What does the term “idle rotation” mean in the context of liquid pumps?

Idle operation of a liquid pump refers to the operation of a backup pump at low speed to serve as a backup and reduce energy consumption. When a normally operating pump experiences an emergency shutdown or requires maintenance, the idling pump is brought up to normal speed to maintain operational stability.

Rotation due to inertia after a power outage is also known as free rotation. The upstairs option is the correct one

In internally compressed air separation, those processes that require a continuous supply of internally compressed products demand that the liquid pump be configured as an online idling standby unit. During idle cold standby, the inlet and outlet valves of the standby pump are both open, while the return valve is set to a certain opening degree based on the operating conditions. When a fault occurs in a pump that is operating normally, the DCS automatically issues commands to increase the speed of the pump according to its speed-up curve, raising the pressure to the design value in a very short time, thereby ensuring uninterrupted supply of the liquid under compression. It is necessary to specify whether the pump should be able to operate in idling mode for standby purposes at the time of ordering, as idling operation requires additional bearing heaters, which is different from conventional pumps

In addition to idle operation in cold standby mode, there is another scenario: in some cases, for the purpose of protecting the equipment, an interlock command may be issued to put the liquid pump into idle operation, for example when the level of the main cooling liquid drops to a certain level

I’m a bit confused about the situation where the outlet valves are open. If the outlet pipelines of the two pumps are connected together, and one pump is operating normally while the other is running idly, wouldn’t this lead to pressure interference? I hope you can share your insights with me :)

If two pumps share one common outlet, then each pump’s outlet will be equipped with a check valve; as long as the check valves function properly, pressure crossover will not occur.

Let me ask Brother czdeyy again: then why not simply close the outlet valve? What if the check valve fails? I’m working at China Coal Yulin. I’m facing an issue with the oxygen pump outlet valve – either the flow direction is from high to low or from low to high. The valve’s design specifies a flow direction from high to low, but the flow diagram shows it installed in the reverse direction. I would appreciate some guidance

The senior moderator is right; if the outlet valve is closed, how can it be used as a backup? You can look up on your own the reasons for installing valves in the reverse direction – generally, it’s to prevent leaks. If the check valve is no longer functional, it needs to be replaced; there’s no other option.