Lap Joint Flanges

A lap joint flange is a two-piece flange assembly consisting of a rotating backing flange and a stub end that is butt welded to the pipe. Unlike many other flange designs, the flange itself does not encounter the process medium. PipingMarket.eu supports industrial projects by sourcing lap joint flange solutions in a wide range of materials, sizes and pressure classes.

How does a lap joint flange work?

The operation of a lap joint flange is based on the combination of a backing flange and a compatible stub end. After the stub end has been welded to the pipe, the backing flange can rotate independently, allowing the bolt holes to be aligned without turning the (seamless) pipe itself. Because the backing flange does not contact the process fluid, it can often be manufactured from a different material than the stub end, providing a cost-effective solution for corrosive service.

Why choose this type of flange?

A lap joint flange is commonly selected for applications where flexibility during installation and maintenance is essential. Its rotating design offers several practical advantages:

• simplified bolt hole alignment during installation;
• faster dismantling for inspection or maintenance;
• reduced installation time on complex piping systems;
• suitability for systems that are assembled and disassembled on a regular basis.

Which specifications should be considered?

Selecting the correct lap joint flange requires careful consideration of both the flange and the matching stub end. Important specifications include the nominal pipe size, pressure class, flange material, stub end material, facing dimensions and the applicable manufacturing standards. Depending on the project, additional requirements such as corrosion resistance, operating temperature and compatibility with existing piping components should also be evaluated.

Related flange solutions

Depending on the system, other types of flanges may be more suitable, for example:

• threaded flanges for systems where welding is not preferred;

• raised face flange solutions for applications requiring improved sealing performance;
• socket welding flanges for smaller-diameter, high-pressure piping systems;
• long welding neck flanges for demanding process conditions and critical applications;
• swivel flanges for subsea, offshore and high-load installations;
• A694 F65 flanges for high-strength piping systems in the oil and gas industry.

Specify your lap joint flange requirements

Whether you are replacing existing flanges or sourcing components for a new piping project, submit your technical specifications through our RFQ platform. Our specialists help you source the right lap joint flange and other piping products based on your required dimensions, material, pressure rating and application, while providing access to a global network of qualified manufacturers.