What Size Air Receiver Do I Need for a CNC Workshop?
Receiver size should be selected around compressor output, usable pressure range, short-term demand, compressor control and the way your CNC machinery actually consumes air — not from motor kW or workshop size alone.
The Short Answer
There is no single receiver size that is automatically correct for a CNC workshop. The required volume depends on compressor output, the pressure band available for storage, the size and duration of demand peaks, compressor control method, pipework volume and how quickly the compressor can replenish the stored air.
A receiver can be extremely useful for tool changes, clamping, actuators and other short pneumatic events, but it does not create extra compressor capacity.
What an Air Receiver Actually Does
Why CNC Workshops Often Benefit From Storage
CNC and fabrication equipment can have very different air-demand profiles. Some machines use relatively steady low airflow while others have short, high-flow events.
- Pneumatic tool changers can create repeated short demand peaks.
- Clamps, cylinders and machine doors can require rapid air volume during movement.
- Multiple machines can initialise or actuate at the same time.
- Air guns and workshop tools can overlap with machine demand.
- Laser or process equipment can have specific pressure, flow and air-quality requirements set by the manufacturer.
- Production demand can vary by job, shift or operator pattern.
The Factors That Determine Receiver Size
| Factor | What to Establish | Why It Matters |
|---|---|---|
| Compressor airflow | Delivered airflow at the actual operating pressure | Determines how quickly stored air can be replenished. |
| Peak demand | CFM or l/min during the high-flow event | The difference between peak demand and compressor output determines how quickly storage is used. |
| Peak duration | How many seconds or minutes the higher demand lasts | A five-second tool-change peak needs very different storage from a five-minute process demand. |
| Pressure band | Maximum stored pressure and minimum acceptable machine pressure | The wider the usable pressure differential, the more usable air can be released from a given receiver volume. |
| Control method | Start/stop, load/unload, sequenced or VSD | Different controls need different system volume to avoid excessive cycling. |
| Pipework volume | Total effective network volume | The distribution system itself adds compressed-air storage. |
| Future demand | Planned machines, shifts or process changes | Future capacity should be considered without blindly oversizing the current system. |
Why “5.5 kW = 270L” Is Not a Sizing Formula
Broad pairings such as 5.5 kW with approximately 270 litres or 11 kW with approximately 500 litres can reflect common package configurations, but they should not be treated as an engineering sizing rule.
Two 11 kW compressors can require very different storage because one site may have steady demand while another has repeated high-flow peaks. Likewise, a smaller compressor can need substantial storage if the process has a short but intense air requirement.
Peak Demand: The Receiver's Most Useful Job
Imagine a CNC machine that normally uses modest airflow but occasionally actuates several pneumatic functions at once. For a few seconds, machine demand can exceed the compressor's instantaneous output.
A correctly sized local or central receiver can supply the difference during that short event and then recharge after the demand falls.
Fixed-Speed vs VSD: Storage Still Matters
Fixed-Speed Compressor
Receiver volume can increase the time between start/stop or load/unload control events. Too little system volume can cause rapid pressure movement and frequent cycling.
Variable-Speed Compressor
VSD adjusts output to match changing demand, but the system still needs adequate volume. If demand falls below the compressor's minimum stable output, storage can help prevent overly frequent cycling.
Wet Receiver or Dry Receiver?
Wet Receiver — Before the Dryer
Can provide storage, allow additional cooling and collect condensate before the air enters downstream treatment. Effective drainage is essential.
Dry Receiver — After the Dryer
Stores treated compressed air close to downstream demand. The dryer and upstream treatment system must be able to handle the compressor's actual flow profile.
Central vs Local Receivers
Any local receiver still needs suitable isolation, pressure rating, drainage, safety devices and statutory consideration. Adding another vessel does not remove the need for the compressor to replenish the stored air.
Vertical vs Horizontal Receivers
Vertical
- Uses less floor area for a given vessel capacity.
- Often suits compact plant rooms.
- Provides a convenient low point for condensate drainage.
- Can sit alongside floor-mounted compressors and dryers.
Horizontal
- Useful where height is restricted.
- Common beneath receiver-mounted piston compressors.
- Can form part of an integrated package.
- Needs adequate floor space and service access.
