DR4 Way valve
The DR4 is an hydraulically operated directional control valve for use with dualine loop or non-return systems.
The valve consists of two sections. A flow control half that directs the pump now to one of the supply lines and a pressure control half that contains the spring loaded pistons against which the pump pressure is directed.
The reversing valve changeover pressure is governed by the spring load which can be adjusted to suit the installation. When all the dualine metering valves in the system have operated, pressure will build up on a pilot piston which acts against a toggle. When the vertical force of this toggle equates that of the spring, it will snap over into the opposite position. This directs a pilot flow onto one end of the flow directing piston and relieves its other end to the reservoir thus moving it over to direct the pump flow to the opposite supply line and relieving the originally pressurised line back to the reservoir. An electric switch is mounted near to the reversing valve and this switch is actuated by a pin attached to the flow directing piston. When this moves to either make or break the switch, a signal is sent to the system controller to stop the pump and start an interval period.
On the DR4 valve (non-return system), the two pipelines do not return to the reversing valve but the reversal pressure is sufficient for the operation of all the measuring valves. This unit is factory set at 310 bar unless it is previously known that higher pressures are required.