Selection starts from the hydraulic calculation, which gives the flow and pressure required at the most remote point. The rated point is then checked against the NFPA 20 curve limits: at 150 per cent of rated flow the pump must still deliver at least 65 per cent of rated pressure, and churn pressure must not exceed 140 per cent. We design the whole pump room, including suction pipework, test and circulation lines, diesel exhaust and fuel tank, and commission the set with a full flow test.
ATypes and components
Horizontal split-case pump
The casing is split horizontally along the shaft line, so the impeller and bearings can be reached by lifting the top half without disturbing the pipework. A double-suction impeller keeps it balanced at high flows, which makes it the usual choice for medium and large installations.
End-suction pump
Water enters along the shaft axis and leaves radially from the top. It is compact and economical, and widely used on small to medium flows; above that range a split-case pump is normally the better option.
Vertical in-line pump
Suction and discharge flanges sit on the same axis, so the pump bolts straight into the pipeline and takes up very little floor space. It suits basement plant rooms where space is tight and flows are low to moderate.
Vertical turbine pump
Used when the water source is below the pump, such as a well, a sunken tank or a seawater intake. The bowl assembly is submerged, the driver sits at the surface, and power is transmitted through a line shaft supported by bearings along the column. NFPA 20 does not allow horizontal fire pumps to operate under suction lift, so in these cases a vertical turbine is the correct solution.
Jockey pump
A small pump that makes up for minor leakage and temperature-related pressure changes, keeping the network at its set pressure. It provides no fire flow and is not counted as a fire pump; its job is to stop the main pump from starting on every small pressure drop.
Electric fire pump controller
Starts the pump automatically from a pressure transducer signal, monitors phase loss and phase reversal, and passes running and fault signals to a remote monitoring point. An NFPA 20 controller has no overload relay that could stop the motor during a fire, only locked-rotor protection, because the pump is meant to keep running to the end.
Diesel engine and controller
The diesel set runs with two independent battery banks, battery chargers and a controller that makes repeated automatic cranking attempts. Fuel tank, exhaust, cooling circuit and plant room ventilation have to be designed together with the engine.
Pump room equipment
Suction and discharge headers, OS&Y valves, check valves, a test line with flow meter, a circulation relief valve and pressure sensing lines are all part of the set. Poor layout of these items can spoil the performance of an otherwise well-chosen pump.
BHow it works
- When minor leakage lowers the system pressure, the jockey pump starts first and restores the set pressure.
- When a sprinkler opens or a hose reel is used, pressure falls below what the jockey pump can hold and the electric duty pump starts.
- If pressure keeps falling to a lower set point, or the electric pump fails to start, the diesel pump starts automatically.
- The main pumps are set up not to stop on their own when pressure recovers; they are shut down manually at the controller once the fire is under control.
CAdvantages
- Calculated flow and pressure, independent of the mains
- Diesel standby against power failure
- Jockey pump prevents unnecessary main pump starts
- On-site performance checks through a metered test line
- Remote monitoring of running, fault and phase alarms
DApplications
- Factories and logistics warehouses
- Shopping centres and hotels
- Hospitals and public buildings
- High-rise residential and office buildings
- Fuel and chemical facilities
- Sites supplied from wells or sunken tanks
EFrequently asked questions
How often should a fire pump be run and tested?
NFPA 25 calls for regular no-flow (churn) runs: weekly for diesel pumps, and weekly or monthly for electric pumps depending on the conditions. Once a year a full flow test is carried out through the test line, recording pressures at zero, rated and 150 per cent flow. The results are compared with the commissioning curve, and a clear drop usually points to impeller wear or a suction-side problem.
Is a diesel standby pump required in every building?
It depends on the occupancy, the hazard class and how reliable the electrical supply is. If power comes from a single source and no generator capacity is reserved for the fire pump, a diesel pump is the most practical way to provide redundancy. The decision should be made at design stage together with regulatory and insurer requirements.
Why does our jockey pump keep cycling?
Frequent starts usually mean a leak somewhere in the system, a check valve that is passing, or wrong pressure settings. Short cycling wears the motor and hides the real problem. We start by checking the jockey and main pump set points, then the valves and likely leak points along the pipework.