1. What NBR 10897 is and when it applies
ABNT NBR 10897 — Fire protection systems by automatic sprinklers — is the standard governing automatic water-based fire fighting in Brazilian buildings: the fixed piping network with automatic sprinklers distributed near the ceiling, which individually burst with fire heat and discharge water directly over the fire, without human intervention. It is the automatic complement to the NBR 13714 hydrant system, which depends on a person opening a valve.
Whether a building needs sprinklers is defined by the state Fire Department Technical Instruction or Technical Standard, as a function of occupancy, area and height — malls, hospitals, logistics warehouses, industrial plants and high-rises are the classic cases. Once required, NBR 10897 says how to design; and on subjects it does not address, the fire department standards themselves refer to the corresponding parameter in NFPA 13, the American standard the Brazilian one was based on.
Within the fire standard family, each standard has a role: NBR 10897 covers automatic sprinklers, NBR 13714 covers hydrants and hose stations (manual fighting), and NBR 16704 — together with NFPA 20 — covers the stationary pumps that pressurize both systems. The same development frequently needs all three, and the pump set is usually sized for the combined demand defined in the design.
2. Hazard classification: light, ordinary and extra
All sprinkler system sizing starts with the occupancy hazard classification — not the building general classification, but a classification specific to the sprinklers, defined by the quantity and combustibility of the contents. The standard works with light hazard (offices, schools, hotels), ordinary hazards I and II (most industries and mid-size warehouses) and extra hazards I and II (processes with flammable liquids, high fire load).
State fire department technical standards make this classification objective via the specific fire load, in MJ/m². The CBMDF technical standard, for example, classifies as light hazard occupancies with fire load up to 300 MJ/m², ordinary between 300 and 1,800 MJ/m² (split into I and II at the 900 threshold), and extra above 1,800 MJ/m².
In buildings with multiple hazards, the system is sized for the sector with the highest hydraulic demand — and that design area is what defines the pump.
| Hazard | Fire load (MJ/m²) | Typical occupancies | Minimum supply duration |
|---|---|---|---|
| Light | up to 300 | Offices, schools, hotels, hospitals (administrative areas) | 30 min |
| Ordinary I | 300 to 900 | Parking garages, bakeries, electronics factories | 60 min |
| Ordinary II | 900 to 1,800 | General warehouses and logistics buildings, print shops, mills | 60 min |
| Extra I | 1,800 to 2,500 | Hangars, flammable-liquid processes, foamed plastics | 90 min |
| Extra II | above 2,500 | Distilleries, plastics, large-scale paints and solvents | 90 min |
3. The density/area method: how the sprinkler defines the pump flow
NBR 10897 hydraulic sizing starts from two quantities read on the standard curves for each hazard: the discharge density — how many millimeters of water per minute must fall over each square meter — and the operation area, the maximum area over which sprinklers are assumed to open simultaneously. In light hazard, the reference is around 4.1 mm/min over 139 m²; in extra hazards, densities rise to the 12 to 16 mm/min range over larger operation areas.
Multiplying the two gives the flow order of magnitude: an ordinary hazard with 6.1 mm/min density over a 139 m² operation area already demands about 850 L/min for the sprinklers alone — before adding hydrant demand. The real calculation is done sprinkler by sprinkler, starting from the hydraulically most unfavorable one at 48 kPa minimum pressure, accumulating flows and friction losses branch by branch to the supply point.
The result — total flow at the required pressure — is the duty point the fire pump must meet.
One design detail fire departments verify: the design area (the plan cutout used in the calculation) must be rectangular, with the dimension parallel to the branch lines at least 1.2 times the square root of the operation area — a rule that prevents "choosing" a convenient area and undersizing the network. The complete hydraulic calculation memorial, from the most remote sprinkler to the pump, is part of the design submitted for review.
