In oil/gas installations there are several units positioned at the sea floor or downhole in oil or gas wells, performing necessary tasks in order to control the production or to transport the hydrocarbons from the well to the sea surface or to land. Many of these units contain equipment being subject to wear and thus have to be repaired or replaced from time to time. These intervals depend on use and the conditions on location, and are therefore difficult to predict. The result is an occasional emergency stop in the production.