Spiral wound filter assembly

A spiral wound filter assembly for membrane filtration of liquids, comprising;

• a housing holding two or more spiral wound filter units in a filter space,
• a feed inlet at one end of the filter space, and a retentate outlet at the other end of the filter space, for feeding a liquid through the filter space in a feed flow direction from the feed inlet to the retentate outlet,
• at least one permeate outlet for draining permeate from the filter space, and wherein each of said two or more spiral wound filter units comprises:
• a membrane filter separating a feed channel from at least one permeate channel, wherein
• the feed channel extends between the feed inlet and the retentate outlet for transporting a liquid along a feed flow path parallel to the membrane filter in the feed flow direction, and
• the at least one permeate channel, for transporting permeate to the permeate outlet, comprises:
• a first part extending between the feed inlet and the retentate outlet for transporting permeate along a first permeate flow path in a direction perpendicular to the feed flow direction,
• a second part for transporting permeate along a second permeate flow path in a direction parallel to the feed flow direction, to the permeate outlet, wherein the permeate channels of the two or more spiral wound filter units are mutually connected via an anti-telescoping device, and wherein
• the at least one permeate channel is provided with at least one flow restriction, for increasing the pressure in the section of the permeate channel upstream of the at least one flow restriction, wherein one of the at least one flow restriction comprises a check valve forming part of the anti-telescoping device, and wherein the permeate outlet flow from the housing is decreased.