Preliminary Energy Audit of a Boiler | Energy Conservation

To conduct or help conducting an energy audit to your boiler these tasks need to be included;

Preliminary Energy Audit of a Boiler | Energy Conservation

  • Prepare for the audit
  • Obtain nameplate information
  • Obtain operational details, including fuel use, medium raised, temperature and pressure, and operating hours
  • Conduct visual inspection of boiler and auxiliaries; determine condition and readings of instrumentation
  • Examine boiler house log
  • Identify test points
  • Determine type of test and instrumentation required
  • Identify conservation opportunities from improved operation
  • Develop action plan
  • Repair/install instrumentation as necessary
  • Identify testing positions
  • Select appropriate test day
  • Perform test
  • Testing procedures and techniques
  • Data collection
  • Evaluate data
  • Calculate efficiency
  • Determine improvements

The first step in evaluating a boiler is to conduct a quick assessment if one has not already been completed before. Such assessment is used to collect information through interviews with key personnel and by visual inspection.
The information includes nameplate data as well as operational details, including fuels used and operating pressures and temperatures. This information can be collected from interviews and confirmed during the visual inspection, or it can be determined in the visual inspection alone.
The visual inspection allows the energy surveyor to see for himself/herself the condition of the plant and its auxiliary equipment and confirm interview information.
The auxiliary systems associated with boilers should be checked including but not limiting the following:

  • Boiler and burner
  • Water system
  • Fuel supply system
  • Heated medium distribution
  • Instrumentation systems

The operator can obtain further information by checking the boiler house log and water treatment reports. The operator and/or energy coordinator should consider the following information when deciding whether to test the boiler:

  • Date of last efficiency check
  • Installed instrumentation
  • Operating condition

If testing is necessary, the energy surveyor should identify the test points and decide what type of test is to be performed and the instrumentation needed. For instance,

  • Full commissioning test
  • Efficiency test to standards established by bodies such as ASME
  • British Standards BS 845 or BS 2885
  • Efficiency test by loss method
  • Combustion test only

The most common test is the efficiency test by the loss Method. The other methods are used less frequently and are variations of the loss method.
Although other tests can be more accurate, the extra cost and time required to carry them out are often not justified.
Last but not least again to identify conservation opportunities such as;

  • Tune-up
  • Improved control
  • Heat recovery
  • Alternative fuels

At the end of the assessment the operator/energy surveyor will complete his evaluation and prepare an action plan. The action plan normally includes a recommendation for a detailed energy assessment unless the initial one indicates that the boiler is in good operating condition. Action plan normally include two levels of recommendations:

Low cost/no cost measures which are mainly related to operational or maintenance procedures

  • Further studies are warranted

During more involved studies the boiler efficiency is measured as well as other factors of boiler operation are investigated to identify opportunities for reducing energy costs. As follows:

  • Installing Thermal Insulation on Boiler and Ancillary Plant
  • Discontinuing Use of Hot Reserve Boilers
  • Reducing Blow-down
  • Reducing Operating Pressure

Before testing boiler efficiency, the operator/energy surveyor must complete some preparatory work. This work includes the following:

  • Recalibrating all instrumentation to be used
  • Ensuring that all test measuring positions are accessible
  • Selecting an appropriate day for testing

The most common technique for evaluating the boiler efficiency is the total losses method which relates all the losses to the fuel input. Accordingly, the efficiency is calculated as 100% minus the percentage of losses such as;

  • Combustion Losses
  • Flue gas losses
  • Incomplete combustion losses
  • Heat Transfer losses
  • Blow Down Losses
  • Cool Feed Water

Blow down is necessary to avoid high TDS concentration inside the boiler drum. Blow down rate decreases due to the use of condensate return (less makeup water).
These losses are attributed to low utilization or heat losses of condensate return. Accordingly, more fuel is used to provide the sensible heating to the water.


 

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