High-precision lobe pump shutdown is mainly formed by the failure of the mechanical seal. Failure is mostly reflected in leakage, leakage reasons are as follows: a. Dynamic and static ring sealing surface leakage reasons are: end surface flatness, roughness does not meet the requirements, or the appearance of scratches; end surface between the particulate matter, forming the two end surfaces can not run the same; device is not in place, incorrect method. b. Compensation ring seal leakage reasons are: gland deformation, preload force is not uniform; device is not correct; seal ring Quality does not meet the specifications; seal ring selection is not correct. Requirements after the suspension of work: a. After the suspension of work should be closed to the pump population valve, to be cooled and then close the valve of the subordinate system. b. Parking should be performed in accordance with the rules of the technical documentation of the equipment, parking should be every 20 to 30min disk half turn, until the pump body temperature down to 50 ℃ stop. c. Parking, when no special requirements, the pump should always be filled with liquid; inlet valve and discharge valve should be adhered to Normally open condition; choose double-end mechanical seal of low temperature pump, liquid level controller and pump seal cavity seal liquid should adhere to the pump grouting pressure. d. Transport easy crystallization, easy condensation, easy precipitation and other media pump, stop the pump to avoid blockage, and timely flush the pump and pipeline with water or other media. e. Discharge the accumulated liquid inside to avoid rust and freezing. The actual use of the role indicated that the seal components fail more parts is the dynamic, static ring end face, pump machine seal dynamic, static ring end face cracking is a common failure phenomenon, the main reasons for mechanical seal failure are: ① poor lubrication of the liquid medium, coupled with the operating pressure overload, the two sealing surface staring rolling is not synchronized. For example, the high speed pump speed of 20445r/min, the seal surface center diameter of 7cm, the pump work after its linear speed up to 75m / s, when there is a seal surface lag can not keep an eye on the rotation, the instantaneous high temperature formed seal surface damage. ② liquid medium vaporization expansion, so that the two end faces are separated by the vaporization expansion force, when the two sealing surface force to fit, the destruction of the lubricating film, thus forming the end face appearance overheating. ③ installation of the sealing surface gap is too large, the flushing fluid is too late to take away the heat of the conflict; flushing fluid leakage from the sealing surface gap, the formation of the end face overheating and damage. ④ Seal flushing fluid orifice plate or filter blockage, forming a lack of oil, so that the machine seal failure. In addition, the seal surface appearance of the slip groove, the end face fit when the gap leads to the failure of the sealing element, the main reasons are: ① liquid medium is not clean, there are small hard particles, with a high speed to slide the seal surface, the end face surface scratch and failure. ② poor coaxiality of machine and pump transmission parts, the pump is turned on every week the end face is shaken conflict once, the dynamic ring running track is not the same center, the formation of end face vaporization, overheating wear. ③ liquid medium oil force characteristics of the frequent occurrence of vibration caused by the pump group, the formation of sealing surface dislocation and failure. Liquid medium corrosion of sealing components, stress concentration, soft and hard material cooperation, erosion, auxiliary seal 0-shaped ring, V-shaped ring, concave ring and liquid medium incompatible, deformation, etc. will form the mechanical seal exterior damage failure, so the damage to the form of comprehensive analysis to identify the root cause, to ensure that the mechanical seal long operation.
May 18, 2022 View: