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Start-up and maintenance of shielded pumps The structure of shielded pumps is relatively complex; therefore, it is necessary to follow the guidelines for their use strictly. Improper use can affect the service life of these pumps or even cause damage to them. The following are the precautions to be taken when starting up a shielded pump: 1. Before installing the pump, the system pipelines must be purged, and a filter screen should be installed before the pump’s inlet. 2. It is strictly prohibited to run the shielded pump at idle; the drive must not be activated until the pump is filled with liquid. 3. If the pump is equipped with cooling water connections, each time the pump is started, it is necessary to ensure that these connections are connected and that the flow rate of the cooling water is adjusted properly. 4. Before starting the pump, fully open the inlet valve and the valves in the reverse circulation circuit; keep the outlet valve closed. Open the pump’s exhaust valve several times to ensure proper venting, so that the pump is completely filled with liquid. Also, if there is no impact, make sure that the valves in the reverse circulation pipeline are completely unobstructed. 5. Once the gas inside the pump has been removed, slightly open the outlet valve, start the pump, and then gradually increase the opening of the outlet valve to adjust the outlet pressure. The pressure difference between the outlet pressure and the inlet pressure should roughly conform to the formula below: Outlet pressure – Inlet pressure = (Head × Specific gravity of the fluid) ÷ 1026. When starting the pump for the first time, it is necessary to monitor the pump’s current, ensuring that it remains within the rated value. One should not attempt to increase the flow rate by opening the outlet valve too wide; a current within the rated range is considered normal. The current level should be determined based on the outlet pressure specified in point 5. 7. After the pump starts operating, observe the movement of the pointer on the TRG gauge located behind the pump. If the pointer moves into the red zone immediately upon startup, it indicates that the phase connections are reversed; in such a case, swapping any two of the phase wires will resolve the issue. If, after operating for some time, the pointer gradually moves into the yellow zone, the pump should be stopped for inspection. If the pointer reaches the red zone, it is absolutely forbidden to restart the pump before carrying out repairs. 8. After the pump starts operating, in order to maintain optimal performance and a longest service life, the flow rate must not be lower than 70% of the designed flow rate. When the system is unstable and this requirement cannot be met, a bypass should be added to increase the flow rate.