Characteristics of reciprocating compressor lubrication

The lubrication system of a reciprocating compressor is divided into internal lubrication in direct contact with compressed gas and external lubrication in contact with compressed gas. The internal lubrication system mainly refers to the lubrication, sealing, anti-corrosion and anti-rust inside the cylinder; the external lubrication system refers to the lubrication and cooling of the moving parts, usually in large-capacity compressors, high-pressure compressors and cross-head compressors. The internal lubrication system and the external lubrication system are independent, using internal and external oils for their respective needs. In the small cross-headless compressor, the lubrication system of the moving parts doubles as the lubrication of the cylinder, and the internal and external oils are common.

The internal lubrication requirements of the reciprocating compressor cylinder have the following functions;

(1) reduce the wear of friction surfaces such as cylinders, pistons, piston rods and packing;

(2) Sealing of the compressed gas (between the piston ring and the cylinder wall);

(3) Anti-rust and anti-corrosion of each component.

After the internal lubricant completes the above mission, it is discharged together with the compressed gas, and at the same time, the exhaust valve is lubricated, and a part of the exhaust valve is discharged through the cooler, and the unseparated oil enters the pipeline in front of the gas storage tank and the pipe. Therefore, the internal lubrication of the reciprocating compressor is full-loss lubrication, and the internal lubrication of the cylinder has three methods: splash lubrication, oil absorption lubrication and pressure oil lubrication.

The external lubrication of the reciprocating compressor is the purpose of lubricating the moving mechanism. In addition to reducing the wear and friction power consumption of the friction surfaces of the moving parts and the crosshead guide rails, it also functions to cool the friction surface and take away the wear debris. . The main way of lubrication of the moving mechanism is pressure forced lubrication, which is characterized by sufficient oil quantity, sufficient lubrication, and can take away the heat and wear debris of the friction surface, so it is widely used by various compressors. In some micro compressors and some small compressors, splash lubrication is often used.

Reciprocating compressors require lubricants with the following properties:

(1) Appropriate viscosity. For compressors with independent internal and external lubrication systems, oils with different viscosities should be used. For general-purpose compressors for internal and external use, the analysis of lubricating oil manufacturers should be selected with internal oils with poor lubrication conditions. Viscosity is generally determined by the lubrication and sealing requirements between the cylinder and the piston ring, based on compression pressure, load and operating temperature. The choice of the viscosity of the lubricating oil in the external lubrication system of the reciprocating compressor is mainly to maintain the formation of the lubricating fluid of the bearing. Generally, the turbine oil or hydraulic oil with a viscosity grade of 32-100 is selected.

(2) Good thermal oxidation stability, and it is difficult to form carbon deposits at high temperatures.

(3) The tendency to generate carbon is small, and the generated carbon deposit is soft and easy to fall off. Generally, the deep refined base oil has a smaller carbon deposition tendency than the shallow refined base oil, and the low viscosity oil is smaller than the high viscosity oil, and the narrow fraction ratio is wider. The fraction is small, and the carbon of the naphthenic oil is softer than that of the paraffinic base oil.

(4) Good rust and corrosion resistance, due to moisture in the air, the moisture condensed by the compressed air causes corrosion to the cylinders, exhaust valves, etc.

(5) Good oil-water separation.