{"id":18987,"date":"2026-10-19T07:10:29","date_gmt":"2026-10-19T07:10:29","guid":{"rendered":"https:\/\/oudianvalve.com\/?p=18987"},"modified":"2026-10-19T07:10:29","modified_gmt":"2026-10-19T07:10:29","slug":"what-are-the-different-ansi-classes-for-valves","status":"publish","type":"post","link":"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/","title":{"rendered":"What Are the Different ANSI Classes for Valves?"},"content":{"rendered":"<section id=\"introduction\">ANSI classes for valves designate standardized pressure-temperature ratings that define the maximum allowable working pressure of a valve body across a range of operating conditions. Rather than representing a fixed pressure threshold, each numerical designation reflects an engineered performance boundary established by industrial standards. These ratings indicate how much internal mechanical stress a valve assembly can manage as thermal conditions fluctuate within a piping network.<\/p>\n<p>The appropriate valve class depends on operating pressure, system temperature, fluid characteristics, body material, and structural design standards. Selecting an inadequate class creates severe operational vulnerabilities, while specifying an excessive class introduces unnecessary weight and capital expense.<\/p>\n<div class=\"img-container\">\n<div class=\"image-embed\" data-image=\"%7B%22src%22%3A%22https%3A%2F%2Fstorage.googleapis.com%2F48877118-7272-4a4d-b302-0465d8aa4548%2F7c0162ef-88b5-4cf7-9ba9-cc48ad7031d3%2F60c56440-3339-4fa4-a954-87e064bb3614.jpg%22%2C%22title%22%3A%22Industrial%20flanged%20valves%20installed%20in%20a%20piping%20manifold%22%2C%22method%22%3A%22text-to-image%22%2C%22generator%22%3A%222%22%2C%22date%22%3A1792393081137%7D\">\n<div class=\"_Media_1itgw_1 _ImageEmbed_1itgw_28\"><\/div>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"understanding-ansi-pressure-classes\">\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_89 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\u041e\u0433\u043b\u0430\u0432\u043b\u0435\u043d\u0438\u0435<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">\u041f\u0435\u0440\u0435\u043a\u043b\u044e\u0447\u0430\u0442\u044c<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Understanding_ANSI_Classes_for_Valves_and_Pressure-Temperature_Ratings\" >Understanding ANSI Classes for Valves and Pressure-Temperature Ratings<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Standard_Valve_Pressure_Classes_from_Class_150_to_Class_2500\" >Standard Valve Pressure Classes from Class 150 to Class 2500<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Governing_Standards_ASME_B1634_B165_and_B1647\" >Governing Standards: ASME B16.34, B16.5, and B16.47<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#ASME_B1634\" >\u0410\u0421\u041c\u042d \u041116.34<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#ASME_B165\" >ASME B16.5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#ASME_B1647\" >ASME B16.47<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Differences_Between_ANSIASME_Classes_and_Metric_PN_Designations\" >Differences Between ANSI\/ASME Classes and Metric PN Designations<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#ANSIASME_Class_System\" >ANSI\/ASME Class System<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Metric_PN_System\" >Metric PN System<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Industrial_Applications_Across_Pressure_Classes\" >Industrial Applications Across Pressure Classes<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Lower-Pressure_Services\" >Lower-Pressure Services<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Medium-Pressure_Lines\" >Medium-Pressure Lines<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#High-Pressure_Facilities\" >High-Pressure Facilities<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Critical_Factors_in_Valve_Class_Selection\" >Critical Factors in Valve Class Selection<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Reading_Manufacturer_Pressure-Temperature_Charts_and_Specifications\" >Reading Manufacturer Pressure-Temperature Charts and Specifications<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Frequently_Asked_Questions_About_Valve_Pressure_Classes\" >Frequently Asked Questions About Valve Pressure Classes<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Does_an_ANSI_Class_150_valve_have_a_maximum_pressure_limit_of_150_psi\" >Does an ANSI Class 150 valve have a maximum pressure limit of 150 psi?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#What_is_an_ANSI_Class_800_valve\" >What is an ANSI Class 800 valve?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#How_does_valve_body_material_affect_the_ANSI_pressure_class_rating\" >How does valve body material affect the ANSI pressure class rating?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Can_an_ANSI-rated_valve_connect_directly_to_a_metric_PN_flange\" >Can an ANSI-rated valve connect directly to a metric PN flange?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Why_does_allowable_working_pressure_decrease_as_temperature_increases\" >Why does allowable working pressure decrease as temperature increases?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/what-are-the-different-ansi-classes-for-valves\/#Summary_of_Valve_Class_Selection_Principles\" >Summary of Valve Class Selection Principles<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Understanding_ANSI_Classes_for_Valves_and_Pressure-Temperature_Ratings\"><\/span>Understanding ANSI Classes for Valves and Pressure-Temperature Ratings<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>ANSI classes for valves establish a standardized relationship between thermal exposure and mechanical containment capability. Many non-specialists assume that a designation like Class 150 denotes an absolute limit of 150 psi, but this assumption is incorrect. A valve rated as Class 150 can handle pressures well above 200 psi at ambient room temperature, yet its allowable working pressure drops substantially as operating temperatures climb.<\/p>\n<p>The American National Standards Institute, working in coordination with the American Society of Mechanical Engineers, created these categories to simplify piping engineering. The baseline pressure rating decreases along a predictable curve as temperature increases because structural metals experience reduced tensile strength in heated environments. Consequently, pressure ratings cannot be evaluated as isolated numbers; they always function as coupled pressure-temperature ratings.<\/p>\n<p>Valve wall thickness, flange dimensions, bolting patterns, and shell geometry are proportioned to support the mechanical loads defined for each class. Specifying an ANSI class confirms that the valve pressure boundary meets strict metallurgical and structural criteria across varied thermal cycles.<\/p>\n<div class=\"highlight-box\">\n<p>A valve class rating is a pressure-temperature envelope, not a static pressure ceiling. The maximum allowable working pressure continually diminishes as fluid or environmental temperatures increase.<\/p>\n<\/div>\n<div class=\"img-container\">\n<div class=\"image-embed\" data-image=\"%7B%22src%22%3A%22https%3A%2F%2Fstorage.googleapis.com%2F48877118-7272-4a4d-b302-0465d8aa4548%2F7c0162ef-88b5-4cf7-9ba9-cc48ad7031d3%2F5f4d20d0-57f6-4767-afe4-755f3198802a.jpg%22%2C%22title%22%3A%22Cast%20steel%20valve%20body%20showing%20raised%20face%20flange%20markings%22%2C%22method%22%3A%22text-to-image%22%2C%22generator%22%3A%222%22%2C%22date%22%3A1792393081037%7D\">\n<div class=\"_Media_1itgw_1 _ImageEmbed_1itgw_28\"><\/div>\n<\/div>\n<p class=\"img-caption\">Standardized markings cast directly onto valve bodies indicate pressure class compliance and material composition.<\/p>\n<\/div>\n<\/section>\n<section id=\"overview-of-standard-valve-classes\">\n<h2><span class=\"ez-toc-section\" id=\"Standard_Valve_Pressure_Classes_from_Class_150_to_Class_2500\"><\/span>Standard Valve Pressure Classes from Class 150 to Class 2500<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Standard industrial piping utilizes eight primary pressure classes defined by ASME specifications. These designations comprise Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500, and Class 2500, alongside Class 800, which is widely adopted for compact forged valves. Each progression to a higher numerical class signifies a heavier body construction, thicker walls, and more robust connection interfaces.