{"id":1999,"date":"2026-09-11T18:53:29","date_gmt":"2026-09-12T01:53:29","guid":{"rendered":"https:\/\/www.songhaiflanges.com\/?p=1999"},"modified":"2026-09-11T18:53:29","modified_gmt":"2026-09-12T01:53:29","slug":"stub-end-flange-type-a-stainless-stub-ends-guide","status":"publish","type":"post","link":"https:\/\/www.songhaiflanges.com\/th\/stub-end-flange-type-a-stainless-stub-ends-guide\/","title":{"rendered":"Stub End Flange Guide: Type A Stub End, Stainless Steel Stub Ends, and Lap Joint Connections"},"content":{"rendered":"

A stub end flange<\/strong> system is a practical solution when a piping line needs easy alignment, frequent dismantling, or cost control for expensive alloy materials. In this system, the stub end<\/strong> is welded to the pipe, while a loose lap joint flange or backing flange rotates behind it. During assembly, the flange bolts to the mating flange, and the stub end face provides the sealing surface.<\/p>\n

Buyers may search for flange stub end<\/strong>, stubend<\/strong>, end flange<\/strong>, stainless steel stub ends<\/strong>, or type A stub end<\/strong>. These terms often point to the same family of products, but the details matter. Stub end type, material, length pattern, radius, flange standard, gasket face, and pipe schedule all affect whether the joint fits and seals correctly.<\/p>\n

What Is a Stub End?<\/h2>\n

A stub end is a short pipe fitting with one end prepared for butt welding to the pipe and the other end formed with a flared face or lap. The loose flange sits behind this lap and presses it against the gasket when bolts are tightened. Because the loose flange does not contact the process fluid in many designs, it can sometimes be made from a lower-cost material while the wetted stub end is made from stainless steel or alloy material.<\/p>\n

This design is especially useful in stainless steel, duplex, nickel alloy, and titanium piping systems. For example, a project can use stainless steel stub ends<\/strong> with carbon steel backing flanges when allowed by the specification and corrosion environment. This can reduce cost while keeping the wetted surface corrosion resistant.<\/p>\n

How a Stub End Flange System Works<\/h2>\n

A typical stub end flange connection includes four main parts: the pipe, the stub end, the loose lap joint flange, and the gasket. The stub end is butt welded to the pipe. The lap joint flange remains free to rotate around the pipe behind the stub end. When the joint is assembled, the flange bolts pass through the two flange bolt patterns and compress the gasket between the stub end face and the mating flange face.<\/p>\n

The rotating flange makes alignment much easier in field installation. If bolt holes are slightly misaligned, the installer can rotate the flange without twisting the welded pipe. This is one of the biggest advantages of a flange stub end system over a fully welded fixed flange.<\/p>\n

Stub End Types: Type A, Type B, and Type C<\/h2>\n\n\n\n\n\n\n\n
Stub End Type<\/th>\nTypical Matching Flange<\/th>\nMain Features<\/th>\nCommon Use<\/th>\n<\/tr>\n<\/thead>\n
Type A stub end<\/td>\nLap joint flange<\/td>\nDesigned with a lap thickness and radius suitable for standard lap joint flange geometry<\/td>\nMost common choice for lap joint flange assemblies<\/td>\n<\/tr>\n
Type B stub end<\/td>\nSlip on flange used as backing flange in some systems<\/td>\nDifferent radius and lap profile from Type A<\/td>\nProject-specific piping where the backing flange design is confirmed<\/td>\n<\/tr>\n
Type C stub end<\/td>\nSlip on or plate flange style backing in selected systems<\/td>\nFabricated or flared from pipe, often with different dimensional practice<\/td>\nLower pressure or custom fabrication applications<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The keyword stub end type A<\/strong> or type A stub end<\/strong> is especially important because Type A is the usual match for a standard lap joint flange. Using the wrong type can create poor seating, interference at the radius, or an incorrect contact area between the backing flange and the stub end lap.<\/p>\n

Long Pattern vs Short Pattern Stub Ends<\/h2>\n

Stub ends are often supplied in long pattern or short pattern designs. Long pattern stub ends provide more length between the weld end and the lap face, which can improve welding access and help with alignment. Short pattern stub ends are more compact and can reduce space, weight, and cost in suitable applications.<\/p>\n

The choice should be based on standard requirements, pipe layout, welding access, stress condition, and project specification. If the drawing or standard calls for a specific pattern, do not substitute another pattern without engineering approval.<\/p>\n

