When the hydraulic pressure of a building’s water supply is not sufficient to meet fire sprinkler, standpipe or foam system requirements, a fire pump is installed to provide a boost of pressure. It’s important to understand the different operating principles, types, and drivers available for fire pumps in order to properly size them based on the most demanding factor – which is usually the flow capacity of the sprinkler system.
Most fire protection engineers use a rule of thumb that takes 1% of the system’s rated flow for finding the pump sizing. But this rule does not fit all applications as it may be too low for systems with higher leakage rates or underground piping. Other factors that should be considered include the nozzles, flow rates and friction losses. For this reason, many fire pump manufacturers offer selection tools on their websites where required flow and pressure can be input and the results show the pumps offered that can meet those demands.
A fire pump can be powered by either an electric motor or a diesel engine. Both drive options are outlined in NFPA 20, and they are what make the pumps work. Electrical motors take electrical power provided by a utility connection, generator or approved power source and spin a shaft connected to the pump’s impeller. The centrifugal pump’s impeller then moves in the direction of the boosted pressure, creating water that is delivered to the hose valves.
Diesel engines can be run on a variety of fuels including diesel and natural gas. They are often more reliable and require less maintenance than their electric motor-powered counterparts, but they are only effective when the generator is running. They are also not as easy to maintain as the horizontal split case or vertical in-line fire pumps, and they need more space because they have a separate casing that must be removed for maintenance access.
The fire pump controller is what monitors the performance of the pump and provides an ON setting to start it and an OFF setting to stop it. The controller can be a bourdon-type pressure switch with mercury or an electronic transducer, and it may provide real-time information via the internet for monitoring and control purposes.
In the past, a pressure switch would detect a drop in system pressure and activate the fire pump’s alarm signal. Today, the fire pump’s alarm signal is often activated when a fire alarm in the building is activated.
A qualified Koorsen technician can inspect, test and repair a fire pump. They have gone through extensive training and have the proper tools to do so in a safe manner. The fire pump is a vital component of the fire sprinkler system, and it’s always best to leave it to a trained professional. Koorsen technicians are trained on fire pumps at our in-house training center before they are sent into the field to perform inspection, testing and maintenance. We are dedicated to providing exceptional service and care for your fire protection systems.