The stability of a self-priming pump in operation is determined by its performance, which is represented by working parameters. Parameters such as flow rate, head, power, and efficiency are interrelated. If the relationship between these parameters is depicted in a graphical form, it is known as the pump performance curve.

Flow Rate, Head, and Power: Their Interchangeable Laws

The head and power of the pump gradually decrease as the flow rate increases, but there is a turning point in the process. As the flow rate increases, the head and power actually gradually rise before declining again. When the flow rate is high, the efficiency is high; when the flow rate Q=0, the pump head and shaft power are about 1.5 to 2 times of the rated values. Self-priming pumps, when operating at low flow rates, can experience a sharp drop in efficiency due to vortices inside the pump, leading to an unstable operating condition, which is not permissible in production.

Do not arbitrarily reduce the flow rate of a self-priming pump, as it may cause the pump to operate in an unstable state, resulting in severe vibration and noise, and a sharp drop in efficiency. This is highly detrimental to the pump's operation.

To reduce the starting power of the engine, the self-priming pump should be started by opening the valve, as the power is lower at this point and it is safer for the engine. Otherwise, the starting power of the motor would be too high, potentially leading to motor burnout.

Self-priming pumps are not suitable for adjusting pump performance with variable valves. During operation, if the pump performance does not meet production requirements, adjustments must be made to the pump performance to meet actual needs. For instance, during winter low water periods or summer flood seasons, the water levels in the intake or discharge pools change, and the previously determined lift height and flow rate are no longer appropriate, leading to reduced efficiency. Therefore, to ensure the pump can meet new requirements while operating at high efficiency, performance adjustments are necessary. How can the performance of self-priming pumps be adjusted during operation?