Butt Weld Pipe Caps — ASME B16.9

What is a Butt Weld Pipe Cap?

A butt weld cap has an elliptical or dished profile and a bevelled open end that is welded to the pipe. It seals a line end, header end or dead leg permanently, with the same pressure capacity as the pipe when ordered in a matching schedule and material. ASME B16.9 gives the cap length for each size, with a longer length for heavier walls. Where the line may need to be opened later, a blind flange is used instead.

Key features

• Elliptical/dished profile per ASME B16.9
• Wall thickness matched to the pipe schedule
• Single butt weld to close a line permanently
• Ends bevelled to ASME B16.25

Specification

Applications

• Header and manifold ends
• Dead-end branches and future tie-ins
• Drip legs and dirt pockets
• Pipeline end closures
• Steam and condensate headers

Pipe cap vs blind flange

A butt weld cap is welded on and is permanent. It is lighter and cheaper than a blind flange and has no gasket or bolting that can leak. A blind flange bolts onto a mating flange and can be removed for inspection, cleaning, pigging or a future extension of the line. Use a cap where the end will stay closed for the life of the plant; use a blind flange where access is needed.