The compressor crosshead keeps burning out!
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The compressor oil pressure is 0.45 MPa, the vibration level is 4.6 mm/s, and all other parameters are normal.
Additional information: Compressor No. 1 completed its 8,000-hour maintenance in September and has since run for 1,300 hours; Compressor No. 2 underwent major repairs in August 2018 and has accumulated over 6,000 hours of operation； Unit 3# has just completed its major overhaul and has now run for 1,400 hours since the overhaul. The lubricating oil for Units 1# and 3# has been newly replaced, while that for Unit 2# has not been replaced. The compressor features two-stage compression, and the crossheads that fail are all those in the first stage.
First, some issues need to be clarified. 1. Are some of the installation requirements for maintenance met (equipment installation manual)? ； 2. Was the addition of lubricating oil carried out in accordance with the specified procedures? It is necessary to use test data to determine whether the quality of the oil in the tank is satisfactory ； 3. Has the connecting rod bearing been overhauled, and is the bearing in good condition? Please give these three options a try.
Were all the values normal during the last maintenance? Crosshead clearance, piston rod play, etc. It seems like it wasn’t burned without any oil. . Has the oil pipe flange above been modified, with a blind plate added or blocked? Which has more severe damage, the upper tiles or the lower tiles? Is the stressed surface heavier?
Do all 3 units have the same problem? 1. If it’s the case in both situations, check the process parameters to see if there have been any significant changes that have resulted in an insufficient reverse angle of the crosshead, thereby causing damage to the small-end bearings. 2. Check the oil quality. Installation record. If only one machine is having problems, 1. Focus on checking the installation records and use the process of elimination to identify the issue. In summary, reciprocating machines have many components, but when a problem occurs, each one must be ruled out one by one. The burning of the small-end tiles is directly caused by poor lubrication. There are many reasons for poor lubrication.
Requirements for describing equipment repairs must be in numerical form. Terms such as good, bad, normal, no problem, etc., are generally not allowed in the records. Because these words can lead to one-sided misunderstandings. There is more data on the compressor, and the failure symptoms are quite alarming.
All three have the same problem. Burnout of the primary crosshead. The process parameters of the compressors are fine; calculations show that the reverse angles are within acceptable limits. There is Mobil Jet 412 available for use, and both compressors have had their lubricants replaced recently. One compressor has been in use for over 1,000 hours, while the other has been in use for 6,000 hours. Unit 1# underwent an 8,000-hour maintenance in September, Unit 3# had a major overhaul and has operated for 1,300 hours each; Unit 2# has not undergone any maintenance and is used as a backup.
The maintenance is carried out in accordance with the user manual; the maintenance provider is the manufacturer, and all inspection and adjustment data meet the requirements specified in the manual. The lubricant is from a brand designed for long-term use, and its quality has passed testing. There are 5 other units in the plant as well; they all use the same lubricating oil, and they are all maintained by the same maintenance team. The connecting rod crosshead bushing was inspected in September, and the readings met the requirements specified in the manual.
The lubricant for the crosshead slideways is supplied to the upper and lower slideways via the lubrication lines from the crankshaft’s main oil passage. Before each startup, maintenance personnel manually pump in the lubricant first, and only after confirming that lubrication is available is the machine started up.
There is a large amount of data, so it isn’t listed one by one. After verifying the compressor’s operating parameters, the pressure and temperature at the inlet and outlet of the medium were consistent with those during normal operation, showing no fluctuations; the current of the drive motor and the temperature of each phase winding were also within normal ranges. The compressor vibration level is 1.2 mm/s during normal operation; in the event of a fault, it is 4.6 mm/s for unit #3, 2.4 mm/s for unit #1, and 1.8 mm/s for unit #2 – all of these values are below the alarm threshold of 7.1 mm/s. During the maintenance in September for Units 1# and 3#, the relevant parameters were checked; the clearance of the crosshead slideway was 25 microns, which meets the requirements specified in the manual.