We have compiled some very basic points for effective designing of a water spray system. For more detailed information, refer to NFPA 15, which is the Standard for Water Spray Fixed Systems for Fire Protection. Water Spray Systems are basically used for fire control, extinguishing, cooling, prevention and/or exposure protection of industrial hazardous locations.
As per NFPA 15, for a typical water spray system, the design density of spray ranges from 4.1lpm/sq.m to 20.4 lpm/sq.m – depending on the application and hazard type. The minimum operating pressure of any nozzle protecting an outdoor hazard is stipulated at 20 psi (1.4 bar).
Major steps in designing effective water spray system
- Establish design area (area to be sprayed)
- Determine dimensions
- Determine water density (application rate)
- Calculate water demand
- Establish nozzles required (K-factor & Spray Angle)
- Determine Nozzle Orientation
- Determine number and type of nozzles required to give adequate water coverage
- Adjust K-factor & Spray angle - Recalculate
- Finalize the design
| Design Objective | Hazard Type | LPM / Sq. Meter |
|---|---|---|
|
Exposure Protection
|
Vessel surface |
10.2 |
|
Horizontal structural steel |
4.1 |
|
|
Vertical structural steel |
10.2 |
|
|
Cable trays / runs |
12.2 |
|
|
Transformers |
10.2 |
|
|
Extinguishment
|
General |
20.4 |
|
Conveyor belts |
10.2 |
|
|
Control of Burning
|
Pumps and compressors |
20.4 |
|
Liquid pool fires |
12.2 |