{"id":1361,"date":"2026-10-12T06:39:17","date_gmt":"2026-10-12T06:39:17","guid":{"rendered":"https:\/\/wdlvalve.com\/severe-service-valve-selection\/"},"modified":"2026-10-12T07:56:55","modified_gmt":"2026-10-12T07:56:55","slug":"%d8%a7%d8%ae%d8%aa%d9%8a%d8%a7%d8%b1-%d8%a7%d9%84%d8%b5%d9%85%d8%a7%d9%85%d8%a7%d8%aa-%d8%a7%d9%84%d9%85%d8%ae%d8%b5%d8%b5%d8%a9-%d9%84%d9%84%d8%a7%d8%b3%d8%aa%d8%ae%d8%af%d8%a7%d9%85%d8%a7%d8%aa","status":"publish","type":"post","link":"https:\/\/wdlvalve.com\/ar\/%d8%a7%d8%ae%d8%aa%d9%8a%d8%a7%d8%b1-%d8%a7%d9%84%d8%b5%d9%85%d8%a7%d9%85%d8%a7%d8%aa-%d8%a7%d9%84%d9%85%d8%ae%d8%b5%d8%b5%d8%a9-%d9%84%d9%84%d8%a7%d8%b3%d8%aa%d8%ae%d8%af%d8%a7%d9%85%d8%a7%d8%aa\/","title":{"rendered":"\u0627\u062e\u062a\u064a\u0627\u0631 \u0627\u0644\u0635\u0645\u0627\u0645\u0627\u062a \u0627\u0644\u0645\u062e\u0635\u0635\u0629 \u0644\u0644\u0627\u0633\u062a\u062e\u062f\u0627\u0645\u0627\u062a \u0627\u0644\u0642\u0627\u0633\u064a\u0629: \u0627\u0644\u0645\u0639\u0627\u064a\u064a\u0631 \u0627\u0644\u0647\u0646\u062f\u0633\u064a\u0629 \u0648\u0627\u0644\u0645\u0639\u0627\u064a\u064a\u0631 \u0627\u0644\u0641\u0646\u064a\u0629 \u0648\u0623\u0646\u0645\u0627\u0637 \u0627\u0644\u0623\u0639\u0637\u0627\u0644"},"content":{"rendered":"<article class=\"wdl-technical-guide\"><strong>Technical review date: October 2026<\/strong><\/p>\n<div style=\"border-left: 4px solid #174a7e; background: #f3f7fb; padding: 16px 18px; margin: 20px 0;\"><strong>Engineering scope.<\/strong> This guide explains how to define and evaluate valves for high differential pressure, corrosive fluids, erosive solids, cryogenic temperatures, high-temperature steam, sour service and low-emission duties. Final selection must be checked against the governing piping code, project specification and the edition of each referenced standard stated in the purchase order.<\/div>\n<p><strong>Severe service valve selection<\/strong> is a system-engineering task rather than a catalogue exercise. Nominal size and pressure class identify only part of the requirement. A technically defensible selection must also address the process envelope, valve function, pressure-temperature rating, flow behavior, material degradation mechanisms, seat leakage, atmospheric emissions, actuator capability and inspection acceptance criteria.<\/p>\n<p>A valve may comply dimensionally with a recognized standard and still fail in service. Typical causes include cavitation at the trim, flashing erosion downstream of the seat, chloride attack on an unsuitable stainless steel, sulfide stress cracking in sour service, excessive operating torque, thermal contraction in cryogenic duty and unstable control caused by oversizing.<\/p>\n<nav class=\"wp-block-rank-math-toc-block\" style=\"border: 1px solid #d8dee6; background: #f8fafc; padding: 18px 22px; margin: 24px 0;\" aria-label=\"Table of Contents\">\n<h2 style=\"margin-top: 0;\">Table of Contents<\/h2>\n<ol>\n<li><a href=\"#design-basis\">\u0623\u0633\u0627\u0633 \u0627\u0644\u062a\u0635\u0645\u064a\u0645<\/a><\/li>\n<li><a href=\"#standards-hierarchy\">Standards hierarchy<\/a><\/li>\n<li><a href=\"#pressure-class\">Pressure class<\/a><\/li>\n<li><a href=\"#valve-architecture\">Valve architecture<\/a><\/li>\n<li><a href=\"#cv-kv-sizing\">Cv and Kv sizing<\/a><\/li>\n<li><a href=\"#cavitation-flashing\">Cavitation and flashing<\/a><\/li>\n<li><a href=\"#material-selection\">Material selection<\/a><\/li>\n<li><a href=\"#leakage-emissions\">Seat leakage and fugitive emissions<\/a><\/li>\n<li><a href=\"#fire-safety\">Fire safety<\/a><\/li>\n<li><a href=\"#actuator-sizing\">Actuator sizing<\/a><\/li>\n<li><a href=\"#inspection\">Inspection and testing<\/a><\/li>\n<li><a href=\"#selection-matrix\">Selection matrix<\/a><\/li>\n<li><a href=\"#rfq-data\">Valve RFQ data<\/a><\/li>\n<li><a href=\"#faq\">Frequently asked questions<\/a><\/li>\n<li><a href=\"#references\">Technical references<\/a><\/li>\n<\/ol>\n<\/nav>\n<h2 id=\"design-basis\">1. Severe Service Valve Selection Starts with the Design Basis<\/h2>\n<p>The design basis must describe the complete operating envelope, not only the normal operating point. Transient conditions during start-up, shutdown, regeneration, line packing, pump trip or emergency isolation may impose a greater load than steady operation.