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We have two auxiliary boilers with a common header. One boiler can support our steam requirement and so we put one of the boilers on stand by too. We are basically doing the same thing: periodic stop-and-start and ramping up every week for switchover to the other boiler. We are actually planning to intall an equalizing line from the header to the steam drum to keep the stand by boiler warm. Can you help me guys evaluate if the steam in the header would be enough to maintain the pressure in the drum of the stand by boiler via the equalizing line.I am also considering the safety issues that could arise from the provision of this line, i.e, the isolation whenever there is a need for maintenance activity.May I hear from any power plant experts.
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The only proper way to do this is to install a steam sparger or a heating coil in the lower drum(s). Contact your OEM for this because it will require some code calcs and code work.
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Haven't read all the other replies yet but I doubt anyone touched on this.Fireye (www.fireye.com) makes a boiler control called a E-340 this control allows one to use the same control as a Steam controller and a Water temperature controller.Once installed along with Steam pressure sensor and Water temperature sensor one only needs to enter in the password and change control operation from Steam to Water and voila boiler is kept warm, no steam is generated and at any time the boiler can be switched back to steam operation without having any "Thermal Shock" issues.Simply using steam from another source added to the "Standby" boiler steam drum will not produce sufficient heat to the entire vessel to protect from Thermal shock upon return to Steam production.Maintaing the vesell water temperature above 180 F will ensure the boiler steel is warmed and ready at any time.This control also has programable boiler warm up sequence. This control automatically monitors the vesell water temperature (start temp is user configured) and does not release for Steam / Water / modulating fire rate operation until the water temperature release set point (user configured) is met. Then the control will automatically change over or release to steam operation.Our company has installed many of these controls with excellent results in most applications.Absolutely ensure you have a regulated power supply to the control(E-340) and ensure a proper Earth Ground is used. Don't say I didn't warn you !
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Another great way is a hot-circ system using a small pump circulating the boiler water through a steam heat exchanger connected to the steam & mud drum. You can run your boiler water at around 190 degrees, this allows for a quick start up without having to keep it steamed all the time.
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The header pressure will not keep the boiler warm. It is that simple.You do not need the manufacturer or consultant to understand this time old question for a third class firemen.The non-return (if you have one and they are not required but at least two-stops valves are required) valve must have the by-pass or as you call it the equalizing line open. A second or first class firemen would know this question and I think this is a great question.If you do open the by-pass, the boiler will flood out in about a week and you will have to bottom blow to lower the water level. That is okay if you are will to accept this routine.Remember the boiler will always have pressure by the method you propose, but it will not heat the boiler or keep it warm. In fact you will have thermal gradients. Not something you want to promote.As a word of caution...Do not allow the boielr to flood out with the by-pass open for you will fill the header with boiler/condensate water. Very dangerous.Glad to read all the interesting responses.Murphy
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Or, you can run your CBD through the mud drum on the standby boiler. This keeps things warm and maintains your chemical residuals at least close to where they should be.
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If you want to learn more, please visit our website Industrial Steam Boiler.
What many plants do is the utilize a lower drum heating coil. These coils are installed in the lower drum and use steam to keep the boiler warm. You may want to talk to the boiler OEM or Babcock & Wilcox about installation of one of these coils.
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RB.....Are you trying to keep the "spared" boiler warm in order to minimize start-up time ? Is there a physical or regulatory reason that you want to do this ?How big is your boiler and mud drum ?Many boiler vendors specify a maximum number of degrees/hour heat-up rate that is too slow for realistic plant operations.What is used by many steam plant operators is a mud-drum "warmt-up coil" that keeps the entire boiler at an elevated temperature. This, of course, requires the availabilty of saturated steam..See page C-58 of this document:http://www.speci-fire.com/mspeci-fire_pdf/C-IWT.pdfAlso, contact a local boiler supplier and ask him about this item. Some boiler configurations cannot be reworked-MJC
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What you are doing is putting the stand-by boiler on a steam blanket. Talk to your chemical rep. because a steam blanket is usually only good for a month, then you would half to cycle the boiler up again. The way our set-up is that we have aquastats in our boiler which keeps them warm if required to run.
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Connecting a line from the steam header to the steam drum will not keep the boiler warm. Because the water in the boiler will be stagnant i.e., not circulating, only the top few inches of water in the steam drum will be heated.You can either a install a heating coil in the mud drum and use steam in the heating coil to heat the boiler water, or b use the surface blowdown from the operating boiler to keep the standby boiler hot. For the latter, see Boiler Operators Workbook, chapter 9. The book is available from The ATP group, formerly known as American Technical Publishers. https://www.atplearning.com/product//boiler-operator-s-workbookDean Wilson
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