f\u0430\u043d"},"content":{"rendered":"<article class=\"zobai-tube-rupture-relief\">\n<style>\n    .zobai-tube-rupture-relief .table-wrap {\n      width: 100%;\n      max-width: 100%;\n      overflow-x: auto;\n      -webkit-overflow-scrolling: touch;\n      margin-block: 1rem;\n    }<\/p>\n<p>    .zobai-tube-rupture-relief .table-wrap table {\n      width: 100%;\n      min-width: 42rem;\n      border-collapse: collapse;\n    }<\/p>\n<p>    .zobai-tube-rupture-relief .table-wrap th,\n    .zobai-tube-rupture-relief .table-wrap td {\n      vertical-align: top;\n      overflow-wrap: anywhere;\n    }\n  <\/style>\n<p><strong>For a credible heat-exchanger tube-rupture case, the safety valve should be sized for the required pressure-relief duty that remains after the actual rupture flow, relieving phase, connected low-pressure-system response, and any technically justified system-flow credit have been established.<\/strong> It should not be sized automatically from normal exchanger flow, connection size, an existing valve, or an assumption that the entire high-pressure-side stream enters the low-pressure side.<\/p>\n<p>Tube rupture is therefore a system overpressure problem before it becomes a valve-capacity problem. The engineer first needs to identify the real high-pressure and low-pressure boundaries, define the postulated internal failure path, determine what can cross that path and in what state, establish what the connected lower-pressure system can legitimately handle, and decide whether a steady-state relief basis is sufficient.<\/p>\n<p>This logic is useful across refinery, petrochemical, chemical-processing, gas-processing, utility, and other shell-and-tube exchanger services because the governing question is not the industry label. It is the pressure relationship between the two sides and the response of the receiving system when an internal pressure boundary fails.<\/p>\n<p>The engineering sequence is: <strong>credible scenario \u2192 HP\/LP boundary \u2192 failure basis \u2192 rupture flow and phase \u2192 low-pressure-system response \u2192 justified system credit \u2192 steady-state\/transient adequacy \u2192 required pressure-relief device (PRD) duty \u2192 later valve sizing and RFQ.<\/strong><\/p>\n<p>  <!--\n  IMAGE_ID: IMAGE-01\n  PLACEMENT: Immediately after the answer-first introduction and before H2-01 \"Confirm the Tube-Rupture Scenario and the Pressure Boundary at Risk\".\n  PURPOSE: Orient the reader to the complete engineering decision chain before detailed analysis begins.\n  VISUAL_DIRECTION: Conceptual engineering flow showing credible tube-rupture scenario -> actual HP\/LP boundary -> postulated failure path -> rupture flow and phase -> LP-system response -> justified system credit -> steady-state\/transient adequacy -> required PRD duty -> later valve sizing\/RFQ handoff.\n  ALT_DIRECTION: Conceptual tube-rupture relief decision path from scenario credibility and actual pressure boundary through failure flow, low-pressure-system response, transient adequacy, and final required PRD duty before valve sizing.\n  CAPTION_DIRECTION: The safety valve should be sized only after the tube-rupture failure path, transferred flow and phase, low-pressure-system response, and required relief duty have been established.\n  VISIBILITY: INVISIBLE_HTML_COMMENT\n  REAL_IMAGE: false\n  --><\/p>\n<section>\n<h2>Confirm the Tube-Rupture Scenario and the Pressure Boundary at Risk<\/h2>\n<h3>Distinguish High-Pressure and Low-Pressure Sides from Shell and Tube Sides<\/h3>\n<p>The first mistake to avoid is assuming that the shell side is always the low-pressure side or that the tube side is always the high-pressure side. Shell side and tube side describe exchanger construction; high-pressure and low-pressure sides describe the actual pressure relationship of the service.<\/p>\n<p>For tube-rupture relief analysis, the relevant question is: <strong>Which pressure system can drive fluid through an internal tube failure, and which lower-pressure pressure boundary could be overpressured as a result?<\/strong><\/p>\n<p>The UK Health and Safety Executive (HSE) recognizes tube rupture among heat-exchanger failure modes that need to be considered in plant safety assessment. AIChE process-safety work likewise treats tube rupture as an internal failure capable of challenging a lower-pressure system. The actual project pressures, allowable limits, and shell\/tube service assignment must be confirmed from the applicable project design basis rather than inferred from exchanger construction alone.