<\/p>\n<div style=\"overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 18px 0;\">\n<table style=\"width: 100%; min-width: 820px; border-collapse: collapse; border: 1px solid #000;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Required data<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Engineering significance<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Frequent specification error<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Fluid composition and phase<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Controls corrosion, elastomer compatibility, toxicity and flow model<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Writing only \u201cwater,\u201d \u201cgas\u201d or \u201cchemical\u201d<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Design and operating pressure<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Defines pressure boundary and normal valve loading<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Using pump discharge pressure without surge review<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Design and operating temperature<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Affects pressure rating, toughness, packing, seats and bolting<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Checking body material but not soft-seat limits<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Maximum differential pressure<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Controls torque, thrust, trim velocity and cavitation risk<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Sizing the actuator at normal differential pressure<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Flow rate, density and viscosity<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Required for Cv\/Kv sizing and velocity assessment<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Selecting the line-size valve without a flow calculation<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Vapor and critical pressure<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Required for choked-flow, flashing and cavitation analysis<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Ignoring vapor pressure for hot liquid service<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Solids and particle distribution<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Influences erosion, blockage, seat protection and flushing<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Specifying only solids percentage without particle size<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Cycles and required stroke time<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Affects packing endurance, actuator duty and surge<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Requesting \u201cfast closing\u201d without transient analysis<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 id=\"standards-hierarchy\">2. Build a Standards Hierarchy Instead of Listing Random Standards<\/h2>\n<p>No single standard completely specifies an industrial valve. A complete procurement document normally combines a piping code, pressure-boundary standard, valve product standard, connection standard, test standard and service-specific qualification.<\/p>\n<div style=\"overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 18px 0;\">\n<table style=\"width: 100%; min-width: 760px; border-collapse: collapse; border: 1px solid #000;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Requirement<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Typical reference<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">What it establishes<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Pressure-temperature rating<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">ASME B16.34<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Materials, ratings, examination, testing and marking framework<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Pipeline valves<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">API 6D<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Requirements for pipeline and piping valve designs<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Valve pressure testing<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">API 598 or ISO 5208<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Shell integrity, closure testing and acceptance<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Control-valve sizing<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">IEC 60534-2-1<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Installed flow-capacity equations and correction factors<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Fugitive emissions<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">ISO 15848-1, API 624 or API 641<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Type qualification of stem or shaft sealing systems<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Sour oil and gas service<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">NACE MR0175\/ISO 15156<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Selection of cracking-resistant metallic materials<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Fire qualification<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">API 607 or API 6FA<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Leakage performance during and after a defined fire test<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The purchase order should identify the required edition. A statement such as \u201cmanufactured according to API\u201d is not technically complete because API 6D, API 598, API 607 and API 641 address different aspects of valve performance.