Filter device and method of cleaning a filter element

A method of cleaning a filter element (3) in the filter device (1) (1) comprising a filter vessel (2) with a fluid inlet (7) for unfiltered liquid;

• a cleaning duct (14) with a cleaning valve (13);
• a cleaning device comprising i) a cleaning fluid vessel containing a cleaning fluid chamber comprising a volume V0 of cleaning fluid, and ii) a pressure vessel containing a pressure chamber at a starting pressure P0, wherein an outlet of the pressure vessel is connected to the cleaning fluid chamber via a pressure inlet of the cleaning fluid chamber such that the cleaning fluid chamber is in open fluid connection with the pressure chamber;
• a filter element (3) located in the filter vessel, the filter element (3) having with a filter inlet (5) that is in fluid communication with the filter vessel and a filter outlet (12), the filter outlet being, via the cleaning duct (14) and the cleaning valve (13), in fluid connection with the cleaning device so that the cleaning fluid chamber is arranged for supplying a volume Vr of cleaning fluid, via the cleaning duct (14) and the filter outlet (12), to the filter element (3);
• a supply pump (22);
• a cleaning fluid supply line (21) connected, via the supply pump (22), to the cleaning fluid chamber for supplying the volume Vr of cleaning fluid to the cleaning fluid chamber while the cleaning fluid chamber is in open fluid connection with the pressure chamber and while the cleaning valve (13) is closed so that the pressure in the pressure chamber rises to at or about the starting pressure P0;
• and a control unit connected to the cleaning valve and adapted i) for opening the cleaning valve for supplying the volume Vr of cleaning fluid, under pressure, from the cleaning fluid chamber to the filter element (3) via the cleaning duct and the filter outlet, and ii) for closing of the cleaning valve, wherein the control unit is adapted to open the cleaning valve in such a manner that the volume Vr is smaller than the volume V0 such that a minimum volume Vmin of cleaning fluid remains in the cleaning fluid chamber, said method comprising the steps of:
• feeding the volume Vr of cleaning fluid to the filter outlet (12) of the filter element (3) from the cleaning fluid chamber containing the volume V0 of cleaning fluid, the cleaning fluid chamber being connected to the pressure chamber comprising a pressurizing fluid, at a starting pressure P0,
• refilling the cleaning fluid chamber with cleaning fluid to contain the volume V0 of cleaning fluid, wherein, the volume Vr is smaller than the volume V0 such that the volume Vmin of cleaning fluid remains in the cleaning fluid chamber, and
• after the cleaning step, the volume Vr is supplied to the cleaning fluid chamber while it is in open fluid communication with the pressure chamber so that the pressure in the pressure chamber rises towards P0.

A filter device (1) comprising:

• a cleaning device comprising
• i) a cleaning fluid vessel containing a cleaning fluid chamber comprising a volume V0 of cleaning fluid, the cleaning fluid vessel having a pressure inlet, and
• ii) a pressure vessel containing a pressure chamber at a starting pressure P0,
• wherein an outlet of the pressure vessel is connected to the cleaning fluid chamber via the pressure inlet of the cleaning fluid chamber such that the cleaning fluid chamber is in open fluid connection with the pressure chamber;
• a cleaning duct (14) with a first end and a second end, the second end including a cleaning valve (13), wherein at a location between the first end and the second end, the cleaning duct (14) is connected to the cleaning fluid vessel;
• a filter vessel (2) with a fluid inlet (7) for connection to an unfiltered liquid source;
• a filter element (3) located in the filter vessel (2), the filter element (3) having i) a filter inlet (5) that is in fluid communication with the filter vessel, and ii) a filter outlet (12),
• wherein, via the second end of the cleaning duct (14) and the cleaning valve (13), the filter outlet is in fluid connection with the cleaning fluid chamber for the filter element (3) receiving a volume Vr of cleaning fluid supplied by the cleaning fluid chamber;
• a supply pump (22);
• a cleaning fluid supply line (21) connected, via the supply pump (22) and the first end of the cleaning duct (14), to the cleaning fluid chamber for supplying the volume Vr of cleaning fluid to the cleaning fluid chamber while the cleaning fluid chamber is in open fluid connection with the pressure chamber and while the cleaning valve (13) is closed so that the pressure in the pressure chamber rises to the starting pressure P0;
• and
• a control unit connected to the cleaning valve and adapted
• i) for opening the cleaning valve for supplying the volume Vr of cleaning fluid, under pressure, from the cleaning fluid chamber to the filter element (3) via the cleaning duct and the filter outlet, and
• ii) for closing of the cleaning valve,
• wherein the control unit is adapted to open the cleaning valve in such a manner that the volume Vr is smaller than the volume V0 such that a minimum volume Vmin of cleaning fluid remains in the cleaning fluid chamber.