The compressor shuts down unexpectedly
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This post was last edited by chensf123 on 2017-1-29 at 10:57. Just before the long Spring Festival holiday, the air compressor suddenly stopped working. The initial display shows a trip due to the interlock action caused by low quick-shut oil pressure. After the interlock is reset, it is not possible to generate the quick-shut oil pressure. Upon checking the stop solenoid circuit, it was found that regardless of whether the power terminal fuse was open or closed, there was 24VDC with respect to ground, and the AC component also had a voltage of several dozen volts. I was completely puzzled; after taking multiple voltage measurements with respect to ground, turning off the fuse and taking measurements again showed that everything was normal (no voltage with respect to ground). After the interlock is reset, oil pressure is established and operation proceeds normally. It is suspected to be caused by electromagnetic interference; after repeated ground measurements and static discharge, it returned to normal.
Check the system’s grounding condition as well as whether there is proper grounding in case of a single-point ground fault; it feels so unfair when such things happen
Although I can’t understand the diagram, I think it’s a sensor contact issue. We have had this phenomenon here.
Was there thunder or any other large machinery starting up at the time of the jump?
This has happened a few times here as well; we replaced the parking solenoid valve with one that operates on 220V
We organized an accident analysis, and I would like to share with you the minutes of that meeting that I prepared: At 7:18 on January 26, 2017, Compressor No. 05 in the air separation unit stopped operating due to an interlock shutdown triggered by low quick-shut oil pressure； The quick-shut oil pressure cannot be established after the interlock is reset. Upon inspection by the instrumentation team, it was confirmed that the supply voltage of 24VDC to the shutdown solenoid valves SV1121 and SV1122 was normal. Even after removing the fuse for SV1122, a voltage of 23VDC was still measured at the solenoid valve’s terminal block. After multiple repeated measurements, the voltage dropped to 0VDC, and the SV1122 fuse burned out during the inspection. After replacing the SV1122 fuse and terminal blocks, a rapid shut-off oil pressure could be established, and the compressor started operating normally at 12:30 on January 26, 2017. Instrument and electrical professionals analyzed that the cause of this trip was that the power cable of the stop solenoid SV1122 was relatively long, about 500 meters in length, with a cable diameter of 1.5 mm2, resulting in high line resistance. Electromagnetic interference in the power supply circuit causes a decrease in the voltage supplied to the solenoid valve; as a result of this voltage drop, the magnetic force generated by the solenoid coil is not sufficient to overcome the load, leading to low oil pressure for rapid shutdown and thus machine shutdown. And after the fuse is disconnected, there is still a voltage at the output terminal of SV1122, which is an induced potential generated due to the inductive effect of the solenoid coil. The meeting classified this derailment as an instrument failure accident. Since the 05 air compressor has tripped due to an interlock caused by low quick-shut oil pressure on two occasions, in order to prevent such incidents from occurring again as a result of electromagnetic interference, the following measures will be taken for the 04 and 05 air compressors: 1: In the near future, the spare core of the power supply cable (multi-core cable) for the SV1122 solenoid valve of the 05 air compressor will be grounded at one end in the control room. 2: During the major overhaul, the SV1121 and SV1122 cables of compressors 04 and 05 will be installed as 2.5mm2 power cables, with separate conduit pipes used for their installation; the path for these conduit pipes will be determined in the near future ； Try to shorten the laying distance and choose a reasonable path. 3: During parking, change the fuses for SV1121 and SV1122 of compressors 04 and 05 from 1A to 1.5A. 4: Purchase SV1121 and SV1122 solenoid valve spare parts as soon as possible, and replace the SV1122 solenoid valve of compressor 05 during shutdown. 5: During the major overhaul, inspect the grounding of the unit’s control system and test the grounding resistance. 6: Clean and rectify similar instrument systems and equipment in various devices.
A similar issue occurred with our hydrogen feed pumps as well; it was caused by one of the signal cable shielding nets not being grounded. After re-grounding the shielding mesh at 100V relative to ground and checking all grounding connections, it has been operating safely for a year now
The solenoids of turbine emergency shutdown valves generally have high power and low coil resistance. Since multi-core cables are used, it is recommended to use two or three 1.5mm2 cores in parallel temporarily, which can reduce the circuit resistance. For Kangjisen’s ITCC parking, the reason for parking can be determined based on SOE data; there is no need to take screenshots of the program logic.