1 principle of mechanical seal
A mechanical seal is a sealing device without packing. It is shown to be sealed by the moving ring fixed on the shaft and the static ring fixed on the pump shell, and the close proximity of the two end faces (sliding by the spring force). In the mechanical seal and water leakage return ring sleeve Gogh Luppi J (Golubiev) reverse spiral groove lifting pressure through the channel is forced into the dynamic ring and the static ring clearance to go, to take away the friction heat and bubble impurities. Pressure seal water, on the one hand, to withstand high pressure outlet water, on the other hand, to move between the static ring, maintain a layer of flow film, so that the dynamic and static ring does not contact. The flow film is very thin, because of the effect of high pressure water, so the discharge of water is very little.
Figure 150CHTA/5SP2 mechanical seal
Problems and analysis in the course of 2 operation
2.1, the poor welding quality of the mechanical seal system seriously affects the safety of the feed water pump. The design of the sealing fluid temperature of the 200MW feed pump is 80 degree alarm and 90 temperature jump pump. When the piping in the operation is slightly leaked, the temperature of the mechanical seal fluid increases slowly (because the mechanical seal fluid of the heat exchanger is reduced, or the mechanical seal fluid is not well cooled), and when the piping is seriously leaked, the temperature of the mechanical seal liquid rises sharply. All of these make the mechanical seal ring and static ring and the paste and surface not very good cooling, so that the static ring is overheated and damaged. During the operation, the leakage of the water supply pump caused by the leakage of the mechanical seal pipe has also aggravated the wear of the mechanical seal. Therefore, higher requirements for the welding quality of the mechanical seal device pipe system are put forward.
2.2 effect of water quality on mechanical seal. Due to the high demands of the quality of the mechanical sealing device, when the deterioration of water quality, the mechanical seal device of circulating pipe system is relatively small, so that the mechanical sealing device emergency clogging caused by mechanical seal liquid temperature; when the water pump in low speed operation, when the deterioration of water quality, due to Gogh Luppi J (Golubiev) to enhance the reverse spiral groove the lower the pressure, the impurities can not be timely water away, resulting in deposition of impurities and surface sealing paste in the mechanical seal ring, scratch paste and surface, the mechanical seal leakage. Therefore, it is necessary to strengthen the supervision of the water quality of the unit's start stop and normal operation.
2.3 the influence of the operation mode on the mechanical seal.
2.3.1 when the unit is in frequent load adjustment, and make the water pump in variable working state or pump start and stop frequently in the state, resulting in water pump shaft moment move, make the pump dynamic and static ring between paste and surface gap is too small, not enough to form a film flow, caused by dynamic and static ring friction the mechanical sealing device is damaged. The #42 water supply pump of the sea power had been damaged by the balance of the pump unit itself, which made the thrust bearing wear out and led to the leakage of the mechanical seal. So in the operation to minimize the large adjustment of the pump group. Prevent mechanical seal damage.
2.3.2 when the water supply pump is in a normal standby state, the pump is at rest at this time. The pump must be put into the warm standby pump device, then although the cooling water into the mechanical sealing device, but because the pump group does not rotate, so the mechanical sealing device in the water can not flow, so the mechanical seal device of Shi Mohuan (static ring) in high temperature above 100 DEG C, and when the standby pump start immediately with a load of more than 100 DEG C, the water flowing through the cooler after suddenly turned into graphite ring above 30 DEG C through the return of mechanical sealing device, the graphite ring quenched and cracks, resulting in leakage of mechanical sealing device. Therefore, a small circulating pump can be added to the flow of the mechanical seal to avoid the above phenomenon when the pump group is in normal reserve.
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