<\/p>\n<p>Class 400 is relatively uncommon in modern industrial procurement because engineers generally step directly from Class 300 to Class 600 components to streamline inventory. In contrast, Class 800 represents an intermediate standard tailored for threaded and socket-weld forged steel valves used in compact utility and bypass lines. The higher tiers, extending from Class 900 through Class 2500, serve severe utility headers, power generation loops, and upstream energy production facilities.<\/p>\n<p>The table below summarizes standard pressure classes, their relative pressure tiers, typical functional scopes, and structural behavior.<\/p>\n<div class=\"table-container\">\n<table>\n<thead>\n<tr>\n<td data-row=\"head\">ANSI Class<\/td>\n<td data-row=\"head\">Pressure Tier<\/td>\n<td data-row=\"head\">Typical Scope<\/td>\n<td data-row=\"head\">Allowable Pressure Behavior<\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 150<\/td>\n<td data-label=\"Pressure Tier\">Low Pressure<\/td>\n<td data-label=\"Typical Scope\">General Utilities<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Maintains ambient capability above nominal designation but declines sharply at elevated heat.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 300<\/td>\n<td data-label=\"Pressure Tier\">Medium Pressure<\/td>\n<td data-label=\"Typical Scope\">Process Piping<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Provides substantial strength margins for moderate thermal processing circuits.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">Class 400<\/td>\n<td data-label=\"Pressure Tier\">Intermediate<\/td>\n<td data-label=\"Typical Scope\">Specialized Lines<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Offers intermediate containment but is frequently bypassed in favor of higher categories.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 600<\/td>\n<td data-label=\"Pressure Tier\">High Pressure<\/td>\n<td data-label=\"Typical Scope\">Refining Units<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Accommodates elevated pipeline pressures across broad operating temperature ranges.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">Class 800<\/td>\n<td data-label=\"Pressure Tier\">Compact Forged<\/td>\n<td data-label=\"Typical Scope\">Small Bore Lines<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Tailored for forged steel bodies operating in demanding auxiliary services.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 900<\/td>\n<td data-label=\"Pressure Tier\">Severe Pressure<\/td>\n<td data-label=\"Typical Scope\">Gas Compression<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Handles severe compression loads with heavy structural wall thickness.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 1500<\/td>\n<td data-label=\"Pressure Tier\">Extreme Pressure<\/td>\n<td data-label=\"Typical Scope\">Power Generation<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Sustains supercritical steam and critical fluid confinement under intense stress.<\/td>\n<\/tr>\n<tr>\n<td data-label=\"ANSI Class\">\u041a\u043b\u0430\u0441\u0441 2500<\/td>\n<td data-label=\"Pressure Tier\">Ultra Severe<\/td>\n<td data-label=\"Typical Scope\">Subsea Extraction<\/td>\n<td data-label=\"Allowable Pressure Behavior\">Delivers maximum mechanical containment under extreme downhole and wellhead conditions.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n<section id=\"key-standards-b16-34-b16-5-b16-47\">\n<h2><span class=\"ez-toc-section\" id=\"Governing_Standards_ASME_B1634_B165_and_B1647\"><\/span>Governing Standards: ASME B16.34, B16.5, and B16.47<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Valve pressure classes operate within an integrated framework of manufacturing and mechanical codes published by ASME. These technical codes establish exact minimum material dimensions, pressure containment metrics, non-destructive examination criteria, and dimensional tolerances. Compliance across these companion standards allows valves, flanges, and connecting pipe spools to mate without structural mismatch.