Low Pressure Water Mist Systems

low_pressureNozzleThe SECURIPLEX Water Mist system is a highly effective extinguishing system that uses water and air to generate a fine water droplet. The Water Mist system uses less water than standard sprinkler systems and provides equivalent or better extinguishing characteristics than gas but without hazard to personnel. Specifically, the Water Mist’s unique characteristics provide the user with:

Low water discharge

The Water Mist system uses less water per discharge than any conventional sprinkler. Post-discharge cleaning time is therefore negligible and consequential damages and losses are minimized. Operations can resume in the shortest time possible.

Highly effective extinguishment

The Water Mist system extinguishes the fire in seconds and, unlike gaseous systems, is highly effective even though limited ventilation is present.

Enviromentally friendly and safe for personnel

The Water Mist system simply uses water and air, which cause no potential risk for the environment or for personnel. Therefore the evacuation of personnel before a system discharge is not essential.

Low pressure

The SECURIPLEX FIRE SCOPE® 2000 Water Mist system operates at a low pressure of 75-85 psig which allows the use of standard piping and the connection to the plant water and air supply, when available. This provides almost unlimited protection time and eliminates the need for water tanks or bottles. Maintenance cost is therefore greatly reduced

Twin fluid

Twin fluid technology uses large water pathway nozzles. Mist is generated by air impingement as opposed to small orifices therefore minimizing the risk of nozzle clogging. The SECURIPLEX FIRE-SCOPE® 2000 water spray system is typically supplied as a fully integrated system including, control, detection and extinguishment, however the FIRE-SCOPE® 2000 can be integrated with an existing detection system.

Water mist technology

The NFPA 750 standard uses water droplet sizing in order to differentiate between water mist systems and other water-based systems such as sprinklers and deluge systems. The NFPA defines water mist as:

  • water spray for which 99% of the total volume of water is in droplets with a diameter less than 1000 microns (Dv0.99) at the minimum design operating pressure of the water mist nozzle.

NFPA 750 also identifies water mist systems available in many configurations with various characteristics as shown in the list below. The itmes in italics are SECURIPLEX exclusive.

NFPA 750 DEFINITIONS

TECHNOLOGY
  • Single Fluid
  • Twin fluid atomizing
OPERATING PRESSURE
  • Low pressure (<175 psi)
  • Medium press. (175 psi up to 500 psi)
  • High pressure (>500 psi)
NOZZLE TYPE
  • Open nozzle, dry pipe
  • Closed nozzle, wet pipe, fusible head
DROPLET SIZE
  • Class 1 droplet size (Dv0.90 < 200 MICRON)
  • Class 2 droplet size (200 MICRON < Dv0.90 < 400 MICRON)
  • Class 3 droplet size ( Dv0.90 > 400 MICRON)

Water mist extinguishes fires by TWO MAIN PRINCIPLES:

  • Removal of heat energy from the fire plume due to vaporization of mist into steam. The large surface area per unit volume inherent in small droplets results in a very efficient and rapid heat transfer process.
  • Localized displacement of oxygen from the fire base due to the production of steam. When water changes into steam, it expands by a factor of 1650 times which creates an important oxygen displacement at the base of the fire.

The use of water mist also has considerable benefits:

  • Attenuation of radiant heat. Suspended water mist particles within a volume will scatter radiant heat energy from a fire, minimizing the risk of adjacent combustibles igniting.
  • Cooling and wetting of combustible. Will prevent the risk of re-ignition.
  • Scrubbing smoke and other combustion products from the air. This is important as it improves the chances of a successful evacuation and survivability of personnel.
  • Extinguishing capabilities in ventilated conditions. Even though it is recommended to shut down ventilation when discharging water mist, in the event of faulty louvers or open doors, the water mist will still efficiently extinguish fires as proven during the FM testing.