The total shut-off head shall not exceed ______ of the total rated head on vertical turbine pumps.

The total shut-off head shall not exceed ______ of the total rated head on vertical turbine pumps.

• A. 120%
• B. 140%
• C. 100%
• D. 150%

Answer: (B)

Vertical turbine fire pumps have a maximum allowable shut-off head to prevent overloading the motor and mechanicals when flow is stopped. The shut-off head is the pressure the pump can develop with zero flow, and it is naturally higher than the rated operating head. By limiting this shut-off head to 140% of the total rated head, the pump can reach high pressure when needed without risking overheating or excessive stress during no-flow conditions. If the limit were higher, components could overheat or fail under shut-off scenarios; if it were lower, it would unnecessarily constrain pump performance. So the correct limit is 140% of the rated head.

Vertical turbine fire pumps have a maximum allowable shut-off head to prevent overloading the motor and mechanicals when flow is stopped. The shut-off head is the pressure the pump can develop with zero flow, and it is naturally higher than the rated operating head. By limiting this shut-off head to 140% of the total rated head, the pump can reach high pressure when needed without risking overheating or excessive stress during no-flow conditions. If the limit were higher, components could overheat or fail under shut-off scenarios; if it were lower, it would unnecessarily constrain pump performance. So the correct limit is 140% of the rated head.