NPT and NPTF

[jeffatmines]

I've got two fittings. One with a male NPTF and the other with a female NPT. I know the two are somewhat interchangeable, but I was wondering if this would work. This isn't a high-pressure application, so some sort of sealing will be used. Thanks

Jeff Parham
Mechanical Engineer
Mining Trucks

 

[pennpiper]

Jeff,
It sounds like you have a Male NPT and a Female NPT.
If this is so and they are both the same size (say 3/4") then they will fit together.
NPT (National Pipe Thread) is very common and is recognizable because it is a tapered thread. If you are using carbon Steel pipe then you could use a common Pipe Dope or Teflon Pipe Tape to make a very tight joint..

 

[crjones]

NPTF is applied to gas fittings being tighter thread.

 

[jeffatmines]

What I have is a 1-1/2" male NPTF (National Pipe Thread Fuel) and a 1-1/2" female NPT (National Pipe Thread). Not two NPT fittings. The questions is, will they work together? NPTF threads have slightly difference roots and crests to allow for an interference fit when they're tightened together; the threads are slightly deformed in the process.

Jeff Parham
Mechanical Engineer
Mining Trucks

 

[hydtools]

NPTF is the designation for Dryseal tapered pipe threads. They have flatted crests and roots to create sealing interference. NPT has sharp crests and roots(theoretically).
Go ahead and use NPTF male with NPT female. Use a thread sealant like Loctite PST.

Ted