What will occur if there is too much clearance between the pump casing and the impeller?

When there is too much clearance between the pump casing and the impeller, it leads to a reduced flow rate. This is primarily due to the fact that the increased clearance allows for more leakage of the fluid back to the inlet side of the pump instead of pushing it towards the discharge. The impeller's design relies on a specific gap to create the necessary pressure difference to move the fluid effectively. If the clearance is excessive, the impeller can no longer take full advantage of its designed capability to generate flow, thereby diminishing the pump's overall performance.

Moreover, larger clearances can disrupt the flow patterns within the pump, resulting in turbulence and cavitation, which further limits the efficiency and flow rate of the pump system. Thus, a proper balance of clearance is vital for maintaining optimal flow and operational efficiency in a pump.