When the compressor Copeland Discus type Piston is severely worn, the elasticity is weakened, or the clearance increases, it will cause the compressor's lubricating oil consumption to increase and the cooling capacity to decrease. During inspection, the Copeland Discus type Piston should be removed for visual inspection and a micrometer should be used for inspection. When one of the following situations occurs, it should be replaced with a new one.

(1) When the radial wear of Copeland Discus type Piston is more than 1mm;
(2) When the axial wear of Copeland Discus type Piston is above 0.2mm;
(3) When the axial clearance of Copeland Discus type Piston in the ring groove exceeds 0.06～0.1mm;
(4) When the total length of the fit gap between the Copeland Discus type Piston surface and the cylinder mirror surface exceeds 30% of the cylinder circumference;
(5) When the Copeland Discus type Piston is severely worn and loses its elasticity.

Because the temperature and lubrication conditions of the several rings on the Copeland Discus type Piston are different during the compressor operation, the first ring wears faster under normal circumstances, but because the thickness of the new and old rings is different, if only the first ring is replaced The ring is not good for the sealing of the cylinder, so it is best to replace all the rings on a piston together when changing the ring.