For a major company in the petrolchemical sector M.W.M. has developed a customised brake-cluch unit, composed by a spring applied brake and an electromagnetic toothed clutch, which is installed on the actuators of underwater huge valves. This group, completely immerged in oil, has been initially tested in hyperbaric chambre at more than 100 bar and then installed underwater. Thanks to this group it’s possible to release the actuator from the valve and to hold it in safety position.