What is the sequence for opening and closing the inlet and outlet valves as well as the pump itself when starting up and shutting down centrifugal pumps and positive displacement pumps?
Thread Content
What is the sequence for opening and closing the inlet and outlet valves as well as the pump itself when starting up and shutting down centrifugal pumps and positive displacement pumps? Starting a centrifugal pump: First, open the inlet valve of the pump, close the outlet valve, start the pump, and then open the outlet valve ； Shutting down a centrifugal pump: First close the outlet valve, then stop the pump, and finally close the inlet valve. Starting a positive displacement pump: First open the inlet valve and the outlet valve, then start the pump. Shutting down a positive displacement pump: First stop the pump, and then deal with the inlet and outlet valves. Is this the correct sequence? ’
Correct. Shutting down a positive displacement pump: 【(If there is a bypass return valve) first shut down the pump, open the return valve, then close the inlet and outlet valves】
The last edit to this post was made by ylb913 on 2016-8-4 at 19:42. 1. Starting a centrifugal pump: First, open the inlet valve of the pump, close the outlet valve, start the pump, and then open the outlet valve – this is roughly correct. The key point is to start the pump with the outlet valve closed in order to reduce the starting current of the pump. It’s basically correct to say that, in most cases, the pump’s outlet valve is in a closed state, and there’s no need to deliberately close it when starting the pump ； There is also the issue of filling pumps, which I believe is well understood by everyone. 2. Shutting down the centrifugal pump: First close the outlet valve, stop the pump, then close the inlet valve. ——Yes, especially when switching pumps, this step is definitely correct. However, pumps can also experience sudden power outages or stop operating. Therefore, under special circumstances, it is permissible to first stop the pump and then close the outlet valve. On the one hand, many pumps do not have any issue with backflow; on the other hand, even for pumps that are prone to backflow, there is a check valve in front of the pump’s outlet valve. 3. Starting the positive displacement pump: First open the inlet valve and the outlet valve, then start the pump. ——Yes. 4. Shutting down the positive displacement pump: Stop the pump first, then deal with the inlet valve and outlet valve. ——Yes. ——I won’t take it too seriously anymore; in fact, the inlet valve of the backup pump is usually left open, with only the outlet valve being closed, and the same is true for centrifugal pumps.
That’s correct, but for high-speed centrifugal pumps, it is common practice to keep the outlet slightly open in order to prevent high pressure after the pump starts, which could make it difficult to open the outlet