Steam Coming out of Main Vent!

Samvk94

I'm a 29 year old caretaker on year three of my low pressure boiler license and am in charge of a 1920 Kewanee Portable Firebox Boiler on a one pipe steam heating system in a 19 unit housing Co-op building in South Minneapolis. I have reached a boiler problem I haven't been able to properly diagnose and in turn haven't been able to solve. I asked the senior most person at our successful local heating and plumbing company that works a lot on old steam boilers and his best guess solution proved unsuccessful so I'm back to the drawing board and could really use some help.

Here is the issue:
One of the Hoffman #75 main vents in the basement sprays wet steam across the ceiling and has started to destroy the ceiling for the second straight winter. Unlike the other vents this vent audibly lets out air but unlike the others it lets out steam as well and runs for a while and soaks the overhead ceiling. I had this vent replaced 2 times as my heating specialist recommended and it's still an issue.

Background conditions:
PRESSURE:
I run the boiler at Cut in .5 and differential 1. The boiler pressure gauge gets up to around 1.5 and I've hardly ever seen it close to 2 so it stays low (assuming our pressure gauge is accurate). Heating units hasn't been an issue except dealing with units having different numbers of radiators. We run the heat at 72 degrees 24/7 most of the winter.
VENTS:

There have been some reports and sounds of gargling wet steam escaping out of individual radiator air vents but generally nothing like the problem of that main vent. There are 4 main vents on the basement piping as well as one for each floor on the return piping, close to the boiler.
WATER:
Water needs to be added manually every few days in the coldest parts of winter. No feedwater system. We treat the water by adding an 8-way Boiler water conditioner which contains Sodium Phosphate, Sodium Hydroxide, Sodium Nitrite. I try to keep the water level 2/3 up the gauge glass on average. Tried keeping it slightly lower as heating contractors recommended this season but didn't seem to help our problem. I do regular surface blowdowns and bottom blowdowns as well as occasional gauge glass blowdowns.
ATTEMPTED FIXES:
Tried replacing the vent twice. Didn't help. Next attempt was replacing the big check valve(which according to the heating specialist was not properly letting water back to the boiler) close to the boiler and cleaning out the mud leg at the base of the returns to ensure condensate was returning to the boiler unimpeded. We got this work done this last summer and the same steam out of the air vent issue has been happening.

Not sure if we have a water issue, a vent issue, or something else! Any recommendations or further line of questioning I should be doing toward figuring out the problem would be so appreciated.

MaxMercy

This didn't happen the first year you were there but the problem exists now? Any chance there's another vent that's not working at all? Sorry, not a steam guy.

ethicalpaul

It would be better if the riser for that vent were coming off the top of the main instead of the side....

otherwise, calling @Jamie Hall !! A young caretaker needs help!

Jamie Hall

How does condensate get out of that steam main where the offending vent is located? Which way does it pitch? I really can't tell from the pictures. However, if it is parallel flow -- pitching away from the boiler -- there should be a drip at the end of that main to a wet return. I would make sure that that drip -- or the wet return to which it is connected -- is not clogged. However, if it pitches back to the boiler, I would double check to be sure that it really does pitch back to the boiler for its full length, and can't possibly allow water to pool at that end, near the vent.

Samvk94

Thanks Jamie, I appreciate the response. It pitches down toward the boiler. According to my measurements there is a pitch, although not major. An inch over 20 feet or so in that area. Overall the line does definitely pitch toward the boiler. Do you think capping this main vent would be a bad idea? I know capping main vents is against common good practice but there are two other main air vents on this line before it reaches the boiler. On of the main vents is about 20 feet away and the other is close to the boiler before it drops down to the boiler. Attached is a photo of the second main vent on the line, close to the boiler labeled #2 in the photo. One recent development and something I've noticed from last year as well: It doesn't seem to spray steam out with the air when the boiler is running very often (this current cold spell in the upper Midwest) but before this it spraying steam across the ceiling and I presume will after this cold spell snaps at the boiler runs less frequently. I don't know enough about behavior of steam to know how this effects the issue. Thanks

EBEBRATT-Ed

@samvk94,

That Hoffman 75 vent is only rated for 3 psi operating pressure. If you get a Hoffman #75H it is rated for 10psi although it may vent slower. Since it is near the boiler it may be seeing slightly more pressure than the other vents.

cap it and see what happens. What have you got to lose? Or remove the vent and install a valve and then put the vent back.

The vent never should have been installed on the side of the steam main. it should have come off the top.

You could move it to the riser that is coming off the main a few feet away.

I would cap it first or put a valve on there and see what happens. Then you could order a #75H

delcrossv

I note a couple of things:




Your gauge is awfully coarse to try to measure a couple of pounds. You may want to start with adding a 0-5 psi gauge to your existing rig. You also may want to put in a pigtail rather than that inverted loop and have the instruments "dry" rather than "wet". That horizontal may be full of crud.

Once you know what the boiler is really running at, things may be more obvious.

Second, your pressuretrol is older than Methuselah . Have you removed it and checked it for function? They do eventually die.

mattmia2

How much detergent are you putting in the boiler? Too much will make it prime.