<\/p>\n<p>The standard ASME B16.34 serves as the primary document governing valves with flanged, threaded, and welded ends. It establishes pressure-temperature tables, minimum wall thickness rules, and testing parameters for cast, forged, and fabricated valve designs. When piping assemblies connect to valves, the matching flange requirements derive from ASME B16.5 or ASME B16.47, depending on pipe diameter.<\/p>\n<div class=\"card-grid\">\n<div class=\"card\">\n<h3 class=\"card-title\"><span class=\"ez-toc-section\" id=\"ASME_B1634\"><\/span><a href=\"https:\/\/oudianvalve.com\/ru\/2026\/10\/asme-b16-34-valve-specification-the-comprehensive-guide\/\">\u0410\u0421\u041c\u042d \u041116.34<\/a><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p class=\"card-text\">Governs valve design, wall thickness, thermal ratings, pressure testing protocols, and acceptable body materials.<\/p>\n<\/div>\n<div class=\"card\">\n<h3 class=\"card-title\"><span class=\"ez-toc-section\" id=\"ASME_B165\"><\/span>ASME B16.5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p class=\"card-text\">Specifies pipe flanges and flanged fittings from small nominal sizes through 24-inch outer diameters.<\/p>\n<\/div>\n<div class=\"card\">\n<h3 class=\"card-title\"><span class=\"ez-toc-section\" id=\"ASME_B1647\"><\/span>ASME B16.47<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p class=\"card-text\">Defines large-diameter steel flanges ranging from 26 inches through 60 inches across standardized pressure classes.<\/p>\n<\/div>\n<\/div>\n<p>Adherence to these standards helps prevent premature metal failure and maintains consistent mechanical behavior across complete industrial processing units.<\/p>\n<\/section>\n<section id=\"ansi-classes-versus-metric-pn-ratings\">\n<h2><span class=\"ez-toc-section\" id=\"Differences_Between_ANSIASME_Classes_and_Metric_PN_Designations\"><\/span>Differences Between ANSI\/ASME Classes and Metric PN Designations<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Industrial <a href=\"https:\/\/valveman.com\/blogs\/the-valve-authority\/what-are-the-different-ansi-classes-for-valves?srsltid=AU7gw4VxYLS4CjAUuE3Z5qZZdqeKyw5-sHgJim9LGJwsC2ZeNibI12ph\">piping<\/a> systems use two predominant rating systems: the ANSI\/ASME class system prevalent in North America and the metric Nominal Pressure, or PN, system standardized under European EN and international ISO codes. While both systems categorize equipment by pressure-handling capability, their baseline testing principles and dimensional assumptions differ significantly. Treating them as identical can lead to dangerous mismatched bolting patterns or inadequate wall dimensions.<\/p>\n<p>A PN designation expresses nominal pressure in bar at a reference temperature of 20 degrees Celsius. In contrast, an ANSI class represents an extensive performance curve across hundreds of thermal increments according to specific metallurgical groupings. The two classification systems do not share identical bolt-hole circles, flange outer dimensions, or gasket surfaces, which rules out direct physical interchangeability in most installations.<\/p>\n<div class=\"list-comparison\">\n<h3 class=\"list-comparison-title\"><span class=\"ez-toc-section\" id=\"ANSIASME_Class_System\"><\/span>ANSI\/ASME Class System<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul class=\"list-comparison-column list-comparison-primary\">\n<li>Employs dimensionless class identifiers like 150, 300, and 600.<\/li>\n<li>Defines allowable pressure across diverse temperature charts by material group.<\/li>\n<li>Utilizes imperial bolt sizing and specific raised face flange geometry.<\/li>\n<li>Governed primarily by ASME B16.34 and companion standards.<\/li>\n<\/ul>\n<h3 class=\"list-comparison-title\"><span class=\"ez-toc-section\" id=\"Metric_PN_System\"><\/span>Metric PN System<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul class=\"list-comparison-column list-comparison-success\">\n<li>Uses bar-based pressure designations such as PN 16 and PN 40.<\/li>\n<li>References maximum working pressure specifically at 20 degrees Celsius.<\/li>\n<li>Relies on metric bolt circles, metric studs, and European flange profiles.<\/li>\n<li>Governed by EN 1092-1 and related international standards.