Gas reg pulsing

metrosilo

Hey everyone

I have an odd problem. I’m working in a commercial building. 10lb gas coming in.
I have 3 sets of boilers in a boiler room and they each have their own regulator. So 3 regs in total. When one or more are firing, the regulator pulses. Almost like hunting. But what’s odd is that all three do it.

Another thing that’s happening is when I take the cap off, it really starts to pulse.
All three regs do this.
however, when I remove the union for the regulator vent, it just pulses like normal.

Regulators are 10lbs to 7-20”

anyone have any experience with a problem like this?

pecmsg

Is that the correct regulator?

67f575b7ed4ac064da0bde19_NGR06Lit-2025v03.pdf

GGross

when you say pulsing are you seeing inconsistent gas pressure? and if so have you measured that? What was the problem that got you called out? how long has this exact setup been installed (boilers and regs) can you take pictures of the complete gas train and boilers?

metrosilo

gas pressure is consistent.
you can hear the regulator pulsing.
when you remove the cap, you can see the rod moving up and down and the regulator starts shaking. (This happens to all the regulators).
One reg going to two Raypak 1,500,000 each

One reg going to two Paterson Kelley. 2,000,000 each

One reg going to one Paterson Kelley. 2,000,000

Building started out with the single PK. The they added the two Raypak and now they added the other 2 PK. These are all on separate boilers systems (piping)

gas trains are what is on each boiler. I don’t think that’s the problem.

Jamie Hall

Do they pulse in unison? Or are they out of phase with each other? And have yu — I assume you have — watched the gas feed pressure — not output, input — just upstream of each regulator? What I suspect is happening is that the gas pressure just upstream drops slightly, the regulator opens to maintain gas pressure downstream (and probably does), but this causes the gas pressure upstream to drop a little more, which in turn causes another regulator to pen slightly — by which time the regulator you were watching sees a slightly higher gas pressure and closes slightly…

Rinse and repeat. I confess — freely! — that I have not seen this with gas — but I have seen it with pressure reducing valves on water supply systems, but it takes a close eye to see it in the pressure variations.

JUGHNE

Do the 3 regs have a common vent pipe to the outside?

Could that piping be plugged?

Don't want to blow air thru any piping if any still connected to the regs.