{"id":2009,"date":"2026-09-16T18:21:58","date_gmt":"2026-09-17T01:21:58","guid":{"rendered":"https:\/\/www.songhaiflanges.com\/?p=2009"},"modified":"2026-09-16T18:21:58","modified_gmt":"2026-09-17T01:21:58","slug":"ansi-pipe-flanges-standard-selection-guide","status":"publish","type":"post","link":"https:\/\/www.songhaiflanges.com\/ru\/ansi-pipe-flanges-standard-selection-guide\/","title":{"rendered":"ANSI Pipe Flanges Guide: ANSI Standard for Flanges, Types, Dimensions, and Selection Tips"},"content":{"rendered":"

ANSI pipe flanges<\/strong> are standardized pipe connectors used to join pipes, valves, pumps, pressure vessels, filters, heat exchangers, and other industrial equipment. They provide a bolted connection that can be assembled, inspected, opened, and maintained without cutting the pipeline apart. In global purchasing, buyers often use terms such as ANSI flange<\/strong>, flange ANSI<\/strong>, ANSI standard for flanges<\/strong>, or ANSI ASME flange when asking for dimensions, pressure class, material, and flange type.<\/p>\n

Strictly speaking, many modern flange specifications are published under ASME rather than ANSI, especially ASME B16.5 and ASME B16.47. However, the term ANSI flange is still widely used in international trade. This guide explains how ANSI pipe flanges work, which standards are commonly used, how to select the right type, and what information should be included in a professional RFQ.<\/p>\n

What Is an ANSI Flange?<\/h2>\n

An ANSI flange is a pipe flange manufactured to a standardized dimensional system historically associated with the American National Standards Institute. In current engineering documents, the same product is usually specified under ASME standards. For example, many buyers say ANSI B16.5 flange, while the current technical reference is commonly ASME B16.5.<\/p>\n

The purpose of the standard is to ensure compatibility. A flange made to the same size, pressure class, face type, and standard should match the bolt hole pattern, outside diameter, thickness, raised face dimensions, and gasket seating requirements expected by the piping system.<\/p>\n

How ANSI Pipe Flanges Work<\/h2>\n

A flange connection works by clamping two flange faces together with bolts and nuts. A gasket is placed between the flange faces. When the bolts are tightened, the gasket compresses and fills small surface irregularities, creating a seal that helps prevent fluid or gas leakage.<\/p>\n

The joint includes several parts: flange body, bore, bolt holes, sealing face, gasket, bolts, nuts, and sometimes washers. The pipe may be welded, threaded, socket welded, or connected through a lap joint depending on flange type. The correct combination of flange, gasket, bolting, material, and tightening procedure determines whether the joint performs reliably.<\/p>\n

ANSI Standard for Flanges: Common References<\/h2>\n\n\n\n\n\n\n\n\n\n
Standard<\/th>\nCommon Scope<\/th>\nTypical Use<\/th>\nImportant Note<\/th>\n<\/tr>\n<\/thead>\n
ASME B16.5<\/td>\nPipe flanges and flanged fittings from NPS 1\/2 to NPS 24<\/td>\nMost standard forged steel pipe flanges<\/td>\nOften called ANSI B16.5 in market language<\/td>\n<\/tr>\n
ASME B16.47 Series A<\/td>\nLarge diameter steel flanges above NPS 24<\/td>\nHigh-load and large pipeline systems<\/td>\nGenerally heavier than Series B<\/td>\n<\/tr>\n
ASME B16.47 Series B<\/td>\nLarge diameter steel flanges above NPS 24<\/td>\nLarge diameter lower-weight flange applications<\/td>\nNot interchangeable with Series A<\/td>\n<\/tr>\n
ASME B16.1<\/td>\nCast iron pipe flanges<\/td>\nLow-pressure water and utility systems<\/td>\nDifferent material and dimensional family<\/td>\n<\/tr>\n
Project drawings<\/td>\nCustom flange dimensions or modified connections<\/td>\nEquipment nozzles, special vessels, replacement parts<\/td>\nDrawing controls over generic naming<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Main Parts of an ANSI Flange<\/h2>\n
    \n
  • Bore:<\/strong> The center opening where the pipe or fluid path aligns.<\/li>\n
  • Flange face:<\/strong> The sealing surface that contacts the gasket.<\/li>\n
  • Bolt holes:<\/strong> Holes arranged around the flange for bolts or studs.<\/li>\n
  • Bolt circle:<\/strong> The diameter of the circle through the center of the bolt holes.<\/li>\n
  • Hub:<\/strong> A reinforced neck or raised section on some flange types, such as weld neck flanges.<\/li>\n
  • Raised face, flat face, or RTJ groove:<\/strong> The face design used to match gasket type and sealing requirement.<\/li>\n
  • Thickness:<\/strong> The flange body thickness needed for pressure class and standard compliance.<\/li>\n<\/ul>\n

