What happens when an operator throttles back on the discharge valve of a centrifugal condenser water pump running in parallel with another pump?

When an operator throttles back on the discharge valve of a centrifugal condenser water pump running in parallel with another pump, the total flow rate to the condenser is reduced. This occurs because throttling the discharge valve increases the resistance to the flow of water being pumped.

In a parallel configuration, the flow from both pumps is combined. When one pump's discharge valve is throttled, its ability to deliver water is compromised, resulting in a decreased flow from that specific pump. Although the other pump continues to operate at its design capacity, the overall flow rate to the condenser will diminish because the total flow is the sum of the individual flows going to the system.

It's important to recognize that this action impacts the system dynamics. Throttling typically leads to an increase in pressure at the discharge of the throttled pump, creating a scenario where the performance of the entire system is influenced by the restriction placed on one of the pumps. However, despite shifts in pressure, there is a clear reduction in the total flow rate to the condenser due to the throttling effect on the discharge valve of the centrifugal pump.