The new compressor lost 8.2 Bar in 22 hours ... Then I discovered, the leak was where I had fitted the supplied Euro QR! (The only joint the user has to make). The QR fitting was supplied with Off white coloured tape pre-applied to the threads. Couldn’t hear the leak, but Diluted fairy liquid was blowing 1” bubbles like crazy. Note the pic where the connector is screwed fully home. I redid the joint with 5 layers of white PTFE Tape. Almost as bad. Tried again with 7 revolutions of tape, better but still small bubbles. ( note fitting was fully in ). Redid it again! This time with 9 layers of ptfe tape. Much better ... almost leak free; but when I put some oil on the joint, you could just see some micro bubbles over a 5 min period. I thought 3 layers of tape was all one needed on a tapered joint? Am I wrong? Note the threads on the fitting and the tank, look clean cut and undamaged. Would It be better to redo it with 11 revolutions of tape or use something like Locktite 572? what is the best thread sealer that would seal these threads, yet undo without heat, or the absolute minimum heat.
I suspect that the female fitting on the tank is BSP parallel ( BSPP ), not tapered ( BSPT ). It is designed to accept a tank end-plug, and seal using an O-ring or a flat rubber disc washer.
10-12 wraps on the thread then keep wrapping around near the end of the thread to create a build up that will form a ptfe washer against the shoulder of the hex as it winds in. Don’t be afraid to put more on.
Maybe the thing to do is get a 1/2 BSPP plug and a dowty washer, and save this non corroding QR fitting for use as a spare on the on board regulator. It does seems to be holding pressure much, much better; but I will see how much air is lost over 22 hours; and if not too significant, just live with it. Or try once more with 11 layers of PTFE!
It probably just needs building up a bit. The theoretical perfect world of what you should use on a thread and how much doesn’t really exist!
The on-board regulators on small compressors are often restrictive, and so it is quite common to replace a tank end-plug with an air connector to get a high flow rate supply for high-consumption air tools.
Sod the PTFE tape you need Loctite 55 cord. Or loctite thread sealant, I forget the number it’s a gel.
What it really needs is an isolating crane valve between the tank and quick fit connector for starters...
Good news, despite seeing micro bubbles (appearing) very slowly last night, when oil was put on the joint. This morning there was no pressure loss. ( well none I could discern with this guage. Either this weeping of air has self sealed (doubtful), or as its much warmer this morning (unheated garage). The air expansion has Compensated for any Minute loss of air Overnight. at least I am on the right track, as before the 50L tank would be almost empty. And now unless I had bubble tested with soapy water and oil I would (incorrectly) say over 12 hours there was zero air loss.
To avoid a repeat of this incident: https://www.mig-welding.co.uk/forum/threads/repairable-clarke-xe37-270.106052/#post-1681951 you may want to consider starting with a 90 degree street elbow, then a ball valve, then the quick-release coupling.
Surely clockwise as you look at the end of the thread, so when you wind it in, its not trying to undo it.
