How to switch the oil pump in a centrifugal compressor

1. The operator inside should monitor the lubricating oil pressure, disable the relevant interlocks, and inform the operator outside that it is safe to switch the lubricating oil pump. 2. The operator at the site should set the control lever of the standby pump to the manual position, open the return valve of the standby pump – it doesn’t need to be opened fully; about five or six turns is sufficient – and close the outlet valve of the standby pump. 3. On-site, the standby pump was rotated to check it; no abnormalities were found. The standby pump was started on-site, and after confirming that there were no issues with vibration or noise, the opening degree of the return valve was adjusted based on the outlet pressure of the standby pump, ensuring that this pressure was slightly higher than that of the pump in operation. Then one person closes the return valve while another opens the outlet valve; pay attention to the pressure at the pump’s outlet during this switching process, until both valves are fully open or fully closed. 4. Slowly open the return valve of the pump that was previously in operation; once a significant drop in pressure is observed, stop the pump immediately, then close the return valve and open the outlet valve. Set the control lever to the automatic position. 5. Notify the operator that the switch has been completed; once the lubricating oil pressure stabilizes, activate the associated interlocks.

The lubrication oil pumps of the engines here are generally not switched over: lol

Won’t do regular switching either? Why?

Our compressors are screw-type and are maintained by the manufacturer; those used in production are reciprocating type, without interlocks. The procedure involves inspection, turning the shaft, starting up, shutting down the other oil pump, and then closing the valve

It seems that we adjust things by opening the return valve of the operating pump and closing the return valve of the standby pump; the outlet valves of the two pumps do not move.

Most oil pumps are equipped with a low-pressure interlock for the auxiliary oil pump. A simple approach is to stop the pump that is currently in operation; the system’s safety features will then start the backup pump, after which the original pump can be switched off remotely to complete the transition. This method is not recommended for centrifugal compressors in operation, as it carries significant risks, and improper handling may lead to shutdown due to the interlock mechanism. The second recommendation involves operating according to the principle of switching between the primary and backup units. The specific procedure is as follows: first, bring the backup pump online, close completely the outlet valve of the backup pump, and open fully the return line. Start the backup pump; then slightly open the outlet valve of the backup pump. Once the pressure in the lubricating oil main line rises slightly, slightly open the return valve of the currently operating pump. After the pressure stabilizes, continue to close the return valve of the backup pump and open its outlet valve. Once the pressure is stable again, open the return valve of the operating pump and close its outlet valve. Repeat this process several times, and finally shut down the operating pump by closing its outlet valve completely and opening the return valve – it’s not necessary to open it fully. During the operation, the changes made must be gradual; the process needs to be carried out smoothly