<\/p>\n<p>For example, two exchangers can look mechanically similar while having opposite pressure relationships. In one service the tube-side stream may be the high-pressure source; in another, the shell side may be. A relief review that starts from \u201cshell equals low pressure\u201d can therefore establish the wrong protected boundary before any sizing calculation even begins.<\/p>\n<p>For broader exchanger relief scenarios beyond the tube-rupture duty question owned by this article, see the <a href=\"https:\/\/zobai.com\/ru\/applications\/heat-exchangers\/\">heat exchanger safety valve application guide<\/a>.<\/p>\n<h3>Define the Connected Low-Pressure Pressure Boundary<\/h3>\n<p>The threatened pressure boundary may extend beyond the exchanger body. If the lower-pressure side remains connected to piping or other equipment during the event, the analysis needs to identify the relevant connected pressure system rather than assuming that only the exchanger itself is exposed.<\/p>\n<p>This does not mean every connected item automatically belongs to one identical relieving calculation. It means the protected boundary must be defined deliberately before the required relief load can be established.<\/p>\n<ul>\n<li><strong>\u0418\u0441\u0442\u043e\u0447\u043d\u0438\u043a:<\/strong> Which pressure system can feed the internal failure?<\/li>\n<li><strong>Receiving boundary:<\/strong> Which lower-pressure equipment and connected piping are exposed?<\/li>\n<li><strong>Open connections:<\/strong> Which paths remain connected during the contingency?<\/li>\n<li><strong>Protection:<\/strong> Which part of that boundary is intended to be protected by the pressure-relief system?<\/li>\n<\/ul>\n<p>A useful design-review habit is to trace the low-pressure side beyond the exchanger nozzle before discussing the valve. If the exchanger remains hydraulically connected to a header, vessel, separator, return circuit, or other pressure-containing equipment during the event, that connection may change the system response. The presence of the connection does not automatically provide relief credit, but ignoring it can produce an equally incomplete model.<\/p>\n<p>If those questions cannot be resolved from the project basis, required-duty work should pause rather than letting an assumed valve size define the protected system retrospectively.<\/p>\n<h3>Separate Scenario Credibility from Relief-Load Calculation<\/h3>\n<p>AIChE tube-rupture process-safety work shows that scenario credibility and the appropriate protection strategy can themselves require engineering assessment. Credibility and relieving-load determination should therefore remain separate decisions.<\/p>\n<ol>\n<li>Determine whether tube rupture belongs in the overpressure analysis.<\/li>\n<li>If it does, determine what load the protection system must handle.<\/li>\n<\/ol>\n<p>A credibility assessment cannot be replaced by a casual statement that tube rupture is unlikely. Equally, recognizing tube rupture as credible does not establish a universal failure area, required flow, or relief-device solution.<\/p>\n<div class=\"table-wrap\" role=\"region\" aria-label=\"Tube-rupture scenario review states\" tabindex=\"0\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Review state<\/th>\n<th scope=\"col\">\u0418\u043d\u0436\u0435\u043d\u0435\u0440\u043d\u044b\u0435 \u0434\u0435\u0439\u0441\u0442\u0432\u0438\u044f<\/th>\n<th scope=\"col\">\u0413\u0440\u0430\u043d\u0438\u0446\u0430 \u043f\u0440\u0438\u043d\u044f\u0442\u0438\u044f \u0440\u0435\u0448\u0435\u043d\u0438\u044f<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Scenario and protected boundary are sufficiently defined<\/td>\n<td>Continue to failure-path analysis.<\/td>\n<td>Do not jump directly to a valve model or orifice.<\/td>\n<\/tr>\n<tr>\n<td>Scenario applicability or protected boundary remains unresolved<\/td>\n<td><strong>\u041e\u0421\u0422\u0410\u041d\u041e\u0412\u0418\u0422\u042c<\/strong> the sizing basis and close the missing engineering input.<\/td>\n<td>Do not use an assumed PSV size to fill the scenario-definition gap.<\/td>\n<\/tr>\n<tr>\n<td>A separate process hazard controls part of the problem<\/td>\n<td>Route that question to the responsible hazard-analysis discipline while retaining the relief interface where applicable.<\/td>\n<td>Do not treat PRD sizing as the complete hazard assessment.