Npt swivel fittings

[92lt]

Can someone please educate me on npt swivel fittings. Are these ok to use for hydraulic? They're rated fairly high for pressure. It seems like they would be prone to leaking.

 

[kennyd]

They work OK...but we try to avoid NPT whenever possible.

Let us know your application, we may be able to suggest something better.

 

[oldnslo]

Like Kenny states these work if they are rated for hydraulic pressures. One note of caution: The mating male fitting MUST have the internal taper for the female swivel to seat on or the joint will leak.

 

[LouNY]

The right hand sidebar of this page has some good information on npt swivel fittings;

Pipe Swivels

 

[92lt]

The right hand sidebar of this page has some good information on npt swivel fittings;

Pipe Swivels

Ok, I see how they seal at the 30 degree chamfer, unlike via standard npt threads seal via the matching threads.


According to this link, the swivels have a parallel thread. So I guess my confusion is why is it ok to screw the standard tapered npt fitting into the npt swivel? Wouldn't the fittings blow apart under pressure because the threads don't line up perfectly?

 

[LouNY]

Ok, I see how they seal at the 30 degree chamfer, unlike via standard npt threads seal via the matching threads.


According to this link, the swivels have a parallel thread. So I guess my confusion is why is it ok to screw the standard tapered npt fitting into the npt swivel? Wouldn't the fittings blow apart under pressure because the threads don't line up perfectly?

The parallel threads are more commonly referred to as straight pipe thread as opposed to tapered pipe thread,
the straight threads have the strength to securely hold the fitting together as the threads per inch are the same.
Also when joining tapered pipe threads together the sealing is actually accomplished by distorting the threads to create a seal.

 

[kthompson]

The parallel threads are more commonly referred to as straight pipe thread as opposed to tapered pipe thread,
the straight threads have the strength to securely hold the fitting together as the threads per inch are the same.
Also when joining tapered pipe threads together the sealing is actually accomplished by distorting the threads to create a seal.

That is interesting. The last sentence. Is that different than threads that are not tapered? No way can I call a thread by it correct name, I have learned to take fitting to store.

 

[/pine]

They are mechanical joints that do not require any sealant etc...I use them exclusively whenever possible I have never had one leak and unlike tapered thread they can be reused as often as required...IMO they are stronger than JIC fittings as there is much less chance of deforming the extruded flare by over tightening or reuse...
To clarify the swivel fittings I am referring to are called NPSM
National Pipe Straight Mechanical

 

[LouNY]

That is interesting. The last sentence. Is that different than threads that are not tapered? No way can I call a thread by it correct name, I have learned to take fitting to store.

Tapered pipe threads are the only ones that I am aware of that seal by distorting the actual threads.
All other fittings seal on a seating surface(flares), or sealing ring, o-rings.
Our american pipe threads are commonly referred to as NPT, either MNPT or FNPT which is National Pipe Taper.

 

[ericm979]

I can buy the argument that NPSM are better than JIC but JIC are very common and easy to find. I've yet to damage one from reuse but on fittings that size I tend to under tighten rather than overtighten. That's probably why I have such a problem with NPT on hydraulics.