Interlock for steam compressor lubrication oil pump in catalytic cracking unit
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The current interlock mechanism is such that the standby pump starts when the pressure falls below 0.18 MPa, with the pressure monitoring point located on the lubricating oil line. In actual operation, a sudden stop of the main pump will cause the steam compressor to shut down as well. Vaguely I remember that the two lubrication pumps of the old steam compressors were interlocked via electrical circuits, with this control being carried out in the power distribution room; when the pump in use lost power, the backup pump would start up. Is that the case?
Regarding this interlock, I recall that during a training session I conducted some research on the topic: among 19 manufacturers’ 22 catalytic cracking units, 19 of them used a low oil pressure protection mechanism for their turbine oil pump interlocks, 2 used the motor operation signal as a basis for such interlocks, and one manufacturer adopted a design that combined both oil pressure and motor operation signals Since there have been no shutdown issues in our equipment due to the oil pressure design, the proposed suggestion is not considered! It is estimated that this problem will be more apparent in some cold regions in the north; that is, even after the oil pump starts operating, the speed at which the oil pressure rises is lower than the value set for the interlock mechanism, which in turn triggers the interlock action
Our lubricating oil pressure is 0.15 Mpa; the backup pump starts automatically when this pressure drops, and the pump stops operating when the pressure falls below 0.1 Mpa. There is also an automatic protection mechanism based on electrical signals, and both of these systems are in use. Our installation has not experienced any incidents where the oil pump stopped operating due to voltage fluctuations
“\"Self-protection is an electrical signal.\" What is self-protection?
The oil pump is equipped with a 1–2 second delay for protection. Large accumulators can maintain stable oil pressure.
1-2 second delay protection – what is it protecting?
In the northwest area, it’s manageable inside the factory buildings during winter; the oil temperature is controlled by oil heaters, and there are also interlock mechanisms in place when the oil temperature drops.
Are the oil pressure for stopping the chain and the oil pressure for starting the auxiliary pump monitored by the same pressure transmitter? Generally, in a chain shutdown, it is another 3-out-of-2 pressure selection in the oil circuit.
The pressure tapping points for increasing and decreasing size are separate; I went to the site to verify this back then!
Electrical self-protection: Our main and auxiliary pumps serve as backups for each other; when one electrical signal triggers a shutdown, the other starts automatically