National Standard Stub End

The national standard lap joint stub end is a core matching pipe fitting of the national standard loose flange connection system. It mainly works with the loose slip-on flange to complete the detachable connection of pipelines, and is widel

National Standard Stub End - The national standard flanged short piece is exclusively adapted to all industrial and m...

National Standard Stub End

The national standard lap joint stub end is a core matching pipe fitting of the national standard loose flange connection system. It mainly works with the loose slip-on flange to complete the detachable connection of pipelines, and is widel

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  • The core advantages of national standard lap joint stub ends are full compliance with national standards, easy disassembly and assembly, zero welding stress, flexible adaptation, stable sealing, and extremely strong versatility. The product
  • dimensional tolerances, lap thickness, bevel angle, and mechanical properties all meet the standards
  • Enables universal interchangeability with national standard pipes nationwide
  • zero obstacles in engineering acceptance. It adopts an integrated structure of straight pipe section + integral lap
  • the end face is flat and smooth, with uniform rounded transitions
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Detailed Introduction

The national standard lap joint stub end is also called a lap joint stub pipe, loose flange lap ring, or lap joint fitting, and is a pipe fitting used in national standard piping systems together with loose flanges. During installation, the loose flange slides freely on the stub end pipe body, and tightening the bolts only presses the lap end face to complete the seal. The pipe body itself does not bear the torsional stress of the flange, so it is suitable for pipelines that require regular disassembly, assembly, and maintenance. Product specifications cover DN15~DN2000, imperial 1/2″~48″, wall thickness follows the SCH standard series, and it can adapt to PN10~PN160 pressure ratings. Materials include carbon steel, stainless steel, alloy steel, and duplex steel. There are three production processes: seamless hot-pressed lap joint, steel plate rolled lap joint, and forged machined lap joint. The lap end face is flat and the rounded corner transition is smooth. We can confirm specific specifications, materials, and quantities according to project requirements. Welcome to contact us for a quotation.

  • The loose flange can slide freely on the pipe body. When tightening the bolts, it only presses the lap end face to achieve sealing. The pipe body itself does not bear the torsional stress of the flange, reducing the risk of weld cracking.
  • Convenient for pipeline inspection and disassembly, suitable for piping systems that require frequent disassembly, assembly, and maintenance.
  • Implements national standard specifications such as GB/T 12459 and GB/T 13402, and dimensional tolerances are controlled according to national standards.
  • Specifications cover DN15~DN2000, imperial 1/2″~48″, wall thickness follows the SCH standard series, and it can adapt to PN10~PN160 pressure ratings.
  • Materials can be selected from carbon steel, stainless steel, alloy steel, and duplex steel, adapting to the needs of corrosion-resistant pipelines.
  • The lap end face is flat and the rounded corner transition is smooth, with no cracks and no delamination, and it has a high degree of fit with the loose flange.
  • Supports non-standard customization, including special straight pipe lengths, thickened lap end faces, special bevel angles, large-diameter special-shaped lap joints, etc.
Product NameNational Standard Stub End
Product CategoriesFlanges & Stub Ends
The parameters of this series of national standard lap joint stub ends fully comply with the latest national standard GB/T12459-2025, and are suitable for national standard pipeline design and acceptance specifications across all domestic industries. Specification rangeNominal diameter DN15–DN3400, imperial NPS1/4–NPS136; divided into two standard structural sizes: short type S and long type L. Wall thickness grades: SCH10, SCH20, SCH40, SCH80, SCH160, XXS extra heavy; pressure adaptation PN10, PN16, PN25, PN40, PN63, PN100, PN160 full national standard pressure ratings. Mainstream materials: 20#/Q235B carbon steel, 304/316L stainless steel, 15CrMo/12Cr1MoV alloy steel, 2205/2507 duplex steel. Forming processes: seamless hot-pressed integrated forming, steel plate rolled and welded forming, forged precision machined forming. End face flatness
CustomizationOur factory possesses full-dimensional modification, upgrade, and non-standard customization capabilities for national standard lap joint stub ends, and can undertake various national standard modification, special-shaped size, special working condition, and special process customization orders. Supports modification of conventional national standard sizes, including custom special straight pipe lengths, thickened lap joint end faces, non-standard rounded transitions, and special bevel angle machining, suitable for restricted installation spaces and special sealing working conditions. Can customize alloy steel high-temperature strengthening, duplex steel super anti-corrosion, stainless steel sanitary-grade polishing, and carbon steel hot-dip galvanizing anti-corrosion upgrade processes as needed, matching severe working conditions such as high temperature, strong corrosion, and cleanliness. Supports large-diameter special-shaped lap joints, eccentric lap joints, extended buffer-type stub ends, and non-standard pressure thickening customization, suitable for old national standard pipeline network renovation, multi-standard mixed pipelines, and special equipment non-standard interfaces. Can provide national standard reference
MOQOur factory's national standard lap joint stub ends adopt an ultra-low-threshold flexible minimum order mode, suitable for various needs such as sporadic replenishment for national standard projects, small samples for pipeline network technical transformation, batch complete-set procurement, and foreign trade order shipment. For common conventional specifications on the market, including DN15–DN600 mainstream nominal diameters, SCH40 standard wall thickness, carbon steel/304 conventional materials, and standard long and short type models, MOQ as low as
Lead TimeThe factory has established a dedicated standardized production line and a large-area constant-temperature warehouse for national standard pipe fittings, with massive regular stock of national standard lap joint stub ends on hand, rapidly responding to urgent delivery needs of national standard pipeline projects nationwide. All conventional wall thickness, carbon steel, and 304 stainless steel national standard long and short type lap joint stub ends in common market sizes DN15–DN600 are in stock, and size re-inspection and sorting are completed within 24 hours after order confirmation
PackagingNational standard lap joint stub ends adopt national standard industrial-grade standardized protective packaging, taking into account both domestic land transportation and international sea long-distance transportation protection needs, effectively preventing port deformation, end face scratches, moisture and rust, and collision damage. Small DN15–DN100 specification stub ends are individually covered with dust-proof protective film and fully wrapped in bubble wrap, with hard plastic protective caps installed on pipe openings to protect welding bevels and lap joint sealing surfaces and isolate moisture and dust. Medium DN125–DN600 products are wholly wrapped in waterproof and rust-proof woven fabric, with key protection for the outward-flanged sealing end faces to eliminate scratches, deformation, and paint loss. Large DN800 and above large-diameter lap joint stub ends use solid wood pallets for fixation, multi-point steel strap flexible reinforcement, and double-layer waterproof sealed wrapping; pallets comply with cross-border quarantine standards and can be directly customs cleared
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Applications

