A diesel fire pump is a piece of equipment that requires regular maintenance to ensure it works properly in an emergency. Fire pumps are the most important safety equipment in a building, and it is crucial that they are tested weekly to ensure they have the ability to function when required. Performing this testing is an essential part of fire protection system maintenance, and should be included in the facility’s emergency operations plan. There are a number of things that need to be taken into consideration when testing a diesel fire pump, including ensuring water flow is available to the engine heat exchanger, closing the discharge valve during test flows, and making sure nobody is holding a hose during a test.
The first step in maintaining a fire pump is ensuring the power supply for the electric motor or diesel engine is adequate. The power sizing requirements vary from UL to FM, but all require sufficient reserve power to handle the maximum flow of the pump during a test. The power reserve can be sized using the NPSH curve or at a point above the head capacity of the pump, depending on the design of the hydraulics.
After the power supply is determined, it is important that all components are inspected to make sure they are in working order. The nozzles should be checked to make sure they are not cracked or damaged, and that the hoses are properly anchored and will not be pulled away during a test flow. If any problems are found during this inspection, they should be corrected as soon as possible to prevent a loss of the fire pump’s full capacity during an actual emergency.
During a flow test, the pump is pushed to its rated capacity using hoses attached to the fire pump’s discharge test header. This is a dangerous operation, and it is important that the hoses are placed in a safe location where they will not be pulled away by the flowing water during the test. This will not only be hazardous to firefighters in the event of an emergency, but it could also damage the fire pump, and possibly the entire system.
The last step is to close the main fire pump discharge valve during the test, as this will help to prevent a water hammer effect on the system. This is done by turning the selector switch located inside of the controller to the off position. Unlike other electrical devices, there are only three ways that a diesel engine driven fire pump can be stopped from operating; running out of fuel, manual operation of the selector switch inside of the controller, or low oil pressure.
A faulty method of providing cooling for the engine from the fire line piping is one of the most common causes of damage to stand-by Diesel fire pump engines. The heat exchangers on these engines are small, and they require constant water flow to operate correctly. When the piping is closed during a fire pump test, there is no way for the water to get to the engine, and the engine will overheat. This can cause extensive damage to the fire pump, and may even destroy the engine.