<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<\/section>\n<section>\n<h2>Define the Credible Tube-Failure Path Before Calculating Relief Flow<\/h2>\n<h3>Define the Postulated Internal Failure<\/h3>\n<p>For relief analysis, a tube-rupture scenario is a defined postulated internal failure path between the higher- and lower-pressure systems. It should not be treated as a synonym for every pinhole, seepage path, or minor tube leak.<\/p>\n<p>The failure basis matters because the amount of fluid that can transfer to the lower-pressure side depends on the path through which that fluid can escape.<\/p>\n<p>The applicable failure geometry is a project engineering input. This article does not assign a universal rupture area, failed-tube count, tube dimension, or other fixed failure assumption.<\/p>\n<p>Consider an illustrative exchanger with a substantially higher-pressure process stream on one side and a lower-pressure circuit on the other. Even if the high-pressure stream has a large normal throughput, the relief calculation does not begin by copying that throughput into the PSV datasheet. It begins by asking what the defined tube failure actually connects and what flow that failure path can transmit under the applicable source and receiving conditions.<\/p>\n<h3>Identify the High-Pressure Source Feeding the Failure<\/h3>\n<p>The high-pressure side defines the source of the event, but <strong>source availability is not the same as rupture flow<\/strong>.<\/p>\n<p>The engineering review should keep three concepts separate:<\/p>\n<ul>\n<li><strong>Source condition:<\/strong> what the high-pressure system can make available to the failure;<\/li>\n<li><strong>Failure-path restriction:<\/strong> what the postulated internal opening allows to cross;<\/li>\n<li><strong>Receiving condition:<\/strong> how the lower-pressure system and fluid state influence what actually enters that system.<\/li>\n<\/ul>\n<p>Normal exchanger throughput may be relevant to the source context, but it is not automatically the rupture flow. Likewise, the entire high-pressure-side stream should not be assumed to cross the failure simply because it exists upstream.<\/p>\n<p>This is also why starting with the existing PSV can send a review in the wrong direction. An installed valve tells you what was previously selected; it does not prove what the current tube-rupture scenario requires. The scenario establishes the duty first. Candidate capacity is compared with that duty afterward.<\/p>\n<h3>Keep Failure Geometry Project-Specific<\/h3>\n<p>Failure geometry can materially affect the flow through the internal rupture path and therefore has to come from the applicable project methodology and engineering basis.<\/p>\n<p>Before the duty is calculated, the project engineering basis must confirm the tube dimensions, postulated failure geometry, number of failed tubes where applicable, effective flow area, and actual high- and low-pressure conditions used in the analysis.<\/p>\n<p><strong>If the failure path has not been defined, do not calculate or accept a tube-rupture required duty.<\/strong> An existing PSV size, exchanger nozzle size, or previous result does not establish the missing failure basis.<\/p>\n<\/section>\n<section>\n<h2>Determine What Actually Crosses the Rupture Path<\/h2>\n<h3>Do Not Use Normal Exchanger Flow as the Default Rupture Flow<\/h3>\n<p>Normal exchanger flow describes intended operation. Tube-rupture flow describes transfer through an unintended internal failure path. They are different engineering quantities.<\/p>\n<p>Normal operating flow may form part of the source or system context, but it should not automatically become the required safety-valve duty.<\/p>\n<p><strong>Normal process flow answers how the exchanger operates. Rupture flow answers what can cross the failure during the overpressure event.<\/strong><\/p>\n<p>This distinction becomes particularly useful during revamps and replacement-valve reviews. A process datasheet may make the normal flow immediately visible while the original tube-rupture basis is missing or poorly documented. The readily available operating flow should not be substituted for the missing relief analysis simply because it is the easiest number to find.<\/p>\n<h3>Do Not Assume the Entire High-Pressure Stream Crosses the Failure<\/h3>\n<p>The opposite shortcut is also unreliable: assuming that the entire high-pressure-side stream automatically becomes the tube-rupture flow.