The piston ring installed in the piston groove should be freely movable. Because the piston ring has interface gap, it has a certain tension. When pressing by hand, the outer circle of the piston ring should be completely buried in the groove and lower than the piston surface. 0.5~1.0 mm or so. The side clearance S of the piston ring in the piston groove should meet the manufacturer's design requirements. If there is no design value, it can be calculated according to the following formula: S=0.01h+H9/d9, h is the width of the piston ring, and the maximum allowable piston ring backlash Refer to Table 4.
As shown in Fig. 2, after the piston ring is installed in the cylinder, the elastic force of the piston ring causes a pre-compression force against the inner wall of the cylinder liner. The piston works on the gas by reciprocating motion, the pressure on the exhaust side is high, and the pressure on the suction side is low, so that a pressure difference is generated on both sides of the piston ring, and the end face of the piston ring is pushed to the side of the ring groove with low pressure, preventing gas along the ring. The groove end face leaks; the gas pressure acting on the inner surface of the ring is higher than the pressure of the gas acting on the outer surface of the ring. Under the pressure difference, the outer circumference of the piston ring is squeezed toward the inner working surface of the cylinder liner, preventing gas from flowing along the cylinder wall surface. Axial leakage. However, when the radial runout of the chrome plated steel rod is seriously exceeded, the outer surface of the piston ring and the inner wall of the cylinder, as well as the area of the piston ring and the end face of the piston groove become smaller, and even the piston ring is stuck in the groove, and cannot move freely, resulting in gas. When the thermal expansion gap is used, the throttling effect is deteriorated, and the internal cross gas is easily generated, so that the compressor discharge temperature becomes high and the process requirements cannot be met.