<\/p>\n<h2 id=\"pressure-class\">3. Pressure Class Is Not the Maximum Allowable Pressure<\/h2>\n<p>ASME pressure class is a designation, not a constant pressure limit. Allowable pressure changes with material group and temperature. The valve body, bonnet, end connections, bolting, packing, gasket and seat must all remain suitable at the design condition.<\/p>\n<p>The following checks are separate and all are required:<\/p>\n<ul>\n<li>Body and bonnet pressure-temperature rating<\/li>\n<li>Flange or welding-end compatibility with the piping class<\/li>\n<li>Low-temperature impact toughness where applicable<\/li>\n<li>High-temperature strength and oxidation resistance<\/li>\n<li>Bolting and gasket temperature capability<\/li>\n<li>Soft-seat, elastomer and packing temperature limits<\/li>\n<li>Thermal expansion between body, trim and seat components<\/li>\n<\/ul>\n<p>A Class 600 body does not make a polymer seat suitable for the same temperature envelope. The lowest-rated pressure-retaining or sealing component limits the assembly.<\/p>\n<h2 id=\"valve-architecture\">4. Select the Valve Architecture by Function and Failure Mode<\/h2>\n<div style=\"overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 18px 0;\">\n<table style=\"width: 100%; min-width: 900px; border-collapse: collapse; border: 1px solid #000;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Duty<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Common architecture<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Critical review<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">\u0639\u0632\u0644 \u062e\u0637 \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 \u0628\u0627\u0644\u0643\u0627\u0645\u0644<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Trunnion-mounted ball valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Seat arrangement, cavity relief, stem retention and operating torque<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">General process isolation<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Gate or ball valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Seat leakage, deposits, thermal locking and maintenance access<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Accurate throttling<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Globe-style control valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Cv, rangeability, noise, cavitation, actuator stiffness and shutoff load<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Large-diameter isolation<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Double- or triple-offset butterfly valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Disc interference, dynamic torque, seat retention and installation clearance<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Reverse-flow prevention<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Swing, axial, piston or dual-plate check valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Minimum velocity, closing response, slam and installation orientation<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Abrasive slurry isolation<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Knife gate or slurry valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Gate guidance, solids packing, flushing, wear parts and bidirectionality<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Cryogenic isolation<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Extended-bonnet ball, gate or globe valve<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Packing temperature, orientation, trapped-cavity relief and thermal contraction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Conventional gate valves should not be used for continuous throttling. Partial opening concentrates velocity around the gate and seat, increasing vibration, wiredrawing and erosion. Quarter-turn valves can provide control, but their pressure-recovery characteristics and dynamic torque must be evaluated rather than inferred from nominal Cv alone.<\/p>\n<h2 id=\"cv-kv-sizing\">5. Cv and Kv Are Capacity Coefficients, Not Selection Certificates<\/h2>\n<p>For a preliminary non-vaporizing liquid calculation in US customary units:<\/p>\n<p style=\"font-size: 1.15em; text-align: center;\"><strong>Cv = Q \u00d7 \u221a(SG \/ \u0394P)<\/strong><\/p>\n<p>where Q is flow in US gallons per minute, SG is specific gravity and \u0394P is valve pressure drop in psi. The approximate relationship between the two common coefficients is:<\/p>\n<p style=\"font-size: 1.15em; text-align: center;\"><strong>Kv \u2248 0.865 Cv<\/strong><\/p>\n<p>This simplified relationship is not adequate for final severe service valve selection. IEC 60534-2-1 calculations introduce corrections for installed reducers, viscosity, pressure recovery, liquid critical pressure, vapor pressure and choked flow. Compressible gases require a different flow model. Slurries and non-Newtonian fluids may fall outside the normal equations and require application-specific testing or validated correlations.<\/p>\n<p>Oversizing is a frequent control-valve error. An oversized valve may operate close to its seat during normal production, reducing useful travel and control resolution. The trim can then experience high localized velocity even though the body size appears conservative.<\/p>\n<h2 id=\"cavitation-flashing\">6. Cavitation and Flashing Require Different Solutions<\/h2>\n<h3>Cavitation<\/h3>\n<p>Cavitation begins when pressure at the vena contracta falls below liquid vapor pressure and then recovers above vapor pressure downstream. Vapor bubbles form and collapse, producing localized impact, noise, vibration and a rough, porous erosion pattern.<\/p>\n<p>A simplified condition is:<\/p>\n<p style=\"text-align: center;\"><strong>Pvc &lt; Pv and P2 &gt; Pv<\/strong><\/p>\n<p>Effective mitigation may include multi-stage pressure reduction, anti-cavitation cages, increased downstream backpressure, valve relocation, controlled flow direction and hardened trim. Multi-stage trim is intended to divide one large pressure drop into several smaller drops so local pressure does not fall below the vapor pressure.<\/p>\n<h3>Flashing<\/h3>\n<p>Flashing occurs when downstream pressure remains below vapor pressure:<\/p>\n<p style=\"text-align: center;\"><strong>P2 &lt; Pv<\/strong><\/p>\n<p>The vapor phase remains downstream and does not collapse. Flashing therefore cannot normally be eliminated inside the valve. The design objective becomes management of high-velocity two-phase flow through body geometry, outlet sizing, flow direction and erosion-resistant materials. Cavitation-resistant trim alone does not solve a flashing application.<\/p>\n<p>For severe pressure-reduction duties, see WDL Valve\u2019s <a href=\"https:\/\/wdlvalve.com\/ar\/%d8%b4%d8%b1%d9%83%d8%a9-%d9%85%d8%b5%d9%86%d8%b9%d8%a9-%d9%84%d8%b5%d9%85%d8%a7%d9%85%d8%a7%d8%aa-%d8%a7%d9%84%d8%aa%d8%ad%d9%83%d9%85-%d8%a7%d9%84%d8%b5%d9%86%d8%a7%d8%b9%d9%8a%d8%a9\/\">industrial control valve solutions<\/a>.<\/p>\n<h2 id=\"material-selection\">7. Material Selection Must Follow the Damage Mechanism<\/h2>\n<p>Material selection should be based on the expected degradation mechanism rather than a simple hierarchy in which every higher alloy is assumed to be better.<\/p>\n<h3>Carbon and low-alloy steels<\/h3>\n<p>Carbon steel is appropriate for many non-corrosive oil, gas, steam and water services. Low-temperature grades may be required for impact toughness. Chromium-molybdenum alloys may be selected where elevated-temperature strength and oxidation resistance are required.<\/p>\n<h3>Austenitic stainless steels<\/h3>\n<p>316 and CF8M improve general corrosion resistance but remain susceptible to chloride pitting, crevice corrosion and chloride stress-corrosion cracking. Chloride concentration, temperature, oxygen, deposits and crevice geometry must be reviewed.<\/p>\n<h3>Duplex and super duplex stainless steels<\/h3>\n<p>Duplex grades combine higher mechanical strength with improved resistance to chloride stress-corrosion cracking. Performance still depends on exact grade, heat treatment, ferrite balance, welding procedure and environmental limits. Review WDL Valve\u2019s <a href=\"https:\/\/wdlvalve.com\/ar\/%d8%b4%d8%b1%d9%83%d8%a9-%d9%85%d8%b5%d9%86%d8%b9%d8%a9-%d9%84%d9%84%d8%b5%d9%85%d8%a7%d9%85%d8%a7%d8%aa-%d8%a7%d9%84%d9%85%d8%b5%d9%86%d9%88%d8%b9%d8%a9-%d9%85%d9%86-%d8%a7%d9%84%d9%81%d9%88%d9%84\/\">duplex stainless steel valve capabilities<\/a> for seawater and chloride-rich service.<\/p>\n<h3>Nickel alloys, titanium and zirconium<\/h3>\n<p>Nickel alloys may be selected for strong acids, reducing conditions, high temperature or mixed corrosion environments. Titanium is effective in many oxidizing chloride services, while zirconium is used in selected severe acid applications. The exact alloy designation must be specified; terms such as \u201cnickel alloy trim\u201d or \u201cspecial alloy body\u201d are not adequate procurement descriptions.<\/p>\n<h3>Sour service<\/h3>\n<p>NACE MR0175\/ISO 15156 material selection depends on hardness, metallurgical condition, H2S partial pressure, pH, chloride concentration, temperature and applied stress. A material name alone does not establish sour-service compliance. Manufacturing records must also preserve the qualified heat treatment and hardness condition.