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Rusty injector pump follow-up NPTF fitting????
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durallymax
Posted 7/4/2015 11:10 (#4661017 - in reply to #4660704)
Subject: RE: Rusty injector pump follow-up NPTF fitting????


Wi
Not always. Some people label stuff that way but it's not proper. I have never found what is proper with NPT though. The best I have found is that if you need to for some reason, put the F/M for femal/male in front of NPT. The F after should stand for fuel. Then there's the people who say NPT =national pipe taper NPS=national pipe straight. Others say national pipe thread taper, some say parallel instead of straight. Sounds like a typical American system lol.

NPTF means National Pipe Thread Taper Fuel. The fuel threads are identical but the root and Crest are slightly different to provide an interference fit for a perfect seal with NO thread sealant or tape. They are a "dryseal" thread. In order for that to work both male and female need to be NPTF. The reason for this is due to issues of contamination from sealants and incompatibility of sealants with whatever is in the pipe. Many hydraulic fittings use NPTF as well. If you over tighten them the first time you use them they may not seal well if RE used since they depend on thread distortion slightly to accomplish the seal.

NPT and NPTF will mate fine but may require a sealant in order to seal.


British pipe taper(BSPT) is identical to NPT in every way except for the flank angle of the threads. They use 55* versus 60* for NPT so they will thread together but they will not provide a good seal. The thread form is also different, NPT uses flat crests and roots while BSPT uses rounded ones.

British pipe is more common worldwide. NPT is only common in North America.
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