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Thread: stainless vs. cast iron boiler

  1. #1
    Join Date
    Aug 2005
    Location
    Red Lodge, MT
    Posts
    112

    stainless vs. cast iron boiler

    hello,

    we are switching from direct fire to steam at our new brewery. our engineer believes we need a stainless boiler, but my plumber and the boiler manufacturer (weil-mclain) think a cast iron one will suffice and save money.

    we will use the low pressure steam boiler strictly for the brew kettle.

    in the next year or two, we plan on brewing one day a week, 2-4 brews per day, turning the boiler off when we are finished for the week. we will add brew days as necessary.

    any input on whether cast iron vs stainless boilers would be appreciated.

    sam

  2. #2
    Join Date
    Jun 2003
    Location
    Louisville, KY
    Posts
    995
    We've used a Weil-McClain cast iron boiler for 12 years to power; kettle, mash tun, and HLT. No problems here.
    Cheers & I'm out!
    David R. Pierce
    NABC & Bank Street Brewhouse
    POB 343
    New Albany, IN 47151

  3. #3
    Join Date
    Sep 2008
    Location
    Fawn Grove, PA, USA
    Posts
    539
    Cast is fine, Weil-Mclain is also a good choice. When I went to price boilers people wanted to sell me every option in the book from $30,000 water pre-treatment systems to very expensive blowdown units. And they will swear up and down that without these systems the boiler will be in shambles in a month. Then after a very long and heated argument with one of these salesmen I explained the usage in more detail and got him to admit that these additional measures were unnecessary. Most of these folks are going of the fact that most boilers are running 24 hours a day in much more stressful industrial applications such as adding water to tubes that are already scorching hot and causing oxidization. But I think most of us are filling cold and then bringing things up to temp, using and then blowing down for the night. Stainless is overkill unless your engineer can truly prove otherwise.

  4. #4
    Join Date
    Nov 2005
    Location
    Raleigh, NC
    Posts
    82

    blowdown and chemicals

    South County,

    I have recently commissioned an old Weil-Mclain LGB-6 cast iron boiler. It's working great. Can you tell me your procedure for proper blowdown and how often?

    Also are you adding any chemicals to your system?

    Thanks in advance.

    Cheers,
    Steve

  5. #5
    Join Date
    May 2004
    Location
    St. John's, Newfoundland, Canada
    Posts
    802
    We do a partial blowdown 3X per week and a full blowdown every 3 months.

    We do not use any boiler treatment chemicals. have done this in the past but our water here is naturally very soft which helps keep our boiler pretty clean and efficient.

    Have used many different boiler treatments in the past but echoing earlier posts, beware boiler treatment salespeople. If you let them, they'll convince you that your boiler will be destroyed.

    Make your blowdowns part of your routine. You can do some pretty simple tests of your blowdown water to evaluate corrosion, pH, particulate etc.

    Stainless steel boiler? I can't imagine a grade of stainless up to the task. Nor do I even want to think about the cost.

    Pax.

    Liam

  6. #6
    Join Date
    Jul 2005
    Location
    Chandler, AZ
    Posts
    209
    We have a Certuss boiler, and they have in the literature to do a 15 second blowdown every day if you're running continuous operation. If not, then do a blowdown every time you shut down the boiler. I've been following those manufacturer's instructions and so far no problems.

  7. #7
    Join Date
    Sep 2008
    Location
    Fawn Grove, PA, USA
    Posts
    539
    Quote Originally Posted by kramling
    South County,

    I have recently commissioned an old Weil-Mclain LGB-6 cast iron boiler. It's working great. Can you tell me your procedure for proper blowdown and how often?

    Also are you adding any chemicals to your system?

    Thanks in advance.

    Cheers,
    Steve
    We are currently still getting thing geared for our startup (spring of 09') but here is a basic procedure that applys to most low pressure units but I am only submitting for example. I would call your boiler manufacturer to verify this will work for your setup.


