Pump comprising a first disc and a second disc , wherein the first and second discs have a respective major surface , the major surface of each disc principally facing the other disc, a drive shaft , the drive shaft connecting to both discs and having an extension along a common geometrical rotation axis , a plurality of stationary piston cylinder arrangements distributed around the geometrical rotation axis , each stationary piston cylinder arrangement comprising a cylinder , a piston head and a piston shaft , the piston head being arranged in the cylinder dividing the cylinder into a first cylinder volume and a second cylinder volume and being connected to the piston shaft , wherein the piston shaft extends in parallel with the geometrical rotation axis whereby rotation of the disc forces the piston shaft to move back and forth thereby providing reciprocal movement of the piston head in the cylinder , wherein each stationary piston cylinder arrangement further comprises a first inlet to the first cylinder volume and a first outlet from the first cylinder volume , the first inlet being provided with a first inlet check valve and the first outlet being provided with a first outlet check valve , whereby the reciprocal movement of the piston head in the cylinder provides a pumping action from the first inlet, via the first cylinder volume to the first outlet, wherein each stationary piston cylinder arrangement further comprises a second inlet to the second cylinder volume and a second outlet from the second cylinder volume , the second inlet being provided with a second inlet check valve and the second outlet being provided with a second outlet check valve , whereby the reciprocal movement of the piston head in the cylinder provides a pumping action from the second inlet, via the second cylinder volume to the second outlet, the pump further comprising an inlet flow channel and an outlet flow channel both extending at least partly around the geometrical rotation axis , wherein one of the inlet flow channel and the outlet flow channel extends around the geometrical rotation axis at an outer position, and wherein the other one of the inlet flow channel and the outlet flow channel extends around the geometrical rotation axis at an inner position, characterised in that the first and second discs are rotatable around the common geometrical rotation axis through the centre of respective disc , that the major surface of each disc has a normal, the normal of each major surface forming an angle with the common geometrical rotation axis , that the outer position is radially outside the plurality of stationary piston cylinder arrangements , at a radial distance from the stationary piston cylinder arrangements , such that the radial distance provides space for a radially inner wall of the inlet flow channel or the outlet flow channel and a radially outer wall for the stationary piston cylinder arrangements that the inner position is radially inside the plurality of stationary piston cylinder arrangements , at a radial distance from the stationary piston cylinder arrangements , such that the radial distance provides space for a radially outer wall of the outlet flow channel or inlet flow channel and a radially inner wall for the stationary piston cylinder arrangements , that each inlet to the first cylinder volume and each inlet to the second cylinder volume is connected to the inlet flow channel , that each outlet of the first cylinder volume and each outlet of the second cylinder volume is connected to the outlet flow channel , and that the pump further comprises a main inlet and a main outlet , the main inlet extending from the inlet flow channel in a direction having a major component transverse to the geometrical rotation axis and the main outlet extending from the outlet flow channel in a direction having a major component transverse to the geometrical rotation axis . <EOS>