Air ingestion 1-3.2
Cavitation means that cavities or bubbles are forming in the liquid that we’re pumping. These cavities form at the low pressure or suction side of the pump, causing several things to happen all at once:
- The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.
- We experience a loss in capacity.
- The pump can no longer build the same head (pressure)
- The pump’s efficiency drops.
The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.
A centrifugal pump can handle 0.5% air by volume. At 6% air the results can be disastrous. Air gets into as system in several ways that include :
- Through the packing stuffing box. This occurs in any packed pump that lifts liquid, pumps from a condenser, evaporator, or any piece of equipment that runs in vacuum.
- Valves located above the water line.
- Through leaking flanges.
- Pulling air through a vortexing fluid.
- If a bypass line has been installed too close to the suction, it will increase the temperature of the incoming fluid.
- Any time the suction inlet pipe looses fluid. This can occur when the level gets too low, or there is a false reading on the gauge because the float is stuck on a corroded rod.
Both vaporization and air ingestion have an adverse affect on the pump. The bubbles collapse as they pass from the eye of the pump to the higher pressure side of the impeller. Air ingestion seldom causes damage to the impeller or casing. The main effect of air ingestion is loss of capacity.
Although air ingestion and vaporization can both occur, they have separate solutions. Air ingestion is not as severe as vaporization and seldom causes damage, but it does lower the capacity of the pump.