Familiarise with High Pressure Terminology

Compressor Dictionary – P

Piston and Piston Rings

Air is compressed in several stages.

According to Boyle's Law, the product of pressure and volume (P × V) stays the same, whatever the pressure (allowing for potential gas leakages). This means that the piston displacement is lower for the higher compressor stages.

Sealing high pressure pistons is problematic. Therefore, BAUER's patented free piston is employed. The power transfer is achieved through a special guiding piston with a large diameter. The actual compression occurs by means of a small diameter piston integrated in the guidance piston.

The free piston is a patented development by BAUER KOMPRESSOREN. The compression and the guiding pistons are not connected. The movable compression piston runs along a steel cylinder line. Lateral forces and the resulting wear are minimised.

The free piston causes the typical hammering sound when starting the compressor. The compression and guiding piston collide during the backstroke because the compressed air in the final stage thrusts the compression piston back. This continues until the pressure equalises in front and behind the compression piston. The sound also occurs, when the » condensate is drained and the pressure in the compressor drops.

If problems occur, compression and guiding pistons have to be both replaced.

The pistons compress the medium to a certain pressure. All but the final stage, which employs the free piston, are standard pistons that are equipped with piston rings:

1. Top piston ring
2. Nose piston ring
3. Oil retaining piston ring
4. Rectangular piston ring
5. Split piston ring

The piston rings will only work if the rings are assembled properly and in the correct order. To ensure optimal efficiency, low weight build and excellent thermal qualities, the maximum velocity of BAUER compressors are only 2 - 4 metres/second. For comparison, car engines move at 7 - 11 metres/second.

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