Causes of failure of metal expansion joints in hot air ducts.
Metal expansion joints absorb thermal expansion in the hot air duct system while reducing duct vibration to protect the hot air duct. The hot air duct is the core part of the ironmaking plant, transporting the high temperature hot air from the hot air furnace to the blast furnace in the middle. Due to the complexity of the metal expansion joint working medium, working conditions and the special nature of the structure. If the metal expansion joint fails during the operation of the blast furnace, it will reduce the loss caused by the long time off air of the blast furnace. Expansion joint of the preliminary selection as the key to determine the later use of the effect. When the problem occurs should analyze what causes failure, to facilitate the selection of models. 1 . High temperature Hot air pipe temperature is high and the internal thermal insulation layer and the amount of thermal expansion of the metal pipe is different, coupled with the long-term high temperature environment, prone to cracking, peeling insulation material after differentiation, the heat is directly transferred to the inner wall of the bellows. 2 . Improper insulation measures taken Metal expansion joint wave shell, pull plate, compound tie rod type of tie rod and other stressed structural parts are clearly not able to insulation. If the insulation of the expansion joint as a whole, the expansion and contraction movement of the bellows is affected. 3 . Instability caused by tensile displacement For expansion joints in the absorption of pipeline thermal expansion, bellows undergoes tensile displacement, at this time the wave distance becomes large, the bellows of the wave belly flat part of the tilt, the wave crest under compressive stress has the tendency to shrink inward, when the tensile displacement reaches the degree in order to deformation coordination will produce the trend of wave crest collapse. Metal expansion joints should be pre-displacement processing, in order to reduce the working state of tensile displacement and improve stability.
