Centrifugal pump
The present invention relates to a centrifugal pump for pumping of liquids containing pollutions mainly in the form of solid particles, which pump comprises a drive unit, a hydraulic unit, whereby the hydraulic unit comprises a pump housing ( 20 ) and a pump impeller ( 12 ) rotationally arranged inside the housing, the pump impeller comprising an upper ( 14 ) and a lower ( 16 ) cover disc and a number of intermediate vanes ( 18 ). The invention is characterised in that a bottom wall ( 22 ) of the pump housing, having a central inlet opening ( 24 ), is arranged with at least one spirally extending back flow affecting means ( 32, 34 ) on the side facing the lower cover disc extending parts of or full turns around the inlet opening.
1. A centrifugal pump for pumping liquids containing pollutions mainly in the form of solid particles, said pump comprising:
a drive unit, and
a hydraulic unit, wherein the hydraulic unit comprises a pump housing ( 20 ) and a pump impeller ( 12 ) rotationally arranged inside the housing,
the pump impeller comprising an upper ( 14 ) and a lower ( 16 ) cover disc and a number of intermediate vanes ( 18 ),
the pump housing comprising a bottom wall ( 22 ) facing the lower cover disc and having a central inlet opening ( 24 ), wherein a circular gap ( 30 ) separates a space 29 arranged between the lower disc ( 16 ) and the bottom wall ( 22 ) from said central inlet opening ( 24 ),
wherein the bottom wall ( 22 ) of the pump housing is arranged with at least one spirally swept, back flow affecting means ( 32 , 34 ) on the side facing the lower cover disc ( 16 ) extending parts of or full turns around the inlet opening, and
portions of said back flow affecting means ( 32 , 34 ) and an upper surface of the bottom wall ( 22 ) being located adjacent the circular gap ( 30 ) are arranged below said circular gap ( 30 ).
2. The centrifugal pump according to claim 1 , wherein the back flow affecting means is arranged as grooves ( 32 ) in the bottom wall.
3. The centrifugal pump according to claim 1 , wherein the back flow affecting means is arranged as ridges ( 34 ) in the bottom wall.
4. The centrifugal pump according to any one of the preceding claims, wherein a wall part of the back flow affecting means facing towards the inlet forms an angle β with the plane of the bottom wall which is in the range 85 to 95 degrees.