Steam pipes banging with radiator off

Brad White_185

At least that is what they call those inner workings.. More technically, the bellows and spring is also known as a "Capsule".

First of all, one does not just replace a trap or the guts unless you have a definite failed trap in question or if it is part of an overall replacement strategy.

Trap workings are said to last an average of three to five years yet I have seen some disc traps in service for fifty years without a problem. Many variables.

I am a fan of "if it is not broken, don't fix it". So let's see if traps have actually failed. Concentrate on those while in parallel checking all in a concerted effort.

When the system is fired up and hot (on the steam side), feel the downstream side of the traps (all of them to be fair!).

The steam side is as hot as you know it to be.

The condensate side (a properly working trap is the gate-keeper between steam and condensate), well, that side will feel much cooler. Still hot, but not nearly so hot as the upstream side. You can tell.

An infra-red thermometer is also useful and keeps your hands from looking like Jack Palance's forehead.

Now, trap guts. If you can get the name of the trap, a photo or a sample spare trap from the superintendent's office (he uses it as a paperweight or an ashtray probably :), get in touch with Tunstall Associates and they can set you up with the appropriate trap innards.

I am not saying that the cause is a trap failure. It may be or it could be something else; it is but one path to explore. However, trap maintenance should be an on-going effort regardless.

To replace the guts, a proper pipe wrench is the only way. Those tops are rather thin castings. You do not want to damage the nut. A little WD-40 (will stink on a hot trap), can help loosen a stubborn one. The capsule fits neatly in there and the cap is replaced. Of course, there is always the more specific "RTFM" method which I always recommend!

Dave_61

Steam pipes banging with radiator off

We have a NYC apartment with 2 pipe steam built in the 20's. There is a supply pipe to the radiator and another with a steam trap. The apartment (1BR) has 2 radiators. One in the living room and one in the bedroom. The bedroom gets so hot that we shut off the radiator in there. However, what we've noticed is that when the heat comes on, the pipes in the bedroom bang like crazy for about 2 minutes and then stop (usually in the middle of the night). I opened the valve today, and no banging. I would like to keep the heat off in the bedroom because it gets so darn hot. Even with the valve barely open,it gets pretty hot. Why would turning the radiator off cause the pipes to bang? Is there anything we can do to stop it? Thanks.
Dave

Brad White_185

Some thoughts

Just a guess but when were your traps last serviced? It may be that a trap is leaking by, allowing steam to enter the return which denies some condensate to leave. The trap may not even be in your apartment.

Your isolated radiator may well be a cause or a red herring but I will take it at your word and that it is not just coincidental.

One other thought is that, if you understand that steam traps are air vents first, it may be that your radiator is a default pathway for air and that the vacuum-breaking ability of that normally open radiator is causing a vacuum to form on the return side. The sudden collapse of steam into vacuum is one cause of banging.

Random drive by thoughts, nothing definitive. Wait for others.

Dave_61

Thanks Brad,

So what would we do? Can we open the steam trap and clean it? It has a star shaped nut on the top. How would we clean it?

Dave_61

I felt on either

side of the trap (radiator side and pipe below trap that goes into floor). It is just as hot on either side. Interestingly, with the radiator on, no banging last night. The trap says Sarco on it (painted over, but that's what it looks like).

Brad White_185

That is good albeit subjective indicator

if you can get a temperature gun to double check all the better but it does seem that you have steam leaking by. Now, can one tell it is that one trap or leakage from another nearby trap? That is the challenge. That is why trap repair or replacement has to be systemic and ongoing to be effective. Sarco is still in business so if you need new traps, not a problem, but I would start with replacement capsules. Check out the Tunstall site and see what they have for literature. A spare body is a great thing to have though, as I mentioned.

Normally there would be about a 10-20 degree difference between the two, so that it feels very close, that is a decent indicator, not perfect but rational.

But if as you said, the trap is painted over (and knowing how often most apartments are painted), I would say that this particular trap has not been touched since the Nixon Administration.