Lap Joint Flanges have the same common dimensions as any other flange on this page, but no raised face. They work in tandem with a "Lap Joint Stub End." The stub end has a flat surface that fits against the inside of the pipe opening. A Lap Joint Flange is used when you want to make an internal connection.
There are three ways to connect a stub end to a pipe: by welding, bolting, or screwing. All stub ends are designed to fit one of these types of connections. Lap joints are for inside use only. They cannot be used as an exit joint because they do not provide enough space for people to get through.
Lap joints are commonly used in houses to connect pipes carrying water to toilets and tubs. These pipes usually have outside diameters of 1-1/4 inches or larger. The stub ends of lap joints can be fitted into matching holes in the pipes (or they can be welded onto the pipes), and then the two parts of the joint are brought together with a special tool. The tool creates a tight seal between the two parts of the joint. This prevents water from escaping around the stub end of the pipe.
Lap joints are also used in piping systems for schools and hospitals.
The most frequent form of flange used in process plant applications is the raised face flange, which is easily identified. The goal of an RF flange is to concentrate greater pressure on a smaller gasket surface, increasing the joint's pressure containment capabilities. The dimensions and height are in accordance with ASME B16.4 standards.
Raised face flanges provide several advantages over flat or domed flanges: they allow for easier assembly and disassembly of pipes and fittings; they help prevent leaks around loose connections; and they increase the effective area of the seal, making them suitable for use with lower-cost sealing materials such as o-rings instead of more expensive gaskets.
RF flanges can be found on steam, gas, and oil pipelines that must withstand high internal pressures. They are made from steel and cast iron and come in single-, double-, and triple-flanged varieties. The type used at a particular location depends on the existing pressure rating of the pipeline itself. For example, if a 10-inch (250 mm) steam pipeline has an existing pressure rating of 60 pounds per square inch (psi), then a 60-psi RF flange would be installed on the end of the pipe. If the pipeline had a pressure rating of 80 psi, then an RF flange capable of withstanding 140 psi would be needed.
Lap joint pipe flanges are most typically used with stub end fittings and slide straight over the pipe. The stub end of a pipe is normally welded, and the lap joint pipe flange is free to spin around the stub end. Lap joint pipe flanges are frequently utilized in applications that need regular disassembly. For example, they are commonly found on heaters where the element can be removed for repair or replacement.
Lap joint pipe is made by cutting parallel grooves into one face of each half lap joint piece. The lap joints are then joined together by welding the exposed faces of the pieces. A bead of weld metal is also used to secure the two halves of the lap joint together when water is being transported.
The groove pattern used to manufacture lap joint pipe is very important. If the mating surfaces are not flat, the pipe will not fit properly and leaks may occur at the point of contact. Also, make sure that the inside diameter of the lap joint piece is equal to or less than the outside diameter of the pipe it will surround. Otherwise, water may leak between the lap joint and the pipe it fits onto.
Lap joints are commonly used on outdoor plumbing projects because they provide a seal against water leakage. They are also easy to remove if needed for maintenance or repairs.
Lap joints were originally designed for aluminum tubing. They are now also available for steel tubing.