Connecting 1/2" NPTF

[Username Taken]

 

[Oldtoad]

And to really kick off the discussion teflon tape is not a sealant it is a thread lubricant.
A good thread lubricant will allow NPT threads to distort and seal with no damage,
so they can be broken apart and reassembled without leaks.

How much do we put on the threads?
Put a call in to the vender, Discount Hydraulic Hose, they agreed.

 

[LouNY]

How much do we put on the threads?
Put a call in to the vender, Discount Hydraulic Hose, they agreed.

The old standard was 3 wraps

 

[ericm979]

LocTite 545. My NPT hydraulic fittings leaked when I used teflon dope no matter how hard I tightened them. 545 and a day to cure and they are dry.

NPT is made for 60 psi water pipes, not 2500 psi hydraulics. It needs something like 545 to work.

 

[dstig1]

LocTite 545. My NPT hydraulic fittings leaked when I used teflon dope no matter how hard I tightened them. 545 and a day to cure and they are dry.

NPT is made for 60 psi water pipes, not 2500 psi hydraulics. It needs something like 545 to work.

+1 on the 545 Loctite

 

[MF RED in MT]

+2 for Loctite 545

KC

 

[LD1]

+3 loctite 545

 

[jdmeth]

Farmed for 25 years. I found out that, at least for me, only Teflon tape would seal NPT hydraulic hose fittings. Any thing else leaked.

 

[ssmewing]

NPTF is made to be used without any type of lube or sealant. It is also known as Dryseal. The thread has sharp crests that bite into the mating fitting which helps with the sealing. So thread goo isn't needed. If you later take it apart you may find that the thread is galled badly.
Eric

Hydraulic NPT fittings are not the same as normal NPT fittings. Only hydraulic NPT fittings should be used, not hardware NPT fittings.

If you examine a female fitting you will see there is an inner mating surface. Then on the male fittings you will see that the end is perfectly machined.

There is easy to find information on the difference with a simple Google search.

 

[ericm979]

NPT is tapered thread. The threads deform to form the seal. That's true for NPT water pipe and hydraulic fittings. You may be thinking of one of the 20 or so other hydraulic fitting types, most of which do not use the threads to form the seal. For example JIC. It uses conical mating surfaces to seal. No thread sealant needed. It is very common and is far superior to NPT. But they make a lot of fittings with NPT. I use it as little as possible and use adapters to get to JIC.

An excellent hydraulic fitting guide:

https://www.discounthydraulichose.com/v/vspfiles/downloadables/thread_guide.pdf

The first type of fitting they discuss is NPT, and they write:

"National Pipe Tapered Fuel (NPTF) This connection is still widely used in fluid power systems, even though it is
not recommended by the National Fluid Power Association (NFPA) for use
in hydraulic applications. The thread is tapered and the seal takes place by deformation of the threads"