Unstable water levels

garyanderson

I have a 5 year old Weil McClain 9 Section cast Iron steam Boiler with a Powerflame On/off/on Burner. This boiler was replaced and we have No Idea where the old water line was. We also believe that the New owners of the building may have made some changes to steam piping in a few Apartments, this is a 5 story building, in the past 4 to 5 years. When we 1st took over there was a small Boiler feed system that was being controlled by a McDonnell Miller 150, 1st switch calls for the pump to come on, 2nd switch kills the Burner. This building is all wet returns and were advised that that tank was not required, so we removed it and replaced most of the Return Piping, single pipe system, and for the Most part it took care of the level issue, bit not the stability. We have installed Vacuum breakers, we have cleaned this thing at least 10 times, to no avail. Currently we are using the HyDro-level VXT water feeder to control the water input levels, at least make up, and this has been a help since we can control input with delay periods. According to some of the old maintenance people the Boiler is the same capacity as the old one, we have not done EDR counts, kinda of hard to do this with it being Peoples homes and now with Covid even harder. So Not to much science on that part. I wanted to get opinions on installing a false water line to see what and if anyone had any thought on this, hell, we may be totally off here thinkin this, so would like discussion.
All Air vents on Radiators are new and functioning, all Main air vents are functioning. Any thought greatly appreciated.

ethicalpaul

How unstable? Like drains the gauge glass unstable?

If you can, send some photos of the boiler and the piping near it, from about 10 feet away showing the area from floor to ceiling

clammy

Is this a single pipe system ? Have you looked at the installation manual and checked to ensure that the near boiler piping was sized and installed properly ? Is the pressuretroll set properly . I would guess the boiler has been skimmed and any and all wet return flushed . Have your main vents been updated or replaced and how about your radiator vents . What you should do observe your system and see if it s going off on low water ,could be slow returns and or the fact that the boiler does not have enough water volume to fill the system w steam before either feeding make up or ahutting off on low water . A resourver tank is a easy way to handle that better then a make up feed pump system in my eyes no moving parts . Peace and good luck clammy

nicholas bonham-carter

Adding to Paul, and Clammy’s wise words, what is the pressure in ounces attained by the system?
The main vents may be working, but do they have enough capacity to allow the air to escape at less than 2 ounces of back-pressure? You need the air to escape in a few minutes, not by the following day!
Excess pressure can temporarily force water into the wet returns at a higher level which lowers the boiler water level. When the burner cuts off, the water quickly returns, putting thermal stress on the sections.—NBC

garyanderson

Gentlemen, Sorry for the long delay. We have checked all the specs of the Sizing requirements and they are correct. Yes the MAINS air vents are properly sized and are adequate for the volume of steam. This system at one time had a boiler feed tank, someone had put in, system was not ever designed for one, and it was removed. According to the building owner, the same problem that exist today with the unstable water level, existed then. The water level is normal at start up, as soon as Boiler starts to generate steam, the water level starts to rise and rises up out of sight, when the boiler makes pressure which is 1 pound, as the steam pressure starts to bleed off, the water level drops and continues to drop, to the point of about 2 inches from the bottom of the gauge glass, which of course by that time is off on the saftey, it slowly comes back up and then starts all back over. This of course causes issues with keeping a constant pressure on the system which affects the people on the top floor. We replaced most of the Return lines, id say at least 85% of them, which are visible, so I do not beleive that is an issue.

Jamie Hall

The water level rises as the boiler pressure increases? That at least is somewhat unusual...

Let me be sure I have at least a vague mental sketch of the system. There is a boiler, with the usual header and equalizer arrangement, and it feeds some steam mains. The steam mains are vented, and in turn they feed a system of risers and one pipe radiators. Somewhere out there in the weeds there are drips which in turn feed wet returns (adequately below the water line of the boiler) which, in turn, feed the boiler -- presumably through a Hartford Loop.

More or less of a back of the napkin description?

The first question may sound dumb, but isn't: where is the pressure gauge and pressure control device (pressuretrol, I presume) connected and placed in relation to the boiler water line? This is not a dumb question because, if the gauge is connected to the boiler below the water line, or becomes flooded, it won't read the steam pressure correctly. It will read the steam pressure plus the pressure from whatever depth of water is over the connection.

One aspect of your description puzzles me a good deal. In brief, you mention "as the steam pressure bleeds off...". Are you referring to what happens when the burner is turned off, presumably by the pressure control? If so, that is decidedly odd. Even in a fairly large system, the pressure should drop quite rapidly -- less than half a minute in most cases -- to atmospheric. The pressure out in the radiators -- and the rest of the system -- will collapse very very quickly, and all the steam will be condensed in a matter of -- at most -- a few minutes.

So we have two very curious things happening: at the location where steam is being produced, the water level is rising. And then when the heat is turned off, the water level drops to below the original level and slowly comes back to normal.