    Common ANSI Flange Types<\/h2>\n\n\n\n\n\n\n\n\n\n\n
    Flange Type<\/th>\nConnection Method<\/th>\nBest Used For<\/th>\nSelection Note<\/th>\n<\/tr>\n<\/thead>\n
    Weld neck flange<\/td>\nButt welded to pipe<\/td>\nHigh pressure, high temperature, cyclic, and critical service<\/td>\nPipe schedule and bore must match<\/td>\n<\/tr>\n
    Slip on flange<\/td>\nPipe slips into flange and is fillet welded<\/td>\nGeneral industrial piping and moderate pressure systems<\/td>\nEasy alignment and lower cost<\/td>\n<\/tr>\n
    Blind flange<\/td>\nBolted to close a pipe end or nozzle<\/td>\nPipeline termination, inspection ports, vessel openings<\/td>\nSpecify tapping if required<\/td>\n<\/tr>\n
    Socket weld flange<\/td>\nPipe inserts into socket and is fillet welded<\/td>\nSmall-bore high-pressure piping<\/td>\nExpansion gap and welding procedure matter<\/td>\n<\/tr>\n
    Threaded flange<\/td>\nScrewed onto threaded pipe<\/td>\nSystems where welding is not preferred<\/td>\nCheck leakage risk and temperature limits<\/td>\n<\/tr>\n
    Lap joint flange<\/td>\nUsed with stub end; flange rotates freely<\/td>\nFrequent dismantling and alignment-sensitive systems<\/td>\nMatch stub end type and flange geometry<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    ANSI Flange Pressure Classes<\/h2>\n

    ANSI pipe flanges are commonly ordered by pressure class, such as Class 150, Class 300, Class 600, Class 900, Class 1500, and Class 2500. The class number is not a single universal pressure value. It represents a pressure-temperature rating family. Actual allowable pressure depends on material group, temperature, and standard tables.<\/p>\n

    For example, a Class 300 carbon steel flange and a Class 300 stainless steel flange may have different pressure-temperature limits depending on material group and design temperature. Therefore, the RFQ should include design pressure, design temperature, fluid, material grade, and applicable standard instead of only asking for an ANSI flange class.<\/p>\n

    ANSI Flange Face Types<\/h2>\n\n\n\n\n\n\n\n\n
    Face Type<\/th>\nDescription<\/th>\nTypical Gasket<\/th>\nCommon Application<\/th>\n<\/tr>\n<\/thead>\n
    Raised Face (RF)<\/td>\nRaised sealing area around the bore<\/td>\nSpiral wound, graphite, PTFE, compressed fiber<\/td>\nMost common industrial steel flange face<\/td>\n<\/tr>\n
    Flat Face (FF)<\/td>\nEntire flange face is flat<\/td>\nFull-face soft gasket<\/td>\nCast iron equipment and low-pressure systems<\/td>\n<\/tr>\n
    Ring Type Joint (RTJ)<\/td>\nGroove machined for metal ring gasket<\/td>\nOval or octagonal metal ring<\/td>\nHigh pressure and severe service<\/td>\n<\/tr>\n
    Tongue and Groove<\/td>\nMating raised tongue and recessed groove<\/td>\nConfined gasket<\/td>\nSpecial equipment and controlled sealing systems<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Materials for ANSI Pipe Flanges<\/h2>\n

