The pump has a horizontal, radially split, single-stage or two-stage (three-stage or four-stage can be used in special cases), centerline-mounted, and between bearing structure. Both the suction opening flange and the discharge opening flange of the pump are on the casing, and both face upwards vertically. The shaft sealing chamber and the casing cover are cast into one, which can contain various mechanical seals. An optional water-cooled chamber jacket is cast outside the shaft sealing chamber.