A filter-box and a retrievable subsea filter module with a filter-box

1 - 13 . (canceled)

14 . A subsea filter-box with a plurality of longitudinal pressure-vessels forming at least one group of longitudinal pressure-vessels, wherein each pressure vessel includes a membrane, a first end section and a second end section;

wherein each first end section, includes a first side face and a first end section end face;

wherein each second end section, includes a second side face and a second end section end face;

wherein the first end section end face faces away from the second end section end face;

at least one feed liquid inlet on the first end section side face;

at least one retentate outlet and at least one permeate/filtrate outlet on the second end section side face;

the subsea filter-box comprising:

a first support plate with a plurality of fixing geometries, each supporting a first end section;

a second support plate with a plurality of fixing geometries, each supporting a second end section, whereby each of the plurality of pressure-vessels extends between a fixing geometry on the first support plate and a fixing geometry on the second support plate;

wherein the at least one group of pressure-vessels includes at least:

one entry pressure-vessel with at least one feed liquid outlet on the first end section side face;

at least one intermediate pressure-vessel with at least one feed liquid outlet on the first end section side face;

at least one permeate inlet on the second end section side face;

at least one retentate inlet on the second end section side face, adjoining and in liquid connection with the entry pressure-vessel;

one end pressure-vessel, adjoining and in liquid connection with an intermediate pressure-vessel; and

a clamp structure, clamping the first support plate and the second support plate to the plurality of pressure-vessels.

15 . The subsea filter-box of claim 1 , wherein the entry pressure-vessel is a 5-port pressure-vessel, the end pressure-vessel is a 4-port pressure-vessel and the at least one intermediate pressure-vessel is a 6-port pressure-vessel.

16 . The subsea filter-box of claim 2 , wherein the entry pressure-vessel furthermore includes a permeate/filtrate outlet on the second end section side face, and the end pressure-vessel includes a retentate inlet on the second end section side face.

17 . The subsea filter-box of claim 1 , wherein the liquid inlet, the retentate outlet, and the permeate/filtrate outlet of a pressure vessel is fixed to the feed liquid outlet, the retentate inlet and the permeate inlet respectively of a neighbouring pressure vessel with releasable liquid couplings.

18 . The subsea filter-box of claim 4 , wherein the releasable liquid couplings provides mechanical joints providing a stiff connection, mechanically fixing the pressure-vessels in a group of longitudinal pressure-vessels to each other.

19 . The subsea filter-box of claim 1 , wherein each pressure vessel includes a permeate end cap sealing a permeate side of the pressure-vessel, the permeate end cap including a permeate channel fixed to a threaded portion of a permeate/filtrate outlet tube of the pressure-vessel with an end cap attachment bracket formed as a tube with internal threads threaded onto the permeate/filtrate outlet tube, and with ports on the side to allow the permeate to flow out of the tube, holding the end cap to the permeate/filtrate outlet tube.

20 . The subsea filter-box of claim 1 , wherein the first end section end face is parallel to the second end section end face.

21 . The subsea filter-box of claim 1 wherein the membrane is a Reverse Osmosis (RO) membrane and wherein the subsea filter-box is adapted to be used for subsea desalination whereby the feed liquid is seawater, the retentate is brine and the permeate is freshwater.

22 . A retrievable subsea filter module with at least one subsea filter-box of claim 1 , including a plurality of groups of longitudinal pressure-vessels further including:

a liquid inlet header in liquid connection with each liquid inlet on each entry pressure vessel;

a retentate header in liquid connection with each retentate outlet on one of each entry pressure vessel or each end pressure-vessel; and

a permeate header in liquid connection with each permeate/filtrate outlet on one of each entry pressure vessel or each end pressure-vessel.

23 . The retrievable subsea filter module of claim 9 , including two subsea filter-boxes wherein a first of the two subsea filter-boxes is located on top of a second of the two subsea filter-boxes, whereby a longitudinal centreline of each pressure vessel of the first subsea filter-box is coinciding with a longitudinal centreline of a pressure vessel of the second subsea filter-box.

24 . The retrievable subsea filter module of claim 9 , further including a subsea desalination template with a retrievable subsea filter module zone;

a retentate outlet pipe extending from the desalination module; and

a permeate and service line extending from the desalination template and to a permeate receiving facility.

25 . A longitudinal pressure-vessel comprising:

a membrane;

a first end section, including a first side face and a first end section end face;

a second end section, including a second side face and a second end section end face;

wherein the first end section end face faces away from the second end section end face;

at least one feed liquid inlet on the first end section side face;

at least one retentate outlet and at least one permeate/filtrate outlet on the second end section side face; and

at least one of a feed liquid outlet on the first end section side face, a retentate inlet on the second end section side face, and a permeate inlet on the second end section side face.

26 . The longitudinal pressure-vessel of claim 12 , wherein the membrane is an RO-membrane, and the pressure-vessel is a desalination pressure vessel.