A pressure exchanger for transferring pressure energy from one third flow to a second where two end covers (13, 14), a rotor (11) and a rotor liner (12) are mounted together via a centre bolt (10) in a pressure housing (1) in order to reduce elastic deformation, essentially tensile stress, and to protect the pressure exchanger against impact or shock. One end cover (13) is arranged for inlet of fluid at high pressure and outlet of the same fluid depressurized in a corresponding end cover (14) via a central course in the rotor. The second end cover (14) has in addition an inlet for fluid at low pressure and an outlet for the same fluid under high pressure. A base (2) which is attached with lease pins at the bottom of the pressure housing (1) has external connections (3, 4) and internal passages, which are connect with the inlet (24) of fluid at low pressure together with the outlet (23) for depressurized fluid in the and cover (14). A sealing ring (28) prevents the mixing of in and outgoing fluid at high pressure which is passed through the pressure housing's wall via external pipe couplings (5, 7). The pressure housing (1) has a top cover (8) which is attached via a multi-sectional locking ring (18) inserted in an internal groove in the pressure housing by means of the locking cover (20).