Issues related to shutting down centrifugal pumps
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Dear Haihao friends: What damage can occur to a centrifugal pump if it stops operating at normal flow rates (with the outlet valve not closed, but a check valve being present in the outlet pipeline)? Will it have an impact on the mechanical seal? I hope fellow sailors can provide an answer.
Should I turn off the power or the inlet valve? Turn off the power; if the outlet pipeline is very long, water hammer may cause damage to the pipeline (as well as damage to the pump) ； Close the inlet valve and let the pump run idle.
If you take a look at the operating procedures for emergency shutdown, you’ll understand: the first thing to do is to open the return valve in order to relieve the pressure.
Power outage. Is water hammer still caused by a check valve installed on a pipe very close to the pump’s outlet? Also, could there be any other effects? For example, could it cause any damage to the mechanical seal?
It’s not an emergency shutdown; I just want to know what effect stopping the pump in this way will have on it What damage can components such as mechanical seals suffer?
In an emergency, the pump is stopped in this manner; once the pump has been stopped, the outlet valve must be handled immediately, and this will not have any impact on the mechanical seal.
According to the process engineers, does seal fluid leak out from the mechanical seal when the pump is stopped in this way? The mechanical seal is a series-type seal – is it the secondary sealing fluid that is leaking?
Pump shutdown water hammer is mainly caused by the rapid closure of the check valve in the outlet pipe; therefore, removing the check valve can eliminate the hazards associated with pump shutdown water hammer. You should install a water hammer eliminator.
If the backflow is too much, the impeller of a regular centrifugal pump may loosen. If it is a magnetic pump, the impeller will loosen and the internal magnet will be damaged
I think if there is a check valve on the outlet, stopping the pump directly will have no effect on the pump itself. We use single-stage mechanical seals, and I have never seen the seal leakage phenomenon described by the original poster
Operating procedures: 1. Before starting the machine, check whether the pump feet are tight and whether the coupling guards and the motor fan covers are in good condition, to ensure the safety of the equipment and personnel. 2. Check whether the inlet valve is open, and open it as much as possible. Check whether the outlet valve is closed. Open the vent valve to release air until no air remains, then close the vent valve. In pipelines equipped with a bottom valve, the pump chamber must be filled with water. 3. Start the water pump; once its speed reaches the normal level, slowly open the outlet valve. At the same time, monitor the ammeter to ensure that the current remains within the rated range of the motor. 4. During operation, the water pump is required to run smoothly, without abnormal noises or significant fluctuations in pressure. If any abnormality is detected, the machine should be stopped immediately. 5. Before shutting down, gradually close the outlet valve first, and then turn off the power supply. 6. For pipelines equipped with check valves, there is no need to close the outlet valve as long as the check valves are in good condition; the pump can be started directly after checking that there is no air in the pump chamber.