Bouncing Level in Sight Glass

Owen

I have a large school steam system with lots of problems, one in particular is very puzzling and problematic. The level in the 94 Series Weil-Mclain bounces terribly and often shuts the burner off on LWCO.

PLEASE DON"T SUGGEST CHEMICALS! it isn't chemical. That has been eliminated as a cause many times.

Last weekend late Saturday I drained the boiler of it's 400 gallons, allowed it to cool overnight, then added 11-1/2 gallons of ChemSearch 100 and filled the boiler back up.

It steamed for 6 hours as per the instructions, then was drained again, cooled, re-filled and drained again, then re-filled again and fired. The idea here was to clean it out of contaminants including oils to see if that was what was causing the bouncing. I did not stop the bouncing. Also, on the last re-fill NO CHEMiCALS WERE ADDED.

Here's the important clue. While steaming with the chemicals in, I SHUT THE BIG STEAM HEADER VALVE; BOUNCING STOPPED!

So, chemicals aren't it, dirt, oil or other contaminants aren't it, it must be mechanical.

The near boiler piping is higher and/or bigger than the specs call for.

Everybody here is totally stumped including the steam fitters who put it in four years ago as a replacement for an old formerly coal fired huge steel fire tube monster.

furnacefigher15

I thought the surging was only on first start of the day

Is that not the case?



Was anything ever done about demand timing?

nicholas bonham-carter

surging, then disappearing waterline

i think you were fighting to reduce the pressure on this system. for every ounce of steam pressure in the boiler, the return waterline will rise up 1.75 inches. this is a lot of water being held outside the boiler, especially if there is a horizontal pipe in that height range [2 -16.3 ft.].

i don't know how closing a main steam valve could interrupt this phenomenon though.

you could monitor the pressure rise with a 0-5 psi gauge, and see at what pressure, the water starts to disappear, then calculate the height corresponding to that pressure and look for piping where the water could hide.

another method is to attach a clear plastic tube to the returns, with it's end open, and secured next to the ceiling. when the boiler is off, the tubing will have the water at the same height as the boiler water. when the boiler fires, you can see the rise of water in the tube to a point corresponding to the pressure. you can then show others what happens to the boiler water when the pressure is out of control. seeing is believing.--nbc

Owen

Surging

Thanks for your interest. I appreciate your advice and excellent questions.



No, the surging is constant. The only time it has stopped is as I mentioned, when I shut the steam main. That's got to be a big clue.

The bringing on-line of HX & etc. has been staggered somewhat, along with the speed the 1/3-2/3 valves are opened. Valve opening was lengthened to 18 minutes.



(The steam fitters say your suggestion to lower the condensate pumped return connection on the equalizer "couldn't hurt". They are thinking we may have to raise the whole riser/header assembly up as far as possible to "dry" the steam. That sounds spendy.)



However, right now the boiler and many of the systems are running constantly (no night setback) as well as at ridiculously high pressure as a result of the Supervisor's desire never to get any complaining phone calls which he blames on my attempts to save nat. gas and thus money. In doing so, he has cost the District $25,000 in two months over what it cost when i was controlling things (somewhat), according to the Energy Nazi. The chickens may be coming home to roost on that one soon.

Owen

NBC

Ah, could you expand on that? I don't understand (2 -16.3 ft.).

On the clear plastic tubing idea, I love it because I need visuals to explain/prove what's going on here (to myself as well). Could you provide a photo or sketch? I'm not grasping that one either.



Some details:

The boiler is WM 2094. The risers and header are as spec'ed (8" & 10") as is the equalizer (4"). The bottom of the header is 36" above the boiler water line. There is a boiler feed pump/tank with 288 gallon capacity with a usual level of around 160 gallons. There are a total of four condensate tanks pumping daisy chain to the boiler feed pump tank and one directly to the receiver in the boiler room.

It is (I think) classified as a "Dry" return.



It would be poetic justice if the problem is made much worse by high pressure, as I don't doubt it is. It's just proving it.

Paul48

Possibilities

http://www.heatinghelp.com/article/95/Problems-that-plague-ALL-steam-heating-systems/88/The-water-is-bouncing-up-and-down-in-the-gauge-glass

Charlie from wmass

I would have the fire rate double checked

Did you ever post photos of the boiler?

Owen

Photos

#1. Early attempt at skimming.

#2. Front: Power Flame burner, front riser, header off-sets, header; left is old N. Boiler

(deceased).