Materials for Stainless Stub Ends and Industrial Systems<\/h2>\n\n\n\n\n\n\n\n\n\n
Material<\/th>\nTypical Grades<\/th>\nWhy It Is Used<\/th>\nBuying Note<\/th>\n<\/tr>\n<\/thead>\n
Stainless steel<\/td>\n304, 304L, 316, 316L, 321, 347<\/td>\nCorrosion resistance and clean process compatibility<\/td>\nConfirm PMI, passivation, and low-carbon grade if welding is critical<\/td>\n<\/tr>\n
Carbon steel<\/td>\nA234 WPB, A105-related systems<\/td>\nCost-effective for general industrial piping<\/td>\nUsually needs coating if exposed to corrosion<\/td>\n<\/tr>\n
Alloy steel<\/td>\nChrome-moly grades<\/td>\nHigh temperature and strength requirements<\/td>\nCheck heat treatment and welding procedure requirements<\/td>\n<\/tr>\n
Duplex stainless<\/td>\n2205, 2507<\/td>\nHigh strength and chloride corrosion resistance<\/td>\nControl heat input and ferrite balance during welding<\/td>\n<\/tr>\n
Nickel alloy<\/td>\nInconel, Monel, Hastelloy type alloys<\/td>\nSevere corrosion or high temperature service<\/td>\nOften used to reduce wetted alloy cost with backing flanges<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Why Use Stainless Steel Stub Ends?<\/h2>\n

Stainless steel stub ends<\/strong> and stainless stub ends<\/strong> are widely used in chemical, food, pharmaceutical, marine, water treatment, and clean process piping. The stainless stub end contacts the medium, while the backing flange may be stainless steel or another approved material depending on project rules.<\/p>\n

This is useful when the fluid requires corrosion resistance but the flange body does not need to be fully wetted. In some systems, a stainless steel stub end with a carbon steel backing flange can reduce cost. In hygienic or highly corrosive service, however, the complete assembly may still need stainless steel or higher alloy material.<\/p>\n

Advantages of Stub End Flange Connections<\/h2>\n
    \n
  • Easy bolt hole alignment:<\/strong> The loose flange rotates freely, which helps field assembly.<\/li>\n
  • Lower alloy cost:<\/strong> The wetted stub end can be expensive alloy while the backing flange can be lower-cost material if permitted.<\/li>\n
  • Convenient maintenance:<\/strong> The connection can be opened for cleaning, inspection, or equipment replacement.<\/li>\n
  • Good for frequent dismantling:<\/strong> Lap joint systems are practical around equipment that needs periodic service.<\/li>\n
  • Useful for large diameter pipe:<\/strong> Rotating flanges help manage alignment in larger assemblies.<\/li>\n<\/ul>\n

    Limitations and Design Cautions<\/h2>\n

    A stub end flange system is not always the best choice. It may have lower fatigue strength than a weld neck flange system in severe cyclic service. The loose flange must match the stub end radius and lap thickness. Gasket seating must be checked carefully because the sealing face is on the stub end, not on the loose flange. For high pressure, high temperature, vibration, or dangerous media, engineering review is important.<\/p>\n

    Another caution is corrosion at the backing flange or crevice area. Even if the stub end is stainless steel, the backing flange and bolts may be exposed to the external environment. In marine or washdown conditions, material compatibility and coating quality should not be ignored.<\/p>\n

    Installation Guide for Stub End and Lap Joint Flange<\/h2>\n
      \n
    1. Confirm dimensions before welding.<\/strong> Check pipe size, wall thickness, stub end pattern, flange class, bolt pattern, and standard.<\/li>\n
    2. Place the loose flange correctly.<\/strong> The flange must be installed behind the stub end before the stub end is welded to the pipe.<\/li>\n
    3. Fit up the stub end.<\/strong> Align the bore with the pipe and maintain the correct root gap for butt welding.<\/li>\n
    4. Weld according to qualified procedure.<\/strong> Use suitable filler metal, shielding gas, and heat input control for stainless or alloy materials.<\/li>\n
    5. Inspect the weld and face.<\/strong> Check for weld defects, distortion, spatter, scratches, and damage to the gasket seating face.<\/li>\n
    6. Install the gasket and tighten bolts evenly.<\/strong> Use a cross-pattern tightening sequence and suitable torque control.<\/li>\n
    7. Test the joint.<\/strong> Hydrotest, leak test, or service inspection should follow the project specification.<\/li>\n<\/ol>\n

      How to Specify a Stub End Flange in an RFQ<\/h2>\n

      To avoid mistakes, include enough details in the inquiry. A complete RFQ for a flange stub end system should include:<\/p>\n

        \n
      • Stub end type, such as Type A, Type B, or Type C<\/li>\n
      • Pattern length, such as long pattern or short pattern<\/li>\n
      • Pipe size and wall thickness or schedule<\/li>\n
      • Material grade and standard<\/li>\n
      • Matching lap joint flange standard and pressure class<\/li>\n
      • Face type, gasket type, and sealing requirement<\/li>\n
      • Dimensional standard, drawing, or project specification<\/li>\n
      • Inspection requirements, such as MTC, PMI, NDE, visual inspection, and dimensional report<\/li>\n
      • Surface treatment, marking, packing, and export documentation<\/li>\n<\/ul>\n

