Classification of sprinkler systems
FPASA BULLETIN FP 11
Automatic Sprinkler Systems – Categories of Protection
A sprinkler system is designed to discharge a specified quantity of water per minute over a predetermined floor area. This is known as the design density of the system and relates directly to the contents of a building, the height of goods storage and the type of process involved. It is therefore imperative that the risk presented by the occupancy or contents of a building be carefully evaluated before determining design densities.
Sprinkler systems are fixed installations and upgrading them by increasing water densities and reducing sprinkler head spacing is impractical. Therefore specifications have been provided to discriminate between installations protecting varying risks. These specifications appear in SABS 0287 and the following installations cater for most occupancies:
- Ordinary hazard systems
- High-hazard systems
The following definitions refer to the terms used in the tables, which follow:
| Heads/valve | the maximum number of sprinkler heads supplied by one set of main valves. |
| Assumed maximum area of operation (AMAO) | The maximum area in m² expected to be involved in any one-fire situation. |
| Floor area | the maximum floor area coverage provided by each sprinkler head. | Design density | the minimum amount of water per minute, discharged from each sprinkler head at any point below it and within the floor area coverage. |
| Flow | the minimum quantity of water per minute discharged through the maximum number of heads for which the system is designed. Note: 1dm³/min equals 1l/min. |
| Reservoir | usually used as a secondary water supply or as a primary supply particularly for high hazard systems where design densities can seldom be met by mains. The minimum capacity of the reservoir excludes any inflow of water through ball valves etc. |
Ordinary hazard
Ordinary hazard systems are used to protect commercial and industrial occupancies where the combustibility of the contents or the process hazards is considered to be moderate.
Example
- Accumulator manufacturers
- Printing works
- Department stores
- Paper mills
- Saw mills etc.
- Hotels
- Offices
Ordinary hazard design criteria
| Heads/valve |
AMAO |
Floor area |
Design density |
Valve pressure |
Flow |
|
1 000 |
216 m² |
12m² |
5 mm/min |
1 100 |
2 500 dm³/min |
High-hazard systems
High hazard systems are used to protect occupancies where the combustibility of the contents or the process hazards are considered to be high.
Example
- Polish manufacturing
- Cotton mill preparatory processes
- Firelighter manufacturers
- Flax, jute and hemp mills
- Match factories
- Paint and varnish manufacturers etc.
|
Heads/valve |
AMAO |
Floor area |
Design density** | Flow | Reservoir |
|
1 000 |
260m² |
9 m² |
7.5mm/min 10mm/min 12.5mm/min 15mm/min 17.5mm/min |
2 300dm²/min 3 050 Ò 3 800 Ò 4 550 Ò 4 850dm³/min |
225m³ 275m³ 350m³ 425m³ 450m³ |
|
400 m² |
20mm/min 22.5mm/min 25mm/min 27.5mm/min 30mm/min |
6 400dm³/min 7 200dm³/min 8 000dm³/min 8 800dm³/min 9 650dm³/min |
575m³ 650m³ 725m³ 800m³ 875m³ |
* The design area can vary between 260m² and 400m² according to varying conditions.
** The design density of discharge relates directly to the height to which stored goods are stacked.
*** Actual flow rates are determined by hydraulic calculation.
Conclusion
The design criteria outlined in this bulletin should be construed as being a guideline only and it is advised that the Automatic Sprinkler Inspection Bureau be consulted for detailed information on the interpretation of specific protection problems.
Published by
Fire Protection Association of Southern Africa
(Incorporated Association not for Gain)
(Reg.No. 73/00022/08)
PO Box 15467
Impala Park
1472
People in Risk
Marcel Wood
Marcel Wood heads Etana’s risk management division. Before starting in insurance he worked for the fire department, rescuing people and (literally) putting out fires. He’s passed through Munich Re and Santam, and has designed the only risk management tool aimed specifically at the insurance industry – ARQ. Marcel is a mean guitarist, a brilliant vocalist and an accomplished soccer player with the personal motto: “Do your best all the time”.
