For operating pumps above the respective system resistance for all volume flows, for a spring-loaded, directly acting overflow valve for limiting the pressure in a system in which a liquid is lifted by a positive-displacement pump and flows through the system with varying rates of flow, the valve chamber (1) and the valve body (22) with the valve head (14) placed therein are constituted in such a way that the valve head, after lifting off from the valve seat (3), has a second active diameter which is bigger than the first active diameter, whereby the valve head (11) simultaneously releases, with increasing stroke of the valve body (22), an enlarging flowing-through cross section, whereby the valve body (22) is constituted in one part as a valve piston (11) sliding in the valve chamber (1) with a third active diameter which is bigger than the second active diameter so that the liquid flowing through the valve chamber (1), the valve being opened, produces a pressure difference which acts onto the valve piston (11) against the action of the first spring (21).
A flow shut off valve for use with a pressurized fluid application and which is actuated in response to a flow rate exceeding a maximum allowable rating, the fluid application including a normally regulated and pressurized fluid supply, a length of a conduit extending from the fluid supply. The valve includes an elongated and substantially cylindrical shaped housing interposed between the fluid supply and the extending conduit, the housing having an inlet end communicating with a first coupling extending from an outlet of the fluid supply and an outlet end communicating with a second coupling extending from an inlet of the length of conduit. The housing further including an axially extending interior extending between the inlet and outlet ends. A seating member is slidably mounted within the axially extending interior and translatable over a selected distance defining an open position permitting fluid flow through the interior and a closed position in which the seating member abuts against the annular shoulder, substantially interrupting said fluid flow. A first biasing spring exerts against an inlet side of the seating member and a second adjustable biasing spring exerts against an outlet side of the seating member, the second spring equalizes a combined force provided by the first spring and the normally regulated fluid supply in the open position. Upon the fluid application switching from a normally regulated condition to an opened and unregulated condition, the combined force acting upon the seating member overcomes the counter force exerted by the second biasing spring and actuates the seating member to the closed position.