#3. Left side: header, back riser & header off-set, header, main supply take-off, horizontal main.

#4. Rear right side: header, off-set, steam supply main riser & horizontal main.

#5. The Old North Boiler, R.I.P., is what the new one replaced.



"We never had these problems with the old boilers!" Duh. It's twice as big, steam chamber-wise.

nicholas bonham-carter

Effect of pressure in the boiler on water level

This will challenge my powers of description, which is good. When I studied automotive engineering, we had to write an explanation of how things work-like a differential! Now I am describing the effects of steam.

Imagine the workings of an old coffee-maker. The water is in the bottom Pyrex flask, and the coffee/filter is in the top flask when it is heated up, the water boils in the lower flask, and because there is a tube extending down from the upper flask, the small amount of steam-pressure will force the boiling water up through the tube and flood the upper flask. This water then drains down when the whole thing is taken off the fire, and water then will be sucked down through the ground coffee by gravity, and vacuum.

The pressure of boiling water in a closed chamber making steam will exert even pressure on the water-line of the boiler as in the coffee-maker. The water forced up by this pressure will rise up in the returns to a height above the boiler waterline equal to 1.75 inches for each ounce of steam pressure in the boiler. So if you have a boiler generating 7 psi, the water in the returns(or the clear plastic tube), will rise about 16 feet! There is a lot of volume in that length of piping, and if there are are horizontals then they will need to be filled by water, before the pressure is equalized.

The plastic tube will enable you to show any doubting Thomases how important it is to keep these pressures low (ounces!!) we had similar water disappearance, and it was only with the plastic tube that showed me how the water can move with pressure into horizontal pipes in the return, robbing the boiler of it's water.--nbc

Owen

Tube

Where would you hook up the tube; where would it go; how big; what's at the other end; how to secure a plastic (flexible?) tube. Sorry, I can be dense; you'll have to spell it out for me, and yes, you'll have to draw me a picture.

Please know it sure is appreciated. i think you guys are going to save me from a heart attack.

nicholas bonham-carter

Plastic tube

Is there any tapping on the wet retun? The same result can be had by hooking it up to the boiler drain. Make sure you have a ball valve on it, unless you have plenty of ceiling height, as the pressurized water will rise up 16 feet in the case of 7 psi.

If there were a horizontal bend in the tube of great length, then the water will have to fill all of that upas it attempts to rise up to 16 feet.--NBC

Owen

Return or Drain

I believe this is a "Dry" return in that all the condensate drains to the boiler feed tank/receiver, not to the boiler. The pumped condensate return goes up to about 10-12 feet from the boiler room floor on it's way from the receiver to the boiler.



Hooking up to boiler drain: do you mean the 2" mud leg/clean-out tappings?

I do have about 16' from the floor.

nicholas bonham-carter

Plastic tube

That would do as well as any other place. It will show the powers that be the power of steam to move more water out of the boiler than should be the case. I also think the closing of the valve should have no effect on this, other than allowing the pressure to rise more quickly.--nbc

Owen

Tube

OK.

Come off the mud leg tapping with a 2x2x1/4" tee, add a 1/4" ball valve, shoot up towards the ceiling and attach the tubing to hang back to the connection.

Then, test the whole thing by opening the valve and seeing how far up the tube the return water goes. That indicates, what, how far up the risers and mains the return is going? Carry-over and priming?

Have I got any inkling here?

nicholas bonham-carter

One more thought

If the water is filling up the returns, then it is probably preventing proper main venting from taking place.

Our horizontal was only a few inches above the boiler water, so it didn't take much for the rising pressure to try to fill up the 20 feet of 2in pipe, so hid quite a bit of water. The ir camera might not show it well unless the water is already quite hot.

Maybe you could dial back the pressure on the pressuretrol, and see at what pressure the water really begins to disappear.. It won't run long at each cycle, because the venting is already inadequate, but it may show you if the water then stays in the boiler, until a certain pressure.

There could still be some oil in the boiler, as when it is drained, the surface oil tends to re-coat the inside, so skimming from the surface is the most certain method of getting it all out. Good luck.--nbc

Steamhead

I think Charlie might be onto something

has anyone checked the firing rate on that PowerFlame? If the boiler is over-fired, that can cause your problem.



If everything else checks out, skim it again. You wouldn't believe how much oil can hide in a boiler.

furnacefigher15

No heat calls

Have they gone away with high steam pressure?