<\/p>\n<p>The amount reaching the lower-pressure side depends on the defined failure path, the available source condition, restrictions between the source and failure, and fluid behavior through the failure.<\/p>\n<ol>\n<li><strong>\u0418\u0441\u0442\u043e\u0447\u043d\u0438\u043a:<\/strong> Establish what can feed the failure.<\/li>\n<li><strong>Path:<\/strong> Establish the postulated internal failure basis.<\/li>\n<li><strong>Transfer:<\/strong> Determine what can cross that path.<\/li>\n<li><strong>State:<\/strong> Determine what phase or state reaches the receiving system.<\/li>\n<li><strong>Response:<\/strong> Only then determine what the low-pressure system and dedicated PRD need to handle.<\/li>\n<\/ol>\n<p>Only the result of that engineering chain should feed the required-duty calculation.<\/p>\n<p>    <!--\n    IMAGE_ID: IMAGE-02\n    PLACEMENT: Within H2-03 \"Determine What Actually Crosses the Rupture Path\", immediately after the explanation that only the engineered failure-path result should feed the relief-duty calculation.\n    PURPOSE: Clarify the difference between high-pressure source availability, the defined internal failure path, and the actual rupture flow entering the low-pressure side.\n    VISUAL_DIRECTION: Generic exchanger schematic showing an HP source, defined internal failure path, and lower-pressure system, without implying a fixed shell\/tube pressure arrangement or rupture geometry.\n    ALT_DIRECTION: Generic heat-exchanger tube-rupture schematic showing high-pressure source flow crossing a defined internal failure path into the lower-pressure system, distinct from normal exchanger throughput or the entire high-pressure-side stream.\n    CAPTION_DIRECTION: Tube-rupture flow is the flow that can cross the defined internal failure path; it is not automatically normal exchanger flow or the complete high-pressure-side stream.\n    VISIBILITY: INVISIBLE_HTML_COMMENT\n    REAL_IMAGE: false\n    --><\/p>\n<h3>Establish the Fluid Phase Reaching the Low-Pressure Side<\/h3>\n<p>Fluid phase is part of the tube-rupture relief basis, not a detail to postpone until valve selection.<\/p>\n<p>AIChE tube-rupture modeling has examined different liquid and vapor-response cases, supporting the conclusion that phase behavior can materially affect the lower-pressure-side pressure response. Depending on the actual service, fluid crossing the failure can remain in a similar phase, flash, or create a mixed or two-phase condition.<\/p>\n<p>One important practical example is a high-pressure liquid that experiences a substantial pressure reduction as it enters the lower-pressure side. The fact that the source stream was liquid upstream does not prove that the relieving condition remains liquid. If flashing becomes relevant, the receiving-system response and eventual PRD duty need to reflect that actual state rather than the upstream label.<\/p>\n<p>The reverse lesson is equally important: do not assume flashing merely because the pressure drops. The actual relieving state cannot be assigned from exchanger type alone. Fluid composition, thermodynamic properties, high- and low-pressure conditions, and the resulting phase behavior must be established from the project data.<\/p>\n<p>The engineer should therefore ask not merely \u201cWhat is the rupture flow?\u201d but <strong>\u201cWhat flow in what state actually becomes the low-pressure-side overpressure challenge?\u201d<\/strong><\/p>\n<p>If phase behavior can materially change the required duty but remains unresolved, the sizing basis should remain on <strong>\u041e\u0421\u0422\u0410\u041d\u041e\u0412\u0418\u0422\u042c<\/strong>.<\/p>\n<\/section>\n<section>\n<h2>Determine How Much of the Event the Low-Pressure System Can Legitimately Handle<\/h2>\n<h3>Define the Connected Low-Pressure System Response<\/h3>\n<p>The flow entering the lower-pressure side is not necessarily identical to the flow that a dedicated pressure-relief device must ultimately pass.<\/p>\n<p>After rupture inflow is established, the next question is how the connected low-pressure system responds. Fluid may move into connected equipment or through another available path, but any such response must be evaluated under the tube-rupture contingency rather than inferred from normal operation.<\/p>\n<p><strong>Rupture inflow is the challenge entering the low-pressure system. Required PRD duty is the portion that the dedicated pressure-relief function must handle after only technically justified system response is credited.