Relay protection for high-pressure fire pumps

Relay protection for high-pressure fire pumps involves using intake pressure relief valves, discharge relief valves, and monitoring systems to prevent overpressure and pump damage during high-rise or relay pumping operations.

Key Components of Relay Protection

Intake Pressure Relief Valves: These valves are critical in relay pumping operations to prevent damage when incoming water pressure exceeds the pump's rated capacity. They can be integral to the pump manifold or added as screw-on devices. When the incoming pressure surpasses a preset level, the valve activates, releasing excess water or pressure to protect the pump. Most are set within 10 psi of the static pressure of the water supply or slightly above, and often include bleeder valves to remove trapped air . Discharge Pressure Relief Valves: High-pressure fire pumps, especially in high-rise applications, may require discharge relief valves to prevent system components from exceeding their pressure ratings. For example, the OCV 108-2HP-FP valve automatically relieves excess discharge pressure, ensuring the fire system operates safely even when relief set points are higher than standard UL/FM approved valves . Motor and Pump Protection Relays: Thermistor and temperature relays, such as PTC relays, protect pump motors from overheating, extending service life. Direction-of-rotation relays ensure pumps operate correctly, and level relays prevent dry running, which is particularly important in high-pressure relay setups .

Operational Considerations

Relay Pumping Setup: In a relay operation, a source pumper supplies water to one or more relay pumpers, which then feed the attack pumper at the fire scene. Each relay pumper must be protected against overpressure from upstream sources and friction losses in long hose lines. Intake and discharge relief valves are essential to maintain safe operating pressures throughout the relay chain . High-Rise Fire Applications: For buildings above 20 stories, pumps must overcome significant back pressure from the water column in standpipes. For example, a 70-story building may require pumps to overcome 303 psi before delivering adequate nozzle pressure. Proper relay protection ensures pumps are not damaged by these extreme pressures, and NFPA 20 standards guide the installation and operation of stationary and booster pumps . Hydraulic Calculations: Accurate hydraulic calculations are necessary to determine friction losses, required flow rates, and pressure settings for relief valves. This ensures that pumps operate within safe limits while delivering sufficient water to the fire scene .

Best Practices

• Regularly inspect and test intake and discharge relief valves to ensure proper operation.
• Set relief valves according to system static pressure and expected operational pressures.
• Use temperature and motor protection relays to prevent overheating during prolonged high-pressure operation.
• Train personnel in relay pumping procedures, including valve operation and monitoring, to prevent accidental overpressure or pump failure.
• Follow NFPA 20 and local fire department guidelines for high-rise and relay pumping operations . By combining mechanical relief devices, motor protection relays, and operational procedures, high-pressure fire pumps can be effectively protected during relay and high-rise firefighting operations, ensuring both equipment safety and reliable water delivery.