Owen

Skimmimg

Then why would it stop bouncing with the steam main shut?

Owen

Whining

The boiler still shuts off on LWCO but there are fewer complaints. I think that is because there are serious drainage problems with the steam & condensate line drainage. The Industrial Arts Building is served by a separate steam & cond. line which has been badly knuckleheaded (an electrician installed conduit in the crawl space and steam & cond. lines were in his way so he knocked support hangers off. The lines are dangling and way out of whack. It's a **** to go down in there so not much enthusiasm exists to fix it, even on my part. I'm 59 for heck's sake. I need a young helper and ain't gonna get one.)

I am quite sure the whole system would run ok at much lower pressure and I'm just waiting for some meetings to take place between the Nazi, the Facilities Director and the Supt. and Asst. Supt. at which I'm hoping my Supervisor's foolishness will be dealt with.

furnacefigher15

surging

"Skimmimg

Then why would it stop bouncing with the steam main shut"



Because, the steam has nowhere to go, and just pushes back on the waterline.



The more the steam can flow, the more steaming will occur, the more the steaming, the more violent.

Owen

Skimming

I have skimmed a total of maybe 30-40 hours over the course of two heating seasons. It isn't easy because of scheduling. During the school days and hours the building can't be without heat and the Supervisor won't permit me to work on weekends. (You try figuring this guy out.) I do it anyway but it's tough to get away with plus I'm doing it for nothing because I don't get compensated time wise. I'm sneaking to do it.

Besides, if you read the above, that was what the ChemSearch 100 was supposed to do, clean out all the contaminants.

I'd hate to back to square one on that (skimming).

Paul48

I'd

bet it's way over-fired. It fits all your symptoms. Read that link I posted, and if you choose, discount the contaminants in the boiler as a possible cause(for now), and focus on the other possible causes.Would the steam leave the boiler too fast if it was way over-fired? And wouldn't you closing that valve slow that?If it is over-fired, might you not also have flame impingement?

furnacefigher15

Old boiler

Is the piping still connected to the old boiler pictured to the left?



If so, are the valves open?

Owen

Old North Boiler

The mains are separated by an 8" valve which is shut but it lets a bit of steam by apparently, because there is a drip coming out of the old boiler's bottom right front mud leg blow-down valve which is open. It leaks I think it was about a pint an hour (I measured it a while ago).

Steamhead

I did read that

but it might not have gotten all the dirt & oil. Check your firing rate first though.

Mark Eatherton

I agree with these guys. I think your kettles got too big a fire...

You need to "clock" the input to the boiler.



Make certain that the only appliance on line is the subject boiler (going to have to do another midnight run, or wait for the linch room to shut down, and turn off other boilers).



Then, using a stop watch, with the subject boiler running at full capacity, go to the gas meter and record the amount of second necessary for one unit (probably 5 Cubic Feet or larger increments) of fuel.



Take 3600 (seconds in an hour) and divided by the elapsed time for one unit of gas.



Take that number, and multiply it times the unit of measure.



Multiply that number times the caloric content per unit of measure (typically 1,050 btu's per cubic foot unless you are in Denver) and you have clocked the input to the appliance.



I've been to my share of factory start ups, and I have NEVER seen a factory tech grab a stop watch and head for the meter, so I seriously doubt this was ever done. Running a boiler in an over fired condition will cause all of the problems you are seeing, AND it will cause an early death of the appliance. You can only shove so many BTU's into a fire box before something gives up the ghost.



EDIT: If clocking is not feasible, then do a combustion analysis. High flue gas temperatures and extremely low oxygen numbers are another dead giveaway of the same problem.



ME

Owen

Clocking

Ok, here's a hypothetical:

The boiler has it's own gas meter (except for the water heater in the boiler room and it's easy enough to turn it off);

It is a digital meter and it takes quite a few minutes for the last digit to flip (I think);

So you would wait for it to flip, start the stopwatch, then wait for it to flip again, which I believe is one therm or 100 cubic feet;

Say it takes 5 minutes (I'm guessing); that would be 5 X 60=300, so 3600 divided by 300= 12; 12 X 100 (cubic feet)=1200X 1000 (BTU)= 1,200,000 BTU's, right?

Now what does one do with that information?

This is a 5,520,000 BTU boiler (Gross I=B=R Output).

