Teflon tape/ Hydraulics

Teflon is bad in light airplane fuel systems--(gravity feed, no fuel pump) because a little sliver can stop up the main jet or needle valve----if you tape too close to the end of the male fitting, it can sometimes squeeze ahead & cut itself loose to wander around

I wouldn't worry about a hydraulic system, they usually have filters & a few passes thru the pump will chop it down fine.---unless you have some pilot operated flow control valves with leetle bitty oryfices...The thread joint compounds with Teflon usualy have the TFE ground up very fine to obviate such circumstances.

If you did a hack job of it and stretched tape across the openings, I could see shreds of tape getting into the fluid stream, and perhaps sticking in valve ports, etc. If you did a proper job it should do nothing of the sort. You would want to be careful to get it all out when removing fittings, as that would be a point where carelessness might result in shreds going into the system.

I expect that you can read somewhere that it's bad, and you can read somewhere else that it's good. If the system is assembled and has been run, there's no benefit to dissasembly now, IMHO. Any shreds that are likely to get in the fluid stream have probably done so, and they will either end up in the filter eventually and cause no problems, or they will end up somewhere that causes a problem.

That said, I'll also note that on _my_ hydraulic system, there are no places teflon tape or pipe dope make any sense at all, as far as I recall. All the connections I've had to open up are sealed either with o-rings, or flare fittings - the threads just bring the sealing surfaces together. Pipe dope might serve as anti-seize, which is no bad thing (some of my connections took two 3-ft wrenches to open up after being connected for up to 34 years), but anti-sieze will work just as well. Your system may well differ and have pipe threads sealing connections.

Thanks guys. I've been reading a lot about home build airplanes (RV-7A to be specific) and that's where I got the idea that Teflon tape was bad...... now I get it .......... in fuel systems. What a relief....... I envisioned the hydraulic wonder I'm making working only when it felt like it....... thanks to the Teflon tape.

SNIP

The above says a lot. Are you working a hydraulic system that is using pipe thread? If using pipe thread then Teflon, properly applied is fine. If your using any other type of fitting then Teflon is not the stuff to use. Teflon tape is designed as a LUBRICANT so that tapered pipe fittings can be tightened correctly without galling. It is not a sealant!

As I understand it, the TFE "problem" is fine shreds of TFE getting into the system snd clogging fine jets (e.g. diesel injectors). If properly applied to pipe threads, it's fine. "Properly applied" means the tape does not cover or extend beyond the last male thread. I think the "don't use" mandate is because you can't count on the ham fisted properly applying it.

Ted

Hot acids will.

How many wraps is "properly applied?

I once set up a hydraulic system to drive a very small servo valve controlling a roller position within very few thousandths. Tiny orifices in that thing, and it was very expensive. The plumbing was mostly mechanical tubing, with very few tapered thread fittings. We used a hardening Loctite product designed to seal hydraulic systems on those. The servo valve, manifold mounted, came with a flushing fitting to allow startup and circulation through the filters for a day before changing the filters and installing the valve. The commissioning instructions were full of cautions about maintaining near clean-room conditions while the system was open.

I suspect there'd be a lot more forgiveness in hydraulics on a backhoe or something similar.

Pete Keillor

It is best not to use Teflon tape as it can shred and clog parts of your system - a problem you will not encounter with Pipe Sealer with Teflon. Another problem I recall was in a plant here in Houston years ago when Teflon tape was used in fittings on a fuel loading hose. Apparently, the tape was thick enough to act as an insulator and allowed static electricity to build rather than discharge to ground. When the operator touched the nozzle to the lip of the filler a spark ignited the gasoline.

Definitely a no-no on fuel dipensing equipment (although you see it all the time) or natural gas/propane systems, it is also dangerous in fuel systems and hydraulics. It CAN be applied in a safe manner, but it is extremely difficult to know if it is actually safe after it is installed, as far as shredding is concerned, and is virtually never checked as far as ground continuity.

AHAA!! - So that's why 'they' made me get that expensive thread sealer for the fuel delivery system at the golf course shop. Live and learn - ain't life wonderful. Regards. Ken.

clogging of orfices, and that most hydraulaics are sealed w/ 37°, 45° or other angle faces, or O-rings against bosses/c-bores, not the threads so do not nead a sealant, though NPT fittings do. Same is true for heating oil lines/fittings. The Teflon does not dissolve in oil (or much of anything) but it doesn't seal oil well either, so tapered thread fittings tend to seep.

I was told three by a gas man. Note that he _only_ uses the heavier yellow stuff.

Ted

Which hot acids? We used to use some pretty nasty stuff, both hot and cold, on germanium. All lab ware used was TFE. None dissolved.

Ted

Oddly enough, some years ago I had very good experience with PTFE tape for that very purpose. We use platinum resistance thermometers to measure seawater coolant temperatures in power station performance tests. The zinc screw on connectors on the cables bind to the stainless top of the PRT when splashed with salt water. I discovered that a turn of PTFE would give enough insulation and lubrication to make the locking rings easy to remove as opposed to locking up enough to need to be cut off after a month or two.

Mark Rand RTFM

Ted I was wrong. I can't find any reference to hot acid resistance. Sorry, false alarm.