  • Pipeline connections requiring frequent disassembly and maintenance, such as municipal water supply and drainage, gas and HVAC, and old pipeline network renovation
  • Anti-corrosion pipeline networks such as acid-base process pipelines, flue gas desulfurization and denitrification, sewage treatment, and seawater desalination in the chemical and environmental protection fields
  • Working conditions with thermal displacement such as boiler auxiliary pipelines and heat transmission pipe networks in electric power and thermal projects
  • Scenarios requiring segmented connections such as process pipelines in industrial plants, external connecting pipelines of equipment, and ventilation and dust removal pipelines
  • Supporting procurement by pipeline design institutes and operation and maintenance teams in pipeline network technical transformation and renovation construction
  • Bulk procurement by wholesalers specializing in national standard pipeline fittings and cross-border B2B traders

Purchasing & Delivery

We use national standard industrial-grade standardized protective packaging. Small DN15~DN100 specifications are individually covered with dust-proof protective film and fully wrapped with bubble film, and pipe ends are fitted with hard plastic protective caps; medium DN125~DN600 specifications are wholly covered with waterproof and rust-proof woven fabric; large DN800 and above specifications are fixed with solid wood pallets, flexibly reinforced with multi-point steel straps, and wrapped with double-layer waterproof sealing. The pallets comply with cross-border quarantine standards. All products are stacked by category according to specifications, materials, and models, with national standard model labels, batch traceability information, and material identification independently attached. Each batch is accompanied by a national standard certificate of conformity, dimensional inspection report, and material certificate. Regular specifications are kept in stock. Within 24 hours after order confirmation, dimensional re-inspection and sorting are completed. For specific minimum order quantities and delivery times, please contact us for confirmation.

Service & Support

Before sales, we provide consultation on national standard specification selection, long and short type model matching, material working condition adaptation, and pressure rating matching. During sales, we synchronize production, national standard re-inspection, protective packaging, and logistics progress in real time, and provide a full set of national standard acceptance documents and Chinese-English customs clearance qualification documents free of charge. After sales, we uniformly provide an 18-month warranty period. During the warranty period, for quality problems such as dimensional deviation, end face deformation, process defects, and sealing failure caused by non-human installation errors, we provide free replacement and reissue. We are equipped with a 24-hour technical team to provide national standard pipeline installation guidance, loose flange pairing and debugging, pipeline network working condition optimization, and remote fault troubleshooting services.

FAQ

How to choose between long-type and short-type lap joint stub ends?

The long type L has a longer straight pipe section and good thermal expansion buffering performance, suitable for pipeline networks with high temperature, large temperature differences, and obvious thermal displacement; the short type S occupies less space, suitable for conventional room-temperature pipelines with limited installation space. For specific selection, please contact us, and we will assist in confirmation according to your working conditions.

Must national standard lap joint stub ends be paired with loose flanges?

Yes, lap joint stub ends are exclusively paired with national standard loose flanges to achieve detachable pipeline connections, and cannot be used with fixed welded flanges.

Does the product comply with the latest national standards?

All products strictly implement national standards such as GB/T 12459 and GB/T 13402, with dimensional tolerances, lap thickness, and groove angles controlled according to national standards.

Can non-standard specifications be customized?

Yes. We support customization of special straight pipe lengths, thickened lap end faces, non-standard rounded transitions, special groove angles, large-diameter irregular laps, eccentric laps, extended buffer-type stub ends, non-standard pressure thickening, etc. We can also customize processes such as alloy steel high-temperature strengthening, duplex steel anti-corrosion, stainless steel sanitary-grade polishing, and carbon steel hot-dip galvanizing as needed. Please provide specific dimensions and quantities, and we will assist in confirming the solution.

How are the minimum order quantity and delivery time confirmed?

Regular specifications are kept in stock, and dimensional re-inspection and sorting are completed within 24 hours after order confirmation. For specific minimum order quantity and delivery time, please contact us, and we will assist in confirming based on your specifications, material, and quantity.

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