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.

 

[RickB]

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.

All hydraulic pressure rated male hydraulic pipe thread fittings I have seen and used have tapered threads regardless if the have the 30 degree chamfer or not. Weatherhead, Gates, whatever. The swivel female fittings could easily be parallel thread, I would not debate that one way or the other.

 

[92lt]

Thank you all for the replies. It gets confusing between sae/orb/metric/bsp/bspt/npt/npt swivel/jic/etc.....

 

[kennyd]

It gets confusing between sae/orb/metric/bsp/bspt/npt/npt swivel/jic/etc.....

You forgot ORFS :laughing:

Yes, it does get VERY confusing unless you work with them everyday.

 

[BukitCase]

92LT, this
https://www.discounthydraulichose.com/mm5/thread_guide.pdf

Is a handy thing to download - I keep a copy of it on my computer AND phone... Steve

 

[BrokenTrack]

It gets confusing between sae/orb/metric/bsp/bspt/npt/npt swivel/jic/etc.....

You forgot:

ORFS=O-Ring Face Seal
A/N=Army Navy Fittings
IF=Inverted Flare

On my genset alone I have, Army-Navy, Tapered Pipe Thread, Straight Pipe Thread, and, Flare Fittings, and Inverted Flare, and that is just to get fuel to the engine!

 

[LD1]

In a perfect world, there would be one type of fitting.

IT aint a perfect world. And you have to deal with whatever components you are using.

Usually, cylinders, pumps, manifolds, etc that have female threads are either NPT or ORB.

An adapter is usually required to get to whatever type fittings you want on your hoses.

I like adapting all my components to JIC and getting hoses with female JIC ends. Because they are usually the cheapest and most readily available. I have no issues using NPSM fittings either on the ends of my hoses. Similar cost, similar sealing method.

But aside from ORB adapters if they are required for components to get to JIC, I personally dont like o-rings. So I try to stay away from ORFS stuff. They are usually alot mroe expensive, not as common for adapters and hose ends at places like oriley or napa. And at the end of the day, I have seen alot of them leak at the fitting with age and heat, because they rely on an o-ring and not a mechanical seal

 

[/pine]

In a perfect world, there would be one type of fitting.

IT aint a perfect world. And you have to deal with whatever components you are using.

Usually, cylinders, pumps, manifolds, etc that have female threads are either NPT or ORB.

An adapter is usually required to get to whatever type fittings you want on your hoses.

I like adapting all my components to JIC and getting hoses with female JIC ends. Because they are usually the cheapest and most readily available. I have no issues using NPSM fittings either on the ends of my hoses. Similar cost, similar sealing method.

But aside from ORB adapters if they are required for components to get to JIC, I personally dont like o-rings. So I try to stay away from ORFS stuff. They are usually alot mroe expensive, not as common for adapters and hose ends at places like oriley or napa. And at the end of the day, I have seen alot of them leak at the fitting with age and heat, because they rely on an o-ring and not a mechanical seal

Why not use the NPSM fittings (angle and adapter included) on the device (cylinder, valve motor etc...) and just buy straight male thread end hoses...they are the cheapest and come with the 30* inside chamfer ??

hoses with straight male threads are simple to measure and there is never any orientation needed if there are angles on both ends etc...

 

[BrokenTrack]

I like ORFS (O-ring Face Seal), and they work well enough if you know how to deal with them. They are used in aviation because they hold full pressure while hand tight.

That is the good part, but the bard part is, no one has them readily available.

The second part of that is, mechanics not used to them see a seal dripping, grab a wrench, and cinch the fitting tight. Then it squishes the o-ring too tight, and either leaks because it is too tight, or rips the o-ring, and it leaks. Either way, when you see a dripping fitting with O-ring Face Seal, just tear it apart and replace the o-ring. But a person's first reaction is: TIGHTEN IT UP. With ORFS, that does not work.