use of teflon tape on fittings for p/s pumps using hyd. fluid????

[TOMBUCK]

Is it OK to use teflon tape on the threads for the ends of hoses that go into power steering pumps?

I was told that it is a big no no to do so by a guy at work today, after it was changed out and rebuilt by him, and it still leaked very bad. So, I took it out again and used teflon tape on the fitting (L-SHAPE) on (HI-PRESSURE) output side, being very careful nut to wrap past the ends of the threads. I figured this would be OK. It stopped the leaked. This guy got all over my case because of it.

 

[Bret Chase]

it actually depends on the fitting type. if it's a tapered NPT/IPT thread then tape is ok as the threads do the sealing. if it's a end sealed straight thread like an AN fitting, you absolutely do not ever use pipe tape/dope on them. what can happen is with enough pressure, the teflon tape can allow the fitting to back off... bad bad deal.

HTH,
Bret

 

[TOMBUCK]

I forgot to mention that there a locking nut and flat washer w/rubber "O" Ring that help to seal and lock the fitting in place once the fitting is tightened into place. The locking nut tightens down onto flat washer which squezzes the "O" Ring aginst the outer seat of the threads. The Locking nut puts positive pull aginst the threads of the fitting that goes into the pumps. The tape acts as a primary seal on the threads and the "O" ring acts as the secondary seal before the flat washed and locking nut. The "L" fitting can only to about a 10 degeree play area to fit to line to steering gear box. The Tape took out the extra play in the fitting connection and brought it up tight to the proper spot good and snug.

The augument at work was that "Not to use teflon with HYD. type fittings." I said BS.. Am I wrong or right??

 

[JohnBrowning]

I have always done this and never had a problem. You use as little teflon tape as possable. I have never had a come back because of teflon tape!

I will say that you should not need them with the seal design you desrcibed. With that said I have seen a lot of Tractors with teflon tape on hydralic fitings!

[ March 08, 2004, 10:01 PM: Message edited by: JohnBrowning ]

 

[MolaKule]

I use Teflon tape on every hydraulic fitting from 1/2" to 2" NPT, and these are 2,000 psi peak systems.

 

[Bret Chase]

quote:

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Originally posted by MolaKule:
I use Teflon tape on every hydraulic fitting from 1/2" to 2" NPT, and these are 2,000 psi peak systems.

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the key there is the NPT tapered thread. teflon is AOK on those. it's the straught threaded ones you can't (or shouldn't) put the tape on. My employer owns a couple of carwashes as a side business.... the automatic uses a 25HP main pressure pump running at a nominal 1800PSI using straight threaded high pressure couplers (I'm not sure the proper name for this type, it's not a AN though.) that I mentioned before. we had a fitting (we're talking a 1.5" line here at 1800 PSI) back off and make a rather huge mess because there was teflon on the threads. the teflon allowed the fitting to slip when the solenoid shut off and spiked the pressure.

-Bret

 

[Ken2]

Don't use teflon tape on any fitting that has a gasket, washer, or o-ring.

I don't even like teflon tape on tapered pipe threads. If the threaded piece is removed and reinserted, some tape will be left in the female threads and possibly pushed into the system. I prefer a paste type of sealant. Permatex has a good hydraulic sealant paste with teflon that has sealed some really torn up hydraulic tapered threads for me when I didn't have replacements.


Ken

 

[labman]

If an O-ring fitting leaks, chances are it needs a new O-ring. Tapered pipe threads are good for water. If you want a hydraulic system to stay clean on the outside, use O-rings or something. There are charts that give the leakage for tapered pipe fittings. Where I do have to use them, I usually use the Locktite paste with Teflon.

At one time, I managed a little factory that used diphthalate oils by the tank truck. I had a good welder working for me. We would weld up as much as possible and finish with groove lock fittings. We still had little piles of Speedidry under the threaded joints we couldn't work around.

 

[jsharp]

The assembly trick with teflon tape is to not allow it to overhang the end of the male thread. Back off 1 thread and start wrapping the male fitting there. Any overhang and you run the risk of the end of the tape tearing off and ending up lodged in the system somewhere. Bad news in a close clearance hydraulic system...

 

[MolaKule]

quote:

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Don't use teflon tape on any fitting that has a gasket, washer, or o-ring.

I don't even like teflon tape on tapered pipe threads. If the threaded piece is removed and reinserted, some tape will be left in the female threads and possibly pushed into the system. I prefer a paste type of sealant. Permatex has a good hydraulic sealant paste with teflon that has sealed some really torn up hydraulic tapered threads for me when I didn't have replacements.

---

I agree Ken, except that IF the paste flakes off and gets into the hydraulic system, you will have globs of sticky goo in the resorvoir which can only be removed by flushing.

I think the secret here is a thin film of paste or wrapping after the first thread and just enough to finish the back threads.