<\/strong><\/p>\n<h3>Credit Existing Outlet or Open Flow Paths Only When Technically Justified<\/h3>\n<p>An existing low-pressure-side outlet is not automatically additional relieving capacity. AIChE work examining lower-pressure hydraulic circuits in tube-rupture protection supports treating such a path as a potential engineering credit only when its role under the contingency has been established.<\/p>\n<p>A common design-review trap is an outlet that appears comfortably open during normal operation. It can be tempting to treat its normal flow as capacity already available during tube rupture. But the real questions are whether that path remains connected, whether it remains available under the contingency, what it can pass under those conditions, and whether the project protection basis is allowed to rely on it.<\/p>\n<p>Before an existing path is credited, four questions should be closed:<\/p>\n<ol>\n<li><strong>\u041f\u043e\u0434\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u0435:<\/strong> Is the path actually connected to the protected system during the contingency?<\/li>\n<li><strong>Availability:<\/strong> Is it expected to remain open and available when tube rupture occurs?<\/li>\n<li><strong>Capacity basis:<\/strong> Has its relevant capacity under the contingency been established rather than inferred from normal flow?<\/li>\n<li><strong>Protection basis:<\/strong> Is relying on that path accepted as part of the project&#8217;s overpressure-protection basis?<\/li>\n<\/ol>\n<p>If any of those questions remains unresolved, normal outlet flow should not silently be deducted from the required PRD duty.<\/p>\n<div class=\"table-wrap\" role=\"region\" aria-label=\"Existing low-pressure-side path credit decisions\" tabindex=\"0\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Existing path status<\/th>\n<th scope=\"col\">Relief-duty treatment<\/th>\n<th scope=\"col\">\u0420\u0435\u0448\u0435\u043d\u0438\u0435<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Availability and contingency capacity are technically justified within the protection basis<\/td>\n<td>Use only the system credit established by the project analysis.<\/td>\n<td>Continue to residual-duty determination.<\/td>\n<\/tr>\n<tr>\n<td>Path exists but availability or contingency capacity is unresolved<\/td>\n<td>Do not assume credit.<\/td>\n<td><strong>\u041e\u0421\u0422\u0410\u041d\u041e\u0412\u0418\u0422\u042c<\/strong> the credit assumption.<\/td>\n<\/tr>\n<tr>\n<td>Path is unavailable for the contingency<\/td>\n<td>Do not rely on it as part of the relieving basis.<\/td>\n<td>Determine the remaining protection requirement without that credit.<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<h3>Separate System-Handling Capacity from the Residual PRD Duty<\/h3>\n<p>The analysis should keep three layers separate:<\/p>\n<ul>\n<li><strong>Incoming rupture challenge:<\/strong> what enters the low-pressure system through the postulated internal failure;<\/li>\n<li><strong>Justified system handling:<\/strong> what the connected system can legitimately accommodate or pass during the contingency;<\/li>\n<li><strong>Residual required relief duty:<\/strong> what remains for the dedicated pressure-relief function.<\/li>\n<\/ul>\n<p>These are conceptual engineering layers, not a universal arithmetic formula. The amount of system-flow credit, if any, must be established from the actual contingency analysis.<\/p>\n<p>An existing valve&#8217;s capacity should not be used to reverse-engineer this duty. The required duty comes from the scenario analysis; candidate capacity is checked afterward.<\/p>\n<p>This is one of the most useful checks in brownfield work. If the reasoning begins with \u201cthe installed valve passes this much flow, therefore the exchanger must be protected,\u201d the logic is backwards. The review should be able to trace the duty independently of the installed valve and only then compare the existing device with the reconstructed requirement.<\/p>\n<p>    <!--\n    IMAGE_ID: IMAGE-03\n    PLACEMENT: Within H2-04 \"Determine How Much of the Event the Low-Pressure System Can Legitimately Handle\", immediately after the distinction between system-handling capacity and residual PRD duty and before reactive-mixing discussion.\n    PURPOSE: Show incoming rupture flow, justified low-pressure-system handling, and residual dedicated PRD duty as separate engineering layers.