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Thread: fluctuating boiler water level

  1. #1
    Join Date
    May 2016
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    Australia
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    27

    fluctuating boiler water level

    Hi everyone,

    The water level in the sight glass of our steam boiler fluctuates a lot, so much that it causes the low-level safety cut-off to trigger several times an hour. Just to be clear: the average level is in the middle of the sight tube, the level isn't actually too low, it's just that as the water oscillates rapidly between high and low it can trigger the cut-off. Obviously this is very frustrating.

    I work in a brewery which has been running for many years before I arrived and apparently this problem has always existed. It's a 1,000,000 BTU steam boiler, our kettle holds 25hl when full to the brim (I usually start a boil with 21.5hl in the kettle).

    Any suggestions about what is going on and how to fix it?

  2. #2
    Join Date
    Aug 2010
    Location
    Enterprise, Oregon
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    1,965
    Your condensate return pump may not be pushing enough pressure anymore. If it can't get up the oomph to push condensate at full boiler pressure, it will do just about what you describe. Time to open the pump up and be sure the turbine isn't worn out.

    Restrictions and/or leaks in the condensate return line can also cause this, and attempting to use steam pressure to push the condensate around will too. All condensate lines should be short and sloped to the condensate return tank. Let the pump do the work.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

  3. #3
    Join Date
    Nov 2009
    Location
    Moab, Utah
    Posts
    581

    Your System is UNSAFE

    For you to say that its reported to " always " have been this way raises black flags.
    While there can be a number of things that can cause this, I am going to posit that your problem is multi-faceted.
    Sadly it can be common for corners to be cut on Steam installs, and there are often things done which compromise the operation and in dangerous ways.
    This is especially true with respect to how make-up water and return pump controls are setup, both mechanically and electrically.
    The condition you have described is potentially dangerous for reasons I am not going to go into today.
    My suggestion is you get an expert in there who is certified to diagnose and repair steam boilers and get an opinion rendered on the total system.
    Tripping limits all the time is real bad news, and you should want no part of this.
    For operations people to have accepted this kind of thing over time as a matter of course is also not a good thing.
    Anyone at all who may be laying hands on a Boiler system in this kind of a setting during a shift can be considered an operator, and should have some basic training on Boiler Operation and Safety. This includes most of all what " not to do ", and how to blow down a Boiler correctly. There should be one person in charge of the blowdown schedule and keeping the chemical feed in trim based on readings that are taken at least once a week.
    I would say there is a serious need for radical change.
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  4. #4
    Join Date
    May 2016
    Location
    Australia
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    Thanks for the helpful replies!

    Quote Originally Posted by TGTimm View Post
    Your condensate return pump may not be pushing enough pressure anymore. If it can't get up the oomph to push condensate at full boiler pressure, it will do just about what you describe. Time to open the pump up and be sure the turbine isn't worn out.
    The pump only needs to come on for a very short time when topping up the boiler, even at full pressure (40psi), so I think it's pumping well.

    Quote Originally Posted by TGTimm View Post
    Restrictions and/or leaks in the condensate return line can also cause this, and attempting to use steam pressure to push the condensate around will too. All condensate lines should be short and sloped to the condensate return tank. Let the pump do the work.
    The condensate pumps coming out of the kettle and HLT jackets go vertically up 1m (3ft) before going through the wall. The level of the return tank is higher than the level of the pipes exiting the jackets, so I can't see a way to fix that without major building works. From what you say, this may be the cause of the problem, in which case I'll just have to put up with it.

    Quote Originally Posted by Starcat View Post
    Anyone at all who may be laying hands on a Boiler system in this kind of a setting during a shift can be considered an operator, and should have some basic training on Boiler Operation and Safety. This includes most of all what " not to do ", and how to blow down a Boiler correctly.
    I'm the only "operator" because I'm the only person who works here (and no I'm not the owner). I've been shown the on/off switch and the reset button, and that's it. That's why I'm asking the question, I'd like to know more about what I'm dealing with here.

    Quote Originally Posted by Starcat View Post
    and keeping the chemical feed in trim
    I have no idea what you are referring to. What chemicals???

