Introduction to refrigeration air compressor oil

Thread Content

1. Rotary compressors: Each model of compressor has different requirements regarding lubricating oil. The function of the lubricating oil in a rotary compressor is to lubricate the blades that slide in and out during the compression process. Lubricating oil is also used as a seal between the blades and the frame, enabling gas compression. Products specified in ISO68-150 generally meet the viscosity requirements for rotary compressors. 2. Reciprocating refrigeration compressors – Reciprocating compressors offer a wide range of discharge pressure capabilities, from 1 bar g to 1000 bar g. Reciprocating compressors use oil to lubricate the cylinders, crankcase components, coils, pistons, valves, and loading rods. Crankcase components include crosshead bearings, crossheads, crosshead guides, and crank pins. Recent refrigeration applications have shown that ISO 15 lubricants with an operating viscosity of less than 10 cSt can provide adequate lubrication. However, the classic application of reciprocating compressors for processing and hydrocarbon gases, operating on the basis of gas molecular weight and flow pressure, is ISO68-680 products. In most reciprocating compressors, a single fluid is used as a lubricant for all components. Smaller reciprocating compressors use splashed lubrication. Larger units typically use an oil pump system to lubricate the components in the crankcase above. Some large equipment uses two different lubricants: one for the cylinders and another for other components that require lubrication. Since the cylinder lubricant must coexist with the gas, it must be compatible with the downward liquid flow process. Cylinder lubricants can be designed to provide lubrication under specific gases or operating conditions. 3. Screw refrigeration compressors: Screw compressors are typically used for compressing hydrocarbons and producing gases, with a pressure range of 1–25 bar g. They have many advantages, including improved compression efficiency, low outlet temperature, high reliability, and less maintenance due to their simple mechanical design. Oil for screw gas compressors must possess several functions. They lubricate the bearings, provide adequate sealing between the screw and the frame, remove heat generated during compression, flush out any particles in the compressor, and protect the system from corrosion. The lower viscosity limit is 10–20 cSt; this value is appropriate for the oil supply temperature to the bearings, while 5 cSt is required under outlet conditions to ensure proper sealing. The viscosity of the lubricating oil at the upper part depends on the ability to provide sufficient lubricating oil to the bearings. The typical upper viscosity limit is 30-100 cSt. Typically, ISO68-220 lubricants meet the viscosity requirements for screw compressors. The exact viscosity grade depends on the operating conditions and gas flow composition. Due to the closed-loop design of the system, the synthesized product is particularly suitable for screw compressors. Lubricating oil and compressed gas enter the separator. The separated oil passes through an oil cooler before returning to the compressor. During this process, the degradation of lubricating oil can lead to compressor problems such as bearing failures, inadequate sealing, or corrosion. In many applications, the use of synthetic compressor lubricants enables efficient hydrocarbon compression and gas production.