An axial split case pump is a pump whose casing is split axially, or whose principal joint is parallel to the shaft centerline; the casing is split into an upper half and a lower half. An axially split case pumps is always a horizontal pump.
A radial split case pump is a pump whose casing split, or whose principal joint, is perpendicular to the shaft centerline. The complete casing assembly is usually referred to as the case and cover.A radially split case pump can be either a horizontal or a vertical pump.
Axial split case:
The pump internal can be inspected by simply removing the top case; there is no need to remove its rotor.
It is relatively inexpensive for three stages, or more, than a radial split case pump.
It is typically limited to 400 degrees Fahrenheit operating temperature due to thermal expansion consideration because:
there is significant differences in the case metal thickness between the upper half and lower half of the pump resulting in differences in thermal expansion;
the pump cannot be supported at the shaft centerline where the pump casing is split in half (at best, it can be supported at near-centerline only.) This results in asymmetrical thermal expansion between the upper half and lower half casing.
It is typically limited to 3600 PSIG maximum working pressure due to the difficulty in bolting with a flat, unconfined, and irregualr case gasket, and due to the non-symmetrical volute and suction areas between the upper half and lower half casing.
Radial split case:
It can be of the inexpensive overhang design for low suction pressure application. Or, it can be of the more costly between-bearing design for high suction pressure application.
It can be of centerline support design suitable for operating at very high temperature of up to 800 degrees Fahrenheit. The centerline support design ensures equal case thermal expansion in the radial direction.
The case and cover design is suitable for higher working pressure than an axial split case pump due to its smaller bolting area, symmetrical bolting pattern, and confined gasket design.
The pump internal cannot be inspected without removing its rotor assembly from inside the casing.
In some multistage pumps the rotor assembly cannot be removed from the casing without removing the driver to clear the way for the rotor assembly.
It is very expensive for three, or more, stages because the pump will have to be of double barrel construction.