Abstract: A system for controlling the working conditions for mechanical pumps supplying associated devices with pressure fluid via a pipe system. A valve means (25) is placed between at least one of the pumps and an appurtenant device supplied by the pump, which valve means is arranged to open only when the pump has started up, and by adjustment of its flow cross-section seeks to maintain its downstairs pressure at a value (P3) which is predetermined from the specifications of the pipe system and said device, but gives priority to restrict its flow cross-section so that counterpressure of the pump does not fall below a given minimum value (P2) determined from the characteristic properties of the pump. The valve means is a regulating valve (25) operating in accordance with this functional principle.

Abstract: A method and a valve apparatus for counteracting harmful pressure pulses caused by rapid retardation of a liquid in a hydraulic system comprising a pump for the supply of liquid to a conduit stretch containing a non-liquid-filled volume. The valve apparatus comprises a main valve having an inlet connected to a reservoir for pressurised gas, a first valve chamber connected in use to said volume, and a regulating unit for controlling the supply of pressurised gas to the first chamber.