The LP long-type lap joint stub end is welded to the main pipe with a butt-weld bevel machined on one end, and the other end is hot-stamped into a flat lap joint flange, which serves as the sealing pressure-bearing end face and forms a detachable connection structure with the loose flange. Compared with the short-type lap joint stub end, its straight pipe section is longer, so welding heat is not easily transferred to the sealing surface, which can reduce the leakage risk caused by flange annealing, warping, and end face deformation. The flange can rotate 360°, making on-site bolt hole alignment convenient, and maintenance and disassembly do not require cutting the weld. The product diameter range covers DN15~DN1200, wall thicknesses include STD, XS, XXS, and SCH series, pressure ratings are Class150~2500LB, and materials such as carbon steel, stainless steel, duplex steel, and alloy steel are available. For specific specifications, materials, and delivery requirements, please contact us to confirm.
Overview
The LP long-type lap joint stub end is a butt-welded lap joint flanged fitting defined by the ASME B16.9 standard, also known in the industry as Type A lap joint stub end, specifically designed for use with loose flanges. One end is machined with a butt-weld bevel for welding to the main pipe, and the other end is hot-stamped and formed into a flat lap joint flange, serving as the sealing pressure-bearing face. The extended straight pipe section is the main difference between it and the short-type lap joint stub end; this distance separates the lap joint sealing face from the welding heat-affected zone, reducing the impact of high welding temperatures on the sealing face and also lowering stress concentration at the weld location. The product diameter range covers DN15~DN1200, pressure rating Class150~2500LB, and materials such as carbon steel, stainless steel, duplex steel, and alloy steel are available, suitable for high-pressure, high-temperature, alternating load, and industrial pipeline projects requiring regular maintenance.
Key Features
The extended straight pipe section separates the welding heat-affected zone from the lap joint sealing face, helping to avoid end-face deformation, annealing, and sealing failure caused by high welding temperatures. The whole body is hot-stamped and formed with no spliced welds, and the lap joint end face is CNC precision-turned for good gasket fit. The matching loose flange can rotate 360°, making on-site bolt hole alignment simple, and maintenance disassembly and assembly do not require cutting welds. Material combinations are flexible: corrosion-resistant materials such as stainless steel, duplex steel, and alloy steel can be selected for the pipe end, while ordinary carbon steel can be used for the flange, making it easy to control project material costs. The product complies with ASME B16.9, GB/T12459, and HG/T21635 standards, and non-standard customization is available according to drawings, samples, or technical agreements.
Applications
The LP long-type lap joint stub end is suitable for industrial pipelines with high pressure and high temperature, corrosive media, and requiring regular disassembly and maintenance. In the chemical field, it can be used for hydrogenation units, rectification units, acid-base corrosive process pipelines, and high-pressure transmission main pipelines; in power plants, it can be used for boiler main and auxiliary equipment pipelines, high-temperature steam pipelines, desulfurization and denitrification high-pressure pipelines, and generator set circulation pipelines; in marine and ship applications, it can be used for offshore platform process pipelines, marine high-pressure seawater pipelines, and offshore equipment transmission pipelines; systems with sealing and cleanliness requirements, such as seawater desalination, pure water industry, and pharmaceutical clean pipelines, can also use it. For projects with fixed equipment nozzle angles, installation in confined spaces, or requiring frequent replacement of pipe sections, the rotational alignment and detachability of the loose flange will be more convenient.
Specifications
The product complies with ASME B16.9, GB/T12459, and HG/T21635 standards, with nominal diameter DN15~DN1200, pressure rating Class150~2500LB, and wall thicknesses including STD, XS, XXS, and SCH series. The connection method is butt welding at one end and lap joint flanged sealing at the other end, used with a matching loose flange. Materials can be selected from carbon steel, stainless steel, duplex steel, alloy steel, etc.; please contact us to confirm the specific grade, service temperature range, and applicable media. Customization is supported for non-standard diameters, extended straight pipe sections, widened and thickened lap joints, special materials, etc., and processing can be done according to customer drawings, samples, or technical agreements.
