How can flow be kept relatively stable with minimal disturbances when manually switching pumps, even if the control valve is not functioning?
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The exam questions are quite difficult to handle; I would appreciate it if experienced operators could provide guidance and share their insights. Thank you.
Which pump should be started? A centrifugal pump?
Start the standby centrifugal pump in parallel; once the pressure gauge shows the maximum value and remains stable, slowly open the outlet valve of the standby pump and gradually close the outlet valve of the main pump until the desired conditions are achieved, which will result in minimal fluctuations in flow rate.
This is the standard approach used in external operations; the flow rate fluctuates, making it impossible to achieve a smooth transition.
Refer to the opening degrees of the inlet, outlet, and bypass valves of the pump that is currently in operation (the length of the valve stem exposed), adjust the opening degrees of the relevant valves for the standby pump that is about to be started, start the standby pump, and simultaneously shut down the pump that is currently in use.
1. The outlet of the standby pump is closed, and the return flow is opened. 2. Start the backup pump. 3. Open the outlet throttle valve of the standby pump while closing the outlet throttle valve of the pump in use; it is important to keep the reading on the pump’s outlet pressure gauge constant. 4. Stop adjusting the outlet throttle valve of the standby pump once the outlet of the pump in use is closed. 5. Stop using the pump.
By stable regulation, you mean the flow rate, or the liquid level. It’s simply a matter of switching the outlet valves for the two pumps while keeping the flow rate (liquid level) constant; this should be used as a reference. Otherwise, there is something wrong with the proposal. It cannot be denied that some question setters show off their knowledge while neglecting the rigor of the questions themselves.
This tests one’s skills in external operations, but experienced individuals can manage it so that there are hardly any significant fluctuations in traffic volume
Look at the pressure gauge: one person should slowly open the outlet of the pump, while another person slowly closes the outlet of the pump that is not in use. The pressure gauge should not show any significant fluctuations, and the two people need to work well together