Steam condensate return humming/vibrating

sean_pdc

I have a 1.6mbtu steam system that has a condensate return system that is humming very loudly in certain units. Building is an older brick structure. Stand up cast iron radiators. Steam rises up to attic and drops down to each unit, enters radiators through a standard angle stop. Each radiator has a mepco steam trap. the resonance/vibrating is happening on a couple stacks and appears to be coming from the condensate return system. We've replaced a few angle stops and steam traps and that appeared to have stopped the issue. Day later we are getting the same vibration/resonance. Any help would be appreciated.

JUGHNE

Pumped return into the boiler?? Does the noise coincide with pump operation....it is really too obvious to suggest but WAG.

Does each attic drop have a drip with trap?

I work on a system designed this way and wonder where the vibs could come from.

Best guess maybe valve with loose washer/disk on seat or maybe check valve in return line.

Any steam in the return venting out of the pump?

sean_pdc

Pump is operating fine and doesn't coincide with the issue.

Each drop does not have a trap. Only traps are on the radiators themselves.

I adjusted the system pressure down from 2psi to 1.5 and it seems to have lessened the vibration noise.

Gonna end up talking to manager about replacing all steam traps and valves, most are original to system. probably 50+ years.

Intplm.

@sean_pdc You might even be able to lower that pressure even more. Try another half pound down for starters and monitor the system.
As to your comment about replacing the steam traps. You can rebuild most steam traps. The parts are commonly available at a much lesser cost than replacing a entire steam trap.

Look up a company by the name of TP Tunstall. They will have replacement parts and rebuild kits for your steam traps. A much better and cost effective way to go than a full replacement.

It will be a great improvement after some fifty years.

nicholas bonham-carter

Barnes and Jones also supply repair kits for traps.—NBC

Dave in QCA

And, Mepco discs are available to do a simple repair to the existing trap and cap. I think there may be several for sale on Ebay at the moment.

Joe_Dunham

Trap manufacturers state that a reverse flow through trap can cause "singing". This can occur due to collapsing action of steam creating a lower pressure or Vacuum on the supply, especially on old cast iron radiators. Plus the supply risers are larger than the returns (greater volume) so they are subject to more collapsing action. You may try installing a check valve connecting the supply to the return somewhere on the main, with the arrow pointing towards the main. This will equalize pressure. if its an old Dunham System, there may have been a vacuum pump instead of the plain condensate pump. the Vacuum pump (just a big mechanical air vent) would insure lower pressure on the return not to mention much more efficient and quiet and thorough distribution of steam.

chrisj85

I'm having this exact issue, also with a Mepco steam trap (1E-VST). It is "singing", consistently emitting a whistling sound at between 400-420Hz. Replaced the steam trap with a brand new one, still "singing". @sean_pdc were you able to identify the root cause? Any help would be greatly appreciated, this sound is driving me crazy

BobC

This is just a WAG but that might be a mechanical resonance issue.

If you wrap your hand around one of the pipes (using something between the pipe and your hand so you don't get burned) does the sound change? If it does see if you can jam something between the pipe and something else to change the resonance point.

Bob

chrisj85

Thanks @BobC — Wrapping my hand around the steam trap doesn't make a noticeable difference, but if I jam something between the pipe and my steam-based PTAC unit it does seem to slightly attenuate the humming/whistling sound. The problem is — what's creating the sound to begin with...

The whistling happens even when I shut the steam going into the unit and let the unit settle for 24 hours.. Mechanical resonance certainly makes sense, but the unit is on the 25th floor of a 50-floor building, so I don't know if mechanical resonance on the pipe would travel this far and also why the units directly below and above do not have this issue

dopey27177

CHECK THE STEAM SHUT OFF VALVE TO THE UNIT.
THERE MAY BE A LOOSE DISC OR WASHER IN THE VALVE.

WHAT YOU HAVE IS DUNHAM METRO SYSTEM WITH A DOWN FEED RISER FEEDING INDIVIDUAL RADIATORS.

IF YOU WANT TO REBUILD ALL THE 1E TRAPS (DUNHAM) NOW MEPCO IS STILL IN BUSINESS, WHY GO TO A GENERIC MANUFACTURER WHEN YOU CAN GET THE PERFECT SPEC OEM ITEM.

jAKE

chrisj85

Thanks for your help! The issue was a worn down actuator valve, which caused the whistling sound. After we replaced it, it worked perfectly. Wanted to post this here in case someone experiences this problem in the future