[AT] Hydraulic fittings

[Dennis Johnson]

It has been an interesting discussion on Teflon Tape for fittings.
 
The first thing that is needed is knowledge of which type of fitting or thread that you have. For pipe theads there are 2 common type in the US - NPT and NPTF (for Fuel). They may go together, but they are different. For either type I would recomend either a paste or a teflon tape. There is also straight pipe threads which may also screw together, but does not seal without some other sealing mechanism such as a combination of a sealer and a jam nut.
 
I have seen tape on JIC and SAE type fittings, and it is a waste of tape and has no real use. These type of fittings are not designed to seal and the seal is on the tapered surfaces. When tape is used here it usually is a band aid to slow down a leak because the seal surfaces are defective. Band aids may slow down some things, and there is a place for band aids, but you need to realize that it is a band aid, and not a cure for the real problem.
 
The other thing that is important is the type of hydraulic system you have. Most gear pump systems with simple control valves and cylinders can tolerate a bit of loose tape. Most older agricultural hydraulic systems, dump trucks, hydraulic winches, etc have no problem with teflon tape. If you have a sophisticated system with computer controled servo valves running in autopilot, I would not let teflon tape anywhere near that system. In such systems I also would not permit many pipe threads, with the possible exeption of large suction fittings on the tank where other fittings are not available.
 
The point is that there are places for teflon tape and in those places it works well. I used some last week end. There are other places where it is does not fit the application, and you might get by with it, and you might have a problem. It is like shaving with an axe - It might be possible, but not recomended. Tree trimming with a razor is just as bad. The use of either in the right place works well.