One pipe radiator banging - Stumped!

Brendan525

A little context…1-pipe steam system in 2-story ~2,000sf home. Pressurtrol running at 0.4psi cut-in with 0.7 differential. Air vent is brand new Hoffman 40. Can almost pinpoint exactly in the radiator where the steam/condensate hitting to cause the popping. 

Issue isn’t the air vent…that was last months saga. Tried every vent under the sun to troubleshoot and landed on Hoffman 40. 

I removed radiator, tipped it over and found a fair amount of water pouring out. This was after boiler had been off and cooled and radiator iso valve was opened to drain. Propped radiator back up on shims to provide pitch to valve AND to pull up the steam piping from below floor. House is 98 years old, and the piping isn’t far behind that. There was a few inches of sag in the pipe that was pooling condensate. That was last months issue with pipes banging…fixed now. 

My bubble level tells me I’m generously pitched toward the valve. Unsure I can really get any more.  I still have some popping when steam is condensing over pooled water. What else is there to try?!

This is all I hav e been thinking about for weeks now since it wakes up my 3 year old who then proceeds to keep us up all night scare of the popping. Need to fix this like a fish needs water.

neilc

how big is that bushing the valve is piped into,
that's holding back condensate,
it's concentric, not offset,
there's your steam over water,
(but it's been like this forever, i know, i know)

I wonder if a slower still vent would calm the hammer,

Big Ed_4

Spin off the bonnet of that steam shut off valve . Look for blockage and see if a pitcher of water flows though while its open .....

Brendan525

@neilc I had a feeling that may be the last piece I needed to check. Will take a look and se Eid I can enlarge/replace with eccentric. 

It probably has always knocked a bit. And honestly it’s really not bad. Just wakes my kid, which wakes me. Personal vendetta right now with a hunk of cast iron. 

Brendan525

@Big Ed_4 removed valve and it flows/isolates just fine. Certainly not a new valve, but in operational condition. 

ChrisJ

Every one of my radiators has a bushing in it and every one holds some water.   Furthermore two are pitched the wrong way.

None of them make noise.

That doesn't help you but it should tell you some water doesn't mean there's an issue.

When does the noise happen?  Is it during operation or only when it first gets steam and then later when it cools?

Brendan525

@ChrisJ the popping happens when the rad is ~75% hot and seems to happen between sections 3 and 4. I’d like to think I could tell the different between expansion and hammer. But I know enough to know nothing at all. 

ChrisJ

Brendan525 said:

@ChrisJ the popping happens when the rad is ~75% hot and seems to happen between sections 3 and 4. I’d like to think I could tell the different between expansion and hammer. But I know enough to know nothing at all. 

Oddly enough expansion noises are often mistaken for banging.

But I wouldn't expect it to happen when yours is.  I'd expect that at the start of the heating and then to stop fairly fast.

If it's pitched good the only thing I can think of is to make sure the valve is flowing good and but some how restricted.


I'm sorry I can't be of more help.  

neilc

ChrisJ said:

Oddly enough expansion noises are often mistaken for banging.

I'm out of practice and glossed right over this,
it's worth a shot to slip little squares of plastic milk jug under the rad feet,
they act as "slips" on the floor,
could it be this simple?