Importance

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Abstract

This disclosure relates to apparatus comprising a reverse osmosis membrane module, a reciprocating pump and a double-acting hydraulic cylinder. The pump includes a piston defining on its opposite sides a first cylinder chamber and a second cylinder chamber which has a smaller cross-sectional area than the first chamber. The first chamber connects with a feed fluid supply conduit provided with a feed valve which opens when the first chamber expands. The membrane module includes an inlet and an outlet. The inlet connects with the first cylinder chamber when the first cylinder chamber contracts in volume, and the outlet connects with the second cylinder chamber through a selector connecting with a concentrate fluid drain conduit. The selector has a first position where the second chamber and the outlet are interconnected and the drain conduit is disconnected from the second chamber and the outlet, and a second position where the second chamber and the drain conduit are interconnected and the outlet is disconnected from the second chamber and the drain conduit. The hydraulic cylinder includes a piston coupled by a rod to the pump piston and defining two chambers on its opposite sides, which are supplied alternately with hydraulic pressure to reciprocate the pistons. The selector is coupled to an actuator connecting with the hydraulic cylinder. The actuator is responsive to the pressure in one of the hydraulic cylinder chambers to shift the selector to the first position immediately before the first cylinder chamber starts to contract, and to the pressure in the other hydraulic cylinder chamber to shift the selector to the second position immediately before the first chamber starts to expand.

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First Claim