English to Italian Tech/Engineering Energy / Power Generation

We are dealing with lubrication system ( gas turbine). The phrase Under normal operating conditions oil is provided to the system by one of two main AC motor driven centrifugal pumps. The selection of LEAD AND LAG PUMPS is made by the oeprator through the turbine control system prior to start up. By alternating the LEAD/LAG pump selection the operating hours can be equalized.

I found a picture that might help at the following link:
http://www.iciprocess.com/products/wastewater.htm
Grazie