Hydraulic hose problem

[Gary Fowler]

I have found that most leaks are caused by over tightening and deforming the threads on NPT threaded fitting. Using an 18" pipe wrench on a 1/2" or 3/4" pipe can certainly over tighten them if you put your full strength of an average man (young man not an old fart like me).
I can't say as I have ever came across a NPTF thread in the construction industry other than the notation on piping drawing NPTF or NPTM for female /male). One might find that designated on pipe drawings BOM to denote a male or female connection fitting.

 

[wdchyd]

Funny how all this talk of pipe threads and no one mentions getting the right hose ends to start with......if Tcreeley had the right hoses custom made, it would have been an easy fix using the correct JIC ends on his hose.....adapters just make more places to leak

 

[Discount Hydraulic Hose]

Out of curiosity I just checked Tractor Supply Company's website for hydraulic fittings, and hoses with factory ends. All of them, from 4000 psi down, are listed as NPT. I'm assuming they are, in fact, only NPT and not NPTF, but I don't know. If the distinction was lost when the descriptions were written, that would be a pretty big error.

It's a pretty common error, though. I can't speak for professionals who manufacture and sell these fittings, but the customers I work with almost always say "NPT" and not "NPTF" when they are ordering fittings. I think it's just human habit to shorten things when speaking. Joseph becomes Joe, and Roosevelt Boulevard (a major artery here in my city) becomes "the Boulevard." Enough people say it, and then it becomes part of the language.

Unfortunately, in the case of NPT and NPTF, there are some distinctions that make it important to know the difference. I wouldn't want someone to buy NPT fittings at the hardware store, and try to use them in a hydraulic system that operates at 2,000 PSI or higher.

The point about these fittings not being intended for re-use is important as well. A hydraulic hose with JIC connectors can be removed and reconnected multiple times without a problem. If you do the same thing with tapered pipe threads, you are going to have to clean the threads and re-apply sealant each time to prevent leaks. Sometimes, even if you do all that, it will leak anyway.

 

[J_J]

So, you don't sell NPT fittings, only NPTF?

What happens if we mix them?

How do we even know what we have?

When you go to a hyd shop for a hose and say NPT ends, they never ask if you really want NPTF?

After you mix/couple the two parts, now what kind of threads do you have.? NPTXXXXX

That kind of mix up will make you want to cross over to JIC fittings, which is much better in my opinion..

 

[tcreeley]

Especially when the fittings are labeled "pipe thread" - not too specific.
Custom made was my next stop- didn't want to add a couple of days and 17 miles into town!

 

[BukitCase]

JJ, I believe the combo of NPT and NPTF would be a NPTAFU ...Steve

Or maybe a NPTFUBAR

OK, I'll quit now

 

[Discount Hydraulic Hose]

So, you don't sell NPT fittings, only NPTF?

We sell a few low pressure NPT fittings, such as malleable iron pipe fittings, but nearly everything else we sell is NPTF.

What happens if we mix them?

Nothing, really. Unless you are trying to use low pressure NPT fittings (iron or brass) in a high pressure application.

How do we even know what we have?

It is very hard to tell one from the other, but if you examine new, undamaged fittings very closely, you may observe that the threads are sharper and with fewer imperfections on an NPTF fitting.

When you go to a hyd shop for a hose and say NPT ends, they never ask if you really want NPTF?

I can't speak for all shops, but I will just sell you NPTF. There is never any danger in upgrading.

After you mix/couple the two parts, now what kind of threads do you have.? NPTXXXXX

There is no danger in mixing NPT with NPTF, as long as have the right material and both fittings have a maximum working pressure (MWP) rating suitable for your application.

When I first started in this business, this company was an Aeroquip distributor. I had to complete several days of Aeroquip product training. The instructor spent a good deal time of telling us how good NPTF is, and why it is superior to NPT. Then, he said "Once you tighten your fittings and take them apart again, it no longer matters. The perfectly cut NPTF threads are now deformed, and the fitting is only as good as regular NPT from that moment forward." I'm paraphrasing from ten years ago, but the point is important. NPTF only has an advantage over NPT the first time you use it.

