Boiler is heated directly by the large flame and explosion-hazardous special equipment, the production is good or bad, which is directly related to the operation and management of the national and people's lives and property safety, is related to the healthy development of the national economy and social harmony and stability. Used in the current horizontal fire tube boiler boiler considerable proportion, the author of more than ten years in the inspection found that horizontal fire tube boiler damage occurs mainly in high end tube plate, the main damage in the form of cracks. How to prepare this type of boiler operation and management and inspection work is the focus of the inspection. Fire tube boiler tube sheet cracks and seriously affected the normal production process in the boiler safe operation.
In effect crack pipe plate production factors, the most critical is the impact of the work of the tube plate temperature difference, after undergoing complex flue gas tube sheet heat transfer process, which includes: radiation, convection and conduction. Burning fuel in the furnace flue gas produced by high-temperature part of the heat released in the furnace, the temperature between about 750-950 ℃, the smoke chamber from the rear tube plate into the pipe, and finally by the smoke pipe into the atmosphere. After the inner wall of the tube plate flow resistance, easy gasification boiler water and precipitation scale, scale further impeded between the boiler water and high temperature flue gas heat exchanger, causing the tube plate temperature to rise further. On the city in the course of regular inspections of boilers found; treatment work better boiler, wall rarely attached scale, tube sheet heat transfer effect is ideal, there is generally no crack problem; rather appears boiler tube sheet cracks, most are attached to the inner wall of the drum thicker scale. And such work is often poor boiler water treatment, or simply did not take any water treatment measures.
Caused by poor circulation due pot " subcooled boiling " is also a leading tube sheet cracks another main reason. In the pipe connecting portion and the tube plate, if the tube during manufacture or repair of the outer wall hole wall clearance is likely to lead to fatigue cracking tube sheet, pipe joints and holes there is a gap, the boiler during operation, due to the ingress of water, there will be an annular water film is formed in the gap. When the water film temperature rise bubbles, but ran out from the cracks in the bubble is not easy, so that the gap between the local water cycle deterioration, resulting in local metal overheating. When the superheated gas ejected from the gap after the pot of water to re-enter the gap, so that the vicious cycle to proceed. Most small and medium sized boilers are combined with intermittent operation, the boiler heating surfaces subjected to repeated heating and cooling changes, before long, the tube plate metal strength will be reduced, resulting in thermal fatigue damage, cracks.
