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ALWAYS INSPECT YOUR BOILER CLOSELYYou can't always see the boiler deposits, In the case of fire-tube boilers the most accessible area for the engineer to view the tubes is via the front plate (shown below Photo 1). This is usually the area of least fouling, despite this closer inspection will often reveal that the deposits can be significant ( remember a 2mm deposit will effectively increase fuel consumption by approximately 5%) FIRE TUBE BOILERS Photo1.
BOILER
FRONT PLATE (Click on Thumbnails)
Photos 2-5 are close ups of the front plate. This boiler has operated for 2 months without Sapec
Photograph 2 appears to show a fairly clean boiler. However at closer inspection the deposits are shown to be at least 2mm thick. Photo 2 shows how the deposit can be prized away from the tube with a screwdriver. Photos 3& 4 were taken after the same boiler had been pre-cleaned with a high pressure water lance. The remaining deposits are still extremely hard and difficult to remove. photo 5 illustrates the thickness of the deposits and how important it is to take a closer look at the boiler heat transfer surfaces. FOULING PROBLEMSThe following photographs show the front plate of a 16t/hr fire-tube boiler that has operated on grade B South African coal for 30 days. Front plate
BOILER REVERSAL CHAMBER The reversal chamber is the first point at which flue gases enter the tube system and the deposits can be very heavy in this area as is shown below. The deposits below are often referred to as "birds nesting" and will normally cause the boiler to be brought of line prematurely , as the boiler tubes block the boiler starts to pressurize.
The three photographs below show fouling in the reversal chamber. Although this type of fouling does not have the impact of birds nesting, as the boiler can continue to operate, it has a more significant effect on the heat transfer rates and therefore will often lead to greater losses.
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