Procurement & Delivery
The LP long-type lap joint stub end is a high-precision sealing-type pipe fitting. At the factory, protective packaging is applied to the lap joint sealing face and the weld bevel. Each product is individually wrapped, with protective film on the sealing face and a protective sleeve on the bevel. Products of the same specification are packed in categories, with moisture-proof desiccant placed inside the box, and the outer layer of the whole box is wrapped with waterproof stretch film. Large-volume orders can be stacked on fumigation-free export pallets and secured with strapping. Packaging can be customized according to customer requirements with English shipping marks, LOGOs, specification labels, and batch numbers. The minimum order quantity, in-stock specifications, and delivery time will vary depending on diameter, wall thickness, material, and quantity. You are welcome to provide dimensions and quantities, and we will assist in confirming the quotation and delivery arrangements.
Service & Support
We provide technical communication for customers purchasing LP long-type lap joint stub ends regarding selection, pressure rating matching, material adaptation, welding installation, and flange matching. Before leaving the factory, products undergo quality inspection items such as appearance screening, dimensional inspection, end-face flatness testing, and non-destructive testing. Specific inspection report requirements can be confirmed with us before placing an order. After the order is shipped, we will synchronize logistics information and assist overseas customers with customs clearance and receipt. The product warranty period is 18 months. During the warranty period, quality problems not caused by human damage can be repaired, replaced, or replenished free of charge, and the after-sales team provides 7×24-hour online response.
FAQ
What is the difference between LP long-type lap joint stub end and SP short-type lap joint stub end?
LP is an extended straight pipe section structure, with a longer straight pipe section, which can separate the lap joint sealing surface from the welding heat-affected zone, reduce the impact of high welding temperature on the sealing surface, and is suitable for high-pressure and high-temperature main pipelines. SP short-type has a shorter straight pipe section and is more suitable for low-pressure and normal-temperature auxiliary pipelines. For specific selection, you can contact us to confirm based on pipeline pressure rating, temperature, and installation space.
Can LP long-type lap joint stub end be used for high-pressure steam pipelines?
Yes. LP long-type lap joint stub end implements the ASME B16.9 standard, with pressure ratings covering Class150~2500LB, can adopt thickened wall thickness and integral hot stamping forming, and can undergo non-destructive testing before leaving the factory. When specifically used for high-pressure steam pipelines, selection needs to be confirmed according to design temperature, pressure, and material requirements. You are welcome to contact us to provide operating condition parameters.
What flanges are matched with LP long-type lap joint stub end?
LP long-type lap joint stub end is used with loose flanges. The flange can rotate 360°, making bolt hole alignment on site convenient, and maintenance and disassembly do not require cutting welds. Pipe ends can use corrosion-resistant materials such as stainless steel, duplex steel, and alloy steel, while flanges can use ordinary carbon steel. For specific flange materials and pressure ratings, please contact us to confirm.
What materials and diameters does LP long-type lap joint stub end support for customization?
Conventional diameters cover DN15~DN1200, wall thicknesses include STD, XS, XXS, and SCH series, and materials can be selected from carbon steel, stainless steel, duplex steel, alloy steel, etc. We support customization of non-standard diameters, extended straight pipe sections, widened and thickened lap joints, special materials, etc., and can process according to drawings, samples, or technical agreements. For specific material grades and size ranges, please contact us to confirm.
How are the minimum order quantity and delivery time for LP long-type flanged stub ends confirmed?
The minimum order quantity and delivery time vary depending on the diameter, wall thickness, material, quantity, and whether there is stock available. Standard stock specifications in conventional carbon steel, 304, and 316 stainless steel are delivered relatively quickly, while non-standard customizations need to be confirmed according to production scheduling. You are welcome to provide the dimensions, material, and quantity, and we will assist in confirming the quotation, minimum order quantity, and delivery time.