\n    VISUAL_DIRECTION: Conceptual system-response diagram showing rupture inflow -> connected LP system \/ conditionally available path -> residual required PRD duty, with existing path credit clearly conditional on contingency-specific technical justification.\n    ALT_DIRECTION: Conceptual low-pressure-side response diagram separating incoming tube-rupture flow, technically justified connected-system handling, and the remaining required PRD duty.\n    CAPTION_DIRECTION: An existing low-pressure-side outlet or connected flow path reduces dedicated PRD duty only when its availability and capacity during the contingency are technically justified.\n    VISIBILITY: INVISIBLE_HTML_COMMENT\n    REAL_IMAGE: false\n    --><\/p>\n<h3>Route Reactive Interstream Mixing to a Separate Hazard Analysis<\/h3>\n<p>Tube rupture can bring two process streams into contact. If mixing can create a separate reaction, vapor-generation, or energy-release hazard, a hydraulic tube-rupture relief calculation alone does not close that risk.<\/p>\n<p>This boundary becomes especially important in process exchangers where both sides contain process fluids rather than a benign utility pairing. The hydraulic transfer load may be only one part of the event if interstream mixing creates an additional hazard.<\/p>\n<p>That condition must be routed to the appropriate process-hazard analysis. PRD sizing may remain part of the protection strategy, but it cannot substitute for assessment of the mixing hazard itself.<\/p>\n<p>Whether such a hazard exists depends on the actual process fluids and conditions and must be confirmed from the project process-safety basis.<\/p>\n<\/section>\n<section>\n<h2>Decide Whether Steady-State Relief Sizing Is Sufficient<\/h2>\n<h3>Identify When Early Pressure Response Can Control the Protection Decision<\/h3>\n<p>A conventional relief calculation asks what flow the protection system must handle. Some tube-rupture cases add another question: <strong>Can the lower-pressure boundary experience a rapid pressure response before a steady-state relief balance is enough to demonstrate protection?<\/strong><\/p>\n<p>AIChE and IChemE technical work on heat-exchanger tube rupture supports considering transient low-pressure-side response where the timing of pressure rise and protection response is material. This does not mean every exchanger requires dynamic modeling.<\/p>\n<p>A useful example is a lower-pressure side containing a substantial liquid inventory with limited compressibility. A sudden high-pressure-side inflow can make the early pressure response an important part of the protection question. In another exchanger with a different inventory, flow path, phase behavior, and pressure relationship, a steady-state basis may be adequate. The analysis method should follow the system behavior rather than a blanket rule.<\/p>\n<h3>Separate Steady-State Capacity from Transient Pressure Protection<\/h3>\n<p>These conclusions are not equivalent:<\/p>\n<ul>\n<li>the valve can pass the established steady-state required flow;<\/li>\n<li>the protected system has been shown to remain adequately protected throughout the tube-rupture event.<\/li>\n<\/ul>\n<p>The second conclusion can require additional system-response evidence.<\/p>\n<p>A larger safety valve should therefore not be treated as a universal solution to a rapid tube-rupture transient. If the unresolved question concerns pressure-rise timing, system response, PRD response, or installation location, additional steady-state capacity does not by itself demonstrate adequate protection.<\/p>\n<p>There is also an important distinction between a conservative number and a conservative engineering basis. Assuming an unusually large flow may appear conservative in a steady-state capacity check, but it does not resolve an incorrect phase assumption, an unverified system-flow credit, an early transient pressure problem, or a protection-device response issue. Conservatism in one input cannot replace a valid model of the scenario.<\/p>\n<h3>Check PRD Response and Location Only Where They Change System Protection<\/h3>\n<p>PRD response and location matter only where they materially affect the protection response of the relevant pressure boundary. This article does not prescribe a response time or installation location; those conclusions depend on the actual system and project analysis.