Should any type of sealant (Loctite) be used when reinstalling pipe connectors with o rings to main control valve on excavator?
Are you talking about this type of face seal fitting that has an O-Ring in the groove and also one under the washer as indicated by the arrows.? This type of fitting does not usually require any type of sealant other than new O-Rings when installing.
In agreement with the above. Straight threads aren't a sealing thread. Now if you've got a tapered thread (NPT) fitting that adapts to an o-ring face or JIC, definitely use thread sealant on the tapered pipe threads. When it comes to hydraulics, I prefer the liquid pipe thread sealant over the tape. Tape has too much potential to break off and stick into the small orifices and valves.
All the dealerships I worked at threw away the liquid sealant years ago and went back to the tape. If you are getting the tape into the hydraulic system, you aren't applying it correctly on the fitting. I never use any kind of lock tight on a hydraulic fitting. They are usually in some kind of tight space where it is hard to get a wrench on anyway and the glue just makes taking them apart again without damaging the nut that much harder if the lock tight works at all. Usually it is contaminated by the hydraulic fluid and can't work anyway.
For clean dry pipe fittings (new stuff) I like the locktite 567 sealant, it doesn't leak and it disassembles fairly easily. Reassembly of used stuff I will use tape, just keep it off the first 2 threads.
I find that the problem with either tape or liquid sealant is when you disassemble it, you have to be very careful to get all the pieces of old tape or old hardened liquid fragments out of the hole ( female threads)
Thanks everyone for you replies. It is a connector going into the main control valve and then the pipe connector connects to it. The connector has a flat face behind the threads where the O-ring goes. See pictures. The first picture shows the connection to the main control block. The second shows the pipe connection end.
That is not pipe and shouldn't need sealer on either end. The tube fitting opposite the o-ring should be a metal to metal seal possibly with a small o-ring on the nipple. Any Teflon on those threads is a good way to strip or split the nut.
Amen to that. And you're usually the one who also has to get the remnants of the sealant, tape, or Loctite out of the centre of something hydraulic that is expensive/unobtainable/complicated (*delete as required) .......
Some folks prefer tape, others the paste, and when I was working as a millwright had some foremen tell me to use both! My main hydraulic shop guy told me that all either does on a pipe thread is lubricate the threads and does little to actually seal. I've seen jobs where high pressure (2500 psi and higher) leak badly because too much tape was applied. I still often use tape on lower pressure applications, but the paste where I'm dealing with over 3500 psi.