How to size an air receiver tank the right way
The air receiver buffers demand peaks, smooths pressure pulsation and limits how often the compressor cycles. This guide shows how to calculate the volume from air demand, the maximum number of motor starts per hour and compressor capacity - with formula, a worked example and a rule of thumb.
View air receiversWhat does the air receiver actually do?
The air receiver is the energy store of the system. It covers short demand peaks so the compressor need not restart immediately, dampens the pressure pulsation of piston compressors and gives condensate time to separate and drain off.
Above all, a sufficiently large receiver limits the cycling of the compressor. Every start stresses the motor and contactors; too many starts per hour cause overheating and wear. The usable stored volume comes from the pressure difference between cut-in and cut-out pressure.
- Buffer for short-term demand peaks.
- Damping of pressure pulsation from piston and screw compressors.
- Limiting motor cycles to roughly 10 to 20 per hour.
- Condensate separation as the air settles and cools.
- Reserve for power loss or emergency-stop functions.
How do you calculate the receiver volume?
The permitted number of cycles is decisive. The maximum occurs at about 50% load, which is why the factor 4 appears in the formula. The required volume is V = (Qc x Pa) / (4 x f x Delta p).
Worked example: a compressor delivers Qc = 60 m³/h, works with a switching difference Delta p = 2 bar and should perform at most f = 15 cycles per hour. Then V = (60 x 1.013) / (4 x 15 x 2) = 60.8 / 120 = 0.507 m³, about 500 litres. In practice you round up to the next standard size, here 500 l.
Match delivery and operating pressure to the demand of your system.
Read the guideRule of thumb and practical selection
Without exact demand data, use a rule of thumb: the receiver volume in litres should be roughly 5 to 10 times the delivery in m³/min; variable-speed screw compressors often need less. Bigger is usually better, because the compressor starts less often and runs more efficiently.
- Piston compressor in intermittent duty: size generously to reduce starts.
- Variable-speed screw compressor: a smaller receiver is fine thanks to stepless control.
- Highly fluctuating demand: add a buffer tank at the point of use.
- Always fit a safety valve, pressure gauge and automatic condensate drain.
- Set the vessel rated pressure above the cut-out pressure.
Frequently asked questions
Why is there a factor 4 in the formula?
The highest cycling frequency occurs at about 50% load, where run time and idle time are equal. The factor 4 accounts for this worst-case operating point when calculating the volume.
How many cycles per hour are permitted?
For typical compressor motors, roughly 10 to 20 starts per hour is a guide value depending on power. The exact figure is in the motor and compressor datasheet and should not be exceeded.
Is a larger receiver always better?
Usually yes, because it reduces the number of starts, smooths the pressure and creates reserve. Limits come from space, cost and the inspection duty under the Pressure Equipment Directive above certain volume and pressure values.
Does the receiver need periodic inspection?
Yes, as pressure equipment under 2014/68/EU air receivers are subject to periodic inspection by a competent person or notified body, depending on their classification.
Looking for the right air receiver?
We supply vertical and horizontal air receivers with safety valve, gauge and condensate drain - CE compliant to PED 2014/68/EU.
Pressure-equipment compliant
Receivers to PED 2014/68/EU and EN 286-1.
Correctly sized
Volume calculated from demand and cycling.
Fully equipped
Safety valve, gauge and condensate drain.
Expert advice
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