3/8” BSPP nipple is very sloppy in BSPP Elbow - is this normal? Or defective?

[Submariner1]

Just got some stainless fittings, but a slight problem. I had hoped the bspp elbow and parallel nipple would be sufficiently tight to cement with Loctitie 577 sealant (that I have) without a leak.

But this joint or mating is really very sloppy. Note I did have my only slight leak using 577, when using BPPT INTO BSPP when they were not tight ( i.e. to get the direction of the fitting correct).
I want to avoid this, because its very fiddly working under the tank with confined access!

I selected a BSPP Nipple rather than a street elbow, to avoid the above leak scenario, and also be able to set the angle of direction exactly as I wanted it.
Note I have not yet removed the std. Drain cock - so no idea if this nipple will lock up into a “shoulder” or will go straight through the tank - hence without this knowledge I need to be able to select the right amount of turns, so the direction is correct, and also avoid the male end going too high in the tank, causing a water trap.
Hence my problem of a sloppy connection - i.e. want to avoid winding in this joint blind, and not sharing the Nipple equally.

Q1. Should BSPP to BSPP fittings be reasonably close, i.e. not wobbly? If so a replacement would solve my issue.

or if its normal to have sloppy fittings ?
Then
Q2. would jamming the nipple whilst the sealant sets work? Albeit only done up hand tight.
or
Q3. Will the sealant overcome this looseness and not leak because it is BSPP to BSPP.?

Ideas to jam the nipple

Apologies for the long winded explanation, but the devil is in the detail.
if I knew whether the tank drain hole had a shoulder to stop the nipple; then I could just go ahead and lock the nipple into that, and then wind this elbow on until it stopped (pointing In the right direction), and if needed, shim it with washers.
But if both ends are free spinning I wont know if the nipple was winding up into the tank creating a water trap, and the elbow hanging on by 2 threads!

plus once I undo the tanks original drain - then the compressor is unusable till I solve this.

 

[8ob]

Have a look at running nipples, you could cut one to length then use a backnut on the elbow and one on the tank.

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[Submariner1]

Have a look at running nipples, you could cut one to length then use a backnut on the elbow and one on the tank.

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That was my first idea, but there is very little clearance below the tank, if one is to preserve the portability aspect.

 

[julianf]

Parallel to parallel is generally, I believe, supposed to seal on a flange (washer) rather than on the thread.

You need one as taper to seal on the thread.

...or so Im under the impression of (as in I'm no expert on it)

 

[bricol]

If you really have to do it this way, use a hex nipple, preferably a taper one, apply sealant, wind it in finger tight and wind elbow on it - apply wrench and tighten to desired position. If a parallel hex nipple, use a copper or dowty washer to play with stopping positions.

I'd would simply used a street elbow, PTFE tape or sealant, wound it in tight and either stopped where I want before it got too tight, or wound it in further with a longer spanner - or wound some more tape on to stop it sooner.

 

[Submariner1]

Try BSPT for the male threaded sections as these are undersize at one end and oversize at the other so will tighten and remove the need for a locknut.

Instead of sealant paste I would switch to PTFE tape as this will fill any small gaps and comes in a range of thicknesses.

yep I might have to go this route with a taper nipple, but it might be too long ref ground clearance. And rules out selecting the exact direction.

another idea was a 10mm o ring to “pull“ the threads together. It seems to provide some tension pulling the threads together and might work enough to allow the sealant to set, with the threads placed together.
- possibly a bit difficult to know exactly where it will lock onto the Tank female thread, re the direction.
or maybe leave the O ring, to provide tension into the tank while the sealant sets, and offers some flexibility for the direction; as the o ring can be compressed.

the locknut just ensures the o ring on straight.

just wish I knew if these parts were faulty or all BSPP to BSPP joints wobble.

 

[Submariner1]

If you really have to do it this way, use a hex nipple, preferably a taper one, apply sealant, wind it in finger tight and wind elbow on it - apply wrench and tighten to desired position. If a parallel hex nipple, use a copper or dowty washer to play with stopping positions.

I'd would simply used a street elbow, PTFE tape or sealant, wound it in tight and either stopped where I want before it got too tight, or wound it in further with a longer spanner - or wound some more tape on to stop it sooner.

