What is High Pressure Water Mist (HPWM)?

High pressure water mist is a highly efficient fire suppression system which uses specially designed nozzles to create a fine mist. Where high pressure water mist shows its real advantage is that it combines the fire suppression effect of gas systems (by preventing fresh oxygen reaching the seat of the fire) and traditional sprinkler systems (more efficient way of cooling the fuel / material), using much less water in the process.

A fire relies on the presence of three elements in order to survive: oxygen, heat and combustible material. This is commonly known as the fire triangle. Unlike traditional sprinkler systems, which only remove heat, water mist systems deliver fire suppression by removing both heat and oxygen from a fire by jetting water at high, medium or low pressure through specially designed nozzles. The nozzles atomise the water into micron-sized droplets, which rapidly expand into steam when they come into contact with a fire, depriving the fire of oxygen. In addition, water mist has a cooling effect on the surrounding area, which prevents re-ignition of the fire source and any other material that may have caught fire.

Water mist fire suppression is not a new technology, it has been around since the 19th century, and has proved its effectiveness in maritime applications where it has been responsible for saving countless lives. It did not become widely used in land-based applications until the 1970’s when the Montreal protocol banned the use of halon gas as a fire suppressant. The technology was more widely adopted following the 1990 Scandinavian Star Disaster.

Advances in nozzle design like those found in Hydrocore’s high pressure water mist nozzles, have now made water mist an effective, efficient and easy to install fire suppression option.

AN OVERVIEW

Types of water mist system

There are three types of water mist system, which are defined by the pump pressure: low, medium and high pressure.

Low pressure water mist systems

Low pressure systems use a water pressure of up to 12bar. Low pressure water mist systems are less aggressive than a traditional sprinkler system and thus will cause less trauma to anyone caught in the proximity of a release event.

 

High pressure water mist systems 

High pressure water mist systems such as Hydrocore’s HPWM operate at more than 35bar pressure, usually at a pressure of around 100 bar and with micro-droplets with the size Dv0.99<1000μm. By increasing the pressure, water consumption is reduced dramatically as compared to traditional sprinklers, dependent on application.

High pressure water mist fire suppression is achieved by using precision engineered nozzles which are designed specifically for their intended application. The Hydrocore nozzle range includes:

  • Closed nozzles which offer a highly targeted fire suppression response
  • Open nozzles for increased fire loads and hazardous environments.

With such low water consumption it is possible to use smaller/small bore stainless steel pipework, making the system easy to install and maintain. Pipework can be discreetly routed through service ducts without compromising building design and aesthetics.

EXTENSIVE TESTING

Extensive testing and experience have shown that high pressure water mist delivers the following advantages:

  • Ease of maintenance: The use of water without any chemical additives and the use of high pressure stainless steel piping makes the system corrosion resistant, enhancing system life and reducing maintenance costs.
  • Quick and efficient fire suppression: The atomising effect of high pressure water mist offers reliable and effective fire suppression.
  • Minimal Damage: Atomised mist causes a quick vaporisation effect which limits water and fire damage.
  • Low downtime: Quick recovery and less downtime compared to other suppression systems which need servicing or recharging post an activation, this means you can get back to work quicker. In a large application, the downtime cost could easily be millions if a facility is shut for a week or more.