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Helpful Member!  mitaco (Automotive)
19 Dec 03 1:32
Hello! I have some problem with the different between pipe thread of PT, NPT, FPT. I used to supply aome air valve with port size from 1/4"NPTF to 1/2" NPTF. Because a customer if require NPTF thread then he /she will states NPTF. But sometimes a US customer only say nedd Pipe taper thread or PT port etc, I will have question on PT, NPT or FPT. Are PT, NPT, FPT same thread?
Helpful Member!(3)  mizkn (Chemical)
30 Dec 03 17:33
PT, NPT, FPT acronyms have the same meaning for American National Standard Pipe Threads. Female NPT threads can be designated as FPT and male NPT threads can be designated as MPT.

NPT:  National Pipe Taper Thread   A sealant or Teflon tape must be used for a leak-free seal.

FPT:  female(internal) National Pipe Taper Threads

MPT:  male(external) National Pipe Taper Threads

NPTF:  Dry-seal American National Standard Taper Pipe Thread (pressure-tight)  No sealant is needed for a seal.

The NPT and NPTF threads are interchangeable with sealants such as teflon tape.  None of the other thread standards are interchangeable.

NPS/NPSM:  American Standard Straight Pipe Thread   Used for mechanical joining -- holding a fitting in place.  An O-ring or a metal seal is required.

Two common pipe thread sizes exist, the tapered National Pipe Thread (NPT) and the straight National Standard Free-Fitting Straight Mechanical Pipe Thread (NPSM).  The tapered threads are for joining and sealing, the straight threads are only for joining. The Dry-seal thread (NPTF) allows for joining without sealants.

The other thread acronyms that exist are:
NPSI:  American National straight intermediate pipe thread
NPSF:  Dry-seal American National Standard Straight Pipe Thread
GHT:   Garden Hose Thread
NST:   Fire Hose Coupling
BSPT:  British Standard Pipe Taper threads
BSPP:  British Standard Pipe Parallel (straight) threads

Hope this helps.

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