Steamhead

You'd have to know for sure

how many cubic feet go thru the meter with every "flip". With some larger meters it indeed is more than one cubic foot. With a boiler like that, if the counter flipped for one cubic foot it would just be a blur.



On the 20-94, the rated input is 6,856,000 BTU per hour according to W-M's site. We will assume the gas contains 1050 BTU per cubic foot (check with your gas supplier). So:



6856000/1050= 6529.5

3600/6529.5= 0.55 (rounded off to two decimal places)



If your meter "counts" in increments of 100 cubic feet, multiply that value by 100:



0.55x100= 55



and the time between "flips" should be 55 seconds.



If the time is not what it should be, you're either running the wrong gas pressure, orifice size, butterfly valve adjustment or any combination of the above.



And figure in the altitude adjustment if appropriate, as ME said.

Mark Eatherton

Correct...

Now that you've got THAT math down straight, here is some more critical information.



Gas fired appliances have to be derated for operation at altitude.



If, for example, you are in Denver, at 5,280 feet above sea level, with your power burner (check with the boiler/burner manufacturer for the recommended derate factors for your assemblage) you'd derate it 4 % per 1,000 feet above sea level. So, roughly 20% derate here in Denver. you would take the input and derate it by 20%. THAT is the number your clocked input should be. In your case, you provided the net OUTPUT. If you know the approximate combustion efficiency (safe to assume 85% in your case) then you would take the net output (5,520,000) and divide by the combustion efficiency (.85) and THAT would be the sea level input (6,494,000 btuH). This is the number that you would also have to derate for altitude, and using the Denver example, then your derated input would be .8 of the sea level rated input, or 5,195,000 btuH.



For those who happen to be in the Denver area, our gas is UN natural. Excel Energy pumps air into the gas for the central and south metro areas and the gas has a caloric content of around 830 btu's/cubic foot, and this too has to be taken into consideration when setting up an appliance.



If you give me the altitude that you are operating at, we can run those numbers.



Once this is all done, you can compare the rated input to the actual input and see if you are over (probable) or under (doubtful) fired. If you are significantly over fired, then you will need to contact the people responsible for commissioning the boiler, and have them come back and re-commission it.



ME

Owen

Math

I am at 4500 feet.

The guys who installed the boiler do the tuning

and I believe it was done in the last month or so because on a vist one of them smelled something amiss downwind of the stack. Prior to that it had not been tuned since it was installed. The Admin. **** about the cost. Their thinking isn't much better than my Supervisor. Spend the couple hundred bucks for a tune and get it back probably the first month. This thing burns about $8,500 a month.

Paul48

AH

Nose-tuning....that explains a lot.

Mark Eatherton

4,500 feet...

@ 4 % per thousand, your derate factor would be 18%.



So, your INput should be 6,586,000 (per Steamhead's findings) times .82, or 5,400,000 btuH.



Sniff testing eh... I won't go there. Maybe he smelled carbon monoxide ;-)



Tuning can't properly be done until the appliance is properly set up. THEN you can fine tune the burner.



Is this a modulating burner or an ON/OFF operation?



ME

Owen

Steamfitters

I would not be too quick to disparage these guys. They are honest, straight-forward, do excellent work and know what they are doing. Everyone can always learn new ideas.

The fellow smelled something wrong, informed his boss who called my Supervisor and then they came and put an analyzer on it and tuned it. I'd say that's pretty much on top of it.

They can't force the Admin. to do the right thing, which would be to tune all the boilers (13- 7 steam & 6 hot water) yearly.

Owen

Carbon Monoxide

...being a colorless, odorless gas is not what he smelled, obviously, but other by-products of combustion that should not have been detectable by the nose. If you smelled something that should not be present would you ignore it? ;-(

I think not.



This boiler has a variable potentiometer.



What is involved with "properly set up" prior to tuning?

Steamhead

He probably smelled aldehydes

which smell a bit like the odorant in natural gas. Any time you have aldehydes, you have CO.



That smell tells me there's a leak somewhere, maybe a bad fire-side gasket or section seal.



Proper setup before tuning might include verifying/re-setting the firing rate/orifice size/gas pressure, head settings, baffles in place (if used), opening the breech damper if the instructions call for it (you'd partially close it later) etc.etc.



You will find specifics in the boiler and burner manuals. Without being there it's hard to include everything.

Mark Eatherton

I was just kidding about smelling CO...

