Skin fitting lock nuts?

[JumbleDuck]

When I went to turn off the seacock outlet at the end of last season, I was mildly surprised to find that the ball valve handle had disappeared. Investigation showed that it had not fallen off; the whole valve had rotated about 120^o on the skin fitting, moving the handle to the back. I suspect that the rotation was because the new outlet hose I fitted in a hurry the previous summer has untwisted a bit, pushing the ball valve round.

I was and am not too worried about this, because the valve is still well screwed on, the threads are fine and a fair amount of grease is stopping any water coming out. However, it has set me wondering ... is it normal just to screw the valve onto the skin fitting and leave it at the right orientation or would there normally be a lock nut to hold it in position?

I am planning to replace the toilet (RM69 -> Jabsco) soon, so there will be a good opportunity to improve the situation, if improvement is needed.

 

[Deleted member 36384]

Lock nuts are available and normally fitted once the valve is positioned correctly. One one of my fittings, I used Loctite because I did not have a lock nut.

 

[LadyInBed]

Probably happened because you used grease rather than sealant or loctite.

 

[prv]

If the orientation's not important then I would tighten it against the end of the thread and let it end up wherever. If the orientation matters, I would add a backnut and tighten it against that.

Either way, it needs to be tightened against something! If yours could be undone by a hose relaxing, it obviously wasn't done up tight.

Pete

 

[vyv_cox]

I am sent many photographs of seacock installations for comment or to be helpful. Thanks to all. A scan of these reveals that locknuts are the exception rather than the rule.

One thread on the subject was posted a year or two ago. In that case the rotation occurred because the owner had wrapped 12 turns of PTFE tape on the skin fitting threads before screwing the valve on. Three is the recommended number, which fills the spaces between thread peak and trough but allows metal to metal contact at the flanks. The friction of these contacts should be sufficient to prevent unwanted rotation.

 

[BabaYaga]

PTFE tape on the skin fitting threads before screwing the valve on. Three is the recommended number, which fills the spaces between thread peak and trough but allows metal to metal contact at the flanks. The friction of these contacts should be sufficient to prevent unwanted rotation.

To prevent rotation AND seal the thread AND leave choice of handle orientation AND allow removal I think Loctite 572 is pretty good.

 

[Plevier]

To prevent rotation AND seal the thread AND leave choice of handle orientation AND allow removal I think Loctite 572 is pretty good.

Yes that's what it is meant for, it is a locking sealant not just a securing threadlock. It's methacrylate based not cyanoacrylate. Excellent stuff.
http://www.loctite.co.uk/loctite-4087.htm?nodeid=8802627158017

 

[lpdsn]

Up to now I've not used lock nuts (or backing nuts as they're sometime referred to) but I've a few seacocks I plan to replace over the next couple of years so bought a few. They're pretty cheap. I decided I could make do with brass for the lock nuts. They're not in contact with the seawater.

 

[JumbleDuck]

Many thanks everyone. Locknuts it will be, I think. I did not install this valve nor have I ever had much to do with it.

 

[prv]

I decided I could make do with brass for the lock nuts. They're not in contact with the seawater.

Yep. Last time I needed any, ASAP only had brass available for exactly that reason.

Pete

 

[Mistroma]

Yes, I had a similar problem many years ago and couldn't find anyone nearby with a suitable Loctite product. I did buy a reasonable amount of a Rocol product and still have about 80% left.

I started out thinking that locknuts were the way to go in order to align the valves but discovered that a mix of elbows and restricted access made it easier to use Rocol (or similar). I had not used Rocol before and therefore applied some Sikaflex externally around each joint after the Rocol had set.

It worked well and all the valves remained correctly aligned without any leaks. I had to undo one recently and simply ran a blade through the Sikaflex before unscrewing the fitting. Probably overkill with the external Sikaflex but it was really easy to dismantle and gripped both parts in use

 

[JumbleDuck]

Yep. Last time I needed any, ASAP only had brass available for exactly that reason.

They list some bronze ones now. I'm not having brass there, so if there is no bronze to fit I shall need to change my approach. Loctite would be ideal if everything was new, but I doubts if I could get all the grease out now ... as I said it wasn't me what put it there, but it looks like Blake's seacock grease or something similar. Unshiftable.

 

[Deleted member 36384]

.... Unshiftable.

I serviced mine last year just before it's launch, after nearly 3 years ashore. I good wire brush first, vacuum up the crud, then a scrub with a small thickness wire brush and degreaser, followed by a rag wrap and reciprocation cleaned the threads up on the seawater inlet strainer skin fitting. I had a bit of room though, as the strainer is right where the engine access panel is.