The piston-compressor

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The piston-compressor is a widely used compressor. It is based on the principle as described in chapter 2.

If the volume in the cylinder increases by moving the piston outwards, pressure in the cylinder will drop. The pressure in the cylinder will get less than atmospheric pressure. On the inlet valve we will get atmospheric pressure on one side and an underpressure on the other side. This makes the valve to go open and air from the atmosphere can enter the cylinder.

After the piston has fully moved outwards it will start to move back in. This causes pressure to rise in the cylinder. The inlet valve will close as soon as pressure in the cylinder reaches atmospheric pressure. The piston will continue to move inwards causing pressure to further rise. When pressure in the cylinder reaches the (high) pressure in the buffer the outlet valve will open and the pressurized air in the cylinder can escape into the buffer.

When the piston moves outwars again, volume will increase, pressure will drop, outlet valve will close, inlet valve will open, atmospheric air can enter, .

Used as single stage compressor the piston-compressor can create a pressure of about 10 bar. If higher pressures are needed then multi-stage is used where more pistons will be placed in series.