Hoffman 75 valves letting out steam

ClearBoiler · December 27

Hello,

I am the caretaker in a building that uses an old steam boiler (100ish years old, I think). It has a single pipe system, and goes to radiators in 19 units spread across four stories.

I have been in the role for just under a year, but this problem existed before I took over. It has been a problem for something like three or four years.

In the basement of the building we have two valves, both Hoffman 75s that consistently lose steam. It doesn't happen every time the boiler cycles on, but it happens multiple times a day on days when it is below freezing. If you tap the vent with a broom handle it works again, and the steam stops escaping.

We have tried replacing the valves multiple times, and that has not solved the problem. We have tried increasing the pitch of the steam line around the valves, and that maybe helped a little bit, but only minimally.

Does anyone have any other ideas?

Thank you!

EBEBRATT-Ed · December 27

What steam pressure are you running at? In most cases you shouldn't exceed 2PSI. The lower you run the better.

To much pressure can cause the vents to leak.

ethicalpaul · December 27

You've replaced them with what model? The same Hoffman 75 model? It's not a very good main vent in my opinion because it costs a fortune and doesn't have much capacity if I recall correctly.

Have you considered a different brand for your main vent such as Gorton?

Post a picture of the scenario near the vents and we can see if anything looks weird.

Look how much $$$!

ClearBoiler · December 27

It is right around 2 PSI, I think lower. They installed a new pressuretrol and gauge not long before I took over the job. I don't know off the top of my head if they changed the PSI it was set too when they did that. The problem existed before and after those replacements were made. It is possible it has been set too high that whole time.

Is the distance between the vents and the boiler correlated with how much pressure affects its potential for leaking?

ethicalpaul · December 27

Is the distance between the vents and the boiler correlated with how much pressure affects its potential for leaking?

No

mattmia2 · December 27

if the vent is undersized the higher velocity will make it more prone to propelling particles of rust from the main in to the vent or of there is water in the main. putting as long a riser as there is space for between the main and the vent will help protect it from water and dirt in the main.

you might be able to clean out whatever is contaminating the seat by soaking it in vinegar and flushing it out with water.

ClearBoiler · December 27

Here are pictures of the two vents. They are on different lines (one on each side of the building), both in the basement. The one in the last two pictures was replaced last week and is still releasing steam.

EBEBRATT-Ed · December 27

Vent tapping's on the side of the pipe are not the best but thats what you have.

I don't know if this will work but it may be worth a try.

Take the vent nipple and elbow off and just leave the short nipple coming out of the main. Put a tee like a 1 1/4 x 1 1/4 x 1/2 " with the branch on the short nipple coming out of the main. Put a 1 1/4 nipple and a reducer and the vent on as long as possible to get the vent up to the ceiling. On the bottom of the tee put a reducer and a valve to be able to blow the rust out occasionally.

It may not help but it will reduce the velocity going to the vent so any water will drop to the bottom. Cheap $$$ to try it. The vents belong on top of the pipe

mattmia2 · December 27

you could also put a strainer somewhere in there to trap the particles before they get to the vent, if i were to do that I would do it in addition to the large diameter chamber with the 1.25" pipe.

Hoffman 75 valves letting out steam

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