Abstract: A multistage pump according to the present invention has a plurality of intermediate casings (2) formed by press-forming a steel plate. The intermediate casing has a cylindrical side portion (21), a stage flat portion (23) with which an axial end face of an adjacent intermediate casing is held in contact, a stage side portion (24) extending axially from the stage flat portion, and a bottom portion (25) extending radially inward from the stage side portion. A relief plate (30) having an outer circumferential end face which is held in contact with an inner surface of a cylindrical side portion of the adjacent intermediate casing is attached to the bottom portion of the intermediate casing. The relief plate, the stage side portion, the stage flat portion, and the inner surface of the cylindrical side portion of the adjacent intermediate casing form a space in which an O-ring (40) is fitted.

Abstract: A centrifugal pump includes at least one impeller (11) fixed to a main shaft (10) and at least one casing which houses the impeller and is formed through press working of sheet metal such as a steel plate. The centrifugal pump further includes a casing cover configured to seal an open end of the casing hermetically, and a shaft seal device (12) provided at a portion where the main shaft passes through the casing cover. The casing cover has a thick member (6) made of castings, and a thin corrosion-resistant lining member (40) which is tightly fixed to the thick member.

Abstract: An impeller (1) according to the present invention has a disk-like main plate (10), a blade (20) joined to the main plate, and a side plate (30) having a suction port. A boss hole (12) is formed in a central portion of the main plate for attaching a boss which engages with a pump shaft to the boss hole. A step portion (14) is formed around the boss hole, which is formed in the main plate, by drawing.

Abstract: A multistage pump according to the present invention has a plurality of intermediate casings (2) formed by press-forming a steel plate. The intermediate casing has a cylindrical side portion (21), a stage flat portion (23) with which an axial end face of an adjacent intermediate casing is held in contact, a stage side portion (24) extending axially from the stage flat portion, and a bottom portion (25) extending radially inward from the stage side portion. A relief plate (30) having an outer circumferential end face which is held in contact with an inner surface of a cylindrical side portion of the adjacent intermediate casing is attached to the bottom portion of the intermediate casing. The relief plate, the stage side portion, the stage flat portion, and the inner surface of the cylindrical side portion of the adjacent intermediate casing form a space in which an O-ring (40) is fitted.

Abstract: An impeller (1) according to the present invention has a disk-like main plate (10), a blade (20) joined to the main plate, and a side plate (30) having a suction port. A boss hole (12) is formed in a central portion of the main plate for attaching a boss which engages with a pump shaft to the boss hole. A step portion (14) is formed around the boss hole, which is formed in the main plate, by drawing.

Abstract: An interstage casing made of sheet metal includes a cylindrical receptacle-like body having a casing end wall on an end thereof and an open end opposite to The end. The omen end has an axial end surface and a radially inner surface which serve as a member of a spigot joint to be joined to the next interstage casing. The cylindrical receptacle-like body also includes a cylindrical side wall, a cylindrical portion joined between the casing end wall and the cylindrical side wall and having an outside diameter slightly smaller than an inside diameter of the open end, and a flat portion joined to the recessed portion and serving as an end surface of the casing end wall. The flat portion is adapted to be engageable with the end surface of the open end of an adjacent interstage casing. The flat portion has an outside diameter slightly larger than an outside diameter of the open end.

Abstract: An interstage casing made of sheet metal includes a cylindrical receptacle-like body having a casing end wall on an end thereof and an open end opposite to the end. The open end has an axial end surface and a radially inner surface which serve as a member of a spigot joint to be joined to the next interstage casing. The cylindrical receptacle-like body also includes a cylindrical side wall, a cylindrical portion joined between the casing end wall and the cylindrical side wall and having an outside diameter slightly smaller than an inside diameter of the open end, and a flat portion joined to the recessed portion and serving as an end surface of the casing end wall. The flat portion is adapted to be engageable with the end surface of the open end of an adjacent interstage casing. The flat portion has an outside diameter slightly larger than an outside diameter of the open end.

Abstract: A multistage centrifugal pump has a plurality of series-connected interstage casings of pressed sheet steel housing respective impellers. Each of the interstage casings includes a central cylindrical side wall, a casing end wall, a first cylindrical wall integrally extending from an end of the central cylindrical side wall and joined to the casing end wall, the first cylindrical wall serving as a male member of a spigot joint, and a second cylindrical wall integrally extending from an opposite end of the central cylindrical side wall and having a flange defining an end opening therein, the second cylindrical wall serving as a female member of a spigot joint. The central cylindrical side wall has an outside diameter larger than outside diameters of the first cylindrical wall and the flange. The interstage casing is formed by drawing and bulging, and is not machined to achieve the desired dimensional accuracy.