That kind of mix up will make you want to cross over to JIC fittings, which is much better in my opinion..

In my opinion as well.

 

[SPYDERLK]

When I first started in this business, this company was an Aeroquip distributor. I had to complete several days of Aeroquip product training. The instructor spent a good deal time of telling us how good NPTF is, and why it is superior to NPT. Then, he said "Once you tighten your fittings and take them apart again, it no longer matters. The perfectly cut NPTF threads are now deformed, and the fitting is only as good as regular NPT from that moment forward." I'm paraphrasing from ten years ago, but the point is important. NPTF only has an advantage over NPT the first time you use it.

And why would that be? It is perfectly mated to the fitting you just unscrewed it from. Both parts have deformed into compliance. ... You can use those parts together again with no problem. Alternately, it seems if the joint had been overtightened both sides would be damaged and substitution of new in either side would be a problem.
larry

 

[J_J]

OK, what is this fitting, really.

Dixon 2404-12-12 Zinc Plated Steel Hydraulic Fitting, Adapter, 1-1/16"-12 NPT Male JIC 37 Degree Flared x 3/4"-14 NPTF Male | AmazonSupply.com

 

[BukitCase]

Holy crap, what a bunch of gobbldy-gook - if that truly is a 12-12, it's a 3/4 NPTF/3/4 JIC fitting, since those dash #'s are in 1/16" increments - that sounds to me like somebody let their secretary figure out what to call that during her lunch break, while texting her friend, eating lunch, and watching Oprah... Steve

 

[k0ua]

OK, what is this fitting, really.

Dixon 2404-12-12 Zinc Plated Steel Hydraulic Fitting, Adapter, 1-1/16"-12 NPT Male JIC 37 Degree Flared x 3/4"-14 NPTF Male | AmazonSupply.com

That there is a terribly mislabeled connector. Nothing in the description matches the picture or even makes sense.

 

[Discount Hydraulic Hose]

OK, what is this fitting, really.

Dixon 2404-12-12 Zinc Plated Steel Hydraulic Fitting, Adapter, 1-1/16"-12 NPT Male JIC 37 Degree Flared x 3/4"-14 NPTF Male | AmazonSupply.com

What you have is a #12 Male JIC (3/4" tube diameter and a 1-1/16 thread diameter) and a 3/4" Male NPTF on the other end.

The error was in someone thinking that JIC is a pipe fitting, and adding NPT to the description of the JIC Male connection. Once you remove that, it becomes more clear.

By the way, Amazon is asking $7.27 for that fitting, and it's only $1.33 on our site.

Steel Fittings: JIC 37° Male x NPTF Male Pipe

 

[Discount Hydraulic Hose]

And why would that be? It is perfectly mated to the fitting you just unscrewed it from. Both parts have deformed into compliance. ... You can use those parts together again with no problem. Alternately, it seems if the joint had been overtightened both sides would be damaged and substitution of new in either side would be a problem.
larry

I'm not an engineer, but the phrase "deformed into compliance" seems jarring and contradictory to me. The specifications for NPTF are, by their nature, more precise than the specifications for NPT. The deforming process isn't controlled enough to create the kind of compliance that those specifications require. Metal surfaces are rubbed against one another. Scratches and other defects are created. It is illogical (to me) that those defects will result in more strict compliance with the NPTF standard.

The fittings will still work as NPT threads, and will seal with proper application of sealant or thread tape. But, they will no longer form a dry seal, which I believe is part of the intent of the NPTF specification.

 

[J_J]

Is the NPT or the NPTF stamped on all your pipe fittings so as to designate the difference.

http://www.parker.com/literature/tube fittings division/General_Technical.pdf

After some research, I have to agree with KEN at Discount Hydraulic Hose and the guys at Parker hose fittings.

The threads are compatible but the NPT or NPTF may not show on every fitting.

They both need sealant or lock fluid.

Parker says after about 2 or 3 times of use, you might think about replacing them if they start to leak,

A bigger hammer or wrench does not work all the time.