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BMP #8 - Boiler/Steam Systems

Background

Boilers and steam generators are commonly used in large heating systems, institutional kitchens, or in facilities where large amounts of process steam are used. This equipment consumes varying amounts of water depending on the size of the system, the amount of steam used, and the amount of condensate returned.

For more information on this and other FEMP Water Efficiency Best Management Practices, please see the resources section.

Operation and Maintenance Options

  • Develop and implement a routine inspection and maintenance program to check steam traps and steam lines for leaks. Repair leaks as soon as possible.
  • Develop and implement a boiler tuning program to be completed a minimum of once per operating year.
  • Provide proper insulation on piping and on the central storage tank.
  • Blowdown, the periodic or continuous removal of water from a boiler to remove accumulated dissolved solids and/or sludges, is a common mechanism to reduce contaminant build-up. Proper control of blowdown is critical to boiler operation. Insufficient blowdown may lead to deposits or carryover. Excessive blowdown wastes water, energy, and chemicals. The American Society of Mechanical Engineers (ASME) has developed a consensus on operating practices for boiler feedwater and blowdown that is related to operating pressure, which applies for both steam purity and deposition control. See boiler/steam system resources for more information.
  • Obtain the services of a water treatment specialist to prevent system scale, corrosion and optimize cycles of concentration. Treatment programs should include periodic checks of boiler water chemistry.
  • Develop and implement routine inspection and maintenance program on condensate pumps.
  • Regularly clean and inspect boiler water and fire tubes. Reducing scale buildup will improve heat transfer and the energy efficiency of the system.
  • Employ an expansion tank to temper boiler blowdown drainage rather than cold water mixing.
  • Install meters on boiler system make up lines.
  • Install meters on make up lines to recirculating closed water loop heating systems so that leaks can be easily detected.

Retrofit Options

  • Install and maintain a condensate return system. By recycling condensate for reuse, water supply, chemical use, and operating costs for this equipment can be reduced by up to 70 percent. A condensate return system also helps lower energy costs as the condensate water is already hot and needs less heating to produce steam than water from other make-up sources.
  • Install an automatic blowdown system based on boiler water quality to better manage the treatment of boiler make-up water.
  • Add an automatic chemical feed system controlled by make-up water flow.
  • To optimize cycles of concentration and reduce the frequency of blowdown, an inert ion such as silica or chloride can be measured in the boiler and the concentration compared to the amount in the boiler feed water. For example, a boiler with a silica concentration of 100 ppm and a feedwater silica concentration of 10 ppm is considered to be carrying 10 cycles of concentration. Monitoring the ion continuously can allow better control and adjustment of the chemical feed rate to optimize the number of blowdown cycles.
  • In large scale boilers, blowdown heat exchangers are a useful technology allowing the heat contained in boiler blowdown to be transferred to boiler feed water. This also allows for the production of low pressure steam which can be returned to the steam system or used in the deaeration of boiler feed water.

Replacement Options

  • Replacement options vary depending on the size of the facility and existing equipment. Consider performing an energy audit to reduce heating load and ensure that the system is sized appropriately. Reducing the size of the boiler system can reduce water requirements.
  • Always purchase the most life cycle cost-effective boiler available for new installations or major renovations.
  • Consider installing a small summer boiler, distributed system or heat-capture system for reheat or dehumidification requirements instead of running a large boiler at part load. Also consider alternative technologies such as heat pumps.
  • For specifics on this technology, consult with experts in the field. Your first resource should be your local or higher headquarters engineers, but do not overlook or rule out the benefits of input from experienced contractors or other Governmental agencies (DOE, FEMP, etc.).

Boiler/Steam System Resources

Some of the following documents are available as Adobe Acrobat PDFs. Download Adobe Reader.

Council of Industrial Boiler Owners, Energy Efficiency Handbook. (PDF 1.5 MB).

U.S. Department of Energy. Federal Energy Management Program, Boiler System Efficiency Improves with Effective Water Treatment.

American Society of Mechanical Engineers, Consensus Operating Practices for Control of Feedwater/Boiler Water Chemistry in Modern Industrial Boilers, 1994. To order: http://catalog.asme.org/ConferencePublications/PrintBook/2006_Consensus_Operating.cfm.

U.S. Department of Energy. Federal Energy Management Program, Steam Trap Performance Assessment, DOE/EE0193 July 1999. (PDF 1.5 MB).