I can appreciate your frustration, “for gods sake how hard can it be” lol.
I was avoiding ptfe tape, as have had leaks or needed another 1/4 turn to seal. The problem is I am feeding this ‘chain of joints” through 2 sets of wheel chassis‘s; mainly so I preserve ground clearance, and also they kind of shield all this pipework against knocks. So as the pipework is threaded through the chassis a) each joint has to point in the right direction, and b) if it means adding more ptfe tape, that would effectively mean disassembly of the whole chain! ( so I can rotate each component in turn ... if that makes sense.
If only this ONE parallel joint was tight enough to take a sealant joint, then it would be a breeze!

 

[Submariner1]

Parallel to parallel is generally, I believe, supposed to seal on a flange (washer) rather than on the thread.

You need one as taper to seal on the thread.

...or so Im under the impression of (as in I'm no expert on it)

Thanks Julian for the advice.
when you say “seal on a flange (washer)” do you mean the parallel thread is supposed to butt up against a flange ?
Not sure how that works, but getting the impression you are saying that they were not designed just to screw up to the desired rotational position and left with sealant?

 

[Brad93]

Loctite 55 and install the cord the correct way.

 

[mechman]

Can't you put a union in the line ( if space allows) it would eliminate the rotational problem.

 

[Submariner1]

Can't you put a union in the line ( if space allows) it would eliminate the rotational problem.

Sadly not enough space.

 

[Munkul]

A BSPP nipple male thread will sink to the bottom of a BSPT female - this is because in a BSPT sealing joint, the female thread is generally parallel, and only the male is tapered. Generally! If you want a tapered female, you'll have to specify this specially.

If a BSPT nipple is screwing all the way to the bottom of the elbow, it's either a bad nipple, or it's not BSPT.

Thread tape works well when you can get a good nip on it... not so good on parallel joints. If the pieces are loose fit, then loctite is NOT the answer - you'll need either cord or PTFE tape to take up the slack.

 

[the artfull-codger]

I use bos white & hemp on my fittings, never fails even when they're a slack fit.

 

[Submariner1]

Loctite 55 and install the cord the correct way.

Appreciate the tip Brad, but I already bought the 577 (which is easier for the other joints I need to make)

 

[awemawson]

I use Loctite 542 and it works every time on air, gas, propane, diesel, water - in fact anything I've used.

The great advantage is that the threaded joints don't have to be tight, so you can align things to point in the right direction and it starts to set in a matter of minutes for handling and after a few hours it's good to go. But also it can be dismantled without undue force.

Superb stuff.

 

[Submariner1]

A BSPP nipple male thread will sink to the bottom of a BSPT female - this is because in a BSPT sealing joint, the female thread is generally parallel, and only the male is tapered. Generally! If you want a tapered female, you'll have to specify this specially.

If a BSPT nipple is screwing all the way to the bottom of the elbow, it's either a bad nipple, or it's not BSPT.

Thread tape works well when you can get a good nip on it... not so good on parallel joints. If the pieces are loose fit, then loctite is NOT the answer - you'll need either cord or PTFE tape to take up the slack.

Thanks Munkul would agree with all the above. Sadly ground clearance pretty much rules out the extra space needed for BSPT; and I am sceptical about Loctite Technicals’ claim it would seal on BSPP to BSPP. (purely based on a failed BSPP female to BSPT male, when I had to back it off 1/3 of a turn to point the right way - seems about the same slackness as this Parallel joint)
Hence I wondered if using the O ring to give the BSPP - BSPP (enough tension not to wobble) would enable 577 to seal it?

I really like this compressor, but wish they had used the bigger wheels to give more ground clearance. Any bigger than the std. drain and if you lifted the handle a tiny bit too much, (drain being behind the wheel axle) and you will catch the fitting on the ground!
All they had to do was use bigger wheels or put the drain hole at the other end! I.e. the end you lift up!
My reluctance in cord is if I get it wrong then I have to undo a chain of joints (in series) to undo the first joint.

 

[awemawson]

Did you back it off once it had started to go off (in which case of course it will leak), or was it liquid at the time that you backed it off?

 

[Sam0117]

Just a random thought if your putting an auto drain in, I assume your not gonna move the compressor at all once in place so could you not remove the wheels and make a stand to lift it up more so you’ll then have the clearance?

 

[Submariner1]

Did you back it off once it had started to go off (in which case of course it will leak), or was it liquid at the time that you backed it off?

I backed it off instantly. I.e did up till it started to lock then backed off to the correct angle