English to Italian Tech/Engineering Engineering: Industrial separatore centrifugo

In addition to its primary role in the power transmission system, the bowl spindle also serves as:
pump for the closing water
supply pipe for the closing water
lubricator for spindle ball bearings
Closing water is pumped through the hollow spindle (B) to the discharge mechanism in the bowl.
For this purpose a ***pump sleeve*** (b4) is fitted in the lower end.

Thank you in advance!