When the transported high-temperature liquid suddenly enters the pump body of the multistage centrifugal pump, the temperature of the pump body changes greatly, and the pump body and the rotor component are deformed due to uneven heating and thermal deformation, and the wear-resistant parts are interposed. There is only a small gap in itself that leads to abnormal contact. If the multistage pump is started in this case, it will cause vibration, bite, and shaft hung due to overheating. Therefore, when a multistage pump is used to deliver high-temperature liquid, it must be fully warmed before starting. The pump can only be started when the pump temperature is consistent. It is not permissible to start the multistage pump urgently in the cold state.
For example, a high-pressure differential multistage centrifugal pump used to pump ash water on a 8.7 MPa coal-water slurry gasification unit of a company has many failures of bearing bushing and machine seal damage after being put into operation, that is, preparation work is not required before each pump is turned on. Sufficient, the pump and exhaust methods are incorrect. After the improvement of the pump, exhaust and other work, the above problems did not occur.
The multistage centrifugal pump balances the axial force by the balance mechanism such as the balance disc and the balance drum. The balance liquid flows out in the balance device, and the balance liquid is connected to the inlet end of the pump through the balance tube to ensure the normal operation of the pump:
(1) The balance tube is absolutely not allowed to block.
(2) If fouling occurs in the balance pipe, it should be cleaned and dredged in time.
(3) Install a pressure gauge on the high pressure side of the balance pipe to monitor the outlet pressure of the balance pipe.
The multistage centrifugal pump for conveying slurry adopts the balance plate. When operating, it is necessary to inject high-pressure sealed water to make the balance plate and balance plate seat work in clean water to prevent the wear of slurry and hard particles against the balance plate and balance plate. The multistage centrifugal pump should pay attention to the inspection of the temperature rise, vibration, sound, etc. of the pump during the inspection. If necessary, to protect the pump from abnormal damage, the axial force and temperature rise of the multistage centrifugal pump, The vibration is set to interlock, and the pump is automatically stopped when the set value is exceeded.
When the multistage centrifugal pump stops working for a long time, the pump shaft is forced in one direction due to the weight of the impeller and the rotor, which easily causes the shaft to bend. The disc should be pumped once periodically, each time rotating the shaft 120° in the same direction.
If the standby multistage centrifugal pump is not closed tightly, the high-temperature medium in the pipeline flows back into the pump, and the pump is bent due to uneven heating of the upper and lower parts of the pump shaft. The alternate multistage centrifugal pump is regularly inspected.