<\/p>\n<h2 id=\"leakage-emissions\">8. Seat Leakage and Fugitive Emissions Are Different Requirements<\/h2>\n<p>Seat leakage concerns internal flow past the closed obturator. Fugitive emissions concern atmospheric leakage through the stem or shaft seal and body joints.<\/p>\n<p>A seat-leakage specification should state:<\/p>\n<ul>\n<li>Test standard and edition<\/li>\n<li>Test medium and pressure<\/li>\n<li>Test direction<\/li>\n<li>Duration<\/li>\n<li>Permitted leakage rate<\/li>\n<li>Whether acceptance occurs before or after functional cycling<\/li>\n<\/ul>\n<p>\u201cZero leakage\u201d has no useful procurement meaning unless the test method and acceptance threshold are defined.<\/p>\n<p>For atmospheric emissions, ISO 15848-1 provides a classification and type-qualification framework. API 624 applies to rising-stem valves equipped with graphite packing, while API 641 applies to quarter-turn valves. A qualification certificate should be checked for valve type, size range, pressure class, packing system, temperature class and mechanical-cycle scope.<\/p>\n<h2 id=\"fire-safety\">9. Fire-Safe Does Not Mean Fireproof<\/h2>\n<p>A fire-tested valve is designed to limit leakage during and after a defined fire exposure. The qualification does not imply that the valve remains undamaged or can be returned to service without inspection.<\/p>\n<p>API 607 is commonly applied to quarter-turn valves and valves fitted with nonmetallic seats. API 6FA addresses fire testing of valves more broadly. The project must specify the applicable standard and confirm that the tested configuration represents the supplied valve.<\/p>\n<p>Secondary metal seating, antistatic continuity and stem retention may all be important, but they are separate design requirements and should be stated explicitly.<\/p>\n<h2 id=\"actuator-sizing\">10. Actuator Selection Must Use the Worst Credible Load<\/h2>\n<p>The actuator must be sized from required torque or thrust at the worst credible condition, not from nominal valve size.<\/p>\n<ul>\n<li>Break-to-open and end-to-close load<\/li>\n<li>Maximum differential pressure<\/li>\n<li>Seat and packing friction<\/li>\n<li>Hydrodynamic or aerodynamic torque<\/li>\n<li>Minimum pneumatic or hydraulic supply pressure<\/li>\n<li>Motor starting torque for electric actuation<\/li>\n<li>Temperature, deposits and aging effects<\/li>\n<li>Required operating time and fail action<\/li>\n<li>Stem, gearbox, bracket and coupling allowable loads<\/li>\n<\/ul>\n<p>Excess actuator output is not automatically safer. It can overload the stem, key, coupling, seat or mechanical stops. The valve and actuator must be assessed as one drive train.<\/p>\n<p>Fast emergency closure also requires a hydraulic-transient review. Reducing stroke time without checking surge pressure can transfer risk from the valve to the pipeline, pump or supporting structure.<\/p>\n<h2 id=\"inspection\">11. Inspection Must Verify the Specified Failure Controls<\/h2>\n<p>Hydrostatic and seat tests are necessary but do not prove material identity, corrosion resistance, low-emission performance or actuator adequacy.<\/p>\n<div style=\"overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 18px 0;\">\n<table style=\"width: 100%; min-width: 780px; border-collapse: collapse; border: 1px solid #000;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Verification<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Purpose<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">EN 10204 Type 3.1 certificates<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Traceability of specified metallic materials<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Positive material identification<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Confirmation of alloy chemistry on selected components<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Hardness testing<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Verification of heat treatment and sour-service limits<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Shell pressure test<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Pressure-boundary integrity<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">High- and low-pressure seat tests<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Closure performance under defined conditions<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">NDE<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Detection of relevant surface or volumetric discontinuities<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Torque or thrust test<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Confirmation of operating load and actuator margin<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Functional fail-action test<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Verification of accessories, stroke time and safe position<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The inspection and test plan should define document-review points, witness points, hold points and acceptance criteria before manufacturing begins.