A device for mechanically purifying liquids in a pipeline includes a rotation-symmetrical sieve chamber forming a section of the pipeline and having an inlet with a central axis, a rotation-symmetrical sieve body having an inner surface and being disposed in the sieve chamber at an angle of substantially 30.degree. to 60.degree. relative to the central axis of the inlet, and a suction removal device for removing deposits from part of the inner surface of the sieve body, the suction removal device being coaxial with and upstream of the sieve body in flow direction of the liquid, and the sieve body and the suction removal device being rotatable relative to each other for successively sweeping all of the inner surface of the sieve body with the suction removal device.