Real Installation: 500L Receiver at KUT Machinery
KUT Machinery, Kidderminster
Compressed Air Systems UK supplied and installed a complete Tanair system for KUT Machinery's showroom, supporting CNC laser cutting, press brake, deburring and sheet-metal fabrication equipment.
- Tanair TAN-S 22VSD compressor
- Up to approximately 113 CFM airflow
- 500-litre vertical air receiver
- TAN-RD-36 refrigeration dryer package
- High-efficiency filtration
- Condensate-management equipment
- Compressed-air distribution pipework
The 500-litre receiver was selected as part of the complete system — not because every 22 kW compressor automatically requires 500 litres.
Pressure Systems Safety Regulations: What CNC Workshops Need to Know
An air receiver stores significant energy under pressure. In UK workplaces, the Pressure Systems Safety Regulations 2000 can require a suitable Written Scheme of Examination and periodic examination by a competent person.
For example, a 500-litre receiver at normal industrial compressed-air pressures is far above that threshold. The exact scope of the Written Scheme, examination frequency and preparation measures are determined by a competent person.
- Use a receiver with a suitable pressure rating for the system.
- Provide correctly rated protective devices, including the required safety valve arrangement.
- Keep drains, isolation and pressure indication accessible.
- Protect the vessel against corrosion and physical damage.
- Do not weld, drill or modify a pressure vessel without suitable specialist assessment.
- Take damaged or heavily corroded vessels out of service pending competent assessment.
Receiver Drainage and Condensate
Wet receivers can collect significant condensate. The drainage method should be selected around operating hours, moisture load and the site's condensate-treatment arrangement.
- Manual drains rely on regular operator action.
- Timed drains can discharge air unnecessarily if poorly set.
- Zero-loss drains can reduce compressed-air loss where correctly selected and maintained.
- Oil-contaminated condensate should be managed using suitable treatment rather than discharged indiscriminately.
What Information Is Needed to Size the Receiver?
- Compressor make, model and delivered CFM
- Normal system pressure
- Minimum acceptable machine pressure
- Peak machine airflow
- Duration of the peak event
- Number of machines operating together
- Compressor control method
- Existing pipework size and approximate volume
- Dryer and filtration arrangement
- Planned future machinery
Related CNC & Compressed-Air Guidance
Air Receiver FAQs for CNC Workshops
What size air receiver do I need for a CNC workshop?
There is no universal size. Receiver capacity should be calculated from compressor output, peak airflow, peak duration, usable pressure range, compressor control method and the effective volume already present in the pipework.
Is 500 litres enough for an 11 kW compressor?
It may be, but motor kW does not determine receiver size. A 500-litre vessel is a common industrial capacity, but the correct choice depends on the actual demand and pressure profile.
Can a bigger receiver fix an undersized compressor?
No. It can support short peaks, but if average or sustained demand exceeds compressor output, pressure will eventually fall.
Does a VSD compressor still need an air receiver?
Usually yes. VSD changes compressor output to follow demand, but adequate system volume still supports control stability, short peak demand and operation when demand falls below the compressor's minimum stable output.
Should the receiver go before or after the dryer?
Either arrangement can be correct. A wet receiver before the dryer can provide cooling, condensate collection and upstream storage; a dry receiver after the dryer stores treated air close to the process. Some systems use both.
When does an air receiver need a Written Scheme of Examination?
HSE guidance identifies a compressed-air receiver and associated pipework as a typical system likely to require a Written Scheme where pressure in bar multiplied by receiver volume in litres is 250 bar-litres or more. A competent person should determine the exact scope and examination requirements.
Can I add a local receiver next to a CNC machine?
Yes, local storage can be useful for short high-flow events, but pressure rating, isolation, drainage, statutory inspection and the compressor's ability to recharge the receiver must all be considered.
How often should an air receiver be inspected?
The examination interval is specified in the Written Scheme of Examination by a competent person where PSSR applies. Do not rely on a universal annual or multi-year interval.
Need the Receiver Sized for Your CNC System?
Send us your compressor output, operating pressure, machine airflow, peak duration and number of simultaneous users. We can help assess the receiver, dryer, filtration and pipework as one complete compressed-air system.