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best boiler type for 100% makeup water

norfitz
norfitz Member Posts: 54
For a 2,000#/hr low pressure steam 100% makeup water application, I am of the opinion that a gas-fired cast iron boiler is a better choice than a steel boiler or any other gas-fired design. I hear there is already a water softener and a crude deaerator (a 119-gallon water heater cranked) feeding the existing failing boiler. What do you think is the best longevity/ease of service/best value design for this application?

Comments

  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,564
    100 percent makeup water boiler

    How old is the present one? Can you post some pictures of the failure area for us to see? Analyzing previous failures can often aid in the development of a plan to prevent a repetition of the old problem.

    I am always worried about the effects of water-softened water on cast iron boilers (search graphitic corrosion+chlorides).--NBC
  • Henry
    Henry Member Posts: 995
    Boilers

    In the food industry we have a number of 100% make up such as in bakeries and pasta manufacturing. A water softner is required an condensate tank with steam injection to keep the make up at 180F reduces thge need for chemicals and removes most gases from the water. If you have cholirdes (salt) in your water, your softner is not working properly. Our boiler of choice is a Bryan modulating water tube. We have installed a good number over 30 plus years with little or no problems, if the user makes regular (weekly at least)  water quality tests. The advantage of the Bryan is that it will get to speed much faster than other types as there is less water in the boiler. Stay away from cast iron boilers for 100% make up. We have replaced several that were used for generating humidity in commercial buildings!
  • jumper
    jumper Member Posts: 1,828
    depends on duty & routine

    Unless makeup is thoroughly conditioned, a watertube boiler will require regular cleaning. Single circuit are best for cleaning. Generally firetube boilers are used with raw water because they don't plug. They should be flushed regularly. Sometimes you get lucky. I remember an abattoir with a Kawnee older than the hills that was supplied with well water. Something about the water?



    Many are too cheap, but I always recommend an unfired boiler for 100% makeup. Sometimes a deaerator is appropriate. It's worth it if your time frame is long enough.



    For higher pressure distillation makes sense. Over the long run it's better than membranes.
  • SpeyFitter
    SpeyFitter Member Posts: 422
    edited August 2012
    Depends on your Chemical Guy

    I would go with an old proven favourite - a Cleaver Brooks Fire Tube Boiler. They are proven in the field with many boilers out I work on that are easily over 40 years old, reliable if maintained reasonably well (you should get at least 50 years out of them if you take care of them), efficient by design (you cant beat the 4 pass design for efficiency - 82-85% efficiency in steam applications typically), easy/cheaper to retube if ever needed compared to water tubes which cost an arm and a leg to repair/retube, and fairly versatile. You can also add several accessories on them to enhance their user friendliness and efficiency, such as the HAWK controller, Oxygen Trim, a High Turn down burner, an economizer, etc. You can outfit this out of hte box, or add them later if you so choose.



    As far as longetivity goes the absolute key to any steam boilers longetivity is the following:



    1) How do you run the boiler? Is it sized correctly? If you keep it hot all the time and minimize temperature swings and on/off cycles (e.g. expansion/contraction of the metal) where your burner and it's modulation range fits well within the confines of your steam requirements,  this will significantly reduce wear and tear on the vessel (typically), and ignition components.



    2) Blowdown Regime - It is imperative that you have a proper control of your TDS (Total Dissolved Solids). This will reduce things like foaming, carryover, etc. Proper water samping will help you establish a blowdown/TDS control regime.



    3) Chemical/Water Treatment - This is probably THE MOST important item. Spending the money and building a relationship on a good, reputable, chemical guy, who actually takes pride in what he does, is critical. Following his instructions, is key. What you put into that boiler on the water side, whether you have 100% make up, or 0% make up, is critical, and a water treatment program that eliminates minerals (e.g. scale), oxygen, carbon dioxide, and other impurities will go a long way to the longetivity of the vessel itself. I have seen boilers that are 5-10 years old that look so new inside you could cut out the tubes and resell them right there, and I've seen some 5-10 year old boilers that have pitting, and corrosion. I have heard of 50 year old Cleaver-Brooks boilers that are extremely well maintained in this regard that that looked almost new on the water side due to a proper chemical/water treatment program.  Also, having chemical/water treatment components like water softener and a good D/A  & Feedwater system is important and part of your program.



    4) If you don't do the annuals yourself (maybe you're not allowed to or don't feel comfortable - check your local regulations/laws), find a reputable company to do them for you. If you choose a Cleaver-Brooks boiler, many states and provinces have a Cleaver-Brooks representative that typically has a service division that should be able to take care of your boiler to factory specs with factory parts.

    There are more Cleaver-Brooks boilers in industrial settings in North America than all other industrial boilers combined. There is a reason for this.
    Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber
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