The overview of the sliding bearing of main oil pump of compressor, event history, treatment measures, cause analysis and some precautions.
01 Equipment Overview
Daniudi Gas Field Station X is located in Xiaohaotou Township, Yuyang District, Yulin City, with a designed natural gas treatment capacity of 50 × 108m3/a. It was completed and put into operation in December 2013, and its main function is to pressurize and export the natural gas after dehydration and de-hydrocarbon treatment.
The core equipment of the station is 11 domestic large electric driven reciprocating natural gas compressors. The model of 2 # natural gas compressor is 6RDSA-1/YZYKK710-6G, the power is 3000KW, and both of them are symmetrical balanced reciprocating piston compressors with six cylinders for one-stage compression. The design flow of a single machine is 151.44-525 × 104m3/d. The inlet pressure is 1.70-4.50MPa, the exhaust pressure is 4.85-6.00MPa, and the lubricating oil pressure is 0.35-0.42MPa.
According to statistics, the main oil pump of 6RDSA type unit in the station has been damaged for 24 times, among which 5 #, 6 # and 7 # compressors are the most prominent, with the shortest interval of oil pump damage of 1200 hours.
02 Event history
On November 5, 2018, the lubricating oil of 2 # compressor was sampled and tested according to the operating time of the compressor. The test results showed that the copper content was up to 15.610ppm, exceeding the standard of copper content in the oil (see Fig. 1). The status analysis of the unit oil pressure and other parameters showed that no abnormal conditions were found. Switch over the unit for inspection. It is found that the sliding bearing of the main shaft of the main oil pump is damaged, the end cover is severely worn and discolored at high temperature (see Fig. 2). After replacing the main oil pump, check that all parameters are normal, and start the machine for trial operation. The operation is normal.
03 Treatment measures
1. Switch the unit for operation.
2. Open the compressor body and check the operating parts of the unit. No abnormality is found. The measured clearance of each part is within the normal range.
3. The main oil pump of the compressor was inspected, and it was found that the sliding bearing of the main oil pump was damaged and the bearing end cap was severely worn.
4. Clean the oil pool and oil passage of the engine body. Replace the main oil pump of the compressor, replace the lubricating oil and oil filter, and the start-up and test run are normal.
04 Cause Analysis
1. Direct cause
The sliding bearing lubrication of the main oil pump of this model has design defects, which are prone to seizure and detachment of the shaft, accelerating bearing wear, causing excessive copper element in lubricating oil and bearing damage.
2. Indirect causes
2.1 The sliding bearing of the main oil pump was damaged due to the unqualified quality of the sliding bearing of the main oil pump, and the wear of the sliding bearing was aggravated due to thermal expansion and insufficient lubrication during the operation of the compressor.
2.2 The sliding bearing of the main oil pump is stuck, and the high temperature of friction causes the high temperature discoloration of the bearing end cover.
2.3 The state detection of compressor operation parameters is not in place in daily operation.
Fig. 1. Lubricant Monitoring Report
Fig. 2. The sliding bearing is damaged
05 Precautions
1. Type III main oil pump is used to lengthen the width and diameter of sliding bearing and reduce the specific pressure of bearing; The shaft is provided with an oblique oil intake hole to guide the lubricating oil of the pressure chamber into the bearing, so as to enhance the bearing lubrication and improve the service life of the bearing. The gear shaft is precision machined to reduce the surface roughness of the gear through grinding.
2. The main oil pump shall be inspected in strict accordance with the quality control requirements.
3. Do a good job of lubricating oil pressure monitoring, and stop the machine for inspection in case of abnormal oil pressure.
4. Regularly inspect the compressor oil sample, and analyze and apply the lubricating oil sample inspection results.
More about EPEN Metallic Sliding bearings：
Sliding friction occurs when sliding bearing works. The rolling friction force mainly depends on the manufacturing precision. The friction force of sliding bearing mainly depends on the material of sliding surface. The general working surface of sliding bearing has self-lubrication function; Sliding bearings are divided into non-metallic sliding bearings and metal sliding bearings according to materials.
Three layer composite bearing is the most widely used metal sliding bearing at present. This kind of bearing generally uses carbon steel plate as the base plate. Through sintering technology, a layer of spherical copper powder is sintered on the steel plate, and then a layer of PTFE lubricant of about 0.03mm is sintered on the copper powder layer. The main function of the middle layer of spherical copper powder is to enhance the bonding strength between the steel plate and PTFE. Of course, it also plays a certain role in carrying and lubricating when working.
