The content is as shown in the figure below

Is there a schematic diagram of the internal structure of the buffer tank? There are two possibilities: 1. The oil inlet extends downward inside the tank. The advantage of this is that the oil entering does not impact the oil surface, preventing the formation of emulsions. The upper part of the tank forms a gas chamber; during operation, pressure is applied, and it takes time to compress the air in the gas chamber to meet the required pressure. During shutdown, the oil inlet pipe of the tank is not equipped with a check valve; air pressure and siphoning effects within the pipe cause the oil to be pumped back into the oil storage tank. 2. The fuel has high volatility. When the operating interval is long, the liquid evaporates and turns into air. This situation is easy to judge; there are clear differences between summer and winter. The first estimate is that the design requires an air chamber to store energy and buffer pressure fluctuations within the tube. If it is not a requirement, a check valve can be installed at the oil inlet, and a vent valve can be installed in the buffer tank to solve the issue. The second type is the manual valve for import and export installations. Shut down.

First of all, thank you very much. The buffer tank is equipped with a vent valve, which is opened before starting the pump each time. It is estimated that the first scenario is less likely, mainly because it is not convenient to observe it at the moment. The oil we use is diesel, and the pipelines are highly airtight, so there is little possibility of evaporation. Currently, it is planned to install a check valve on the inlet pipe and a manual valve on the outlet pipe, so that the valves can be closed when the pump is stopped. Regardless of the outcome, I will reply with a post at that time.

There are no valves at the pump’s inlet and outlet, nor any check valves; after the pump stops operating, siphoning effects cause the oil in the self-priming tube to be drawn away. Install valves for import and export; simply close the valves immediately after stopping the pump. Adding a check valve is better.

If there are two pumps, run a pipeline from the outlet of each pump to the negative pressure tank in front of the other pump; in other words, one pump running will replenish the liquid in the tank of the other pump.

It is preliminarily assumed that siphon backflow occurred after the pump was stopped; it is recommended to try installing a check valve at the inlet

Adjust the return oil pipe to the buffer tank, and adjust the oil inlet port to the upper part of the buffer tank, and that’s it

It must have been siphoned back. One can try installing a valve at the higher point of the suction pipe; once oil is supplied, the valve can be opened to drain the liquid from the suction pipe. Drawing in air through the suction pipe is unsafe, so another safe gas can be used instead.

It’s my pleasure if it can help you.