A compressed air receiver is sized from three values: the compressor flow, the band between its cut-out and cut-in pressure, and the number of starts per hour it can handle. The usual formula is V = 0.25 × Q × p₀ / (f × Δp). For a 1,700 l/min screw compressor, with a 1 bar band and 60 cycles per hour, it gives about 430 L, so a standard 500 L receiver.
What the receiver does
- Stores air to supply demand peaks without waiting for the compressor.
- Spaces out starts. Without a reserve, the compressor starts and stops constantly, which wears the motor and contactors.
- Stabilises network pressure, so tools work at a steady pressure.
- Collects part of the water. The air slows down and cools inside: water settles at the bottom, where it must be drained.
A receiver does not make up for an undersized compressor. If demand exceeds the flow for a long time, the reserve empties and the pressure drops anyway. The receiver is also pressure equipment, with its own inspection rules: they are covered in our guide on air receiver regulations.
The formula, term by term
V = 0.25 × Q × p₀ / (f × Δp)
- V: receiver volume.
- Q: compressor flow, as free air delivery (FAD), read on its data sheet.
- p₀: atmospheric pressure, 1.013 bar. This is a standard physical value, at sea level.
- f: the maximum number of cycles, meaning starts, allowed per hour.
- Δp: the band between cut-out and cut-in pressure, in bar.
In practice, with Q in l/min and f in cycles per hour, the formula becomes: V (L) = 15 × Q × 1.013 / (f × Δp). The factor 15 comes from unit conversions (0.25 × 60).
Where does the 0.25 come from? The compressor fills the receiver with the surplus of its flow over demand, then the receiver empties at the rate of demand. The maths shows that cycles are closest together when the workshop uses exactly half the compressor's flow. The 0.25 matches this worst case: the calculated receiver keeps within the start limit whatever the demand.
Our air receiver size calculator applies this formula. Its default values are orders of magnitude: a 1 bar band and 60 cycles per hour for a screw compressor, 2 bar and 20 cycles for a piston compressor, which tolerates fewer starts.
Example 1, a standalone screw compressor
An S 110 delivers 1,700 l/min at 8 bar. It comes without a receiver. With a 1 bar band and 60 cycles per hour:
- 15 × 1,700 = 25,500
- 25,500 × 1.013 = 25,832
- 60 × 1 = 60
- 25,832 / 60 = 431 L, so a standard 500 L receiver.
If you narrow the band to 0.5 bar for steadier pressure, the volume doubles: 861 L, so 900 L. The pressure band is the setting that weighs most.
The same calculation for the S series, with a 1 bar band and 60 cycles per hour:
| Model | Flow (data sheet) | Calculated volume | Standard receiver |
|---|---|---|---|
| S 55 | 600 l/min at 8 bar | 152 L | 200 L |
| S 75 | 1,100 l/min at 8 bar | 279 L | 300 L |
| S 110 | 1,700 l/min at 8 bar | 431 L | 500 L |
| S 150 | 2,200 l/min at 8 bar | 558 L | 720 L |
| S 220 PM | 3,200 l/min at 10 bar | 811 L | 900 L |
Example 2, a piston compressor
The E 75 delivers 0.9 m³/min, or 900 l/min, with a built-in 180 L receiver. With a 2 bar band and 20 cycles per hour, the formula gives 15 × 900 × 1.013 / (20 × 2) = 342 L.
The formula can also be turned round to find the cycles a given receiver imposes: f = 15 × Q × 1.013 / (V × Δp). With the 180 L receiver: 15 × 900 × 1.013 / (180 × 2) = about 38 cycles per hour in the worst case.
That fits the intended use of a piston compressor: intermittent running, with breaks. If air is used for much of the day, a bigger receiver is not the first fix: it is a sign that a screw compressor is better suited.
Example 3, a 4-in-1 unit with built-in receiver
The K series compressors have a built-in receiver of 420 L (K 75) or 340 L (K 110 and K 150), along with the dryer and filtration. They run at variable speed: when demand falls, the motor slows down instead of stopping, and there are far fewer starts than the formula assumes. The receiver still handles peaks and the periods when demand falls below minimum speed. If your tools draw air in strong bursts, an extra receiver on the network is still useful.
When to go bigger
- Bursty demand or a paint station: choose a receiver above the calculated minimum.
- Planned expansion: an extra workstation in two years is best planned for now.
- A very strong peak at one workstation: a buffer receiver close to that point is sized on the length of the burst, as in our article on a buffer receiver for an optical sorter.
A larger receiver does not make you use more energy: it spaces out starts and stabilises pressure.
Choosing the receiver itself
- Pressure: its maximum pressure must exceed the pressure set on the compressor. For a 13 bar machine, take a 13 bar receiver.
- Inner protection: a galvanised receiver resists corrosion even when the incoming air is wet, with no dryer upstream. A painted steel receiver suits installations with a dryer before it.
- Position: as close to the compressor as possible, with a drain at the low point, and the dryer after the receiver.
Our compressed air receivers come as 1,000 L vertical units, at 10 or 13 bar, painted or galvanised, and as a horizontal version. Run the numbers with the air receiver size calculator, or let the configurator suggest a compressor, receiver and dryer package based on your tools. For an existing network, mention the receiver already in place in your quote request.