<\/li>\n<\/ul>\n<\/div>\n<p>While approximate performance parallels exist, such as pairing PN 20 with Class 150 or PN 50 with Class 300, mating an ANSI flange directly to a metric PN valve requires specialized transition adapters.<\/p>\n<\/section>\n<section id=\"application-tiers-low-medium-high-pressure\">\n<h2><span class=\"ez-toc-section\" id=\"Industrial_Applications_Across_Pressure_Classes\"><\/span>Industrial Applications Across Pressure Classes<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Valve classes correspond to distinct operational tiers across municipal, processing, and energy facilities. Lower-tier systems rely on economical valve bodies with lighter structural profiles, whereas severe service plants demand forged shells and specialized alloys capable of resisting deformation. Selecting the correct tier protects equipment integrity and avoids unnecessary project costs.<\/p>\n<div class=\"three-columns\">\n<div class=\"column-card\">\n<h3><span class=\"ez-toc-section\" id=\"Lower-Pressure_Services\"><\/span>Lower-Pressure Services<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Class 150 valves serve domestic water treatment, low-pressure steam, HVAC circulation loops, and municipal distribution pipelines.<\/p>\n<\/div>\n<div class=\"column-card\">\n<h3><span class=\"ez-toc-section\" id=\"Medium-Pressure_Lines\"><\/span>Medium-Pressure Lines<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Class 300 and Class 600 components support chemical processing, refining units, industrial gas pipelines, and manufacturing circuits.<\/p>\n<\/div>\n<div class=\"column-card\">\n<h3><span class=\"ez-toc-section\" id=\"High-Pressure_Facilities\"><\/span>High-Pressure Facilities<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Class 900, 1500, and 2500 assemblies operate in boiler feed headers, supercritical power stations, and subsea petroleum extraction wells.<\/p>\n<\/div>\n<\/div>\n<p>Ball valves, gate valves, and globe valves within these pressure categories utilize distinct internal seat seals to complement their outer bodies. Soft elastomer seats frequently handle moderate conditions in lower classes, whereas metal-to-metal seating becomes standard practice as valves enter severe high-temperature and high-pressure duties.<\/p>\n<div class=\"img-container\">\n<div class=\"image-embed\" data-image=\"%7B%22src%22%3A%22https%3A%2F%2Fstorage.googleapis.com%2F48877118-7272-4a4d-b302-0465d8aa4548%2F7c0162ef-88b5-4cf7-9ba9-cc48ad7031d3%2F032738aa-76f9-4fa1-beed-43ed8ef9eb67.jpg%22%2C%22title%22%3A%22High%20pressure%20ball%20valve%20assembly%20in%20an%20energy%20transmission%20pipeline%22%2C%22method%22%3A%22text-to-image%22%2C%22generator%22%3A%222%22%2C%22date%22%3A1792393080937%7D\">\n<div class=\"_Media_1itgw_1 _ImageEmbed_1itgw_28\"><img decoding=\"async\" src=\"https:\/\/storage.googleapis.com\/48877118-7272-4a4d-b302-0465d8aa4548\/7c0162ef-88b5-4cf7-9ba9-cc48ad7031d3\/032738aa-76f9-4fa1-beed-43ed8ef9eb67.jpg\" alt=\"High pressure ball valve assembly in an energy transmission pipeline\" \/><\/p>\n<div class=\"_Buttons_1itgw_5\" contenteditable=\"false\" data-media=\"true\"><\/div>\n<\/div>\n<\/div>\n<p class=\"img-caption\">High-pressure isolation valves in energy transmission lines rely on reinforced body shells to contain continuous line pressures.<\/p>\n<\/div>\n<\/section>\n<section id=\"factors-in-valve-class-selection\">\n<h2><span class=\"ez-toc-section\" id=\"Critical_Factors_in_Valve_Class_Selection\"><\/span>Critical Factors in Valve Class Selection<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Selecting the proper valve class requires evaluating all operational dynamics rather than relying strictly on line gauge pressure. A process line with modest operating pressure may still demand a heavy valve class if continuous operating temperatures weaken the valve body metal. Systematic review of line criteria prevents catastrophic structural failures and premature packing leaks.<\/p>\n<ol class=\"list-numbers\">\n<li>Determine the maximum coincident pressure and temperature conditions, accounting for normal operations, thermal relief events, and upset scenarios.<\/li>\n<li>Identify the body material group, such as carbon steel, stainless steel, or specialized duplex alloys, as each metallurgy displays unique derating curves under heat.