What are they?
Stub Ends are fittings used in place of welded flanges where rotating back up flanges are desired.
They are also called Lap Joints and Vanstone Flared Laps.
How do they work?
A rotating back up flange seats itself against the back surface of the Stub End. When bolts are added, the clamping action of the bolts presses the rotating back up flange against the back of the Stub End. The gasket surface of the Stub End then presses against a gasket and another gasket surface providing joints like standard flange joints. The seal is made by the gasket surface of the stub end alone, the flange only provides the clamping pressure on the joint.
Since Stub Ends are made from material compatible with the designed piping system, back up flanges do not have to be made from the same material. The flange can be made from less expensive material because it never comes in contact with the process fluid.
Stub Ends are typically manufactured by two methods. Type A & B Stub Ends are made similar to forged fittings such as Elbows and Flanges. Type C Stub Ends are made by forming pipe to the desired dimensions.
Stub Ends are available in two standard lengths, MSS and ANSI.
Stub Ends are normally provided with a standard weld bevel
Stub End dimensions are found on our fitting dimensions page.
These Stub Ends are for use with standard Lap Joint Flanges and Slip On Flanges.
The Lap of a Type "C" is flared over - leaving a rounded edge at the I.D. of the Lap. If required this radius can be made nearly square.
The Lap thickness is 75% of the pipe wall under consideration.
The Type "C" has a very short outside fillet radius small enough to accommodate any back up flange.
The Lap face on a Type "C" is not machined and is smooth.