Air Receiver Tanks
Air receivers buffer compressor output, reduce short-cycling, and store compressed air for peak demand. Learn sizing, installation, and maintenance of receiver tanks.
Purpose of an Air Receiver
- Dampens pulsation: Smooths the pulsating output of reciprocating compressors. Gives a steady supply to the system.
- Reduces short-cycling: Provides a buffer of compressed air so the compressor doesn't start and stop frequently. Reduces motor wear and energy waste.
- Stores peak demand: Stores compressed air for short peak demands that exceed compressor capacity. Prevents pressure drop during high-demand events.
- Removes moisture: As air cools in the receiver, moisture condenses and is drained. Acts as a preliminary moisture separator.
- Settles contaminants: Large particles and oil droplets settle in the receiver, reducing load on downstream filters.
Sizing
The general rule for receiver sizing: receiver volume (litres) = compressor FAD (L/s) x 8 to 10. For example, a compressor delivering 500 L/s would need a receiver of 4,000 to 5,000 litres.
For systems with variable demand, size the receiver to handle peak demand events. Calculate the additional air needed during the peak (excess demand x duration), and size the receiver so it can supply this without dropping below minimum acceptable pressure.
Quick sizing formula
Receiver volume (L) = (Compressor FAD (L/s) x (unload pressure - load pressure) x time between starts) / (atmospheric pressure x number of starts per hour). For most applications, a simpler rule is: receiver volume = 10% of compressor FAD per bar of working pressure, in litres.
Installation
- Location: Install downstream of the compressor and aftercooler, before the dryer. This allows the receiver to cool the air and condense moisture before the dryer.
- Orientation: Vertical tanks save floor space and drain condensate more effectively than horizontal tanks.
- Drain valve: Install an automatic drain valve at the lowest point. Manual drains require daily attention and are often neglected.
- Safety relief valve: Must be installed on the receiver, sized for maximum compressor capacity. Test annually.
- Pressure gauge: Install a gauge visible from floor level. Verify accuracy annually.
- Isolation valve: Install a full-bore isolation valve between the compressor and receiver for maintenance.
Maintenance
- Drain condensate: Daily for manual drains. Check automatic drains weekly for proper operation.
- Test safety valve: Annually, lift the try lever to verify the valve is free. Recertify per local regulations.
- Inspect for corrosion: Annually, inspect the tank exterior and interior (if accessible) for rust and pitting. Ultrasonic thickness test if corrosion is suspected.
- Check pressure gauge: Verify accuracy annually. Replace if incorrect.
- Inspect supports and foundation: Verify the tank is properly supported and the foundation is sound.
Pressure vessels require certification
Air receiver tanks are pressure vessels. In Australia, they must comply with AS 1210 and be registered and inspected per state regulations. An uncertified or expired receiver is illegal and dangerous. Keep certification current. PlantLogica's compliance module can track inspection dates automatically.
Tip: If your compressor is short-cycling (starting and stopping frequently), the most likely cause is an undersized receiver. Increasing receiver size will reduce cycling, save energy, and extend compressor and motor life.