A first storage control device is provided with a virtual LU for showing a logical volume possessed by a second storage control device as if it were its own volume. Simple lockability and demountability are brought about by virtue of the plug means comprising a sealing plug for interaction with the sides of the passage opening, a retaining means, connected to the sealing plug, for interaction with a hook means connected to the passage, and a flexible resilient connecting element between the sealing plug and the retaining means. The reduction gearbox is driven by an intermediate shaft angled relative to the turbine output shaft.