End-Suction Pump vs Horizontal Split Case in Fire Fighting Application

End-Suction pump vs Horizontal Split Case in Fire Fighting Application

Centrifugal pumps are the most common pumps used in firefighting applications, in this article we will clarify the basic differences between most common types of centrifugal pumps, "End Suction" & "Horizontal Split Case", we will discuss the design, construction of each type and compare between capacities range, initial cost, maintenance, and space requirements for each type.





Definitions:





Centrifugal pump.

A pump in which the pressure is developed principally by the action of centrifugal force, the video below illustrates the principle of operation of centrifugal pump and its advantages and disadvantages.

End Suction Pump.

End-Suction Pump

A single suction pump having its suction nozzle on the opposite side of the casing from the stuffing box and having the face of the suction nozzle perpendicular to the longitudinal axis of the shaft. usually of "overhung hung impeller" type in which the impeller is mounted on the end of a shaft which is “overhung” from its bearing supports.

End suction pumps are available as close coupled in which the impeller is mounted directly on the motor shaft or separately coupled in which the impeller is mounted on a separate pump shaft supported by its own bearings.

Horizontal Split-Case Pump.

Horizontal Split Case pump

A centrifugal pump characterized by a housing that is split parallel to the shaft. usually of "Impeller Between Bearing" type in which the impeller is mounted on a shaft with the bearings at both ends.

Horizontal split case pumps are available as separately coupled single stage or multistage type.







Capacities range The durability of the horizontal split case pumps design allows the pump to be used for very large water flows in excess of 5000 gpm as the pump casings are often heavier and designed to handle higher working pressures, moreover, the design of "Impeller between bearing" and since the water enters the two sides of the impeller (double suction), these pumps can withstand the large amount of vibration and thrust forces often caused by water turbulence in the suction piping.

For end suction pumps and since water is entering one side of the impeller, and due to the design of "Impeller overhung", these pumps cannot be used for large water flow applications and usually not exceeding 1500 gpm of flow.







Initial Cost: Due to the large flanges required for the split casing sealing joint, larger impeller, and overall large size, horizontal split case pumps are normally heavier and cost more than comparable end suction pumps which has lower initial cost.



However, requiring long operating life, the cost of maintenance of end suction pumps and down time may far exceed any initial cost savings.







Maintenance:

Horizontal split case pumps are easy for maintenance as the top half of the casing can be removed, so the internal components (Bearing, shaft, impeller, and etc.) are exposed without disturbing the suction or discharge piping, or moving the motor.

On the other hand, maintenance of end suction pump are more difficult due to their compact design, for example, the removal of the impeller requires removal of the motor to provide a space for pulling the impeller back out of the casing.









Space required One advantage of end suction pumps is that it is space saving by means of its compact design, while the horizontal split case pumps requires more space









References of this article: NFPA 20 - 2019 edition (Standard for the Installation of Stationary Pumps for Fire Protection)























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