Fire Fighting Systems
Active fire protection: detection, suppression and life safety.
Industrial fire systems combine detection (smoke, heat, flame), water-based suppression (hydrants, sprinklers, deluge, water mist), foam and gaseous systems, and pumps that pressurise the network per NFPA / TAC norms.
How it works
- 1
Jockey pump maintains network pressure.
The jockey pump (small, high-head, ~1 % of main pump flow) makes up minor leakage and keeps the ring main pressurised at about 7 bar so the main pumps never start for a dripping valve. Its cut-in is set above the main pump's start pressure.
- 2
On pressure drop, main electric pump starts automatically.
If a hydrant or sprinkler opens, pressure falls below the main pump's start setting and the electric pump auto-starts through its pressure switch and starter. It runs until manually stopped — automatic stopping is not permitted on fire duty under NFPA 20.
- 3
If pressure still falls, diesel pump starts as backup.
If mains power is lost or the electric pump fails to build pressure within the set delay, the diesel engine pump cranks automatically from dual battery banks (six attempts, three per bank). Fuel is held for the full design run time and the engine is exercised weekly.
- 4
Sprinklers/hydrants discharge water; deluge floods risk areas.
Water reaches the risk through hydrants, hose reels, or sprinklers. Sprinkler heads operate individually when the glass bulb bursts (68 °C standard, 79/93 °C for hot areas), so only heads over the fire discharge. Deluge systems have open heads and a deluge valve opened by detection — the whole zone floods at once for transformers, LPG bullets and cable galleries.
- 5
Foam proportioners inject concentrate for flammable liquid fires.
For flammable liquid risk, a bladder tank or inline balanced-pressure proportioner injects 3 % or 6 % AFFF concentrate into the water stream; foam pourers or monitors then lay a vapour-sealing blanket over the fuel surface.
Key components
Dedicated, always-full static storage sized for the full design flow duration (commonly 4 hours). Fitted with duplicate make-up, level alarms and an anti-vortex plate; the fire draw-off is set so that process users can never drain the fire reserve.
Small multistage pump, roughly 1 % of main pump capacity at slightly higher head. Keeps the network topped up. Continuous hunting (frequent start/stop) is the earliest warning of a network leak or a passing valve.
Horizontal split-case or vertical turbine pump, 100 % duty, driven by a fire-rated starter on a dedicated feeder. Must deliver 150 % of rated flow at 65 % of rated head and no more than 140 % shut-off head — proved in the annual flow test.
Identical hydraulic end driven by a dedicated diesel engine with twin batteries, day tank, heat exchanger or radiator cooling, and a controller that cranks automatically. Weekly 30-minute run test with battery, fuel and coolant checks.
Wet-riser hydrants with landing valves, hose boxes and branch pipes; sprinklers on wet, dry, pre-action or deluge risers protected by alarm valves and flow switches. Maintain 1 m clearance below heads and never paint or hang from a sprinkler.
Smoke (optical/ionisation), heat (rate-of-rise), flame (UV/IR) and linear heat cable, wired to an addressable fire alarm panel with zone displays, hooters, manual call points and interlocks to HVAC dampers, gas release and plant shutdown.
Typical operating parameters
Problem solving videos
Safety notes
- •Never isolate valves without hot-work permit & compensating measures.
- •Weekly no-flow start test on pumps.
- •Monthly full-flow test as per NFPA 25.
Maintenance schedule
- •Weekly: pump run test, battery check.
- •Monthly: hydrant, valve, gauge inspection.
- •Annual: flow test, foam concentrate assay, sprinkler survey.
Problem solving matrix
| Issue | Likely cause | Fix |
|---|---|---|
| Jockey pump hunting | Network leak | Isolate & find leak |
| Main pump won't start | Pressure switch / control | Test PS and starter |
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