Hydraulic Fitting Thread Sealer

[Captain Dirty]

A jaundiced view of thread sealants: The sealant provides lubrication so one can more easily turn the fittings to distort (or re-distort) the NPT threads. (oldnslo's caution about over tightening is appropriate.) After distortion the openings between the threads are so minuscule the hydraulic pressure cannot overcome the adhesion/cohesion of the sealant. As kennyd noted, curing increases the cohesiveness of the sealant. (Loctite 545 curing time is 2 hrs unless the surface is "primed".)

 

[Thunder chicken]

Right or wrong, I’ve used this stuff in my firewood processor. I’ve had a few hoses off multiples of times to fix/tinker with other issues. All NPT fittings. I put a tiny dab of this or one like it on. Some are still dirty. Sometimes I can’t wait for it to dry to get back to work. I never have any leaks to speak of.

Permatex® High Temperature Thread Sealant

OEM specified. Locks and seals threaded fittings. Resists leakage, vibration loosening, moisture, hydraulic fluids and diesel fuels. Lubricates threads for easy assembly and disassembly. Wont shred or wear like Teflon® tape. Parts may be repositioned up to 4 hours after application. Temperature...

www.permatex.com

 

[TractorGuy]

On pipe threads for fuel and oil I use Aviation Permatex.

 

[ericm979]

Loctite 545 is made for sealing hydraulic threads. It works far better than teflon pipe dope. It will work on NPT fittings that have already been used once. You do need to let it cure overnight.

 

[John0829]

Loctite 567 is what we use (Arial Lift Equipment OEM) for all hydraulic threaded fittings.

SM

I recently had two hydraulic lines I could not get to stop leaking, new fittings, new everything and it still leaked. Used every type of recommended tape or liquid sealant available, this went on for nearly 2 months, finally got some Loctite 567 and no more leaks.

 

[3Ts]

There is another thread on here about a hydraulic leak I was having with pipe threads. All the stuff from local hydraulic shops did not work. A recommendation here was to use Loctite 545. Couldn't find it anywhere, ended up having to order it from Amazon and it worked very well. It's expensive, but for what it does, it's worth it.

Note: I try not use pipe threads on hydraulic fittings, but sometimes you have to and sometimes you have to reassemble them multiple times, 545 works really well then.

 

[sdunt]

If you have a valve that leaks past the O rings, use better 'O -Rings' as in X or Double X profile: McMaster-Carr or McMaster-Carr.

You have to buy a bag of them.. OR, they offer an assortment of common sizes that costs a little more than a single bag, but you wind up with something in the shop you'll actually use: McMaster-Carr

I have corrected some leaking 45 year old control valves and hydraulic cylinder with the X profile O rings..

 

[Jofang]

Have a log splitter with leaky control valve.... Spent a few dollars and got a "O" ring kit and rebuilt valve, still leaks (Grrrr).... OK... So now I am going to replace valve.... The issue is someone has been into hydraulics before and nipple between valve body and female connection to ram has a lot of pipe wrench marks.... Going into this with a little trepidation because of unknown things PO may have done...

Main question is what is good thread sealer to use on high pressure hydraulic (NPT) threads.... Not a great fan of PTFE tapes... So its probably going to be a liquid sealer .... Any suggestions...

We are a manufacturer of hydraulic power units and hydraulic rams we would never use NPT or BSPT threads on hydraulic fittings. These threads are designed for lower pressure operation, not the pressures you have with hydraulic oil systems. For hydraulics you need parallel threads on a flat faced fitting with either an O ring, if the female unit has been designed to use an O ring, or a Dowty washer with a flat faced male fitting going into the flat face of the female fitting. An hydraulic ram operating at 2,000 psi hydraulic can experience pressure spikes of up to 10,000 psi when the ram hits something hard. You won't see this on a gauge, as the needle moves too slow, but you'll see it on a digital pressure transducer. So, your NPT fitting will not work well with your hydraulic system and I would doubt if the female thread in your ram is actually a taper thread. Maybe the previous owner didn't realise the thread was parallel and forced a taper thread fitting into it. If the flat face on the female thread is still in OK condition you may possible get away with replacing the fitting and using a Dowty washer.

 

[dennis morgan]

Have a log splitter with leaky control valve.... Spent a few dollars and got a "O" ring kit and rebuilt valve, still leaks (Grrrr).... OK... So now I am going to replace valve.... The issue is someone has been into hydraulics before and nipple between valve body and female connection to ram has a lot of pipe wrench marks.... Going into this with a little trepidation because of unknown things PO may have done...

Main question is what is good thread sealer to use on high pressure hydraulic (NPT) threads.... Not a great fan of PTFE tapes... So its probably going to be a liquid sealer .... Any suggestions...

when working on high pressure air compressors and hyd. cylinders i found that a sealer called PST

 

[WranglerX]

We are a manufacturer of hydraulic power units and hydraulic rams we would never use NPT or BSPT threads on hydraulic fittings. These threads are designed for lower pressure operation, not the pressures you have with hydraulic oil systems. For hydraulics you need parallel threads on a flat faced fitting with either an O ring, if the female unit has been designed to use an O ring, or a Dowty washer with a flat faced male fitting going into the flat face of the female fitting. An hydraulic ram operating at 2,000 psi hydraulic can experience pressure spikes of up to 10,000 psi when the ram hits something hard. You won't see this on a gauge, as the needle moves too slow, but you'll see it on a digital pressure transducer. So, your NPT fitting will not work well with your hydraulic system and I would doubt if the female thread in your ram is actually a taper thread. Maybe the previous owner didn't realise the thread was parallel and forced a taper thread fitting into it. If the flat face on the female thread is still in OK condition you may possible get away with replacing the fitting and using a Dowty washer.

I understand your comment but 9 out of 10 log splitters I have looked at or dealt with have had NPT fitting on cylinders and control valves with JIC or SAE or what ever a host of various fittings manufacturer chose to use .... Unless you are willing to do a retrofit on my cylinder I have to go with NPT and splitter control valve also has NPT fitting on all ports (with adapters to JIC or what ever manufacture chose to use)...

Please explain how my analyzation of issue is wrong....

NPT Nipple on return side.

Leak at control valve .

Example of connection on pressure (extend) side of cylinder