Four-cylinder air compressors

Four cylinders are found in two very different groups of machines. Large oil-lubricated pumps with 7.5 kW give over 800 l/min, while small four-cylinder machines up to 3 kW compress air without oil for laboratories and surgeries. What both groups share is that four smaller pistons run in balance and spread the heat.

#showmore#

Two groups of four-cylinder machines

Large oil-lubricated four-cylinder machines

Seven belt-driven machines with 7.5 kW and a 270 or 500 l tank, one also on a base frame. They include the cast-iron WALTER WK1500 with 1,100 l/min, the HWK1200 at 13 and 15 bar, the ABAC CA2 at 11 bar and the ATMOS Perfect 7,5T at 12.5 bar. The higher-pressure machines compress in two stages. The cast-iron WALTER machines are described in the range WALTER.

Small oil-free four-cylinder machines

Five oil-free direct-drive machines up to 3 kW: the ABAC Tech ATFS-3, for 230 or 400 V, and the dental Clean Air CLR-2,0, one of them with a dryer. Here, four cylinders let an oil-free machine supply 240 to 245 l/min at 1,400 rpm.

More cylinders, more air?

Not always. At 7.5 kW, four-cylinder machines give 814 to 1,100 l/min, but twin-cylinder machines of the same power give 510 to 1,170 l/min — what decides is the specific pump, speed and pressure, not the number of cylinders. At 3 kW the oil-free four-cylinder machines give 245 l/min, oil-lubricated twin-cylinder machines of the same power 316 to 426 l/min — here oil matters more than cylinders. Above all, four cylinders bring smoother running and a lower temperature, which you will appreciate on a machine that runs for much of the day.

When four cylinders, and when fewer

A large four-cylinder machine belongs in a workshop or production plant where the compressor runs for much of the day and around a thousand litres per minute are needed; with its higher pressure, the HWK1200 is also listed among 15 bar air compressors. Twin-cylinder machines are the most widespread design and you will find them under twin-cylinder air compressors, and cast-iron machines with three cylinders under three-cylinder air compressors. All types are in our overview of air compressors.

Frequently asked questions

Are there four-cylinder compressors for 230 V?

The small oil-free ones, yes — the ABAC Tech ATFS-3 and the Clean Air CLR-2,0 dental compressor. Large oil-lubricated four-cylinder machines need 400 V.

Do all four-cylinder compressors have two stages?

No. Two stages are found on the large oil-lubricated machines with higher pressure; the small oil-free four-cylinder machines compress in a single stage.

Where are oil-free four-cylinder machines used?

In surgeries, laboratories and food production, where the air must not contain oil. Clean Air CLR dental compressors are built for dental units, the ABAC Tech ATFS for industrial sites.

How much does a four-cylinder compressor weigh?

Small oil-free ones from 50 kg; large oil-lubricated ones on a 500 l tank weigh 320 to 390 kg — these belong in a fixed place in a compressor room.