Loctite 577 Thread Sealer question

[Submariner1]

OK Ordered some of this, to seal the Air Filter Connections.
Being a series of right angles, it was a pain to get all the joints tight and pointing in the correct direction.
Some needed 4 wraps of ptfe, and some needed 8!, and then if it leaked, nipping it up a 1/4 of a turn to seal it, meant the angle was wrong.

Apparently the joints don't have to be tight with 577, you just need to leave it to set off 48 to 72 hours before pressurising it.

My question is regarding getting it as tight as possible.
Can you tighten it up till hand tight, and then back it off say 1/4 revolution to point in the right direction. Will it still seal perfectly?
Or does one have to count how many revolutions until the exact position (to avoid going past the correct position) ?

How difficult is it to remove? I know you can use heat to 250C if its difficult.

Do you recommend coating the whole of the 1/2” BSP male thread that will engage? (And wipe off the excess)
or just put a decent ring around the male thread?

 

[Brad93]

I’ve never used 577, loctite 55 is the industry standard

 

[CKJDJK]

577 is a thicker version of 572. Its suitable for stainless as well as other materials. It is also suitable for oil and diesel pipework. I found it sealed well when unable to fully tighten joints but more difficult to dissemble at a later date. Put a ring round near the end of the male fitting. No point using too much. I found it sealed almost instantly so easy to check for leaks. Full strength in a few hours. Good vibration resistance as well.

 

[daleyd]

I’ve always tried to nip up to the right orientation wherever possible, though a liquid sealant will probably work if you have to back it off a touch afterwards as it should flow into any small gaps - probably not ideal though so try and avoid it if you can.

 

[awemawson]

I’ve always used Loctite 542 and swear by it. You can back off to the correct angle if done immediately and getting fittings aligned is a doddle.

use it for air, water, diesel, oil.. Extremely handy stuff. Reasonable strength in about an hour and full strength overnight.

 

[8ob]

Looks like a job for a union elbow.

 

[waddycall]

Put 12 wraps of ptfe on and wind it up till it’s getting tight then keep going till it points the right way. The more tape you put on the more there is to compress which gives more room for manoeuvre. If you put too much on it’ll get pushed off. Rub your finger and thumb around it near the start of the thread so it self amalgamates a bit before winding the fitting in. Loctite 55 is great but that jobs very doable with ptfe.

 

[Pete.]

I’ve never used 577, loctite 55 is the industry standard

Loctite 55 is brilliant stuff. The idea of how you have to apply it takes some getting used to but it never fails to seal IMO.

 

[Brad93]

Loctite 55 is brilliant stuff. The idea of how you have to apply it takes some getting used to but it never fails to seal IMO.

Two wraps then cross it over, 5 more wraps. Something like that isn’t it.

 

[Pete.]

Two wraps then cross it over, 5 more wraps. Something like that isn’t it.

Yeah it's the criss-cross part that seems odd, you wonder how it's ever supposed to seal when it's criss-crossed, but it does.

 

[addjunkie]

577 is the orange one if I remember correctly, its suitable for alchols methanol etc which some others are not.

This over wrapping with ptfe tape isnt the way forward. More likley to have it blow out. If its so bad try new fittings or a dart unions as above.

 

[fzr phil]

I use 577 a fair bit for refrigerant fittings / relief valves e.t.c (smear bad o-rings) at work. Also a big fan of 55, will use it for all sorts of water fittings small to big. Both are great stuff and i rarely get leaks nowaday's.
It would probably be ok to use 577 as you suggest for those air fittings. i try and give at least 1hr to cure before putting under pressure. I would generously apply to ~ half the thread or so of a male tapered fitting. It's pretty mucky stuff, so maybe use gloves and be sure to wipe off spanners it set's hard on them.
Undoing should be ok without having to apply heat.

 

[Kayos]

If its a taper thread, 1.5 turns past hand tight is the correct way to tighten them, ptfe, loctite etc needs a bit of practice but it's easy enough. I'd use ptfe as it never leaks for me and is about 20p a roll

 

[bricol]

There's a lot of over-thinking going on - if it leaks, undo, add some more tape/sealant, or even both. Do it up. With a longer spanner if needed.

I never really got on with 55 - which is why I've got a couple of pretty much unused tubes of the stuff. I've had a big tube of 575 for 15 yrs or so - works perfectly nearly every time.

 

[timgunn1962]

577 is pretty effective stuff, though I've had equally good results on pneumatics with liquid PTFE from Screwfix, at a fraction of the price, for several years.

You have a pretty good chance of it working if you tighten and have to back off a little to clock the fitting, but it's always best to undo, reapply and clock the fitting on the tightening rotation.

Undoing isn't too bad. If you use a ratty adjustable spanner on a brass fitting, you're asking for trouble. If you use a correctly-sized ring spanner, 6-point socket or flare nut spanner, you'll have no real problem. At least that's been my experience.

 

[Submariner1]

I’ve never used 577, loctite 55 is the industry standard

I thought 55 was a cord like product.

 

[Submariner1]

Looks like a job for a union elbow.

Got 2 of them in the 7 couplings

 

[Hitch]

577 is the only one we use at work. It's good stuff. Very rarely get problem when using that.

I usually do a couple of lines perpendicular to the thread, then assemble. No need to murder them up, but a bit tighter than hand tight really.
Better to wipe the excess off than not have enough in it.
Be fine backing it off quarter of a turn before it's set.

 

[Submariner1]

577 is the only one we use at work. It's good stuff. Very rarely get problem when using that.

I usually do a couple of lines perpendicular to the thread, then assemble. No need to murder them up, but a bit tighter than hand tight really.
Better to wipe the excess off than not have enough in it.
Be fine backing it off quarter of a turn before it's set.

577 is the only one we use at work. It's good stuff. Very rarely get problem when using that.

Thanks for the advice.
Loctite Techy said its what he used for airlines.
Ref my issue of lining up the direction, he felt at 150 psi, there was no need to even achieve hand tight.
I will have a go when it arrives.

I thought I would also redo the unregulated QR outlet, that I used ptfe tape on. Although it holds pressure over night, the soapy test does produce (slowly) micro bubbles, despite 10 wraps of ptfe.

 

[waddycall]

If you use ptfe again. Put more of it on. You’re not using enough! It’s very thin and has to fill all the imperfections between the two threads.