Why is there also a check valve at the front end of the auxiliary oil pump? Is it necessary?

Does that mean this valve setting is unnecessary? ? Don’t worry; nowadays, designers also strive to do things better. It would be embarrassing if something went wrong with this, don’t you think?:) Just imagine: if the main pump is working properly but there is no check valve at the outlet of this auxiliary pump (which is likely a gear pump), then a pressure difference will arise between the pump’s outlet and inlet. The oil at the pump’s outlet will push the gear pump to rotate, causing the oil to flow back into the tank, which in turn will result in too low a pressure in the oil system. Let’s talk about the necessity of this setting: before the equipment starts up, lubricating oil must be supplied to all the lubrication points in order for the conditions for starting the equipment to be met. Once the equipment starts operating, the main shaft drives the main oil pump to gradually increase the pressure. When the pressure exceeds the preset threshold, the main oil pump shuts down automatically. At that point, the check valve also closes quickly due to the drop in pressure from the auxiliary pump, thereby ensuring the proper operation of the equipment. What if there is no check valve here? The oil will flow back quickly, causing the equipment to trip due to low oil pressure. Additionally, no other valves can be installed at this location for manual operation; it is believed that the speed at which operations can be carried out is not fast enough to keep up with that of the check valve. I hope this explains things clearly enough; it’s just for reference. Oh, the suggestion is “Is it necessary?” ”It’s best not to have such doubts, as they carry a critical tone. If it is the supervisor of the design engineer, the “Chief Engineer,” they can ask in this way. I’m not an engineer; if I were one, I wouldn’t answer you like this.

Bro, a one-way valve at the outlet is definitely necessary. I want to know why a check valve is also installed at the inlet, on the front end of the auxiliary oil pump; P

My elder brother is in the design field, right? It’s purely a technical discussion; the questions are asked without any emotional undertones. Please forgive any rudeness on my part! :handshake

I’m sorry, I misread the question. Can it be considered as double insurance; P. A check valve is installed in front of the pump; this is because the oil pump is usually placed above the oil level. When the pump stops, the oil in front of it flows back into the tank. The shaft seal operates under internal pressure, and if external pressure is applied, air will enter, which can cause air to get into the oil pump. Once the pump is activated in an emergency, air will be introduced into the oil system. So, a check valve needs to be installed.

Well, your analysis makes a lot of sense! However, the fuel tank is on the second floor, while the fuel pump is on the ground floor.

There are many differences between the design and actual use on site; for changes to settings like these, certain procedures are required, but usually no one bothers with them. You’re right; if there is pressure before the pump, this check valve doesn’t serve any purpose.

1. Is it just on the drawing? Is it really like this in practice? 2. It’s also possible that it was an error made during the design process; the inlet of the oil pump is usually a standard gate valve, and there isn’t much difference in the drawings, so perhaps it was accidentally included as a result of such an error? 3. The explanation given by Senior Shirai regarding air entering the oil pump inlet is overly far-fetched: in reality, the oil that reaches the oil pump inlet comes from the lubricating oil tank, and since the tank is a vessel at atmospheric pressure, it is essentially connected directly to the atmosphere. Moreover, the oil must pass through multiple filtration stages before reaching the oil pump inlet, so conditions that would allow air to enter the inlet do not exist.