{"id":1982,"date":"2026-08-24T23:43:18","date_gmt":"2026-08-25T06:43:18","guid":{"rendered":"https:\/\/www.songhaiflanges.com\/?p=1982"},"modified":"2026-08-24T23:43:18","modified_gmt":"2026-08-25T06:43:18","slug":"asme-vs-ansi-flange-class-standards-guide","status":"publish","type":"post","link":"https:\/\/www.songhaiflanges.com\/es\/asme-vs-ansi-flange-class-standards-guide\/","title":{"rendered":"ASME vs ANSI Flanges: ASME Class, ANSI ASME Standards, and Buying Guide"},"content":{"rendered":"

The terms ANSI ASME<\/strong>, ANSI and ASME<\/strong>, and ASME vs ANSI<\/strong> appear constantly in flange purchasing. Many buyers still ask for \u201cANSI flanges,\u201d while many drawings and modern project specifications call for ASME B16.5 or ASME B16.47. The wording can be confusing, but the goal is simple: order a flange that matches the correct standard, dimensions, pressure class, material, and inspection requirements.<\/p>\n

This guide explains how ANSI and ASME relate to pipe flanges, what ASME class<\/strong> means, why ASME standards are widely used, and how to write a clear RFQ for industrial flange projects.<\/p>\n

ANSI and ASME: What Do the Names Mean?<\/h2>\n

ANSI stands for the American National Standards Institute. ANSI is mainly an accreditation and coordination organization. It does not normally write every technical detail of a flange dimension table itself. Instead, it helps approve and coordinate standards so industries can work with consistent rules.<\/p>\n

ASME stands for the American Society of Mechanical Engineers. ASME develops many engineering standards used for pressure equipment, piping, fittings, flanges, valves, and related mechanical components. In flange purchasing, the most common ASME standards include ASME B16.5 for pipe flanges and flanged fittings, and ASME B16.47 for large diameter steel flanges.<\/p>\n

ASME vs ANSI: What Is the Difference for Flanges?<\/h2>\n

The practical difference in ASME vs ANSI<\/strong> flange discussions is this: ANSI is often used as a market term, while ASME usually identifies the actual technical standard. When someone says \u201cANSI flange,\u201d they often mean an ASME-standard flange, especially ASME B16.5 or ASME B16.47.<\/p>\n

This older terminology remains common because earlier standards and purchasing habits used ANSI language. Today, if a pressure piping project needs accurate dimensions and ratings, the safest wording is to specify the exact ASME standard, pressure class, size, flange type, facing type, and material grade.<\/p>\n

What Is ASME Class?<\/h2>\n

ASME class<\/strong> refers to the pressure class rating system used for flanges and related components. Common ASME flange classes include Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500, and Class 2500. These classes are not simple pressure numbers in psi. They represent pressure-temperature ratings that depend on material group and operating temperature.<\/p>\n

For example, a Class 150 carbon steel flange and a Class 150 stainless steel flange may have different pressure-temperature limits at elevated temperatures. A higher class generally means a stronger and thicker flange with different bolting, but the exact allowable pressure must be checked against the standard and material.<\/p>\n

Why ASME Class Matters in Flange Selection<\/h2>\n

Choosing the wrong ASME class can cause bolt-up problems, gasket failure, leakage, or unsafe operation. A Class 150 flange may be suitable for low-pressure water, air, or some vacuum services, while Class 300, 600, 900, 1500, or 2500 may be required for higher pressure, higher temperature, or more severe industrial service.<\/p>\n

Pressure class also affects dimensions. A Class 300 flange is not simply a stronger version of a Class 150 flange with the same bolt pattern. Flange thickness, bolt circle, bolt size, number of bolts, raised face details, and hub dimensions may change. Matching the pressure class of the mating flange is essential.<\/p>\n

ASME B16.5 and ASME B16.47<\/h2>\n

ASME B16.5 covers many common pipe flanges and flanged fittings in sizes up to NPS 24. It includes pressure classes, dimensions, tolerances, marking, materials, and pressure-temperature ratings for standard flange types.<\/p>\n

ASME B16.47 covers larger diameter steel flanges, commonly used for large pipelines, pressure vessels, and heavy industrial equipment. It includes Series A and Series B flange designs. Series A and Series B are not interchangeable in many cases because dimensions and bolt patterns differ. Buyers should always specify the series when ordering large diameter ASME flanges.<\/p>\n