In other words, no net change in water level over the cycle. So, in addition to my first question, I would ask what are the possible sources of the water which makes its way into the boiler as the pressure in the boiler rises and what is the source of pressure which is pushing it into the boiler? And second, where does the water go as the pressure in the boiler drops? Well, and a third: what is holding the system pressure up so that it bleeds off rather than collapsing?

Can you find a handy dandy place somewhere near the boiler on the header or a steam main where you can mount a low pressure (0 to 3 psi) gauge? I'd like to know what the system pressure is actually doing.

JUGHNE

Just a WAG here; possibly water held up in drip loops by vacuum that is broken when a little steam pressure is applied? Or a sticking check valve hiding in the return somewhere? Slow return until pressure applied?

kenlmad

How many risers are installed on this 9 section boiler? Are you getting a tilted waterline to the outlet due to high exit velocity?

(Ref: LAOSH, Chapter 4 page 49)

EBEBRATT-Ed

@garyanderson

Does this boiler have the correct size hartford loop/equalizer. Sounds to me as if when it starts building steam you pushing water back.

Something tells me the steam header is not equalized to the return piping.

Is there a check valve in the return on the system side of the equalizer?? As @JUGHNE mentioned. If so your not equalizing from the steam header to the return

clammy

As Ed eluded to the equilizer sizing what’s the btu rating ? Where the return tapping on the boiler reduced . Some larger boilers call for the use of both returns to be used and teed together before rising and tying into the equilizer . Thinking about it I ve seen undersized eq on welded piped boiler have rising water lines and always figured that was it . Having only 2 inch on a 800,000 btu boiler ain’t gonna cut it border line equilizer sizing can be a issue . Check those pipe sizes . Has-the water been tested ph tds that also could be a issue hi ph and priming on the water side . I guess even w the hi low fire could the boiler be over fired or have flame impingement . Peace and good luck clammy

garyanderson

Gentlemen, I have had piping , sizes at least checked , with what the factory calls for, that is all correct. I will get some photos and send. The pressure gauge and vaporstat is above the boiler water gauge glass.

clammy

Has anyone ever pulled the return plugs out of the boiler washed it out and cleaned the boilers water side . A dirty boiler even without oils and such in it will surge and perform badly when the bottom of the boiler is caked w mud . Make sure the water side passages are clear that none of your boiler return piping into the boiler is clogged been there cleaned it and performance was back to normal . I would also suggest check water chemistry ph and tds hi ph and hi tds will and in cases effect and cause water line surging and foaming and priming . All steam boilers water side should be flushed and cleaned other wise the stuff just builds up and even the smallest amount of mud and rust in the bottom of a dry base boiler will effect heat transfer as for wet base the same applies except I feel the wet based boiler will collect even more garbage on it water passages plus most never remove the plug and leave a ball valve for blow down . I still think your equilizer line is to small and a large one would have given more leeway and of course lessen the chance of a pressure drop between the boiler outlet and return . I have always done 2 inch eq up to about 500 mbtu and 21/2 for up to about 750,800 mbtu and then follow the manafactures suggested size or you can t go wrong sizing the eq to the boilers return tapping . Hope this helps peace and good luck clammy

neilc

what if ?

are you sure the top stop on the sight glass is open, and clear into the boiler?
is the bottom one clean also?
I could see the top stop being closed, and as you build steam, the water in the glass rises as air leaks out the seal at the top of the glass, then as everything cools / collapses, pulling water back down the glass,
is that top stop open?

can't see another way for water to rise in the boiler, excepting the tilted water level,
risers and header pictures?

garyanderson

Yes they all are clear. We kinda thought this may be an issue, so we shut down , drain and pulled all plugs, found all very clean actually. Good thought!

garyanderson

All Piping has been checked per the manufacture and according to their specs, all is correct. Now, I will tell you, we are not tee'd at the rear, we only have the 1 side return in the rear piped in, so, maybe adding the tying in to the other rear return may be an option

clammy

I think you may be on the right track w using both returns inlets . I don’t know what the specs call for but it s a fair sized boiler . . It does make sense that a undersized or inadequate inlet return would cause a un equilizer condition between the inlet and outlet just enough to raise and drop the water level .i know that some of the larger cast iron sectionals i and o manuals would show the use of both return tappings with details for proper swing joints as to not crack the bottom end from expansion . If your not learning just hope your remembering Would like to know the out come peace and good luck clammy

nicholas bonham-carter

Maybe a description of how the waterline behaves at each stage of system operation will shed some light.
1. Heating from cold start.
2. Making pressure, (how many ounces?), and pushing the air out.
3. Steam arrives at radiators,
4. Radiators properly hot, (how many ounces?).
at what stage is the waterline misbehaving?—NBC