<\/p>\n<div class=\"table-wrap\" role=\"region\" aria-label=\"Steady-state and transient tube-rupture review\" tabindex=\"0\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">\u0418\u043d\u0436\u0435\u043d\u0435\u0440\u043d\u044b\u0439 \u0432\u043e\u043f\u0440\u043e\u0441<\/th>\n<th scope=\"col\">If sufficiently resolved<\/th>\n<th scope=\"col\">If unresolved and material<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Does the steady-state basis adequately represent the required protection decision?<\/td>\n<td>Continue toward duty freeze.<\/td>\n<td>Escalate to the required transient or dynamic review.<\/td>\n<\/tr>\n<tr>\n<td>Could early system pressure response affect protection adequacy?<\/td>\n<td>Retain the validated engineering basis.<\/td>\n<td>Do not claim steady-state capacity alone closes the case.<\/td>\n<\/tr>\n<tr>\n<td>Are PRD response or location material to the system response?<\/td>\n<td>Proceed using the established basis.<\/td>\n<td>Include those effects in the responsible system analysis before final selection.<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<p>If the adequacy of steady-state analysis remains unresolved, the duty basis remains on <strong>\u041e\u0421\u0422\u0410\u041d\u041e\u0412\u0418\u0422\u042c<\/strong> pending the required transient or dynamic review.<\/p>\n<p>    <!--\n    IMAGE_ID: IMAGE-04\n    PLACEMENT: Within H2-05 \"Decide Whether Steady-State Relief Sizing Is Sufficient\", immediately after the steady-state\/transient HOLD boundary and before H2-06 \"Freeze the Required Tube-Rupture Relief Duty Before Selecting the Safety Valve\".\n    PURPOSE: Clarify the boundary between steady-state relief-capacity analysis and time-dependent protection adequacy.\n    VISUAL_DIRECTION: Non-numeric decision diagram with one path proceeding from justified steady-state analysis to duty freeze and another routing unresolved early pressure response, PRD response\/location, or system dynamics to transient verification before duty closure.\n    ALT_DIRECTION: Decision diagram distinguishing tube-rupture cases that can proceed with a justified steady-state relief basis from cases requiring transient system-response verification before required PRD duty is finalized.\n    CAPTION_DIRECTION: Adequate steady-state valve capacity does not by itself prove protection for every rapid tube-rupture event; where system response is material, transient verification must be resolved before the duty is frozen.\n    VISIBILITY: INVISIBLE_HTML_COMMENT\n    REAL_IMAGE: false\n    --><br \/>\n  <\/section>\n<section>\n<h2>Freeze the Required Tube-Rupture Relief Duty Before Selecting the Safety Valve<\/h2>\n<h3>Document the Approved Failure and Phase Basis<\/h3>\n<p>Before valve sizing starts, the engineering file should identify which pressure system is the high-pressure source, which connected lower-pressure boundary is protected, the approved tube-failure basis, the relieving fluid, and the phase or state used in the analysis.<\/p>\n<p>The pressures, geometry, fluid properties, failure assumptions, and calculated rupture flow used to establish that basis must come from the actual project engineering data.<\/p>\n<p>This documentation discipline matters in new projects and in existing facilities for the same reason: a future engineer should be able to understand why the valve duty exists without having to infer the scenario from the valve that happens to be installed.<\/p>\n<h3>Document Any Justified System-Flow Credit<\/h3>\n<p>If the required PRD duty relies on an existing low-pressure-side flow path, that credit should be visible in the engineering basis rather than hidden inside the final relieving-load value. The record should show that the path was evaluated for the contingency and identify the role it is expected to perform.<\/p>\n<h3>Define the Remaining Required Relief Duty<\/h3>\n<p>Only after the failure path, rupture flow, phase behavior, connected-system response, and required analysis mode are sufficiently resolved can the tube-rupture required duty be frozen.<\/p>\n<p><strong>What required flow and relieving state must the dedicated pressure-relief function handle for the approved tube-rupture basis?<\/strong><\/p>\n<ul>\n<li>Is the scenario approved for analysis?<\/li>\n<li>Is the protected HP\/LP boundary explicit?<\/li>\n<li>Is the failure-path basis explicit?<\/li>\n<li>Is rupture flow distinguished from normal process flow and total source flow?<\/li>\n<li>Is the relieving phase\/state established?<\/li>\n<li>Is every system-flow credit technically justified for the contingency?<\/li>\n<li>Has the steady-state versus transient question been resolved?