The GA-203 pump in Qilu Petrochemical Co., Ltd. cracking plant is the bottom circulating pump of DA-203 tower. It delivers lignosulphurized high-concentration lye to the top of the tower for recycling. The pump in the initial running good condition, but often run for some time after the leak, the maintenance frequency increases, an increase of maintenance costs and product costs, affecting the long-term stability of the device. (1) Failure Analysis General mechanical seal failure mainly in 4 forms, namely, corrosion, heat loss, wear and tear, installation, operation and other factors caused the failure. The pump seal surface after the dissolution of no scratches and wear and tear, so you can rule out the sealing surface physical damage reasons. Taking into account the sealed chamber more than the crystal and rust skin, combined with the failure of many mechanical seal performance, the initial judge of the transport medium easy to crystallize and corrosive is the main cause of seal failure. (2) improvement measures a. Change the structure of elastic element: Change the elastic element from spring to bellows. The bellows is not only the elastic element but also the auxiliary ring of the moving ring, omitting the O-ring between the prime ring and the sleeve, The end of a seal to seal the material here, so that both the O-ring seal and compensation to resolve the conflict, but also the original quasi-static seal into a fully static seal, the seal to improve reliability. The use of bellows also eliminates the need for a spring-mechanical seal drive pin and the mating surface between the moving ring and the moving ring seat to avoid malfunctioning of the moving ring due to the deposition of solid particles and further improve the overall performance of the mechanical seal . Bellows provides both elastic compensation and torque, with better followability and compensation. b. Static ring compensation instead of moving ring compensation: the mechanical seal components in the ring part of the mass far more than the static part of the ring, so the operation of the rotation momentum is also large. To static ring compensation to reduce the rotational momentum, improve the stability of the mechanical seal components and reliability. c. Increase the clearance between moving ring and sleeve: Increase the clearance to avoid the deposition of crystal and rust skin, and increase the diameter of moving ring or reduce the inner diameter of sleeve under the premise of ensuring the specific pressure on the face. According to the information recommended, the gap increased from the original 0.38mm to 0.5mm. d. Properly increase the diameter of the flushing line: For the actual situation of more crystallized material and scale, increasing the flushing volume can effectively solve the deposition of solid particles, so the diameter of the original flushing line should be increased from 12.7mm to 19.05mm. However, it should be noted that increasing the aperture excessively reduces pump efficiency. e. Increase the number of inlet filters: Increasing the number of filters can effectively prevent the solid particles from entering the sealed chamber, providing a better working environment for mechanical seals.