Common ASME Flange Types<\/h2>\n

ASME-style flanges are available in many designs. Each type serves a different purpose:<\/p>\n

    \n
  • Weld neck flange:<\/strong> Butt welded to pipe and preferred for high pressure, high temperature, cyclic loading, and critical service.<\/li>\n
  • Slip on flange:<\/strong> Slides over pipe and is fillet welded, often used for general low to medium pressure service.<\/li>\n
  • Blind flange:<\/strong> Closes a pipe end, vessel nozzle, valve outlet, or inspection opening.<\/li>\n
  • Socket weld flange:<\/strong> Used for small-bore piping where the pipe inserts into a socket and is fillet welded.<\/li>\n
  • Threaded flange:<\/strong> Used with threaded pipe where welding is not required or is restricted.<\/li>\n
  • Lap joint flange:<\/strong> Used with a stub end and loose backing flange for alignment flexibility and alloy cost control.<\/li>\n<\/ul>\n

    ANSI ASME Terminology in Purchase Orders<\/h2>\n

    Because both terms remain common, a purchase order may say \u201cANSI ASME flange.\u201d This is usually acceptable as informal language, but the technical line item should be more precise. A better description is: \u201cASME B16.5, NPS 6, Class 300, raised face, weld neck flange, ASTM A182 F316L, Schedule 40 bore.\u201d<\/p>\n

    This level of detail removes ambiguity. It tells the supplier which standard, size, class, facing, type, material, and bore are required. It also reduces the risk of receiving a flange that looks similar but does not match the system.<\/p>\n

    ANSI vs ASME and International Projects<\/h2>\n

    International projects may use ASME, EN, DIN, JIS, GOST, API, AWWA, or customer-specific flange standards. An ASME flange may not bolt directly to an EN or DIN flange, even when the nominal size looks similar. Bolt circle, hole diameter, face type, thickness, and pressure rating systems can be different.<\/p>\n

    If an overseas buyer asks for ANSI flanges, confirm whether the project truly requires ASME dimensions or simply uses \u201cANSI\u201d as a general term for American-style flanges. When replacement parts are involved, photos, drawings, and measured dimensions are very useful.<\/p>\n

    How to Choose the Right ASME Class<\/h2>\n

    ASME class selection should be based on design pressure, design temperature, material group, fluid, gasket, bolting, corrosion allowance, and project code. Do not select class only by habit. A low-pressure system may not need a high class flange, while a high-temperature system may require a higher class than expected because allowable pressure decreases with temperature.<\/p>\n

    Engineers should check the pressure-temperature rating tables in the applicable ASME standard and confirm compatibility with the pipe, valves, gaskets, and equipment nozzles. Buyers should avoid substituting a lower class flange without written engineering approval.<\/p>\n

    Flange Marking and Documentation<\/h2>\n

    ASME flanges are typically marked with size, pressure class, material grade, heat number, standard or specification, and manufacturer identification. These markings help verify traceability during inspection and installation.<\/p>\n

    For industrial projects, documents may include material test certificates, heat treatment records, PMI reports, NDT reports, pressure test reports, and third-party inspection certificates. Documentation requirements should be stated in the purchase order, not requested after production if the project is critical.<\/p>\n

    Common Mistakes to Avoid<\/h2>\n

    Do not order only by saying \u201cANSI flange.\u201d Do not assume ANSI and ASME mean exactly the same thing in every document. Do not mix ASME B16.47 Series A and Series B. Do not assume Class 150 equals 150 psi in all temperatures and materials. Do not mix ASME and EN bolt patterns without checking drawings.<\/p>\n

    Also avoid using the wrong flange class to match inventory on hand. A flange that bolts up physically may still be wrong for pressure-temperature rating, material compatibility, or project code compliance.<\/p>\n

    Buying Checklist for ANSI ASME Flanges<\/h2>\n

    When requesting a quotation for ANSI or ASME flanges, include the following details:<\/p>\n