I only use that joke around trained tradesmen... At first you get blank stares, then you get chuckles. Probably shouldn't be joking about something so deadly...



Proper set up is the clocking procedure, orifice checking, linkage preliminary adjustments, spark gap settings etc to get the burner to fire under the correct conditions. Then, they will fine tune the burner at low and high burn rates to optimize the appliance efficiency.



The burners with modulating capabilities are real critical when adjusting the low end, because that is where the boiler will spend most of its life.



Let us know what you find.



ME

Owen

It is With Gratitude...

that I say thank you all.

Where in the hell would a dope like me hope to find assistance like this? I or anybody trying to do this job would be doomed to repeat the same stupid behaviors for time immemorial.

Here I am again thanking my lucky stars, and lucky they are indeed, for Dan Holohan and this amazing tool he has created to disseminate valid technical information to anybody who needs help with an obscure arcane art. For free.

Thanks most of all to him.

bob_46

Input

Owen , a couple things you might check first. I would contact Engineered Products in Denver And find out if your boiler burner package was ordered as a standard sea level package or if it was ordered for 5280 Ft. . With power burners if you order them to fire at sea level ratings at altitude the burner mfg. will increase the size of the blower to compensate for altitude and you won' have to derate. . When you clock the meter you need to know if it is a pressured meter or not . If the meter is operating at a pressure above 7" w.c.you will have to multiply

the btu content of the gas times a correction factor. The higher the pressure the higher the btu content.

furnacefigher15

I wonder

If the old boiler surged too, but you never new it.



I just noticed the old boiler has it's LWCO mounted on a surge column.



Do check the firing rate, but if the burner modulates, and the fire was too much, the issue would be diminished in low fire.



As far as the plastic tubing ran to the ceiling, that will not do much for you, you don't have gravity returns connected directly to your boiler. The water will climb 2.3 feet per pound of pressure, so for the 14 psi or whatever ungodly high pressure your running, the ceiling may not be high enough to contain the 32 feet the water will climb.



As was pointed out, returns need venting if they have restrictions blocking air flow, such as check valves.



"(The steam fitters say your suggestion to lower the condensate pumped return connection on the equalizer "couldn't hurt". They are thinking we may have to raise the whole riser/header assembly up as far as possible to "dry" the steam. That sounds spendy.)"



That raising of the header would probably help.



Either way, I still think the real problems you are facing have less to do with the boiler, and more to do with what the steam boiler produces is being asked to do.



The pressure was driven up in response to areas that don't heat. Find out what keeps the heat from working, if the only thing that ever prevents the heat from working is the boiler being off on low water, then try adding a surge column to stabilize the water line in the lwco. (look at the old boiler)

Owen

I Agree

I am going to do everything ME, Steamhead, furnacefigher, Bob and others suggested but I am wondering if that is truly the cause of the bouncing. My suspicion is that it is a combination of all the problems that have been identified. EXCEPT FOR CHEMICALS.



That is what I thought about the tubing idea. We do not have "wet" returns. At 8# (the current setting) it would rise to 18.4'. The ceiling is 16'.



There are check valves all over but I hadn't paid much attention to them. Venting costs money, so I'll have to go a-beggin'. That should be do-able.



Demand is a huge issue because I think we need a new smaller adjunct boiler to handle the two HX in the boiler room.



That may be possible right now.

Bank of America just paid for a study of this District's energy use and apparently are looking to move into loaning School Districts money to do the necessary repairs in return for interest, probably around 4-5% which is better than they can get from T-bills or homeowners obviously. School Districts are gold because a well run one (here, at least financially) have high credit ratings. They have nowhere to park their billions in other words. The fellow I talked to from the project said they were talking in the $1.5 million range. I could do a lot with that, energy savings wise.



My long nightmare may be close to being over.



Surge tube idea: I'm going to do a google search of that. The old boiler has been scavenged, so I don't know if a guy can learn much from it, I don't know. I'll for sure be starin' at it for a while. Better yet, take a photo and stare at that.



You can of course post a drawing or photo of a "surge tube" or a narrative of same and I'll try to follow along.



Right now I'm goin' to bed.

Thanks again all.

Alan (California Radiant) Forbes

Wonderful & Fascinating

It's like reading a crime novel with highly regarded detectives trying to figure out the scene of the crime and the perpetrator.



I agree, closing off the main valve to stop the surging is a big clue, but the answer is beyond me.



Keep at it, Owen and you will find the answer.