What issue is referred to when an impeller has air in it?

The issue referred to when an impeller has air in it is known as pump cavitation. Cavitation occurs when the pressure at the pump's impeller drops below the vapor pressure of the liquid being pumped, causing the formation of vapor or gas bubbles within the liquid. When these bubbles travel through the impeller and enter higher-pressure regions, they collapse suddenly, leading to vibrations, noise, and potential damage to the pump components.

Understanding cavitation is crucial for gas technicians because it can lead to inefficient pump operation and significant mechanical failure if not addressed. Proper system design, monitoring, and maintenance practices, like ensuring adequate suction pressure and preventing air leaks, can mitigate the risk of cavitation.

Other issues, such as pump overheating, water hammer, and vortex effects, do not specifically relate to the presence of air in the impeller but are instead connected to different hydraulic or operational problems within pumping systems. Therefore, recognizing and diagnosing cavitation is essential for maintaining optimal pump performance and longevity.