This invention relates to marine jet drive systems and, more particularly to marine jet drive systems which include or are retrofitted with a preloader for reducing cavitation. The invention also relates to such a preloader which may be retrofitted to a standard marine jet drive system. The invention further relates to a method for reducing cavitation during operation of a marine jet drive system. The preloader comprises a water propelling device mounted on a shaft and rotatable within an intake housing of a marine jet drive unit ahead of and in axial alignment with the eye of the jet drive pump impeller whereby the water propelling device causes water to be drawn from the intake housing into the pump such that the pump impeller is preloaded with water across the eye of the impeller cavitation is reduced.
Laying apparatus and method for cables, lines, conductors or suchlike. The apparatus comprises at least a hydraulic circuit provided with a variable delivery feed pump and with a motor connected to the feed pump in order to drive laying members for the cables and suchlike. The hydraulic circuit comprises detectors able to detect the value of pressure of the oil inside the hydraulic circuit and to compare it with a pre-determined pressure value, and valves connected to the detectors and able to reduce the delivery of the feed pump in the event that the pressure measured exceeds the pre-determined pressure value.
Laying apparatus and method for cables, lines, conductors or suchlike. The apparatus comprises at least a hydraulic circuit provided with a variable delivery feed pump and with a motor connected to the feed pump in order to drive laying members for the cables and suchlike. The hydraulic circuit comprises detectors able to detect the value of pressure of the oil inside the hydraulic circuit and to compare it with a pre-determined pressure value, and valves connected to the detectors and able to reduce the delivery of the feed pump in the event that the pressure measured exceeds the pre-determined pressure value.
