Teflon tape on hydraulic fittings

[Lineman North Florida]

I have used teflon tape on NPT fittings on farm equipment my entire life, maybe I have been lucky, but never one problem.

 

[Will S]

I asked this same question at 2 different hydraulic shops in the few weeks, and both said they use teflon tape, but to start 2 threads away from the end. Ironically, they both sell pipe thread sealant.

Personally, I do not use it. I will use either Leak Lock (rated for up to 10,000 psi all fluids except alcohol, or I also have PTFE thread sealant, which I wouldn't hesitate using on hydraulic fitting.

 

[3Ts]

I try to use hydraulic fittings that are not tapered pipe, but if I have to, I'll use Loctite 545. The Teflon tape is reserved for other pipe fittings such as water and air, but even then I prefer a paste type sealant.

 

[5030]

If your going to use tape start couple threads from the beginning.

EXACTLY. Never allow the tape to go past the end of the fitting. Always start it a couple threads proud of the end. I use all sorts of thread sealant but I prefer DDEC anaerobic thread sealant which you probably cannot purchase as it's a Detroit Diesel maintenance part.

 

[Rob REECE]

in a forum on FB I belong to, the age old argument got going about sealing hydraulic joints. In particular the use of Teflon tape on hydraulic fittings. I say NO don’t use the stuff, as it can get into things causing issues. Only use a good pipe Dope.

what say you?

You shouldn’t have to use any kind of sealant if you are connecting them properly.

 

[Hilbilly]

I've had all kinds of issues with NPT threads not sealing properly. Example, on Friday I bought a brand new HLA light duty root grapple and when I started using it, I found 2 hydraulic fittings that were leaking. Both were NPT fittings and my tractor only has 2200 psi hydraulic pressure and these grapples are made for Skid Steers with much higher pressures. Both of these fittings had some kind of pipe dope on them and both were leaking. I pulled them apart and using teflon tape and put them back together and now there is no leaking. I've had similar issues in the past with NPT threads and could not get them to seal without using teflon tape. I don't doubt this stuff could cause problems if it gets into the system and would prefer to find a better solution. Maybe one of the methods suggested above would be better.

I hate the hassle involved in cleaning the tape out of threads if I have to redo a fitting and wonder if there is a sealant that can be used with NPT threads and can be taken apart to be redone if neccessary?

 

[barts]

When I worked in the Ag Engineering research shop at UC Davis for a summer (a long time ago) the shop foreman said:

• Straight threads never get anything; if it leaks, replace the o-ring.
• Tapered pipe fittings need a thread lubricant (not a sealant) so the fitting can be tightened enough to distort the threads to seal. Don't use Teflon tape in hydraulics to prevent hanging up valve spools and pilot orifices; if the threads need tape to seal, replace them. They used Rector Seal #5 PTFE dope - I still use this on hydraulics and steam fittings with excellent success.
• Teflon tape works well for plastic pipe, and metal pipe carrying water

I've since learned that tapered stainless fittings are particularly subject to galling; using both PTFE and Rector Seal #5 is recommended here. Special tapes & dopes are available for stainless steel as well.

- Bart

 

[Ed Weber]

Teflon tape is for sealing tapered threads.
Hydraulic fitting's don't seal via the threads.
If you're using teflon tape on hydraulic fittings, you're either trying to patch something in the field to hold on till you can get it to the shop and properly fixed OR you don't know what you're doing.

 

[Lineman North Florida]

Teflon tape is for sealing tapered threads.
Hydraulic fitting's don't seal via the threads.
If you're using teflon tape on hydraulic fittings, you're either trying to patch something in the field to hold on till you can get it to the shop and properly fixed OR you don't know what you're doing.

I don't know what I'm doing then , if I don't use the teflon tape on fittings for hydraulic cylinders and hoses I have leaks , if i do use it I don't have leaks, I try to go with what works.

 

[barts]

"Hydraulic fittings" doesn't describe the type of threads/sealing employed in the fitting which is what matters.

This article contains a good discussion of the various types of fittings commonly seen in the US.

https://www.powermotiontech.com/technologies/fittings-couplings/article/21122173/hydraulic-fittings-and-flanges

- Bart