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Service Solutions No. 3 • August 2009 Water washing of pin tube elements Soaking followed by water washing combined with compressed air is an efficient and affordable method for cleaning the smoke gas tubes. Aalborg Industries can supply a special pin tube water washing kit. Boilers with pin tube elements Many MISSION™ boilers from Aalborg Industries feature pin tube elements due to their unique heat transfer capacity. The designs are basically self-cleaning when the boilers are operated correctly and within the design parameters. Washing procedure The cleanliness of the convection section (pin tubes) has great influence on a boiler’s efficiency. If soot starts building up (on the heat transfer surfaces), less convection heat is transferred to water/steam thus resulting in a higher exhaust gas temperature typical of too low boiler efficiency. Therefore, it is of the utmost importance to keep the boiler heating surfaces as clean as possible. One of the best methods to verify optimal combustion is using a smoke density analyzer to ensure correct air/fuel ratio and limit emissions. Poor combustion will lead to soot accumulation on the heating surfaces and has to be removed. Cleaning of the pin tube elements Air/water washing of pin tube elements has proved to be efficient for removing residual carbon coating/soot. The effect is due to the comThe process is completed by draining the boiler of washing water and flushing it with clean water. The washing procedure is fairly simple. When the boiler has been cooled down, access the furnace (in most cases by removal of the burner) and open the uptake. Fix plugs (tube closing devices) to the bottom of the pin tube elements and tighten the screws. Hook each plug to a collector so a steady flow of compressed air can be injected around the pin tube elements once the smoke tube has been filled with freshwater (also via the collector). If the soot contamination is light, the effect of the compressed air in the water is enough to loosen the carbon residues once the smoke tubes have soaked in freshwater for a few hours. Depending on the degree of contamination of the surfaces, it may be necessary to add chemicals to the cleaning water. Several or all of the pin tube elements can be cleaned simultaneously. Washing water may have to be replenished as necessary during the entire process. bined effect of soaking with clean water aided by the turbulence of the compressed air in the washing water. The Aalborg Industries plug/ collector solution means that the combustion chamber can be kept dry while cleaning the smoke tubes.

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