    Common ANSI flange materials include carbon steel, stainless steel, alloy steel, duplex stainless steel, super duplex stainless steel, nickel alloy, and low-temperature carbon steel. Carbon steel is cost-effective for general industrial service. Stainless steel is selected for corrosion resistance and clean process environments. Alloy steel is used for high-temperature or high-strength systems. Duplex and nickel alloy materials are selected for severe corrosion service.<\/p>\n

    Material should be chosen according to process fluid, temperature, pressure, corrosion allowance, external environment, welding requirements, and lifecycle cost. For critical applications, request material test certificates, heat number traceability, PMI testing, and dimensional inspection reports.<\/p>\n

    How to Select the Right ANSI Flange<\/h2>\n
      \n
    1. Confirm the standard.<\/strong> Decide whether the project requires ASME B16.5, ASME B16.47 Series A, ASME B16.47 Series B, or a custom drawing.<\/li>\n
    2. Define size and pressure class.<\/strong> Provide nominal pipe size, pipe schedule, and pressure class.<\/li>\n
    3. Choose flange type.<\/strong> Select weld neck, slip on, blind, socket weld, threaded, lap joint, or custom flange based on service and installation.<\/li>\n
    4. Select face type.<\/strong> Match RF, FF, RTJ, or special facing with the gasket and service conditions.<\/li>\n
    5. Specify material.<\/strong> Include grade, standard, heat treatment, corrosion requirement, and any low-temperature or high-temperature requirement.<\/li>\n
    6. Check bolting and gasket.<\/strong> The flange, gasket, and bolting must work together as a sealing system.<\/li>\n
    7. Confirm inspection needs.<\/strong> State MTC, PMI, NDE, dimensional report, coating, marking, packing, and third-party inspection requirements.<\/li>\n<\/ol>\n

      Common Mistakes When Ordering ANSI Flanges<\/h2>\n
        \n
      • Using ANSI and ASME loosely:<\/strong> Market language is common, but purchase orders should state the exact standard.<\/li>\n
      • Ignoring Series A vs Series B:<\/strong> ASME B16.47 Series A and Series B large diameter flanges are not interchangeable.<\/li>\n
      • Forgetting pipe schedule:<\/strong> Weld neck flange bore must match the pipe wall thickness.<\/li>\n
      • Choosing pressure class by habit:<\/strong> Pressure-temperature rating must be checked against material and temperature.<\/li>\n
      • Mismatching gasket and face type:<\/strong> RF, FF, and RTJ faces require different sealing designs.<\/li>\n
      • Missing documentation:<\/strong> Export and project orders often require certificates and inspection reports.<\/li>\n<\/ul>\n

        RFQ Checklist for ANSI Pipe Flanges<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
        RFQ Item<\/th>\nExample<\/th>\nWhy It Matters<\/th>\n<\/tr>\n<\/thead>\n
        Standard<\/td>\nASME B16.5, ASME B16.47 Series A<\/td>\nControls dimensions and compatibility<\/td>\n<\/tr>\n
        Size and class<\/td>\nNPS 6 Class 300<\/td>\nDefines flange dimensions and rating family<\/td>\n<\/tr>\n
        Flange type<\/td>\nWeld neck, slip on, blind, threaded<\/td>\nControls connection method<\/td>\n<\/tr>\n
        Pipe schedule<\/td>\nSch 40, Sch 80, XS, XXS<\/td>\nNeeded for bore and weld end matching<\/td>\n<\/tr>\n
        Face type<\/td>\nRF, FF, RTJ<\/td>\nMust match gasket and sealing requirement<\/td>\n<\/tr>\n
        Material<\/td>\nA105, A350 LF2, A182 F304, A182 F316L<\/td>\nControls strength, temperature range, and corrosion resistance<\/td>\n<\/tr>\n
        Documents<\/td>\nMTC, PMI, dimensional report, NDE<\/td>\nSupports quality control and project acceptance<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        How Songhai Flanges Supports ANSI Flange Projects<\/h2>\n

