The hydraulic power pack and the electrical cubicle are fixed on the same frame. To operate many valves is possible with the same equipment: in this case each valve has got an independent circuit, but with a common pressure supply.
The valve is holded in opening with the hydraulic pressure, it is necessary to compensate the internal hydraulic leakages, risponsable of a falling pressure and then a, not desirable, progressive closing of the valve. Two different technologies can make this « leakage control cycle » (Automatic cycle) :
a) Technology with limit switch : When the « leakage control » switch, located few degrees before the « opening » limit switch, switches on, the hydraulic pump starts. This technology is supplied in standard.
b) Technology with accumulator. A « low pressure » pressure gauge starts the hydraulic pump in order to blow up the accumulator.