Baseboard radiator banging (two-pipe steam)

Johnson2113

Hello, I recently moved into the 6th floor of an 8 story apartment building from 1929. The bedroom and living room each have a baseboard two-pipe steam radiator.

Whenever the heat first comes on, I get several loud bangs from the bedroom radiator that calm down after a few seconds, but they're loud enough to wake us up. Occasionally a bang or two will come through after the heat is fully on.

The living room radiator is nearly silent.

The superintendent has tried:
- Fully opening the supply valves to both radiators. That didn't change the banging, but caused both rooms to get very hot of course.
- Shimming up the far right side of the radiator to tilt it down towards the supply side. I'm not sure if this is even the correct direction to pitch it. It seemed to improve the noise by about 20%, but I might just be imagining.

Next he's going to try replacing the supply valve and the steam trap. I noticed that the supply valve feels "sticky" and doesn't fully stop the steam when closed.

I've attached an audio of the noises, pictures of the heater, and a video of turning the valve: https://imgur.com/a/c1SOGPG

Any ideas? Thank you very much

PS: If he replaces the supply valve, should I request a thermostatic valve instead of a simple one? I'd like to still be able to fully shut the heat off in the bedroom for (hopefully) silence.

Jamie Hall

Is there a possibility that you could post a picture of the outlet of the radiator? There should be a trap on it -- and the radiator should be pitched towards the outlet.

Johnson2113

Thank you for your response, Jamie. Please forgive my near-zero knowledge of steam heat.

This outlet trap is different from the steam trap shown on the right-hand side of the radiator? My understanding is that steam flows left-to-right through the fins, then down the steam trap, then flows as condensate right-to-left under the fins, back into the wall.

I've added three photos to the imgur showing where the condensate leaves the radiator, as well as the shim he installed to try to pitch the radiator.

Jamie Hall

Photos didn't load, sorry. But from your description it sounds as though the general arrangement is OK, but I'll bet the pitches aren't. The finned part should pitch right towards the steam trap -- but the pipe from the steam trap back into the wall needs to pitch left, AWAY from the steam trap. Thing is, air leaves through that line as well as condensate, and if that line is pitched the wrong way water will be stuck in there and the air can't get out, or at best the air trying to get out will blow the water around and bang.

Johnson2113

Thanks Jamie- your thoughts and experience are really appreciated. This link doesn't work? https://imgur.com/a/c1SOGPG
If not, I've attached the banging sounds (as mp3 files in a zip) and pics here.

KC_Jones

The entire run in front of the trap is holding water, see attached picture. It most likely had an eccentric reducer originally and that's what it should have remained, but that's speculation on my part.

As far as slope, the feed valve should be the highest point, radiation sloping down towards the trap, then the trap is the highest point of the return line and it slopes down towards the return from there. I can not tell from the pictures exactly what is going on with that, only a level on the pipes can tell the story.

Jamie Hall

Those look a lot like Hoffman valves and traps -- definitely vapour. And @KC_Jones 's commonts are exactly right. Nothing like a picture...

A thought. If you did put an eccentric reducer on in place of that concentric one between the fins and the trap, you could reduce the slop of the fins to almost nothing and make sure in the process that the return had enough slope.

Johnson2113

Thank you @Jamie Hall and @KC_Jones !
I've attached detail of the steam trap and concentric reducer.

The other heater in the living room (which is virtually silent) has the same parts & appearance, including a concentric reducer! I've attached a picture of that heater's valve & trap (which looks very similar to the bad heater's valve, just not painted over).

I like your idea of an eccentric reducer. I'll more carefully check the slopes of the fins and return to ensure both are "downhill".

Johnson2113

@Jamie Hall @KC_Jones I never did find a satisfactory resolution to this (and later moved out), but I just wanted to thank you for your efforts in helping a random stranger on the internet. Best wishes.