      \n
    • Standard: ASME B16.5, ASME B16.47 Series A\/B, ASME B16.36, or project drawing<\/li>\n
    • Nominal pipe size and pipe schedule or bore requirement<\/li>\n
    • ASME class: Class 150, 300, 400, 600, 900, 1500, or 2500<\/li>\n
    • Flange type: weld neck, slip on, blind, socket weld, threaded, lap joint, or custom design<\/li>\n
    • Facing type: raised face, flat face, RTJ, tongue and groove, or special face<\/li>\n
    • Material grade: carbon steel, stainless steel, duplex, alloy steel, or special alloy<\/li>\n
    • Service data: design pressure, design temperature, fluid, corrosion environment, and design code<\/li>\n
    • Inspection and documents: MTC, PMI, UT, PT, MT, RT, hardness, pressure test, or third-party inspection<\/li>\n
    • Quantity, marking, coating, packing, delivery schedule, and destination<\/li>\n<\/ul>\n

      Conclusion<\/h2>\n

      ASME vs ANSI<\/strong> in flange purchasing is mostly a terminology issue, but it can create real procurement mistakes if the technical standard is unclear. ANSI is associated with standards coordination and accreditation, while ASME develops the flange standards most commonly used for steel pipe flanges. The safest approach is to specify the exact ASME standard and ASME class<\/strong> required by the project.<\/p>\n

      Songhai Flanges supplies ANSI\/ASME-style weld neck flanges, slip on flanges, blind flanges, socket weld flanges, threaded flanges, lap joint flanges, pressure vessel flanges, stainless steel flanges, large diameter flanges, and custom forged flanges. If your project requires clear ANSI ASME<\/strong> flange selection, sharing drawings and service conditions will help the engineering team recommend the correct standard and class.<\/p>","protected":false},"excerpt":{"rendered":"

      Understand ASME vs ANSI for pipe flanges, including ANSI ASME terminology, ASME class ratings, ASME B16.5, ASME B16.47, flange pressure classes, and how to specify industrial flanges correctly.<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[230,253,214,268],"tags":[998,997,1000,960,368,957,972,765,1002,996,1001,179,1003,1004,999,106,975,979,980,976,977,978,458,459,155,463,292,462,648,633,188,964,263,464,476,254,348,470,941,962,475,1006,1005,733,345,352,479,461,465,478,232],"class_list":["post-1982","post","type-post","status-publish","format-standard","hentry","category-product-guide","category-product-knowledge","category-technical-guide","category-technical-reference","tag-ansi-and-asme","tag-ansi-asme","tag-ansi-asme-flanges","tag-ansi-flange-standard","tag-ansi-flanges","tag-ansi-standard-flanges","tag-asme-b16-47-flange","tag-asme-b16-5-flange","tag-asme-b16-9-fitting","tag-asme-class","tag-asme-flange-standard","tag-asme-flanges","tag-asme-pressure-class","tag-asme-standard-flanges","tag-asme-vs-ansi","tag-blind-flange","tag-class-150-flange","tag-class-1500-flange","tag-class-2500-flange","tag-class-300-flange","tag-class-600-flange","tag-class-900-flange","tag-custom-flange-manufacturer","tag-custom-forged-flanges","tag-flange-dimensions","tag-flange-factory-china","tag-flange-inspection","tag-flange-manufacturer-china","tag-flange-material-selection","tag-flange-pressure-class","tag-flange-specifications","tag-flange-standard","tag-high-pressure-flange","tag-industrial-flange-manufacturer","tag-industrial-flanges-supplier","tag-lap-joint-flange","tag-large-diameter-flange","tag-large-diameter-flange-manufacturer","tag-mtc-certificate","tag-pipe-flange-dimensions","tag-pipe-flange-manufacturer","tag-pipe-flange-specifications","tag-pipe-flange-standard","tag-pmi-testing","tag-pressure-vessel-flange","tag-slip-on-flange-2","tag-socket-weld-flange","tag-stainless-steel-flange-manufacturer","tag-stainless-steel-flange-supplier","tag-threaded-flange","tag-weld-neck-flange"],"_links":{"self":[{"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/posts\/1982","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/comments?post=1982"}],"version-history":[{"count":1,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/posts\/1982\/revisions"}],"predecessor-version":[{"id":1983,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/posts\/1982\/revisions\/1983"}],"wp:attachment":[{"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/media?parent=1982"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/categories?post=1982"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/es\/wp-json\/wp\/v2\/tags?post=1982"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}