Centrifugal compressor lubrication system
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The company specializes in the production of methanol. There are two centrifugal compressors in the compression section, and they share one oil station. The lubricating oil, seal oil, and speed control oil are handled through a series-connected system: the lubricating oil is pressurized by a pump, and then divided into two streams – one of which goes to the high-level oil tank, entering from the middle of the tank and exiting from the bottom to supply the bearings of the machinery； The other portion enters the seal oil pump to continue increasing pressure, is then sent to the high-pressure seal oil tank, and subsequently enters the unit’s seal and speed control oil systems. The speed control oil inlet pipe is equipped with a check valve, and there is a pressure regulator afterward. Modification details: One of the lubricating oil pumps was originally a motor-driven centrifugal pump abroad; upon returning to China, it was replaced with a triple-screw pump that provides the same flow rate and head. Nothing else has been changed. Phenomenon: 1. During operation, after the main lubricating oil pump stopped working, the main engine also stopped operating after 3 seconds; by observing the oil pressure curve, it was found that the auxiliary lubricating oil pump took 26 seconds to compensate for the pressure loss. 2. After parking, during the static test of the system, once the auxiliary oil pump starts, it is sufficient to ensure that the pressure in the lubricating oil system rises again before it drops to the pressure level that triggers shutdown. Dear sea friends, welcome to help analyze the reason.
One of the reasons for this is to check whether the accumulator for the main pipeline oil pressure is in use, as this affects the oil pressure fluctuations when the standby pump starts up.
The main pipe does not have an accumulator, and as can be seen from the manufacturer’s original oil system diagram, none is present on site either.
Some screw pumps come equipped with a pressure regulation device. I’m not sure what kind of pump you have; please send a picture so I can take a look
Based on your description of the issue, it seems that after the main oil pump stops operating, the auxiliary oil pump takes too long to start up and raise the pressure. You can discuss this with the instrumentation team to find out whether the interlock value set for low oil pressure is too low, or if there are problems with the transmission of the instrument signals.
Phase-wise summary: 1. It is believed that the oil system does not have an accumulator; based on the existing compressor system, either there is no accumulator or there is a high-level oil tank (the height of which generates a pressure greater than the shutdown pressure, until the auxiliary pump restores the pressure)； 2. The low oil pressure required to start the auxiliary pump should be increased. I look forward to everyone continuing to offer good suggestions. Thank you.
1. Is the pressure corresponding to the interlocked start of the auxiliary oil pump the pump outlet pressure? Still the manager? In the case of the pump outlet, if the pressure drop is too rapid and the auxiliary oil pump cannot keep up, the probability of the machine shutting down due to interlock is high; perhaps a delay could help in such situations ； In the case of a main pump, the pressure drop is relatively slow; the auxiliary oil pump can quickly replenish the pressure, thereby ensuring that it remains above the shutdown threshold. 2. The starting cascade pressure can be set a bit higher to improve the pressure replenishment effect. 3. If possible, an accumulator should be considered for the lubricating oil main pipe.
1. As mentioned above, consider installing an accumulator on the main pipe. 2. Check whether there is any delay in the startup of the auxiliary oil pump. 3. The interlock pressure sampling point should be changed to the pump outlet pressure.
Pay attention, learn*. Why do the runtime and static tests show different times for the auxiliary oil pump to reach the set pressure? Looking forward to an answer
Was the original poster’s problem solved? Looking forward to the results after your renovation