Fire pump are essential in any water-based fire sprinkler system and are often the most complicated and expensive single piece of equipment in a building. They bridge the gap between system demand and available water supply, making up for the difference in flow and pressure. Specifically designed, tested, and listed for fire protection, they propel water through pipes at high-pressure, quickly delivering 126 gallons of water per minute to an active sprinkler system.
Most fire pumps are electrical motor-driven, requiring a reliable power source. They can be powered by an electric utility connection, generator, diesel engine or spark-ignition gasoline/fuel engines. Each type has its own set of advantages and disadvantages, but they all need to provide the same basic service.
The motors drive a shaft that connects to the impeller. The motor is what makes the fire pump turn on and off, depending on whether the pressure in the sprinkler system falls below or above a certain point. When the pressure falls below a specified point, a pressure switch inside the fire pump activates the motor, causing it to spin. This starts to build up the system pressure, bringing it back to the system’s demand, or “primary rating point.”
When sizing a fire pump, it is important to find the correct one for a specific application. The fire sprinkler system designer should be involved in the process of selecting and specifying a suitable fire pump, ensuring that all installation requirements set forth by NFPA 20 and other referenced standards are met. The local Authority Having Jurisdiction should also be involved in this process, to ensure that the final installation is acceptable to them.
Once the fire pump has been installed and commissioned, it should be regularly tested by a qualified professional. Testing should be conducted weekly and monthly, as well as annually. During the testing process, the fire pump is run through its full range of speeds and pressures. Its primary and secondary rating points are tested by opening the 2-1/2-inch fire department valve outlets on both sides of the fire pump. It is then slowly brought back to churn condition. The motor and pressure readings are documented to ensure that the fire pump meets all required criteria.
A fire pump requires a special controller to operate. These devices are built to a higher standard than normal motor controllers and have more rigorous monitoring capabilities. The controller is responsible for starting and stopping the fire pump when conditions are appropriate, as well as monitoring the status of the fire pump in a continuous manner. The controller also monitors other conditions that could affect the operation of the fire pump and alerts a fire safety professional if they become problematic. This allows the fire safety professional to take corrective actions before a potential problem becomes a serious issue.