Teflon or thread seal on hydraulic hoses?

Gary Fowler · Feb 8, 2009

I prefer to use the white teflon paste for all my threaded connections on oil and gas. Teflon tape if fine for sealing the threads, if you want to use it, just be careful when wrapping it to make sure you only cover the threads. I usually use 2 full wraps wrapping the tape in the directions of the threads then pulling it tight to break the tape. You want enough wraps that the tape does not spin in the threads when you screw in your fitting.
The problem with Teflon tape is not so much when you make it up as when you take it apart. Then you leave all the little particles in the female joint which can get loose in the system and give you a bad time with tiny orifices stopping up.like on pressure gauges for instance. As long as you can clean all the tape out of both male and FEMALE threads when you take the fitting apart, tape is fine. Most engineering specifications do not allow tape on instrument connections because of the risk of getting the tape particles in a system when changing out instrumentation which always goes bad at some point.

IslandTractor · Feb 8, 2009

Don't tighten too much! I ruined a couple of hose fittings by making sure things were really snug. It's not hard to split some of these fittings. Use the teflon tape, tighten with just your fingers on the wrenches and then try out the circuit. If it leaks, tighten a little more.

PILOON · Feb 8, 2009

Sometimes when I can't find pipe dope handily I have used FLEXTRA caulking as a pipe joint sealant.
It basically is a polyurathane caulking and works wery well.
Use sparingly.

banjodunn · Feb 9, 2009

Stick to the liquid teflon I would do two to three jobs a month where the owner has used too much tape or has had a fitting off and not been careful and it usually finds it's way into control valves or relief valves I dont mind but customers not happy with some jobs up to $1000+ as far as tightening the joint goes you should be able to get them more than tight enough wjth your shifters

HayDR · Feb 9, 2009

kennyd said:
You should use a Teflon based PTFE paste. Tape, if not used VERY carefully can find it's way into the system and cause problems.

You had better listen to kennyd. If you get some of that tape in a valve seat then you will have a problem that will not go away.

Gary Fowler · Feb 9, 2009

Also go sparingly with the paste. You only need a tiny amount of lubricant/sealer on threads. Many people will glob it on and then it gets all over everything and everybody that walk within 10 meters of your machine. I usually wipe up all the excess after making up a joint also so I dont ruin all my clothes with it later on.

Soundguy · Feb 9, 2009

Zephrant said:
I'm new to hydraulics. I bought a hose/fitting/gauge to measure my bypass pressure, but am not sure if I should use some kind of a thread seal when assembling them. I'm used to using teflon tape, or the pipe joint compound as needed, but that is on low pressure stuff.

I don't want to put the threads together dry- what should I use?

If pipe thread hose.. you can use some joint compound.. just keep it off the first thread. Pipe thread seals by thread deformation. ( except on swivel which has a lip and seat that mate. )

JIC and ORB seal with lip and seat and oring.. and need no thread prep..

tape is nasty stuff in hyds.. as shreds can sure gum up a hyd sytem by getting stuck in valves and spools..

soundguy

Egon · Feb 9, 2009

You only need a tiny amount of lubricant/sealer on threads.

Very true but the stuff expands and jumps to any available surface!

kennyd · Feb 9, 2009

CCI said:
You had better listen to kennyd. If you get some of that tape in a valve seat then you will have a problem that will not go away.

Thanks for the backup

quarencia · Feb 25, 2009

So...Just bought a 1/4" QD for gauge to test hyd pressure. I've always used tape, but I read this thread and took your advice. Made the joint with PTFE paste, connected it and...IT LEAKED!

Not a little either, it leaked a lot. Tightened it some more, then tightened it a lot. Still leaked. I didn't over do the sealer, but there was enough that a bead had to be wiped off when tightened.

Took it apart, cleaned, and remade with 2 wraps of teflon tape. Not nearly as tight as with paste. No leak.

Anybody need a slightly used can of paste?