Several types of mechanical seal

Ordinary bellows mechanical seal failure forms currently used bellows mechanical seal and its auxiliary system of the main form of seal failure are the following. 1, the bellows mechanical seal manufacturer miss or fracture caused by seal failure. Corrugated pipe in use process, the fire pump mechanical seal or stiffness elastic will gradually decrease, the elasticity decrease phenomenon is often called miss. Experiments and practical application show that the amount of miss when bellows design more than the initial amount of compression of 18% ~ 20%, the bellows mechanical seal leakage occurs. Metal corrugated pipe sealing at temperature below 200 ℃ miss phenomenon is not obvious, but at high temperature ( More than 300 ℃) Soon after use, driving pump leakage, will use the machine to be removed is sealed by chi mechanical seal quantity found resistant metal corrugated pipe component height is an average of 2 ~ 3 mm before installation. Bellows miss is mainly due to permanent deformation or stress relaxation stage pump mechanical seal, and a kind of situation is working medium crystallization precipitation or solidification in the aperture of corrugated pipe, corrugated pipe deformation ability to decrease or loss of the deformation ability. As a result, high temperature and load is the main cause of bellows miss [ 1] 。 In addition, in the high temperature and quantity of corrugated pipe compression or contact pressure is bigger, corrugated pipe fracture happens; The higher the temperature, the greater the load, the higher the probability of fracture bellows in. 2, paired friction pair in graphite ring seal failure caused by excessive wear. Usually, dismantle the machine seal failure under examination revealed graphite sealing ring wear. Through analysis and experiment found that the metal corrugated pipe sealing face specific pressure affected by effective diameter of bellows, and the effective diameter is changed along with the change of pressure. Friction vice friction due to pressure is too large, serious, graphite ring excessive wear cause leakage. 3, paired friction pair in the surface of the cemented carbide ring seal failure caused by cracking. Through inspection found that the hard alloy ring seal friction pair appeared by hardfaced center spread to many of the different thickness of radial crack, it is caused by thermal cracking of seal failure. Cracking is the main reason for the high local heat stress, including tungsten carbide ring and ring the linear expansion coefficient of two kinds of material, adopt welding structure or the overall structure, the type of seal cooling system of irrigation rinses, flushing mode and flow of the size of the fit can cause cracking of the seals.