Mating Problem!

Thread-Gremlins always show up when you least expect them to..

Just like with nuts and bolts, thread size and thread pitch must match 100%.
A bit problem is - It is never that simple when dealing with fittings.

In the US, we use NPT as our standard.
Outside of the US, the rest of the world usually uses BSPP / BSPT

They are not interchangeable. Even though they are close..

NPT will have more of an angled thread pitch - BSPP threads will be straighter.

IF the fittings that you have aren't of the same type - Most likely that could be your issue.

I've worked with hydraulic and pneumatic fittings a LOT over the years, 
so I know what a p.i.t.a. this sort of thing can be.

Don't force or over-tighten the fittings. That can and will usually damage the threads.

You can check the thread/pitch styles if you have other fittings that you KNOW are either NPT or BSPP.

IF you've lucked out to the point that you can finger tighten the male into the female, 
and they appear to 'fit', but just don't hold air - Well - There's a cheat to get them to hold pressure, 
but it is very temporary, and really shouldn't be relied on. It's not a 'fix'.

Yellow Thread Tape. Yellow tape has a bigger mil thickness compared to white tape, 
so you'll get a much better seal with it. It is usually used on gas lines / fittings.. 

I actually use it on all of my threaded applications now - even if it isn't actually needed..

The tape will fill the gaps in the threads very well.
If you know that you don't have the right threads, but can get the tape on, and adapters assembled..
Just tighten them in small increments at a time - as to be sure you're not getting them too tight..
Check for air leaks. Tighten a little. Check for air leaks.

Chances are - That's the issue. 
Companies / People don't always use the same parts, so it's up to us as the end-users 
to figure it out.

Sam -

Everthing in Sam's post above is true. However, the type of fitting you have is none of the above and they are made to mate with each other. They are a JIC female fitting on the coalescing filter to a JIC male connection on the hose. They seal together by tightening only. Chances are you've not wrenched them together tight enough to seal. JIC fittings do not seal together by adding tape or sealants.

This may be a silly question but can't you just eliminate that fitting and screw the hose directly to the canister like how it is on the one next to it? 

Everthing in Sam's post above is true. However, it appears that the type of fitting you have is none of the above and they are made to mate with each other. Those are a JIC female fitting on the coalescing filter to a JIC maile connection on the hose. They seal together by tightening only. Chances are you've not wrenched them together tight enough to seal.  JIC fittings do not seal together by adding tape or sealants.

Click to expand...

This right here. With a JIC fitting that last little 1/16 of a turn is usually what it takes to seal.

Joes41 - hard to tell in pic but those JIC fitting are usually clamped on the hose via hydraulic press.

A JIC fitting is basically a high pressure flare fitting.

In case you don't know about this type fitting, here is a tip...

Looks like a burr on the fitting from the pic, but can't see it too clearly on my phone. Anyhow, best to check and clean, de-burr all threads/mating surfaces, lube threads/flare surfaces very very lightly with a non petroleum oil/grease (lightly is the key word here). The fittings should thread together easily by hand till the flares meet at almost the end of the threads, thats where the sealing happens. You need 2 wrenches that fit perfectly on the fittings, flare nut wrenches work best, but big adjustables will work. Once hand tightened all the way down then hold the stationary fitting firmly (maybe wrench against a hard stationary surface) from moving and then tighten down the fitting that spins. It needs to be very tight. Check it with a spray bottle of soap suds after it is pressurized, if it leaks tighten it some more. Do not use any Teflon tape, pipe dope, sealer, nothing at all on this type fitting. A good burr free lightly lubed fitting put together right will seal leak free for ever..

jmo

Thanks for the information and 'schooling' you guys!

I'm pretty sure that this is the first time that I've seen what you're calling a JIC fitting.
After giving it a second look, I can see the convex section in the left hand connector, 
and what you explained makes perfect sense how the two sections would lock together, seat, and seal.

It's nice to learn something new!

*Thumbs Up*

Sam -

moonlitnite, Glad to hear that you got everything sorted out, and that you're back in action!
You sure do have a way with words, and I was cracking up while reading your post.

As for the expense of the moisture-traps [oil/water separators]
I found a much cheaper option, and am in the process of getting it all here and assembled..

This is a similar high psi inline filter - just cotton plugs - nothing fancy.
https://www.ebay.com/itm/PCP-Air-Filter-Compressor-Oil-Water-Separator-High-Pressure-300bar-40Mpa-Pump/264111150482?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Here is some Molecular Seive - which will trap impurities / moisture much more efficiently:
https://www.amazon.com/gp/product/B06Y2B4CPK/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

I'll be making a '5-chamber-setup' inside of the tube.. From side to side it will be:
Cotton, then M.S. then Cotton, then M.S. then Cotton.
[Unless I opt for cotton on the ends and M.S. in the center later on]

I'm sure this will be just as effective, and at a fraction of the price..

Sam -

Sam’s $30 black filter has 1% of the moisture removal capacity of Michael’s coalescing water separator combined with his much larger capacity gold moisture filter. With similar compressor setups the black filter will have to be serviced frequently in comparison. The black filter is fine with an adequate coalescing tower which Yong Heng class compressors compromise on. Dive compressors have them but they also have moisture filter towers too which makes an additional filter unnecessary. Michael’s setup is most needed by the Yong Hang class of compressors which have undersized water separators. The first coalescing tower extracts 99% of the moisture before the moisture filter has to absorb the remaining 1%. The dual process setup costs more but requires less servicing. A black filter on a Yong Heng class compressor working without a water coalescing tower catches all of the moisture and is quickly saturated regardless of how it’s packed.