<\/p>\n<h2 id=\"selection-matrix\">12. Severe Service Valve Selection Matrix<\/h2>\n<div style=\"overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 18px 0;\">\n<table style=\"width: 100%; min-width: 920px; border-collapse: collapse; border: 1px solid #000;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Service condition<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Dominant risk<\/th>\n<th style=\"border: 1px solid #000; padding: 9px; text-align: left;\">Typical engineering response<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">High liquid pressure drop<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Cavitation, noise and vibration<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Pressure staging, anti-cavitation trim and hardened surfaces<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Downstream pressure below vapor pressure<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Flashing erosion<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Angle body, enlarged outlet and erosion-resistant flow path<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Entrained sand or catalyst<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Erosion and seat damage<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Protected seats, controlled velocity and hard-facing<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Abrasive slurry<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Blockage and wear<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Knife gate\/slurry design, flushing and replaceable wear parts<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">Chloride-rich seawater<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Pitting, crevice corrosion and SCC<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Qualified duplex, super duplex, titanium or other alloy<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">H2S-containing production fluid<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">SSC, HIC and stress-corrosion cracking<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">NACE MR0175\/ISO 15156 material and hardness control<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">LNG or cryogenic liquid<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Thermal contraction and packing leakage<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Extended bonnet, cavity relief and cryogenic-qualified seals<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">High-temperature steam<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Oxidation, galling and seal degradation<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Alloy body, hard-faced trim and suitable graphite sealing<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #000; padding: 9px;\">VOC or hazardous gas<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Atmospheric stem leakage<\/td>\n<td style=\"border: 1px solid #000; padding: 9px;\">Qualified low-emission packing and controlled stem finish<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 id=\"rfq-data\">13. Minimum Data for a Technically Complete Valve RFQ<\/h2>\n<ol>\n<li>Valve function and preferred architecture<\/li>\n<li>Nominal size, pressure class and end connections<\/li>\n<li>Applicable standards and required editions<\/li>\n<li>Design and operating pressure-temperature envelope<\/li>\n<li>Fluid composition, state, density and viscosity<\/li>\n<li>Maximum differential pressure and required flow rate<\/li>\n<li>Vapor pressure for liquid throttling service<\/li>\n<li>Solids concentration and particle-size distribution<\/li>\n<li>Body, bonnet, trim, stem, seat, packing and bolting materials<\/li>\n<li>Required shutoff direction and leakage acceptance<\/li>\n<li>Fugitive-emission, fire-test and sour-service requirements<\/li>\n<li>Actuator type, fail position, supply pressure and stroke time<\/li>\n<li>NDE, material certification and third-party inspection scope<\/li>\n<li>Installation orientation, coating, preservation and documentation<\/li>\n<\/ol>\n<h2 id=\"faq\">\u0627\u0644\u0623\u0633\u0626\u0644\u0629 \u0627\u0644\u0634\u0627\u0626\u0639\u0629<\/h2>\n<h3>Can a valve be used for both isolation and throttling?<\/h3>\n<p>Only when its body, trim, characteristic and actuator are designed for both duties. A conventional gate valve should not be selected for continuous throttling.<\/p>\n<h3>Is a higher pressure class always a safer choice?<\/h3>\n<p>No. A higher class increases pressure-boundary capacity but does not correct incompatible materials, cavitation, excessive velocity, unsuitable seats or inadequate actuator sizing.