About oil pumps

There are two scenarios: 1. One in use and one as backup； 2. The auxiliary oil pump operates before the main unit is started, while the main oil pump operates during startup; at the same time, the auxiliary oil pump stops.

The auxiliary oil pump is used for pre-lubrication before starting the machine. After the main oil pump unit starts operating, it is driven by the unit itself

I’m not sure what kind of large-scale equipment you use. In our company, the installation of oil pumps for large-scale units is done in two ways: first, two lubricating oil pumps are installed at the lubricating oil station; second, one oil pump is installed at the lubricating oil station, with the lubricating oil pump inside the unit being driven by gear transmission or sharing a shaft with the main engine. In the first case, where two lubricating oil pumps are installed at the station, there are differences between these two pumps. For our company’s steam turbines, centrifugal compressors, main fans, and backup main fans, the oil pump models are the same, and they are both placed above or beside the oil tank, with one pump in operation and the other as a backup, controlled by interlocks. Before the unit starts up, the main oil pump begins to supply oil; once the unit is running, the main oil pump continues to operate. When the pressure in the main oil inlet line exceeds 3 kilograms, the auxiliary oil pump remains in standby mode, while it automatically starts up when the oil pressure drops below 1.5 kilograms. Second, an oil pump is installed at the lubricating oil station; within the unit equipment, there are oil pumps that use gear drives or share a shaft with the main engine. These are the differences between the two types of oil pumps. Our company’s large reciprocating compressors and centrifugal booster fans fall into this category. The oil pump models are different: one is placed on or next to the lubricating oil tank in the oil supply station, while the main oil pump of the reciprocating compressor is located at the front end of the crankshaft and is driven by gears on the crankshaft; this pump is also known as an end-cap oil pump. The auxiliary oil pump of the centrifugal pressure booster fan is located above the tank in the oil station, while the main oil pump is driven by gears on the speed increaser of the booster fan. Before starting up, the auxiliary oil pump at the fuel station operates first; once the unit is started, the main oil pump also starts running simultaneously. The auxiliary oil pump stops when the oil pressure reaches above 3 kilograms, and it automatically restarts when the oil pressure drops to 1.5 kilograms. In short, one pump is in operation at a time, with the other one starting up when the oil pressure drops, so as to ensure that the unit has an adequate supply of lubricating oil

Let me be more specific. There is one reciprocating compressor and two lubrication oil pumps, and these two lubrication oil pumps are divided into a main oil pump and an auxiliary oil pump. That’s what I’m asking: since both are lubrication oil pumps, why are they separated into a main oil pump and an auxiliary oil pump?

Actually, the third floor has already provided a very detailed answer. Regarding your addition regarding the fourth floor, the explanation is as follows: There are two scenarios: 1. If the two lubricating oil pumps are identical in terms of specifications and model, then it is possible to change their definitions periodically. In other words, after three months or some time, the original main oil pump is replaced with the auxiliary oil pump, and the auxiliary oil pump is then changed to the main oil pump. The control logic remains unchanged ； 2. If the two lubricating oil pumps consist of one shaft-mounted pump and one electric pump, then undoubtedly the shaft-mounted pump is the main pump, while the electric pump is the auxiliary pump (in large units, there is also a DC-driven electric pump). Electric pumps do not only perform pre-lubrication during startup; for certain models of units, the auxiliary oil pump also runs periodically for about 15 minutes even when the unit is in standby mode. In one sentence, the fundamental purpose of defining the main and auxiliary oil pumps is for logical control.

There is no difference; one is in use and the other is as a backup, with interlocking functionality. When the oil pressure drops, the backup pump starts up to ensure a continuous supply of lubricant.

The main oil pump, also known as the shaft-mounted pump, is driven by the main shaft (the large gear shaft), while the auxiliary oil pump is driven by a separate motor. After the machine starts operating, the auxiliary oil pump shuts down after a delay, and the main oil pump begins to supply oil. In cases of failure of the main pump, low oil supply pressure, or when the machine stops, the auxiliary oil pump takes over to supply oil~~

The equipment in question falls under the first category, right? The auxiliary oil pump, as the name suggests, is a pump that provides assistance; it assists the main oil pump. What I mentioned above is that it starts on its own when the oil pressure is low; it serves as a backup to the main oil pump to ensure an adequate supply of lubricating oil while the unit is operating. I mentioned something less earlier: when the main oil pump fails and needs to be repaired, compression is still in operation. If there is only one main oil pump and no auxiliary oil pump, the unit must be shut down before the main oil pump can be repaired. However, with an auxiliary oil pump, even if the main oil pump fails, activating the auxiliary oil pump allows the unit to continue operating normally, thus avoiding disruptions to production or any short-term fluctuations as a result of shutting down the unit. Under normal circumstances, once the low oil pressure interlock is set up, it becomes clear which pump is the main oil pump and which one is the auxiliary oil pump. Once the compressor starts operating, the interlock remains active, and the designated main oil pump continues to run. If there is no distinction between a main pump and an auxiliary pump, with one pump being used today and another one tomorrow, then the low oil pressure interlock would need to be adjusted repeatedly; therefore, it is necessary to have a main oil pump and an auxiliary oil pump.

This post was last edited by space ★ Xuan on 2016-6-16 11:13. Hehe, the person above has explained all the basic operational relationships clearly. The two oil pumps are referred to as the main oil pump and the auxiliary oil pump; this is simply a way of making a distinction between them. There is no difference; all the functional parameters of the pumps are the same. Before starting up, the pump that is in operation is the main pump, while the one that serves as a backup is the auxiliary pump. There is essentially no difference. Just like our usual A and B pumps – there’s a primary negative one and a secondary negative one, but I don’t think so; the A and B specified here serve the same purpose as the primary and secondary ones. It’s just that these main and auxiliary oil pumps are designed to start each other automatically in a logical manner. The degree of automation is higher.

What do you mean by this chain? Why change it? Surely, if the original auxiliary oil pump is operating and the main oil pump serves as a backup pump, it should start automatically when the oil pressure drops, right?