        Stub End vs Weld Neck Flange vs Slip On Flange<\/h2>\n\n\n\n\n\n\n\n
        Connection<\/th>\nMain Benefit<\/th>\nBest For<\/th>\nWatch Point<\/th>\n<\/tr>\n<\/thead>\n
        Stub end with lap joint flange<\/td>\nRotating alignment and possible alloy cost saving<\/td>\nMaintenance lines, alloy piping, large assemblies<\/td>\nMatch stub end type and backing flange geometry<\/td>\n<\/tr>\n
        Weld neck flange<\/td>\nStrong stress transition and reliable severe service performance<\/td>\nHigh pressure, high temperature, cyclic loading<\/td>\nHigher cost and stricter bore matching<\/td>\n<\/tr>\n
        Slip on flange<\/td>\nSimple installation and lower cost<\/td>\nGeneral industrial piping and moderate service<\/td>\nLower fatigue strength than weld neck<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Quality Control for Stub Ends<\/h2>\n

        Quality control should cover material certificates, heat number traceability, dimensional inspection, wall thickness, ovality, lap diameter, lap thickness, radius, sealing face condition, and weld end preparation. For stainless steel stub ends, PMI testing and surface cleaning may be requested. For alloy steel, heat treatment and impact testing may be required depending on service conditions.<\/p>\n

        Packing also matters. The lap face is the sealing surface, so it should be protected during shipping. Scratches, dents, or deformation at the face can cause leakage during installation.<\/p>\n

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

        Songhai Flanges supplies lap joint flanges, stub ends, stainless steel flanges, carbon steel flanges, alloy steel flanges, weld neck flanges, slip on flanges, blind flanges, socket weld flanges, threaded flanges, plate flanges, large diameter flanges, and custom flange products for international piping projects. We support standard products and drawing-based manufacturing with material traceability and inspection documentation.<\/p>\n

        If you need stub end flange<\/strong> assemblies, flange stub end<\/strong> matching, type A stub end<\/strong> selection, or stainless steel stub ends for corrosive service, provide your pipe size, schedule, material, standard, pressure class, and operating conditions. Our team can help check compatibility before production.<\/p>\n

        Conclusion<\/h2>\n

        A stub end flange system is a smart choice when a pipeline needs easier alignment, frequent dismantling, or reduced cost for alloy wetted parts. Type A stub ends are commonly used with lap joint flanges, while other types require careful matching. For reliable performance, specify the correct material, pattern length, radius, pressure class, gasket face, and inspection requirements. A properly selected stub end can make installation easier and long-term maintenance more efficient.<\/p>","protected":false},"excerpt":{"rendered":"

        An original technical guide to stub end flange systems, flange stub end selection, Type A stub end dimensions, stainless steel stub ends, lap joint flange matching, installation, inspection, and procurement tips.<\/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":[1192,1196,1197,759,1061,1191,458,1189,463,462,1183,460,464,476,1200,254,756,1199,758,1195,475,1201,1198,356,465,773,1185,1186,255,757,1190,1187,1184,1188,1193,1194],"class_list":["post-1999","post","type-post","status-publish","format-standard","hentry","category-product-guide","category-product-knowledge","category-technical-guide","category-technical-reference","tag-alloy-steel-stub-end","tag-asa-stub-end","tag-asme-stub-end","tag-backing-flange","tag-butt-weld-stub-end","tag-carbon-steel-stub-end","tag-custom-flange-manufacturer","tag-end-flange","tag-flange-factory-china","tag-flange-manufacturer-china","tag-flange-stub-end","tag-forged-flange-manufacturer","tag-industrial-flange-manufacturer","tag-industrial-flanges-supplier","tag-lap-joint-connection","tag-lap-joint-flange","tag-lap-joint-stub-end","tag-long-pattern-stub-end","tag-loose-flange","tag-mss-stub-end","tag-pipe-flange-manufacturer","tag-pipe-stub-end","tag-short-pattern-stub-end","tag-stainless-steel-flange","tag-stainless-steel-flange-supplier","tag-stainless-steel-stub-end","tag-stainless-steel-stub-ends","tag-stainless-stub-ends","tag-stub-end","tag-stub-end-flange","tag-stub-end-flange-system","tag-stub-end-type-a","tag-stubend","tag-type-a-stub-end","tag-type-b-stub-end","tag-type-c-stub-end"],"_links":{"self":[{"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/posts\/1999","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/comments?post=1999"}],"version-history":[{"count":1,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/posts\/1999\/revisions"}],"predecessor-version":[{"id":2000,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/posts\/1999\/revisions\/2000"}],"wp:attachment":[{"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/media?parent=1999"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/categories?post=1999"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/th\/wp-json\/wp\/v2\/tags?post=1999"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}