Air behaviour in pipelines

Freely dissolved air exists in all fluid transmission systems

The principal sources for this air are:

• Incomplete filling of the line - which leaves air pockets in high places and in different accessories
• Air dissolved in the fluid that is released when the pressure drops and/or there is a rise in temperature
• Vortexes in the fluid, at the points where it is pumped, introduce air into the system
• Air is sucked into the system through openings and accessories

The lack of control over the air present in a fluid system can result in damage:

• If destructive vacuum conditions are created
• The presence of air can have a detrimental effect on system drainage efficiency
• Reduced air pockets in the system cross sectional area, higher energy losses, tremors in the systems and in extreme conditions; the entire stoppage of flow
• High pressure surge
• Metal parts in the system and system accessories corrode at higher rate
• Lower pumping efficiency
• Physical risk - when large volumes of air under pressure are released at high velocities
• Inaccuracies in the measurement of fluid volumes
• Accelerated wear of moving parts and flow gauges
• Cavitation damage