A pump airlock, also known as vapor lock, is a condition where air becomes trapped inside a pump, preventing it from properly functioning and potentially leading to pump failure. This trapped air disrupts the pump's ability to create suction or pressure, effectively halting the flow of liquid.
Understanding the Mechanics of an Airlock
A pump works by creating a vacuum or pressure differential to move fluids. When air is present, it occupies space that should be filled with the liquid being pumped. Because air is far less dense than most liquids, it compresses easily, preventing the pump from establishing the necessary pressure or vacuum to move the fluid efficiently, or at all.
Causes of Pump Airlocks
Several factors can contribute to airlocks:
- Improper Priming: Many pumps, especially centrifugal pumps, require priming—filling the pump and suction line with liquid—before starting. Failure to do so leaves air in the system.
- Leaks in the Suction Line: Even small leaks in the suction line (the pipe bringing fluid into the pump) can allow air to be drawn into the system.
- Low Fluid Levels: If the fluid level in the source tank or well drops below the suction line inlet, the pump can suck in air.
- Outgassing of Fluid: Certain fluids, especially when heated or agitated, can release dissolved gases, forming air pockets.
- System Design Flaws: Poorly designed piping systems with high points where air can accumulate are prone to airlocks.
Consequences of Pump Airlocks
An airlock can lead to several undesirable consequences:
- Reduced Pump Efficiency: The pump's ability to move fluid decreases significantly.
- Pump Overheating: The pump motor may overheat because it is running without moving fluid, which normally provides cooling.
- Pump Damage: Prolonged operation with an airlock can damage the pump's internal components.
- System Downtime: The system relying on the pump will be non-operational until the airlock is resolved.
- Increased Maintenance Costs: Repairs or replacements due to airlock-related damage can be costly.
Resolving Pump Airlocks
Several methods can be used to remove an airlock:
- Priming the Pump: Manually filling the pump and suction line with liquid can displace the trapped air. This is often done by opening a priming port or valve.
- Bleeding the System: Many systems have bleed valves at high points where air tends to accumulate. Opening these valves allows the air to escape.
- Increasing System Pressure: Increasing the pressure in the system can sometimes force the air pocket to dissolve back into the liquid or be pushed through the system.
- Adjusting Piping: Redesigning the piping to eliminate high points or install air vents can prevent future airlocks.
- Automatic Air Vents: Installing automatic air vents at strategic locations will automatically release trapped air.
Prevention Strategies
Preventing airlocks is generally more efficient than dealing with them after they occur. Implementing these strategies will save time and money:
- Proper Installation: Ensure the pump and piping system are installed correctly, minimizing potential air traps.
- Regular Inspections: Inspect the suction line for leaks and ensure the fluid level in the source is adequate.
- Correct Priming Procedures: Follow the manufacturer's instructions for priming the pump before startup.
- Use of Automatic Air Vents: Install automatic air vents to prevent air accumulation.
- Selecting Appropriate Pumps: Ensure that the pump is suitable for the application and the fluid being pumped. Self-priming pumps are specifically designed to handle air.