        Songhai Flanges manufactures and supplies industrial pipe flanges for global projects, including ANSI pipe flanges, ASME flanges, weld neck flanges, slip on flanges, blind flanges, socket weld flanges, threaded flanges, lap joint flanges, plate flanges, large diameter flanges, stainless steel flanges, carbon steel flanges, alloy steel flanges, forged flanges, and custom flange products.<\/p>\n

        If your project needs an ANSI flange or flange ANSI specification, provide the standard, size, pressure class, flange type, material, face type, pipe schedule, gasket requirement, and inspection documents. Our team can help review dimensions and manufacturing requirements before production to reduce installation risk.<\/p>\n

        Conclusion<\/h2>\n

        ANSI pipe flanges are essential standardized connectors for industrial piping systems. They work by combining flange geometry, gasket compression, and bolting force to create a reliable, serviceable joint. The best flange choice depends on the exact standard, pressure class, size, material, face type, gasket, bolting, and operating conditions. Clear specifications help ensure that the flange fits correctly, seals reliably, and performs safely in long-term service.<\/p>","protected":false},"excerpt":{"rendered":"

        An original technical guide to ANSI pipe flanges, ANSI standard for flanges, ANSI flange types, pressure classes, face types, materials, dimensions, sealing principles, and procurement checks for industrial piping projects.<\/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":[903,1019,252,1292,944,1291,368,973,952,948,972,765,634,106,355,975,976,977,458,1290,635,259,462,964,488,249,464,1293,254,683,475,1005,487,261,352,479,356,465,478,232],"class_list":["post-2009","post","type-post","status-publish","format-standard","hentry","category-product-guide","category-product-knowledge","category-technical-guide","category-technical-reference","tag-alloy-steel-flange","tag-ansi-asme-flange","tag-ansi-flange","tag-ansi-flange-class","tag-ansi-flange-dimensions","tag-ansi-flange-sizes","tag-ansi-flanges","tag-ansi-pipe-flange","tag-ansi-pipe-flanges","tag-ansi-standard-for-flanges","tag-asme-b16-47-flange","tag-asme-b16-5-flange","tag-asme-flange","tag-blind-flange","tag-carbon-steel-flange","tag-class-150-flange","tag-class-300-flange","tag-class-600-flange","tag-custom-flange-manufacturer","tag-flange-ansi","tag-flange-bolting","tag-flange-gasket","tag-flange-manufacturer-china","tag-flange-standard","tag-flat-face-flange","tag-forged-flange","tag-industrial-flange-manufacturer","tag-industrial-pipe-flanges","tag-lap-joint-flange","tag-pipe-flange-connection","tag-pipe-flange-manufacturer","tag-pipe-flange-standard","tag-raised-face-flange","tag-rtj-flange","tag-slip-on-flange-2","tag-socket-weld-flange","tag-stainless-steel-flange","tag-stainless-steel-flange-supplier","tag-threaded-flange","tag-weld-neck-flange"],"_links":{"self":[{"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/posts\/2009","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/comments?post=2009"}],"version-history":[{"count":1,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/posts\/2009\/revisions"}],"predecessor-version":[{"id":2010,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/posts\/2009\/revisions\/2010"}],"wp:attachment":[{"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/media?parent=2009"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/categories?post=2009"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/ru\/wp-json\/wp\/v2\/tags?post=2009"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}