The compressor is put into operation less than 2 hours after stopping and replacing the three-stage inlet valve. There is abnormal noise in one cylinder. The main engine current rises from 135A to 140A. The noise in the cylinder tends to be louder and the vibration of the first cylinder intensifies. The compressor is put into operation less than 2 hours after stopping and replacing the three-stage inlet valve. There is abnormal noise in one cylinder. The main engine current rises from 135A to 140A. The noise in the cylinder tends to be louder and the vibration of the first cylinder intensifies. Inspection of piston found that: tetrafluoro support ring offset, 30 angle with piston center; three piston rings (material JT20-40B), one broken, the other two also trapped in the ring groove to become dead rings; piston ring groove was filled with molten aluminium sheet, supporting ring groove also has part of molten aluminium sheet; the upper part of the front half piston wear larger, from the end surface. When it reaches 6 mm depth, it is fan-shaped along the axis and terminates after about 200 mm. Because the wear part of the piston body is directly above the piston, it has no effect on the axial balance, so only the cylinder sink part is deburred; the front half piston face is roughly on the surface of C650 lathe, and the feed rate is about 1 mm, which mainly solves the deformation of the edge area caused by high temperature, so as to restore the axial balance of the piston body. The ribbon is perpendicular to the sliding surface, which is conducive to scraping oil and bringing out very thin oil film on the sliding surface. When the piston rod goes back, all the oil film is recovered due to the action of the rib angle of the sliding ring, thus the lubricating oil can not reach the cylinder and realize oil-free lubrication. On the other hand, the very thin oil film in the low-pressure side of the filler, which has a high viscosity, is not only difficult to enter the high-pressure cylinder end, but also has auxiliary sealing performance.

Oil-free lubrication compressor requires packing seal with certain elastic-plastic, follow-up, chemical stability, impermeability, self-lubrication and high temperature resistance. Therefore, the design of packing seal is very important to achieve oil-free lubrication. Secondly, the bypass valve and control pipe, pressure reducing valve and suction valve of the original air compressor are removed and plugged. The original main air duct is connected to the lower part of the main engine of the screw air compressor. Finally, a pipe and a ball valve are added to the main air duct (i.e. the lower part of the relief valve), and the left side of the drilling rig is placed at the outlet of the pipe, so that the ball valve can be opened first, then the load-relief push rod can be pushed and the ball valve can be closed after the air pressure rises. At the same time, it is convenient to observe the situation of oil carrying with the wind in the future.