Issues related to the cost calculation for replacing the unit’s lubricating oil pump

1. The backup pump fails to reach full flow rate due to air accumulation in it; this is an operational issue. With a screw pump, even if air is not removed, the oil pressure will remain low for some time. Of course, screw pumps can self-priming, and it’s better when there is no air locking. 2. The oil systems of the units I have worked with are mostly screw pumps, and they perform very stably in operation. For procurement, parameters such as pressure and flow rate are required; it is recommended to discuss these matters with the compressor design manufacturer, as there are certain margin requirements in place. Additionally, the design of the control system may vary; centrifugal pumps can be regulated using outlet valves, while screw pumps are controlled through self-acting valves on the return flow. Regarding this issue, in one oil system I worked on that belonged to a foreigner, the check valve at the outlet of the standby pump had a small return hole; in addition, there was a check valve at the inlet of the standby pump. As a result, the standby pump (gear pump) kept rotating in reverse at a slow pace, which also ensured that the pipes at the inlet and outlet of the standby pump remained filled with liquid, thus allowing the pressure to reach the required level immediately after startup

What will be the consequences if the check valve at the auxiliary pump outlet does not have this hole?