  5. #5
    Join Date
    Aug 2010
    Location
    Enterprise, Oregon
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    1,965
    The chemicals Warren refers to are boiler water treatment to keep the boiler vessel from rusting and rotting away. You absolutely must have a water treatment program in place, preferably a dosing pump on the make-up water input.

    At this point, with a high-pressure boiler in unknown condition, you may be sitting on a time bomb. When was the boiler last inspected? Has it ever had a water treatment program? At 40 psi, it's a potentially deadly bomb sitting in the brewery.

    You need expert help with this, and you need it now.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

  6. #6
    Join Date
    Oct 2013
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    Stuart, FL
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    468
    Quote Originally Posted by TGTimm View Post
    The chemicals Warren refers to are boiler water treatment to keep the boiler vessel from rusting and rotting away. You absolutely must have a water treatment program in place, preferably a dosing pump on the make-up water input.

    At this point, with a high-pressure boiler in unknown condition, you may be sitting on a time bomb. When was the boiler last inspected? Has it ever had a water treatment program? At 40 psi, it's a potentially deadly bomb sitting in the brewery.

    You need expert help with this, and you need it now.
    Or worse yet, it doesn't rot away, but rather scales up and clogs. If you don't know what the Langelier Saturation Index is, best heed the advice and get an expert on it.

  7. #7
    Join Date
    Mar 2003
    Location
    Minocqua WI
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    821
    Is your return lines insulated? This could be caused by cold return pumping into a hot boiler.
    Brewmaster, Minocqua Brewing Company
    tbriggs@minocquabrewingcompany.com
    "Your results may vary"

  8. #8
    Join Date
    May 2016
    Location
    Australia
    Posts
    27
    There are three plastic tanks near the condensate tank, two are connected to each other and are fitted with some kind of controller device which the condensate tank's water supply passes through, the other has a thin tube running into the condensate tank opening via a pump. Obviously this is the set-up for the required chemical feeds, it's all covered in cobwebs and has been unused for several years at least. I'll do some research to work out what the hell I'm supposed to be doing with it.

    The boiler, condensate tank, etc are all located outside in the back alley, it's an area which is not accessible by the public. The condensate return line is not insulated outside the building, neither is the tank itself. Today is a cold winter's morning, it was frosty earlier and it's still very chilly in the alley. I've had the boiler on for about 2 hours and the water temperature in the tank is about 75C, so it's not cold, but I understand what Ted Briggs is saying: injecting cooler-than-100C water might cause fluctuations. Having said that, I don't see fluctuations in the pressure guage at all. It's only the level in the sight glass which moves up and down.

  9. #9
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    Aug 2010
    Location
    Enterprise, Oregon
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    Even with the boiler outside, a vessel rupture at 40 psi could cause significant damage to your building and those surrounding it. Don't underestimate the power and violence of a pressure-vessel rupture!

    Get a boiler inspection ASAP. You might not like the results, but it simply isn't working right now.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

  10. #10
    Join Date
    Sep 2005
    Location
    Louisville, KY
    Posts
    956
    I know exactly where you are, I have been there. You should absolutely get chemical treatment going asap. A person will come and test your water and chem balance monthly. You will not have any idea whats going on inside your boiler until you get someone (even yourself) there testing the water, start off daily until you get the treatment tuned in. You need a conductivity meter, and a water hardness test kit minimum. Log sheets are all over the internet.
    Outdoor condensate tank in the winter is a nightmare. The condensate temp is important and should not be below 190F. You can insulate the tank if needed, you can install a water heater element if needed. If your make up water is too cool (when you are not brewing) it causes multiple issue, all of them bad. Scale building up and rotting out your entire system is the worst, thermal cycling is playing hell on the boiler seals, you are wasting a lot of energy, the boiler was not designed to operate this way and will fail.

    How often do you blow down your boiler? I can not stress enough to you to get a water treatment professional in there asap. The expense is minimal and the consequences of not can be dire.

