According to the invention there is provided a control valve of the pilot-operated kind comprising a valve body which includes a main valve seat; a movable main valve cooperating with the main valve seat to open and close the valve; a piston carrying the main valve member; a control chamber behind the piston for exerting fluid pressure thereon; a first passage for coupling the control chamber to the up-stream side of the main valve seat; a second fluid passage for coupling the control chamber to the down-stream side of the main valve seat; both first and second passages being enabled to be open when the main valve is open so that some fluid is by-passed around the main valve via the first and second passages, and at least one auxiliary control valve in the second fluid passage effective to control the flow of fluid therein.

With this arrangement, opening of the auxiliary control valve can be arranged to reduce the pressure in the control chamber substantially to down-stream pressure so that the main valve opens. Closing of the auxiliary control valve can be arranged to increase the pressure in the control chamber to up-stream pressure so that the main valve closes.

The auxiliary valve may be a simple on/off valve. Preferably however, the auxiliary valve is capable of offering a controlled restriction in the second passage.Cast Steel Valves This allows the pressure in the control chamber to be accurately controlled to maintain the main valve at a required intermediate position. Preferably, the auxiliary valve is controlled by the absolute pressure on the downstream side of the main valve and is so arranged that it controls the main valve to limit the absolute downstream pressure, and thus the flow rate through the main valve, to a predetermined level.

In a preferred embodiment of the invention the control valve is of a mechanically operated kind, there being an additional inlet passage from the up-stream side of the main valve seat to the control chamber and a mechanical pilot valve controllable from outside the housing and effective to control ports which couple the control chamber alternatively to the additional inlet passage and the said second passage. Forged Steel ValvesThis arrangement allows the control valve to be of a mechanical preset kind in which the mechanical pilot valve is operated by a linkage from a preset counter coupled to a flow meter measuring the flow through the valve. The flow is thus automatically cut off at a preset volume. Additionally, the auxiliary valve in the second passage can be set to limit, in the manner described, the maximum flow rate through the valve.WATER POWER CONTROL VALVE This allows the flow through the meter to be limited to the maximum meter rating.

Another embodiment of the invention provides a remotely controlled valve having many of the components of the mechanical preset valve. However, instead of the mechanical pilot valve, this kind of valve has remote controlled solenoid, pneumatic or hydraulic valves for controlling the inlet pressure to the control chamber in addition to the auxiliary valve. The auxiliary valve of the remotely controlled valve may be the same kind of pressure control valve as described above in relation to the mechanical preset valve.

In a preferred embodiment of the invention, the second passage includes a reservoir chamber, and the auxiliary valve is situated in an outlet of the reservoir chamber and is effective to control the flow from the reservoir chamber to a duct communicating with the downstream side of the valve.

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2011-12-31

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