The issue of switching screw pumps!
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Our workshop’s fuel oil system uses screw pumps; when the main pump fails, we switch to the backup pump. During this switching process, the pressure in the fuel oil system fluctuates significantly. I would appreciate it if someone could advise me on how to switch the screw pumps properly!
Under normal conditions, the pressure of a screw pump remains stable. However, its operation requires that both the inlet and outlet valves be fully open at startup. In the absence of any control mechanisms, pressure fluctuations can occur during the switching process; therefore, it is recommended to add a bypass line from the pump outlet to the tank. When starting the standby pump, first open fully the bypass valve leading to the return tank, and then proceed with the relevant switching operations while paying attention to pressure, so as to prevent excessive fluctuations during the process. Additionally, if the pump has a interlocked start function, it is sufficient to keep the bypass valve for the standby pump’s return tank closed under normal conditions
Yes, screw pumps generally should have a return line. Before starting the pump, the return line is turned on first; once the pump is operating properly, the outlet valve is gradually opened while the return line is closed
The screw pump is also a positive-displacement pump, and its switching process is similar to that of a piston pump. To prevent fluctuations in the system, a secondary line is necessary; it is this secondary line that enables adjustment
:Loveliness: We use screw pumps. One in use, one as backup. All have export return lines. To minimize fluctuations in the outlet pressure, you need to fully open the inlet and outlet valves of the standby pump, as well as the outlet return line; then slowly open the outlet return line of the pump that is currently in use, but not too much. At that point, start the standby pump. After normal operation, slowly close the outlet return line of the standby pump, and then shut down the pump.
I didn’t realize that using a screw pump could be so complicated.
The return line at the exit of our workshop is connected to the main pipes at the outlets of the two pumps. According to what was said upstairs, this design seems incorrect; should there not be a separate return line for both the main pump and the backup pump?
The outlet return line should be connected to the inlet pipeline (before the pump), and this line is used to control the outlet pressure and flow rate
Each pump has its own return line; operate slowly, and you’ll get the hang of it after a few attempts