    Technical Tips - Boiler Blow-Down

    When a boiler is generating steam, the feedwater continuously carries dissolved mineral impurities into the boiler. These dissolved impurities stay behind in the boiler water when steam is made; only pure water leaves the boiler as a gas. These dissolved impurities concentrate in the boiler water until the water can no longer hold all the impurities in solution. Once these impurities have reached a saturation level they will begin to drop out forming a sludge or scale. If this sludge is not properly removed from the boiler deposits will begin to form on the boiler water-side surfaces. To prevent an excessive accumulation of dissolved and undissolved solids which will interfere with proper boiler operation, a blowdown program must be established.

    The amount of blowdown or number of times the boiler is blown down each day depends upon the concentration of impurities in the boiler water. Boilers operating with soft water or high quality feedwater will require less blowdown than boilers operating on hard water. The higher the level of impurities in the feedwater, the higher the sludge potential. Boilers operating on soft water will require more top or skimmer blowdown to remove dissolved solids whereas boilers operating on hard water will require more bottom blowdown to remove the settled solids. Frequency of blowdown will vary greatly based on water quality and percentage of condensate return. Recommendations of a qualified water treatment professional should be followed regarding blowdown procedures.

    Bottom blowoff valves are primarily meant to be used as drain valves; however, it is frequently necessary to use the blowoff valves to get rid of mud and sludge that have settled to the bottom of the boiler. Generally, when boilers are being operated at or near rated capacity the circulation is great enough that mud and sludge do not have much chance to settle out. The boiler should be blown down at lower firing rates. If the boiler is to be shut down for a short period of time or taken off line, it must be blown down to remove the suspended material. If this is not done, the suspended material will settle out on the boiler surfaces and be baked on during the next firing. Blow down at this time is critical to keeping boiler surfaces clean.

    When necessary to blow down the boiler through the blowoff valves, they should be opened slowly and carefully. The boiler should be equipped with either two slow-opening valves or one quick-opening valve and one slow-opening valve. If the boiler has more than one bottom blowdown connection, a second quick-opening valve is needed.

    The following steps should be taken to blow down a boiler:

    1.

    Open the quick-opening valves ( ones closest to the boiler ).
    2.

    Open the slow-opening valve.
    3.

    Blow down the boiler for the amount of time specified by your water treatment consultant by opening and closing the slow-opening valve. Pay close attention to the water level in the gauge glass.
    4.

    Some boilers require several short blowdown cycles to maintain the proper water level
    5.

    Close the slow-opening valve.
    6.

    Close the quick-opening valve (s).
    7.

    Open the slow-opening valve again to drain the line between the quick and slow-opening valves.
    8.

    Close the slow-opening valve again and double check that the shutoff is tight after the valve has cooled.


    CAUTION:
    bullet

    Never pump the quick-opening valve to blow the boiler. Such action could cause water hammer and damage the piping and valves. It could also cause personal injury.
    bullet

    Never leave an open blowdown valve unattended.
    bullet

    Remember the valve (s) closest to the boiler must be opened first.

    This is usually done under light load to provide adequate evacuation. As we all know steam is dangerous so the use of a blow down tank or other safe methods of isolating the hot water/steam are recommended and often required by state code.

    Continuous blowdown or surface blowdown from a location designated by the boiler manufacturer is generally preferable to intermittent bottom blowdown for control of dissolved solids. Automatic blowdown controllers are available for boilers that have a top or skimmer blowdown port. Automatic blowdown controllers provide superior solids control along with outstanding energy savings. Further savings may be found through the installation of a blowdown heat recovery unit.

    Proper boiler blowdown is critical to a successful water treatment program. Chemical treatment is only one aspect of a successful program. Proper start-up and shut-down procedures must be followed along with proper off-line storage to have a successful program.

  8. #8
    Join Date
    Nov 2005
    Location
    Raleigh, NC
    Posts
    82
    Excellent thanks a lot! This gives me a lot better idea..

    Cheers,
    Steve

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