CAVITATION
Calculation of Z1 is important for correct working of the pump without the occurrence of cavitation phenomena. Working in CAVITATION conditions occurs when the absolute pressure at the impeller inlet drops to such values as to allow the formation of bubbles of steam inside the fluid, so the pump works irregularly with a reduced head. The pump must not operate in cavitation because, apart from generating a noise similar to a metal hammering (due to implosion of the vapour bubbles), it can cause irreparable damage to the impeller. Shown below is an image of a cast iron impeller which operated in cavitation. The beginning of erosion near the blades of the suction port is clearly visible
INSTALLER’S
INSTALLER’S
MANUAL
MANUAL 3 37