<\/li>\n<li>Verify compatibility with adjacent piping components, confirming that flange facings, bolt ratings, and wall schedules correspond with the selected valve rating.<\/li>\n<li>Evaluate fluid hazards, establishing appropriate safety margins for volatile, toxic, flammable, or highly abrasive process media.<\/li>\n<li>Consult mandatory jurisdictional and project piping codes to confirm minimum rating thresholds for the intended service environment.<\/li>\n<\/ol>\n<p>Applying this sequence helps verify that the specified valve body maintains adequate mechanical resilience across the full operational life of the piping installation.<\/p>\n<\/section>\n<section id=\"evaluating-pressure-temperature-charts\">\n<h2><span class=\"ez-toc-section\" id=\"Reading_Manufacturer_Pressure-Temperature_Charts_and_Specifications\"><\/span>Reading Manufacturer Pressure-Temperature Charts and Specifications<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Manufacturer pressure-temperature charts provide the definitive metric for confirming valve integrity under service conditions. Standard ASME tables group metals into distinct material categories, such as Group 1.1 for common carbon steels and Group 2.2 for austenitic stainless steels. Because each metal responds differently to elevated temperatures, two Class 300 valves constructed from different alloys can feature distinctly different pressure limits at an identical operating temperature.<\/p>\n<p>Engineers must cross-reference actual continuous operating points against the material group tables published in ASME B16.34 or the manufacturer catalog. In addition to shell wall limits, internal trim elements, elastomeric stem packing, and polymer seat rings can lower the effective working limit below the structural rating of the metal casing. Reviewing both the shell rating and the soft-goods rating chart helps avoid unexpected internal seat degradation during operation.<\/p>\n<div class=\"warning-box\">\n<p>Always verify both the shell rating and the internal seat material limit. A valve body may mechanically withstand high pressure, but internal soft seats or packings can fail if thermal boundaries are exceeded.<\/p>\n<\/div>\n<div class=\"img-container\">\n<div class=\"image-embed\" data-image=\"%7B%22src%22%3A%22https%3A%2F%2Fstorage.googleapis.com%2F48877118-7272-4a4d-b302-0465d8aa4548%2F7c0162ef-88b5-4cf7-9ba9-cc48ad7031d3%2F44ca3e14-601c-46d3-b8b5-75bb4bc6c6d9.jpg%22%2C%22title%22%3A%22Technician%20inspecting%20an%20industrial%20valve%20data%20plate%20on%20site%22%2C%22method%22%3A%22text-to-image%22%2C%22generator%22%3A%222%22%2C%22date%22%3A1792393080837%7D\">\n<div class=\"_Media_1itgw_1 _ImageEmbed_1itgw_28\"><\/div>\n<\/div>\n<p class=\"img-caption\">Nameplate data stamped on the valve bonnet confirms material classification, body class, and allowable operating parameters.<\/p>\n<\/div>\n<\/section>\n<section>\n<h2><span class=\"ez-toc-section\" id=\"Frequently_Asked_Questions_About_Valve_Pressure_Classes\"><\/span>Frequently Asked Questions About Valve Pressure Classes<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"faq-item\">\n<h3 class=\"faq-question\"><span class=\"ez-toc-section\" id=\"Does_an_ANSI_Class_150_valve_have_a_maximum_pressure_limit_of_150_psi\"><\/span>Does an ANSI Class 150 valve have a maximum pressure limit of 150 psi?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"faq-answer\">\n<p>No, an ANSI Class 150 valve does not have a static 150 psi limit. At ambient temperatures, a carbon steel Class 150 valve can handle pressures up to 285 psi, with allowable pressure declining as temperatures rise.<\/p>\n<\/div>\n<\/div>\n<div class=\"faq-item\">\n<h3 class=\"faq-question\"><span class=\"ez-toc-section\" id=\"What_is_an_ANSI_Class_800_valve\"><\/span>What is an ANSI Class 800 valve?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"faq-answer\">\n<p>An ANSI Class 800 valve is a compact forged steel valve standard established for small-bore piping under API and ASME guidelines. These valves typically feature socket-weld or threaded connections and provide an intermediate pressure rating between Class 600 and Class 900.