Burnt bearing shells in D-type symmetric reciprocating compressors
Thread Content
The gas is associated gas from an oil field; the compressor features three stages of compression arranged in a D-shaped configuration, with the first stage having its own cylinder while the pistons of the second and third stages are connected in series. The suction pressure is 0.08 MPa, and the discharge pressure at the third stage is 2.2 MPa. After 480 hours of normal operation, an alarm is triggered if the oil pressure drops below a certain level (to 0.15 MPa), causing the machine to shut down automatically. Once the quality and level of the oil have been checked and found to be satisfactory, the machine can be restarted. It should run under no-load conditions first, after which the oil pump should be started; the pressure should then be normal (0.3 MPa). After that, the intake valve should be opened, after which the oil pressure will drop rapidly, and smoke will begin to come out of the crankcase vent holes (white smoke). Seeing this, the machine was shut down urgently for inspection of the crankcase; many metal residues were found at the bottom of the crankcase, which was attributed to wear of the bearing shells. The big ends of the two connecting rods were removed to examine the bearing shells – the bearing shell on the first shaft was in good condition, but when the big ends of the second and third shafts were removed, it was found that the bearing shells were misaligned, the crankshaft was worn, and the bearing shells on both the large and small ends had been damaged. An internal check showed that the oil quality was fine, there was no lack of oil, and the oil holes in the crankshaft were not blocked
The first mistake is shutting down the machine due to oil pressure issues; attempting to restart it blindly without first investigating the problem. Should the barring be performed again? When posting discussion topics, information such as the water and vapor flow within the equipment, the overall appearance of the equipment, and any damage should be included. It’s not appropriate to immediately seal the door and conclude that \"a self-check shows no issues with the oil quality, there’s no lack of oil, and the crankcase oil holes are not blocked.\" This is because a decrease in oil pressure can also be caused by factors such as damage to the oil seals at various points in the oil system, or breaks in the oil pipes. The correct approach is to restart the oil system and perform a crank test to check for any abnormalities in rotation. There is a difference in the supply pressure between the auxiliary oil pump and the main oil pump; it’s not possible to generalize based on one example. For reference.
It’s indeed incorrect to shut down the compressor due to low oil pressure and then restart it without first identifying the problem. The images showing wear are on the 3rd floor; the model is of the D-type, with 3-stage compression, where stage 1 cylinder operates independently while stages 2 and 3 operate in series. There were no issues with the crankshaft rotation. After restarting the oil pump and confirming that the oil pressure was normal, the compressor was started at the first inlet pressure level. Once the pressure reached the second inlet level, smoke began to come out of the breather holes in the crankcase, so the machine was stopped for inspection. Upon opening the crankcase and draining the oil, metal shavings were found at the bottom of the tank. When the big ends of the connecting rods in stages 2 and 3 were inspected, it was found that the bearing shells were misaligned
A low oil pressure definitely indicates a problem. Prove that a bearing shell has worn out and has a large clearance
Babbitt coating on bearing shells? These small tiles are generally standard components, and no additional shaping is required. It’s important to know the duration of use as well as the manufacturer. In the case of coated tiles, even a minor crack can, due to the presence of lubricant and stress, cause the crack to spread throughout the entire tile. With such levels of damage, it’s impossible to determine from which point the crack originated macroscopically; in such cases, tiles made of aluminum-magnesium alloy can be used as a replacement.