Low oil pressure interlock trip
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Let’s discuss the situation where the vehicle shuts down due to low hydraulic pressure; even though the backup pump starts automatically, it still fails to prevent this issue. There is no leakage in the system, no misoperations by anyone; the level of the liquid in the tank is fine, and the pump is also working properly. I think it might be due to false values, or problems with the feedback signals received by the DCS, or issues with the output signals. Please make it clear.
The value of the standby pump is too close to the low-low interlock value, or the oil pressure becomes too low due to an excessively long start-up time for the standby pump
Our oil pumps have had this problem as well. Reduce the low-low interlock value of the oil pump, and at the same time decrease the start-up delay time of the standby oil pump.
The question is: what causes low oil pressure? The system isn’t leaking, and the oil pump is working properly – so what could be the cause?
Yes, let’s first analyze the reasons. Thank you all for your effort
The drop in oil pressure usually occurs gradually; when it reaches the low alarm level, the backup pump starts automatically. There are two possible outcomes: either the oil pressure returns to normal, or the system shuts down due to the low-pressure interlock. If the latter occurs, measures can only be taken at the interlock level, such as conducting tests to raise the low-pressure alarm threshold for the automatic start of the standby pump, and using signals related to the operation of the main pump as well as its current level as conditions for the automatic start of the standby pump.
The above view is inappropriate; if you change the LL interlock value of the oil pump, our operation and maintenance staff do not have the necessary qualifications. Opinions from the compressor manufacturer are needed. Changing the LL value like this is very risky!
Low oil pressure interlock fault: 1. Compare the readings on the field instruments with those in the control room to determine whether issues such as faulty instrument probes or transmitters are causing the interlock shutdown. 2. If there are no problems with the instrument contacts, it may be that the backflow valve behind the pump (if present) or the temperature control valve is leaking, resulting in insufficient oil pressure
Why does the backup pump start up while the compressor shuts down due to interlock? Let’s analyze it. The compressor shuts down due to a failure in one of the oil pumps or power fluctuations, which cause the lubricating oil pressure of the compressor to drop to the interlock level, thereby triggering the shutdown signal. The conditions for starting the standby pump of a compressor are as follows: 1. The operation signal of the main pump disappears; 2. The lubricating oil pressure reaches the L value; 3. A delay of 3–5 seconds is applied. Under normal circumstances, it takes about 15 seconds from the disappearance of the main pump’s signal to the start of the standby pump. Causes compressor shutdown: The main reason is delayed start-up of the standby pump; an electrical inspection is recommended.
Generally, when the oil pressure drops and the system shuts down, there should be an alarm signal first. If the filter is fine and the oil pressure drops suddenly, it’s likely a false reading