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Achieve Optimum Boiler Efficiency with Routine Maintenance

Key Points
  • Poor maintenance can result in energy losses of up to 20% and higher costs.
  • Preventive maintenance and annual inspections can optimize energy performance.
  • Before the inspector arrives, check the operation of the boiler's interlock controls.

Source: www.bls.gov
boiler inspection

Because boilers consume large amounts of energy, they present significant opportunities for energy-cost savings. Proper maintenance and operational practices can reduce operating costs, increase equipment life, and prevent up to 20% in energy losses. To achieve optimum savings, it is important for all inspections and maintenance to be performed by a qualified boiler technician.

Basic elements of the annual inspection should include the following:

  • Inspect and clean the fireside to remove soot and non-combustible material to avoid loss of efficiency.
  • Inspect and clean the waterside after the boiler has cooled to 120ºF to avoid the possibility of scalding.
  • Inspect economizers, deaerators, blow down tanks, and condensate receivers.
  • Check the refractories on the fireside for cracking or erosion and patch as necessary following the manufacturer's recommendations.
  • Open the burner and inspect the components to make sure all parts are moving freely; they should not make contact with each other. Clean all components to like new condition.
  • Detach the controls and inspect them for proper operation, then reinstall them and check once more before restarting the boiler.
  • Check the fluid levels on the hydraulic valves and repair any signs of leakage.
  • Check the filters and clean or replace them as needed.
  • Check the boiler feedwater and recirculation pumps and replace or recondition if necessary.
  • Empty the condensate receivers, wash them out, and inspect the insides. If necessary, overhaul and check for proper operation.
  • Check the electrical connections on starters and relays for tightness. Clean all electrical terminals.
  • Make adjustments to optimize flue gas composition and record composition, firing position, and temperature.

The U.S. Department of Energy also recommends performing a variety of maintenance tasks on a daily, weekly, and monthly basis. For instance, an overall visual inspection should be done daily to ensure that the equipment is operating safely. Relief valves should be checked for leaks weekly, and the fuel system should be checked monthly.

Preliminary Boiler Checklist

Boiler operation is compromised if there are signs of overheating, excessive scale, corrosion, or damaged pressure vessel components. The inspector's job is to identify and repair any of these conditions. If your facility's boiler is being checked by an outside inspector, there are some preliminary steps that should be taken prior to the inspector's arrival.

Perform an operational check of the boiler's interlock controls. Required controls vary with fuel type, burner capacity, number of burners, and whether the burner is forced draft or natural draft. Minimum controls found on all burners include the following:

  • Safety valve (steam) or safety relief valve (hot water)—does the safety valve lift freely and reset properly? Leaking valves may indicate a dirty or worn valve seat.
  • Low-level cutoff—cuts off fuel in the event of low water level and requires manual reset to resume boiler firing.
  • Flame scanner—shuts off fuel flow if burner flame is lost and requires manual reset to resume fuel flow.
  • Temperature control (hot water)—turns burner on and off to maintain a set-point temperature.
  • High-temperature cutoff (hot water)—if water temperature exceeds the high-temperature safety set point, this shuts off fuel flow to the burner and requires manual reset to resume boiler firing.
  • Pressure control (steam)—similar to the temperature control, but maintains a steam pressure set point.
  • High-pressure cutoff (steam)—if steam pressure exceeds the high-pressure safety set point, this shuts off fuel flow to the burner and requires manual reset to resume boiler firing.

There is also a way to make sure the boiler will pass the pressure test. Prior to draining the boiler for cleaning, fill it with water. With the boiler at operating pressure, close the valves to isolate the boiler from the system. If the pressure drops, the boiler will fail the inspection. The leaks will need to be identified and repaired if possible. Start by checking the valves (isolation, drain, and water level) because they are most susceptible to small leaks that could cause the boiler to fail the test.

In addition, the boiler waterside should be inspected and cleaned. Draining and flushing the boiler will help to remove scale and sediment.

  • Make sure the proper American Society of Mechanical Engineers (ASME) stamp is installed on the boiler (U for unfired pressure vessels, H for heating boilers, and S for power boilers).
  • Make sure the water treatment system is working properly to prevent problems resulting from scale buildup, sediment, and corrosion.
  • If the boiler has not been operating during the summer months, test the water in the boiler prior to putting the boiler back on-line.
  • If a significant amount of water is added at any time, the water must be heated to at least 180°F immediately to drive off dissolved gases (to avoid corrosion).
  • Check for and repair obvious defects—unusual noises, deformed door gaskets, damaged insulation. Drains should be clean, clear, and running freely.

When bringing a boiler on-line, crack the valves and check for unusual noises or vibrations prior to fully opening the valves. If a boiler is coming on-line with other boilers, make sure all of the operating temperatures and pressures are the same before opening the supply and return isolation valves. For steam boilers, be sure to drain condensate from the steam feed line prior to opening the steam outlet valve to avoid slugging condensate into the steam main.

Check the Code

The ASME Boiler and Pressure Vessel Code establishes rules of safety relating to the design, construction, operation, testing, and maintenance of boilers, and other pressure systems. Currently, all provinces of Canada and 49 of the 50 United States have adopted, by law, various sections of the Boiler and Pressure Vessel Code's 2010 edition. Two types of boilers are covered:

  • Power boilers—steam or other vapor is generated at a pressures exceeding 15 psig; operating pressures and temperatures exceed 160 psig and 250°F, respectively
  • Heating boilers—steam or other vapor is generated at a pressures not exceeding 15 psig; operating pressures and temperatures do not exceed 160 psig and 250°F, respectively

Resources

O&M Best Practices Guide, Release 3.0, Chapter 9. O&M Ideas for Major Equipment Types, U.S. Department of Energy. (Last accessed October 10, 2012).

Stephen Kleva. "Boiler Efficiency and Performance Tips," HPAC Engineering, March 31, 2009. (Last accessed October 10, 2012).

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