Lubricating oil pressure interlock

You can try setting the auto-start pressure higher, or check whether the auto-start time in the interlock logic is appropriate

What type of lubricating oil pump do you have? Generally, a sudden increase in pressure occurs. Could you provide more details about your situation? It’s necessary to identify the cause of this increase and then come up with targeted solutions

Regarding this issue, there are likely two reasons: one is that the interlock value for low lubricating oil pressure is set too low, and the other is that no test was conducted to switch between the main and auxiliary oil pumps during the pre-operational testing of the oil system. First, let’s discuss the issue of overly low interlock values. Conventionally, the pressure measurement point for the lubricating oil system is located at the highest point at the farthest end of the lubricating oil main pipe. If the aforementioned problem still occurs even when the measurement point is in this location, it can be concluded that the interlock value is too low. If it is not this position, then the difference between the actual position and the conventional position needs to be corrected. Next, let’s talk about the switching test. Before the unit is put into operation, a trial run of the oil system is carried out, during which this switching test is performed: when the main oil pump stops, the oil pressure will gradually drop. It is necessary to check whether the oil pressure at the time the auxiliary oil pump starts is equal to the set interlock value; if it is lower than this value, the interlock value needs to be increased (by adding the difference between the measured value and the interlock value), or it is necessary to check whether there are any elements in the control system’s startup circuit that can be adjusted to reduce the time required, as well as whether there are any elements in the electrical control circuit that can be adjusted in the same way. This is the approach we commonly use, for reference.

Generally, the interlock that starts a backup pump when oil pressure drops is an instrument-based interlock, which is suitable for situations where oil pressure decreases gradually. There is also an electrical interlock; what you mentioned seems to refer to the situation where the operating pump suddenly trips. Electrical interlocking is suitable for such situations: when the main pump motor fails and stops operating, or due to power fluctuations or intentional shutdowns, the backup pump will start immediately, without waiting for the oil pressure to drop to the level at which mechanical interlocking would trigger the startup of the backup pump. There is another scenario in which the self-acting control valve may not function and thus not be in use; in that case, the oil pressure is not automatically regulated via the bypass line.

Electrical interlocking can be used; the unit control system keeps track of the operating status of the main and backup pumps. When the main pump stops operating, the backup pump starts automatically, which is faster than starting it via oil pressure.

By adding appropriate accumulators to the lubricating oil system, it is possible to effectively slow down the decline in lubricating oil pressure that occurs when the oil pump stops operating, ensuring that the oil pressure does not drop to the interlock level when the backup oil pump starts up

In addition to the issues mentioned above, it is also possible to set a delay for the interlock action; this is usually set at 2 seconds, so that the interlock action does not occur once the oil pressure from the oil pump stabilizes. The 2-second setting is based on practical experience; on one hand, the oil supply is stabilized by an energy storage air bag, and the main pipeline is maintained by a high-level oil tank, so there will be no problems within 2 seconds before the radial oil pump starts operating.

First, verify whether the setting values for starting the pump in case of low oil pressure and shutting it down in case of very low oil pressure are too close to each other. The actual value can be determined by operating one of the two pumps automatically while the other is operated manually; by shutting down the manually operated pump, the automatically operated pump will start. Then, check the difference between this automatic start value and the lowest allowable oil pressure value. After repeating this verification process, the final setting values for starting the pump at low oil pressure and shutting it down at very low oil pressure can be determined by taking the maximum difference and adjusting it accordingly. Next, assess whether the design of the lubrication system is reasonable and whether the accumulator can meet the buffering requirements. Finally, check the electrical and instrumentation signals to ensure that there is no excessive delay, and consider replacing any relevant components if necessary

This post was last edited by ningsongsong6 on 2020-9-25 09:17: add a accumulator, set electrical interlocks, and adjust the interlock delay time