    FYI the two vessels connected together with a controller feeding the condensate tank are most likely a water softener, ours also has a brine tank that we must add salt to every other month. The controller is set to backflush every so often to prevent it from clogging.
    Don't get overwhelmed, just get it done. A boiler had multiple low water shutoff failures and melted down 4 months after I was hired at my first brewjob. I saw an 8 inch pipe on top of the boiler turn orange, I did not know anything about boilers, instinctually I ran over and turned the circuit breaker off and told everyone to get out of the building. The boiler tech told me if the condensate tank had pumped in makeup water at that point they would have been picking up pieces of the boiler and me outside the building.
    Joel Halbleib
    Partner / Zymurgist
    Hive and Barrel Meadery
    6302 Old La Grange Rd
    Crestwood, KY
    www.hiveandbarrel.com

  11. #11
    Join Date
    Apr 2003
    Location
    Farmville, NC
    Posts
    40

    chemical dosing levels

    For what it's worth, it has happened to us that we've experienced boiler water level "bouncing" in the site-glass. We determined that this was due to over-dosing chemicals into the feed water. If you aren't doing any chemical treatment at all, it sounds like this isn't precisely your problem, but it is evidence that the chemical composition of the water can influence this phenomenon. Good luck.

    Cheers,

    Paul Philippon
    The Duck-Rabbit Craft Brewery
    Farmville NC

  12. #12
    Join Date
    Sep 2009
    Posts
    18
    Muddy,

    Water treatment may be part of it, but you could have a other issues you don't know about.

    The boiler water level should be maintained by the boiler feed pump, or condensate return pump if that is how your system is set up. Larger systems will include a condensate pump at a common drain point of the HLT and the kettle that will push condensate back to a storage tank for blending with makeup water and treatment, if needed. Treatment will typically include amine, softeners, and other chemicals depending on the local water source. Steam boilers don't like hard water or water with high ph. Sounds like you have a system, but its not used.

    What I have seen in the past with boiler that experience frequent level issues is a controls issue with the boiler feed pump. The pump should be monitoring boiler level and sending water in as it is operated. Some systems will use a fixed speed pump to send water to the boiler(s) and then utilize a control valve to meter the flow to the boiler based on the drum level. These systems usually incorporate a boiler feed water loop that sends water back to the condensate storage tank. Its useful for systems where you have non-steady steam output from your boiler. Basically the pump is brought online, stays at a steady state condition, and then as the boiler is used the control valve will bleed off flow from the loop as it is needed. This can be done in a simple control method with a float hooked to a level that opens and closes the control valve. This sounds complicated, but pumps operate more efficiently if you can keep them on and at a constant load. Motors prefer steady operation. Constant on/off operation will decrease the overall life of your equipment.

    There are several boiler inspection companies out there. You should have one come in and give you an inspection soon. Prior to that, I suggest you find as much of the operational history, maintenance history, inspections, and drawings of the system. These will help with any inspection and root cause analysis.

    Final thought. If you are using steam traps to collect from the HLT and kettle, and then a pump afterwards, you may have two things fighting each other if they are close-coupled.

    Good luck with the brewery and the boiler!
    Homebrewer/Future part-time brewer
    but I do have 1 professional brew under my belt and on the books, and its still on the menu at that particular bar even though its not being served right now.

  13. #13
    Join Date
    Sep 2005
    Location
    Louisville, KY
    Posts
    956
    When the valve on the outlet of our makeup water pump is wide open the pump pushes so hard it causes the water inside the boiler to bounce causing the float controlling the make up water pump to bounce on and off a few times once it shuts of. The solution was to throttle the makeup water valve down a little bit.
    Joel Halbleib
    Partner / Zymurgist
    Hive and Barrel Meadery
    6302 Old La Grange Rd
    Crestwood, KY
    www.hiveandbarrel.com

  14. #14
    Join Date
    Mar 2003
    Location
    Nashville
    Posts
    859
    If there isn't a mechanical problem, it sounds like the conductivity of your boiler water is too high. That can make the level in the sightglass/ level control assembly bob up and down.

    Call a couple of the local boiler companies and get a recommendation for a water treatment company. They will come in and give you a baseline of where you are and what needs to be done. You need chemicals for oxygen scavenging, scale treatment, ph adjustment, etc. They will get you on a program, and tell you how often you should be blowing down your boiler.

    Most insurance companies and most states require periodic boiler inspections. Ours are every two years. They pull the doors off the boiler and inspect all the internals. If this hasn't been happening, you might be in violation of state codes, and if something were to happen to destroy the boiler, your insurance company could deny the claim.
    Linus Hall
    Yazoo Brewing
    Nashville, TN
    [url]www.yazoobrew.com[/url]

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