<\/p>\n<\/div>\n<\/div>\n<div class=\"faq-item\">\n<h3 class=\"faq-question\"><span class=\"ez-toc-section\" id=\"How_does_valve_body_material_affect_the_ANSI_pressure_class_rating\"><\/span>How does valve body material affect the ANSI pressure class rating?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"faq-answer\">\n<p>Valve body material directly dictates the pressure-temperature curve of a given class. Different metals belong to distinct ASME material groups, meaning a carbon steel valve and a stainless steel valve of the same class share different working pressures at elevated temperatures.<\/p>\n<\/div>\n<\/div>\n<div class=\"faq-item\">\n<h3 class=\"faq-question\"><span class=\"ez-toc-section\" id=\"Can_an_ANSI-rated_valve_connect_directly_to_a_metric_PN_flange\"><\/span>Can an ANSI-rated valve connect directly to a metric PN flange?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"faq-answer\">\n<p>Direct connection between ANSI and metric PN flanges is generally not possible without specialized adapters. Bolt-hole quantities, bolt circle diameters, and flange thicknesses differ between the two standards, preventing proper alignment and gasket compression.<\/p>\n<\/div>\n<\/div>\n<div class=\"faq-item\">\n<h3 class=\"faq-question\"><span class=\"ez-toc-section\" id=\"Why_does_allowable_working_pressure_decrease_as_temperature_increases\"><\/span>Why does allowable working pressure decrease as temperature increases?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<div class=\"faq-answer\">\n<p>Allowable working pressure decreases at high temperatures because structural metals experience reduced yield and tensile strength under heat. ASME standards account for this thermal derating to prevent valve body distortion, bolt stretch, and joint leakage.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"conclusion\">\n<h2><span class=\"ez-toc-section\" id=\"Summary_of_Valve_Class_Selection_Principles\"><\/span>Summary of Valve Class Selection Principles<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Correctly identifying the right ANSI valve class requires analyzing simultaneous operating pressures, temperature profiles, and fluid risks against standardized performance tables. Reviewing manufacturer pressure-temperature charts and project engineering specifications remains an indispensable step before finalizing any valve procurement. Adhering to these mechanical guidelines protects piping infrastructure and supports stable industrial operation over the long term.<\/p>\n<\/section>","protected":false},"excerpt":{"rendered":"<p>ANSI classes for valves designate standardized pressure-temperature ratings that define the maximum allowable working pressure of a valve body across a range of operating conditions. Rather than representing a fixed pressure threshold, each numerical designation reflects an engineered performance boundary established by industrial standards. These ratings indicate how much internal mechanical stress a valve assembly [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":18982,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[976],"class_list":["post-18987","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry-news","tag-what-are-the-different-ansi-classes-for-valves"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/oudianvalve.com\/wp-content\/uploads\/2026\/10\/API-600-Gate-Valve-1.jpg","_links":{"self":[{"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/posts\/18987","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/comments?post=18987"}],"version-history":[{"count":1,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/posts\/18987\/revisions"}],"predecessor-version":[{"id":18988,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/posts\/18987\/revisions\/18988"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/media\/18982"}],"wp:attachment":[{"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/media?parent=18987"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/categories?post=18987"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/oudianvalve.com\/ru\/wp-json\/wp\/v2\/tags?post=18987"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}