Air receivers and storage tanks

The usual rule for a fixed speed machine is somewhere between six and ten litres of storage for every litre per second the compressor delivers — so a machine giving 50 l/s wants between 300 and 500 litres as a minimum, and more if the demand is peaky.

The real test is starts per hour. Most motors in this class are happy with six to ten starts an hour and unhappy above about twenty. If your machine is cycling more than that, the receiver is too small and adding one is cheaper than anything else you could do.

A variable speed machine needs less storage for cycling, because it does not cycle, but it still needs storage for peaks and for separation. The common mistake is assuming a VSD means no receiver.

Where the demand has a large short peak — a big blow off, a cleaning cycle, a burst of tools — a separate receiver close to that demand is worth more than the same volume back at the compressor.

A receiver is a pressure vessel and in every country we trade in it is subject to periodic inspection. Which authority, at what interval and to what standard varies, and we will tell you what applies where the vessel is going.

Vessels are supplied with their material certificates and their test records. Keeping those together with the machine matters more than people expect — an inspector who cannot see the documents will often fail a vessel that is perfectly sound.

Material matters for the same reason. Q235-B covers general duty, Q345R is used where the pressure or the size demands it, and S30408 stainless is specified where the air is in contact with food, pharmaceutical or medical processes. The table below states which material each build uses rather than leaving it to be asked.