Lapped Joint Flange

The two parts of a lap joint flange (LJF) are a stub end and a lap joint ring flange, which is also called a "lap joint flange." The stub end is not a part of a lap joint flange, to be precise. But a lap joint flange is always used with a stub end. Together, these two parts are often called a "lap joint flange."

Because of how they are made, lap joint flanges always have a smooth, flat face. But when the stub end is added to it, the sealing face is raised. This is because the face of the stub end that seals is above the bolting plane of the flange.

The sealing face is on the stub end, not on the lap joint flange.

A ring-type joint can be made with a plain, serrated, or grooved sealing face on a stub end.

There are many sizes and classes of lap joint flanges, and they can handle high temperatures and pressures. In most cases, a lap joint flange and a welding neck flange can be used for the same things.

To put together a lap joint ring flange and stub end, the stub end must slide into the hole in the flange ring and then be butt welded to the pipe. One side of the stub end is the sealing face, and the other side presses against the lap joint flange ring (when the flange is assembled). After the stub end is welded to the pipe, the lap joint flange ring can still turn because it is not physically attached to the stub end. When the flange joint is put together, the lap joint ring can no longer turn.

The benefits of the design of the lap joint flange are:

Inexpensive.

Suitable for uses where there is a lot of corrosion.

Needs only one butt weld that goes all the way through.

The process medium only touches the short end.

It's easy to move to line up with the mating flange (the flange can be rotated until the bolt holes align).

It comes in almost every size of pipe diameter.

Ideal for systems where the flange needs to be taken apart often, such as when it needs to be cleaned or inspected.

The lap joint flange can be made of a cheaper grade material, like carbon steel, because only the stub end must match the material/grade of the pipe it is connected to. This can save a lot of money.

There are some limits to how the lap joint flange can be used, mostly because it is bigger and has more parts. Small pipes can't be joined with lap joint flanges.