How do I seat tail flange to valve rim?

[MonsterMonster]

I'm in the process of replacing a heated wet towel rail but forgot to recover the original tails and examine how they were seated before dumping the old rail.

After showing pictures of the existing lockshield type valves that are still attached to the flow and return pipes the plumber merchants sold me new tails which I believe are called "Standard Tails" (http://gasboilerforums.com/changingaradiator.html).

Towel Rail New Tail

• MonsterMonster
• 20 Oct 2015

New rad tail and connecting nut to connect to lockshield valve.

Towel Rail Lock Shield

• MonsterMonster
• 20 Oct 2015

Existing lockshield valve on flow. Same on return.

The tail has a flange that sits within the threaded rim of the lock shield and is held down by the large nut. There are no rubber o-rings around the flange, in the nut or on the lockshield valves. There were no rings or olives when I removed the original fittings and no signs of leaks.

When the tail flange is pushed down on to the rim is the seal purely bare metal on bare metal or should I use some sort of sealing compound within the valve seat and/or on the flange and PTFE on the external thread of the valve seat?

Is it ok to reuse the existing valves that are still attached to the pipes?

Thanks

 

[Madrab]

Ideally new fitting would be used. I take it you don't want to remove as that will require a depressurise/drain down?

That fitting as it's brass acts like an olive. If you are going to keep then with any re-used fitting clean up mating surfaces with a scotch pad/green scourer and then use some PTFE on the male end to avoid any leaks.

 

[stardanny]

Don't used PTFE on it. Smear jointing compound on flange of tail. That is all it need. PTFE would not do anything on thread part of valve.

Daniel.

 

[MonsterMonster]

Ideally new fitting would be used. I take it you don't want to remove as that will require a depressurise/drain down?

That fitting as it's brass acts like an olive. If you are going to keep then with any re-used fitting clean up mating surfaces with a scotch pad/green scourer and then use some PTFE on the male end to avoid any leaks.

Yep you're right, I was hoping not to drain the system and thought it straight forward to reuse the valves.

 

[Madrab]

PTFE tape (gas type as it's thicker) would be used on the curved brass flange of the rad tail, jointing compound could also be used of course, which to use is a personal preference IMO. I wouldn't use anything on the threads. I would want it to seal at the mating surfaces, if it doesn't seal there then it will leak out of the top of the nut.

 

[jeff the gasman]

I wonder why I never come on the open forum. It stresses me out.

 

[Madrab]

OK, thanks for that useful comment ... now either try and be constructive or at least don't be so elitist

 

[MonsterMonster]

Just out of interest what is the correct name for the joining of this type of tail flange to a valve rim? I would have said "compression" but I assume that is where an olive is permanently compressed around the pipe though not in this case.

 

[Nige F]

It's a taper seat union