The difference between axially split and radially split centrifugal pumps

The terms "Radially Split" and "Axially Split" describe two fundamentally different casing designs for centrifugal pumps. The core difference lies in the direction of the casing split, which directly dictates their maintenance procedures and pressure-handling capabilities.

1. Radially Split Pumps

Structural Definition: Also known as horizontally split pumps, their casing is divided into two parts—a lower casing and an upper cover—along a horizontal plane that passes through the centerline of the pump shaft. This is known as the "split plane."

Key Characteristics & Implications:

Maintenance Method: This is their most significant advantage. For inspection or repair, workers only need to unbolt and lift off the upper cover. This exposes the entire rotor (impeller, shaft, seals) without moving the pump, its suction/discharge piping (typically attached to the lower half), or the driver motor. This drastically simplifies maintenance and reduces downtime.

Pressure Capacity: The presence of a long horizontal gasketed joint limits its pressure containment ability. Therefore, radially split pumps are typically designed for medium-pressure applications.

Typical Applications: Valued for their easy maintenance, they are widely used in high-flow, general industrial services like municipal water supply, power plant cooling water circulation, and large-scale irrigation.

2. Axially Split Pumps

Structural Definition: Also known as vertically split or barrel pumps, their casing is a cylindrical barrel without a horizontal split. The casing is sealed by front and rear end covers bolted to the central barrel, with the split perpendicular to the shaft.

Key Characteristics & Implications:

Maintenance Method: This is their main drawback. Maintenance requires disconnecting the piping, moving the driver motor, and then disassembling the non-drive end cover and bearings to slide the entire rotor assembly axially out of the barrel. This process is more complex, time-consuming, and requires significant axial space.

Pressure Capacity: This is their core advantage. The cylindrical barrel casing is a pressure vessel with superior structural integrity, free from the weakness of a horizontal split. It is designed for high-pressure and ultra-high-pressure services.

Typical Applications: Chosen for extreme duty, they are used in demanding applications like high-pressure boiler feed pumps, petrochemical process pumps, water injection pumps, and nuclear reactor coolant pumps.

Summary of Fundamental Differences

The choice boils down to a fundamental trade-off:

Radially Split pumps prioritize ease of maintenance at the expense of ultimate pressure capacity, making them ideal for general-purpose, medium-pressure services.

Axially Split pumps prioritize structural strength and high-pressure capability at the expense of maintenance convenience, making them essential for severe, high-pressure duties. This is why high-pressure boiler feed pumps exclusively use the axially split (barrel) design.