Hydraulic thread sealant opinions?

[tomrscott]

What do you recomend for hydraulic thread sealant when you have to use NPTx fittings?

I would rather use some fitting that seals better and more easily than NPTs, but the fact is that a lot of what I am going to run into is going to be NPT and not ORFS or something else more appropriate to HP. So what works the best for you?

The guy behind the counter at the local hydraulic service shop said he prefers Loctite Hydraulic Sealer, but he warned, "Just be sure you've got it put together the right way the first time! Gosh awful hard to get apart if you goof. But I've never seen it leak!"

My dad got me started using Permatex #2, the black pasty stuff, because it seals real well (for general plumbing and gas, but haven't used it for HP Hyd), and with some effort you can get it back apart. It never turns rock hard, but quickly reaches the consistency of cold tar. I believe the container says it is good for hydraulics. I think dad became sold on it back during WWII at Lockheed when they used it on aircraft hydraulics (could be wrong about that, I'll ask him). I have never had any trouble with Permatex #2, ever, even with really ratty threads cut in pipe made of cheap steel. Just don't wipe it on a pair of jeans you ever want your wife to let you wear out to dinner! /forums/images/graemlins/grin.gif

Seems like I've read somewhere here a recomendation against teflon plumbers tape which sounds like it is probably real good advice.

Anything else I should try?

Do you have to be careful not to put too much on so that you don't get any excess squeezing inside that could contaminate a cylinder or valve?

Also, I've noticed on the high pressure fittings I picked up at Columbia Hydraulic Service, that the threads start to get tight almost as soon as you get one or two threads engaged. How much torque is appropriate for 1/4", 3/8", and 1/2" NPT threads?

I am about to thread together a few fittings to hook up a pressure gauge, need one or two more things first, but thought I would see what experiences others here have had.

Thanks! I appreciate the collected wisdom here.

 

[Deerlope]

I have uesd with good results a teflon paste type on both types of hyd fittings.

 

[slowzuki]

I have used teflon tape, just very careful about not getting it in the lines or over the front of the fitting.

I try to use JIC fitting as much as possible, they are very common on ag tractors and attachments. Some o-ring stuff but not much.

Ken

 

[MadReferee]

We have discussed this several times before. Never use teflon tape. Use a teflon paste. It will not contaminate your fluid.

I use Master Plumber TFE Paste which was recommended by my friend who owns a hydraulic repair shop. You can buy it at most hardware stores. A 4oz bottle will last a lifetime and cost only about $5. It's good from -50F to +500F and up to 10,000 psi for liquids and -50F to +400F and 3000 psi for gasses. It's also non-hardening and lubricates as it seals.

I have never used nor seen my friend use a torque wrench for hydraulic fittings but I am sure there is a torque spec around somewhere. I would not worry about it. NPTF seals on the crushing of the threads anyway so just tighten it down a turn or two after you meet moderate resistance. You can always chase the female threads with a tap if they are not perfect before making the connection.

 

[Youare]

I attended a hydraulic seminar put on by the Vicker pump people years ago. The only thread sealing material they recommend being used was LocTite thread sealer with teflon.

The teflon is used to lubricate the two metal surfaces because of the interference fit of an NPT fitting. Teflon tape was never to be used on a hydraulic system. A small piece of tape can enter the system and get caught in spool valves of close tolerance hydraulic pump components. They mentioned and had evidence of damaged pumps and valves because of teflon tape.

That was the opinion of the "experts" a few years ago, I would assume nothing has changed and I try to follow that advice.

Randy

 

[Henro]

<font color="blue"> I attended a hydraulic seminar put on by the Vicker pump people years ago. The only thread sealing material they recommend being used was LocTite thread sealer with teflon.
</font>

I'm sure that would be good stuff.

I use the same thing that MadRef recommended above, following a past recommendation of his. It is white and also has teflon in it if I remember right.

In fact, it could even be made by the same company as the Loctite brand is, and just be in a container with a different label on it for all I know. My guess is that both, being paste, work equally well.

I would use whichever I found first, but would be sure that whatever I got at minimum met the specs that MadRef mentioned above...

 

[slowzuki]

As I said, you have to be careful using tape. I have worked at several places and most industrial mechanics use it when assembling NPT stuff. I have seen the high dollar green stuff used too, don't know what the difference is.

When applying tape only limited amounts where used and not near the beginning of the threads.

I wouldn't let someone else use teflon tape on my equipment though, shops tend to let apprentices and such assemble this type of stuff, they can be careless.

 

[JerryT]

I went in to a parts store that did hydraulic work and bought a new fitting for my tractor and asked them what to use for a sealant, and they told me "nothing". I believe that this was a standard npt fitting. So I used nothing and it doesn't leak. I am new to hydraulics, so what am I missing here?
Thanks

 

[PineRidge]

We used to use a product in the HVAC business that was called Leak Lock. Still use it for any hydraulic connection myself and we see it sold in our local hydraulic shops so it is endorsed. It is a nice product to work with and keeps forever. Fact is if it ever dries out in the container you simply add a little rubbing alcohol to thin it down. Usually put it on a fitting and give it a minute for it to slightly thicken before putting the connections together.

You can read more about it here

TC-40D SS web pictures click here

 

[Youare]

The teflon pipe tape and the paste with teflon both provide the same thing, a lubricant between the two threaded surfaces. NPT fittings are interference fit, meaning the interference between the two tapered threads is what makes a leak tight seal.

The tape can fill an area that doesn't have metal to metal contact to a certain degree as well as the liquid sealant but its main function is lubrication. When assembling stainless steel fittings galling is more likely to happen than with standard carbon steel making a greater need for lubrication.

If a person is careful applying tape, making sure it doesn't hangover the inside of the fitting it will work. However a liquid pipe sealant is the best choice.

Randy