<\/li>\n<li>Are separate reactive or process hazards routed to their proper analysis?<\/li>\n<\/ul>\n<p>If an unresolved item can materially change the required duty, the correct result is not a guessed valve size. The duty basis remains on <strong>\u041e\u0421\u0422\u0410\u041d\u041e\u0412\u0418\u0422\u042c<\/strong>.<\/p>\n<p>This article stops before determining a safety-valve model, orifice, candidate certified relieving capacity, or project-specific compliance conclusion. For that next step, use the <a href=\"https:\/\/zobai.com\/ru\/blog\/safety-valve-sizing-and-certified-relieving-capacity-guide\/\">\u0420\u0443\u043a\u043e\u0432\u043e\u0434\u0441\u0442\u0432\u043e \u043f\u043e \u0440\u0430\u0441\u0447\u0435\u0442\u0443 \u043f\u0440\u0435\u0434\u043e\u0445\u0440\u0430\u043d\u0438\u0442\u0435\u043b\u044c\u043d\u044b\u0445 \u043a\u043b\u0430\u043f\u0430\u043d\u043e\u0432<\/a>.<\/p>\n<h3>Hand Off the Duty to Valve Sizing and RFQ Review<\/h3>\n<p>API&#8217;s pressure-relief framework separates relief-system analysis from the later sizing and selection of the pressure-relief device. Once the required tube-rupture duty is approved, valve candidates can be evaluated against a defined requirement instead of reconstructing the scenario from an existing valve size or exchanger connection.<\/p>\n<p>A practical sizing\/RFQ handoff should include the approved required relieving duty, relieving fluid and phase\/state, relevant project pressure basis, downstream or back-pressure basis where applicable, project-specific governing requirements, and any conditions from the tube-rupture analysis that affect later PRD selection.<\/p>\n<p>For refinery, petrochemical, chemical-processing, gas-processing, utility, or other exchanger services, the handoff principle remains the same: <strong>the valve supplier should receive an approved duty basis, not be asked to invent the process scenario from a nozzle size or an old nameplate.<\/strong><\/p>\n<p>The tube-rupture duty basis should be established and approved by the responsible project or relief-system engineering discipline. The later valve-sizing process then determines which candidate has adequate documented capacity for that approved requirement.<\/p>\n<aside>\n<p><strong>\u0421\u043b\u0435\u0434\u0443\u044e\u0449\u0438\u0439 \u0448\u0430\u0433: \u0438\u043d\u0436\u0435\u043d\u0435\u0440\u043d\u044b\u0439 \u0430\u043d\u0430\u043b\u0438\u0437 \/ \u0437\u0430\u043f\u0440\u043e\u0441 \u043f\u0440\u0435\u0434\u043b\u043e\u0436\u0435\u043d\u0438\u044f (RFQ)<\/strong> prepare the confirmed high-pressure\/low-pressure boundary, approved tube-failure basis, relieving fluid and state, required relief duty, any justified low-pressure-side system-flow credit, and relevant downstream conditions. If you want a candidate review after those inputs are available, <a href=\"https:\/\/zobai.com\/ru\/ask-an-engineer\/\">submit the engineering basis to ZOBAI&#8217;s Ask an Engineer review<\/a>. Missing process-hazard inputs should remain with the responsible project engineering discipline rather than being guessed during product selection.<\/p>\n<\/aside>\n<\/section>\n<\/article>","protected":false},"excerpt":{"rendered":"<p>For a credible heat-exchanger tube-rupture case, the safety valve should be sized for the required pressure-relief duty that remains after the actual rupture flow, relieving phase, connected low-pressure-system response, and any technically justified system-flow credit have been established. It should not be sized automatically from normal exchanger flow, connection size, an existing valve, or an&#8230;<\/p>","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[74],"tags":[],"class_list":["post-56790","post","type-post","status-publish","format-standard","hentry","category-sizing-performance-engineering"],"_links":{"self":[{"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/posts\/56790","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/comments?post=56790"}],"version-history":[{"count":2,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/posts\/56790\/revisions"}],"predecessor-version":[{"id":56792,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/posts\/56790\/revisions\/56792"}],"wp:attachment":[{"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/media?parent=56790"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/categories?post=56790"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zobai.com\/ru\/wp-json\/wp\/v2\/tags?post=56790"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}