When should a positive displacement pump be operated?

A positive displacement pump is designed to move a specific volume of fluid with each cycle, making it crucial for its operation that both the suction and discharge valves are open. When these valves are open, the pump can draw in the fluid and properly discharge it, which ensures that the pump operates effectively and efficiently.

Operating a positive displacement pump with both valves open allows the pump to build pressure and maintain flow to the system it serves. This design is distinct from that of centrifugal pumps, as a positive displacement pump relies on trapping fluid and forcing it through the discharge rather than relying on the movement of fluid surrounding an impeller.

If the discharge valve is closed while the suction valve is open, pressure can build to excessive levels, which may lead to pump damage or failure. Conversely, if both valves are closed, the pump would be unable to take in fluid, possibly leading to operational issues or damage. Therefore, ensuring that both the suction and discharge valves are open is essential for the safe and effective operation of a positive displacement pump.