Valve used to control the movement and locking of the actuator in both directions by realising the controlled descent of the load that does not escape dragged by its own weight, as the valve does not allow any cavitation of the actuator. It is insensitive to back pressure and is therefore used where normal overcenters do not function properly at load control, allowing the pressure set by the system to be used to operate several actuators in series. Flange connections allow the valve to be mounted directly onto the actuator.