Q [L/min] ≈ densidade [mm/min] × área de operação [m²]Sprinkler system reference flow (order of magnitude; the design value comes from the sprinkler-by-sprinkler hydraulic calculation)
4. Wet pipe, dry pipe, preaction and deluge: what changes for the pump
The wet pipe system is the Brazilian default: network permanently full of pressurized water, sprinkler bursts, water flows immediately. The dry pipe system keeps the network with compressed air and admits water only when a sprinkler opens — used in freezing-prone areas or where leakage would be critical. Preaction conditions water admission on an automatic detection signal, protecting data centers and collections against accidental discharge. In all three, the density/area sizing logic is the same.
The special case is deluge: open sprinklers, no heat-sensitive element, all discharging simultaneously when the deluge valve trips — the protection for transformers, hangars and flammable-liquid areas. Here there is no "partial operation area": the demand is the total flow of the protected circuit, and the resulting pump is typically 2 to 3 times larger than that of an equivalent conventional sprinkler system.
Specifying a conventional sprinkler pump for what is actually a deluge design is a classic cause of rejection.
Between the pump and the sprinkler network sits the alarm check valve assembly (in Brazil, VGA — válvula de governo e alarme), installed on the main feed riser: it sections the system, triggers the flow alarm when the first sprinkler opens and is the reference point for the test connection. Each main riser serves a maximum protection area per floor, which in large buildings multiplies risers, valves — and the flow arriving at the pump room.
5. Water supply and pump: what the standard demands from the set
The sprinkler system must have a dedicated water volume — the fire water reserve (RTI) — in an automatically operating tank, sized by the design area hydraulic demand multiplied by the hazard operating time. When the volume is not calculated, fire department technical standards set tabulated values: in the CBMDF standard, from 25,000 liters for light hazard to 515,000 liters for extra hazard II.
That is too much water for improvisation: the tank, the suction pit and the pump room are born together in the design.
From the pump, the standards demand a coherent package: a centrifugal main pump sized for the design area demand, a jockey pump keeping the network pressurized within the supervision range, automatic start on pressure drop and manual-only shutdown at the panel. Electric pumps require power from two independent sources; diesel pumps require exhaust routed outside and a fuel tank with minimum 8-hour autonomy at full load, per state technical standards.
The preferred installation is flooded suction — pump shaft below the tank usable level.
Pump sizing and installation leave NBR 10897 and enter NBR 16704 and NFPA 20: characteristic curve meeting the envelope (100% flow at 100% pressure, 150% flow at minimum 65% pressure, shutoff capped at 140%), driver, panel and tests. NBR 10897 delivers the input — the design area demand — and receives back a pump that must prove that delivery at the acceptance test, with flow and pressure measurement.
- Dedicated fire water reserve in an automatically operating tank — volume by calculation (demand × hazard time) or tabulated by the state standard
- Main pump + jockey with individual pressure-drop automation; manual-only shutdown
- Electric: two independent power sources | Diesel: isolated exhaust and minimum 8 h autonomy
- Preferred flooded suction, with suction pit sized against vortex
- Pump sizing and testing per NBR 16704 / NFPA 20
6. Common specification mistakes in sprinkler systems
Four mistakes repeat in the designs that reach application engineering. First: classifying the hazard by the building "general" occupancy instead of the fire load of the most demanding sector — the calculation is born undersized. Second: ignoring the combined sprinkler and hydrant demand, sizing the pump for only one of the systems. Third: treating a deluge design as conventional sprinkler.
Fourth: buying the pump from the catalog before the hydraulic calculation memorial exists — when the calculation is done, the real duty point does not match the purchased pump.
The path that gets approved is always the same: hazard classification per the state instruction, density and operation area from NBR 10897, hydraulic calculation to the supply point and only then the pump set specification per NBR 16704/NFPA 20. FB Bombas application engineering runs this path from the designer memorial — or from the building data, when the memorial does not yet exist — and returns the complete FBFS skid specification (main, standby, jockey and panel) within 48-72 business hours.