Dope fills the spiral clearance along tapered threads and lubricates them so they make up fully without galling. Formulations are rated for gas, water, steam, oxygen or hydrocarbons, and some carry PTFE. Fitters apply it to male threads only, starting a thread or two back from the end so it does not get pushed inside the pipe. Tape and dope together is a common belt-and-braces approach on gas.
Pipe dope on the male threads only, and don't glob it on the first thread, I don't want it in the regulator.
Also heard as
- dope
- thread sealant
- joint compound
Related terms
NPT
National Pipe Taper: the tapered pipe thread used for threaded valves and fittings in North America.
Make up
To screw a threaded joint together and tighten it, or to assemble and torque a flanged joint.
Union
A three-piece threaded fitting that lets a section of pipe or a valve be disconnected without turning the pipe.