First, the case background

One model of a chemical plant was the LS25S-350HHWC Sullair air compressor. In 2015, the oil change process was carried out. After the oil change, the lubrication of the equipment did not appear abnormal. In October 2016, the customer reported that the air compressor oil had thickened and a black gel was found in the fuel tank. It is hoped that the gel will be analyzed to understand its cause and source.

Second, the testing program

The infrared component analysis of the gum showed that the sample was a dimerized linoleic acid/glycol copolymer.

According to the detection results of the infrared spectrum, it is presumed that an alcohol substance may be mixed in the compressor. After communicating with the customer, it was learned that the oil originally used for the equipment was a brand-specific oil, which was replaced by other special oils in 2015. The first brand of special oil used was PAG (polyethylene glycol) synthetic oil, and the special oil used in 2015 was oil. The two were not compatible. After mixing, it reacted at high temperature to form a gel. . Since the oil at the bottom of the air compressor head is not involved in the circulation, it cannot be discharged. When the oil was changed in 2015, some of the synthetic oil used before 2015 was still left in the nose. This part of the oil reacted with the special oil added to the system at the high temperature of the machine head to produce dimerized linoleic acid/ Glycol copolymer "gel.

Third, case enlightenment

1. Lubrication should be reasonably selected for equipment lubrication. Compared with synthetic oils, mineral-type lubricating oils have poorer high-temperature oxidation resistance and are not suitable for use in equipment with higher temperature. They must be properly selected according to the on-site operating conditions of the machine and the product description of the lubricating oil.

2. When the equipment is subjected to oil change treatment, care should be taken to thoroughly clean the oil circuit, especially the position of the dead corner. If it is not possible to thoroughly clean, the oil mixing test should be carried out before the oil change, and the risk of oil change should be evaluated based on the test results.