Hydraulic hose fitting type question. NPT and NPTF

[Nicfin36]

I need to fabricate two 5' hydraulic hoses. I will have 1/2" Pioneer quick couplers on each end of the hoses, so I am ordering the hoses with male fittings. I can only find 1/2 NPTF male ends for the selection. I am pretty sure this will work, but for those than know this stuff, I was hoping you could confirm it for me.

 

[ctfjr]

Its my understanding that nptf threads deform each other on connection giving a (supposedly) leak proof seal without any pipe dope. NPT threads do not and require some kind of pipe compound.

 

[TheOldHokie]

I need to fabricate two 5' hydraulic hoses. I will have 1/2" Pioneer quick couplers on each end of the hoses, so I am ordering the hoses with male fittings. I can only find 1/2 NPTF male ends for the selection. I am pretty sure this will work, but for those than know this stuff, I was hoping you could confirm it for me.

NPT and NPTF are both taper pipe thread forms that seal with flank interference. The difference is in the fit on the root diameter of the thread. NPT is a clearance fit and requires some sort of thread sealant to close the tiny helix opening left when the mating parts are assembled. NPTF ( aka DRYSEAL) has a root interference fit and seals without the need for sealant. For all practical purposes if you use a thread sealant during assembly they are interchangeable. As a matter of practice I use PTFE tape with both thread forms.

I also dislike both forms in hydraulic systems and convert them to JIC whenever possible.

Dan

 

[85Hokie]

For all practical purposes if you use a thread sealant during assembly they are interchangeable. As a matter of practice I use PTFE tape with both thread forms.


Dan

Dan,

when you wrap with the tape - do you cover the first thread or not? I have always heard never cover the first thread specially when hydraulics lines are used.

 

[TheOldHokie]

Dan,

when you wrap with the tape - do you cover the first thread or not? I have always heard never cover the first thread specially when hydraulics lines are used.

The wrap should always start a minimum of one thread back of the first thread as should any other form of sealant.

Dan

 

[Pau7220]

Recommendation is to use a liquid sealant on threads for hydraulics. Risk comes from the follow up repair when someone does work on an existing fitting with tape sealant on it.

 

[Nicfin36]

OK, thanks for the help.

I just had to order some couplers. It seems like some parts are becoming hard to find right now, especially couplers and other connectors/adapters.