<\/p>\n<h3>Does stainless steel eliminate corrosion risk?<\/h3>\n<p>No. Stainless steel can suffer pitting, crevice corrosion, stress-corrosion cracking and galvanic attack. The exact grade must be checked against the complete chemical and thermal environment.<\/p>\n<h3>Are API 598 and ISO 5208 identical?<\/h3>\n<p>No. They address similar pressure-testing objectives, but the procedures and acceptance provisions should not be assumed interchangeable. The purchase order must identify the governing standard and edition.<\/p>\n<h3>Does fire-safe mean the valve will remain undamaged?<\/h3>\n<p>No. Fire testing evaluates leakage under defined test conditions. A fire-exposed valve still requires isolation, inspection and an engineering decision before any return to service.<\/p>\n<h2>Conclusion<\/h2>\n<p>Effective severe service valve selection aligns the process envelope, failure mechanism, valve architecture, materials, sealing system, actuator and inspection plan. Each choice must support the same design basis.<\/p>\n<p>WDL Valve supplies standard and custom valve solutions for corrosive, erosive, cryogenic, high-temperature and high-pressure applications. For a technical review, send the operating conditions, material requirements and applicable standards through the <a href=\"https:\/\/wdlvalve.com\/ar\/%d8%a7%d8%aa%d8%b5%d9%84-%d8%a8%d9%86%d8%a7\/\">WDL Valve enquiry page<\/a>.<\/p>\n<h2 id=\"references\">Technical References<\/h2>\n<ul>\n<li><a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/b16-34-valves-flanged-threaded-welding-end\" target=\"_blank\" rel=\"noopener noreferrer\">ASME B16.34 \u2014 Valves, Flanged, Threaded and Welding End<\/a><\/li>\n<li><a href=\"https:\/\/www.api.org\/products-and-services\/standards\/important-standards-announcements\/spec6d\" target=\"_blank\" rel=\"noopener noreferrer\">\u0645\u0648\u0627\u0635\u0641\u0627\u062a API 6D<\/a><\/li>\n<li><a href=\"https:\/\/www.api.org\/products-and-services\/standards\/standards-plan\" target=\"_blank\" rel=\"noopener noreferrer\">API Standards Plan<\/a><\/li>\n<li><a href=\"https:\/\/www.iso.org\/standard\/65111.html\" target=\"_blank\" rel=\"noopener noreferrer\">ISO 5208 \u2014 Pressure Testing of Metallic Valves<\/a><\/li>\n<li><a href=\"https:\/\/www.iso.org\/standard\/61441.html\" target=\"_blank\" rel=\"noopener noreferrer\">ISO 15848-1 \u2014 Fugitive Emissions<\/a><\/li>\n<li><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/2461\" target=\"_blank\" rel=\"noopener noreferrer\">IEC 60534-2-1 \u2014 Control-Valve Sizing<\/a><\/li>\n<li><a href=\"https:\/\/content.ampp.org\/standards\/book\/1139\/ANSI-NACE-MR0175-Petroleum-and-Natural-Gas\" target=\"_blank\" rel=\"noopener noreferrer\">NACE MR0175\/ISO 15156<\/a><\/li>\n<li><a href=\"https:\/\/www.emerson.com\/en\/final-control\/catalog\/products-and-software\/valves\/control-valves\/control-valve-handbook\" target=\"_blank\" rel=\"noopener noreferrer\">Emerson Control Valve Handbook<\/a><\/li>\n<\/ul>\n<div style=\"border-top: 1px solid #999; margin-top: 28px; padding-top: 14px; font-size: 0.95em;\"><strong>Prepared by:<\/strong> Wong WP, Sales Manager, Xiamen WDL Valve Co., Ltd.<br \/>\n<strong>\u0645\u0644\u0627\u062d\u0638\u0629 \u0641\u0646\u064a\u0629:<\/strong> This article provides general engineering guidance. Project-specific valve selection must be verified against the governing piping code, process data and purchaser specification.<\/div>\n<\/article>","protected":false},"excerpt":{"rendered":"<p>A standards-based engineering guide to severe service valve selection, covering pressure class, Cv sizing, cavitation, flashing, materials, emissions, fire testing, actuation and inspection.<\/p>","protected":false},"author":1,"featured_media":1378,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_kad_post_transparent":"default","_kad_post_title":"default","_kad_post_layout":"default","_kad_post_sidebar_id":"","_kad_post_content_style":"default","_kad_post_vertical_padding":"default","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"categories":[52],"tags":[],"class_list":["post-1361","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/posts\/1361","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/comments?post=1361"}],"version-history":[{"count":15,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/posts\/1361\/revisions"}],"predecessor-version":[{"id":1377,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/posts\/1361\/revisions\/1377"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/media\/1378"}],"wp:attachment":[{"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/media?parent=1361"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/categories?post=1361"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wdlvalve.com\/ar\/wp-json\/wp\/v2\/tags?post=1361"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}