4. Low-flow operation

Operating at zero flow, or simply at low flow, is always a trial for a pump, and often a danger. In previous articles, we have seen that low-flow operation leads to recirculation, much higher periodic stress on impeller and diffuser blades, increased vibration levels, the possibility of dynamic instability of the pump-circuit system, radial stress with shaft bending for volute casing pumps without diffusers, increased risk of shaft line instability, and a significant increase in power consumption for propeller pumps.