Boilers do not operate at rated efficiencies and the running efficiencies are found to be 3%-12% lesser than rated efficiencies. Boilers efficiency should be monitored.
Although “Boiler Efficiency” is an important parameter in the boiler specification when buying a new boiler, little attention is given to it once the boiler is steaming. The myth is that the boiler will always continue to generate steam at the rated efficiency. The truth is that one of the most critical parameters in boiler operation is its delivered efficiency in actual operation.
Our surveys plant after plant after plant show the true delivered boiler efficiency to be lower by 3% to 12% than rated. And yes, all these plants thought they were getting the rated efficiency, or may be just slightly lower.
Usually ignored, the boiler continues running at lower efficiency and consuming much fuel more than it actually should.
The table below presents a comparison between the average rated efficiencies for a boiler and the efficiencies obtained during actual operation.