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Water Mist is an excellent extinguishing agent with an enormous range of applications, from protecting delicate machinery and electrical areas, through to high-risk waste recycling processes! Although these applications are a world apart, the water mist technology is based on the same principle – the breakdown of water droplets for improved efficiency and less agent usage.
Water mist is so effective (and uses very little water) due to the process of breaking the water into millions of tiny droplets. This provides the water with a significantly larger surface area, enabling it to absorb the heat of the fire. As the water absorbs the radiant heat (which is what causes fire spread and flashover), the tiny droplets quickly turn to steam which expands, displacing the oxygen and creating an environment where there is insufficient oxygen for flames to occur. This means that, of the three elements in the Fire Triangle, two (Oxygen and Heat) are removed.
In High-Pressure Water Mist Systems, the droplets can be less than 100 microns. This means that delicate electrical parts can be protected by this system, as the tiny particles cannot conduct electricity. This unique reaction makes water mist a great choice for almost any application. Read on to find out more about the difference between the various types of water mist and applications, or get in touch to discuss your requirements in more detail.
High Pressure vs Low Pressure Water Mist
High Pressure Water Mist is typically used in special application protection, most commonly from a fixed bank of cylinders. From generator turbines through to server rooms, high pressure water mist is an excellent choice due to it’s low water usage, tiny water droplet size and low footprint. Another huge benefit is the fact that it doesn’t require an airtight room to operate (unlike gaseous suppression systems).
Low Pressure Water Mist is most commonly used in process or large area protection applications. From the reception hall of a waste recycling facility, through to a listed building or hospital, a pumped low pressure water mist system provides excellent protection, low water usage and is a more cost-effective solution than sprinkler systems.
The larger droplet size of low pressure water mist makes it very well suited for protecting potentially high fire load areas within the waste recycling industry, whilst optimizing the effectiveness of the water used to minimize the risk of waste water runoff.
Cylinder Based Water Mist System
Cylinder suppression systems have both the extinguishing agent and the pressurising gas stored in a ‘bank’ of large high pressure cylinders.
On detection of a fire, the stored pressure cylinders release the nitrogen gas inside to begin the discharge of the water cylinders through the discharge pipework and nozzles.
These systems are ideal for protecting a mechanical asset, and are good value for money. However, after discharge the system needs to be totally and the nitrogen cylinders replaced, which can be quite costly. For this reason we don’t recommend cylinder based systems for protecting a process – pumped systems are more appropriate.
Pumped Water Mist Systems
Pumped water mist systems draw their water from the mains water supply coming into the building, with a break tank holding a stored supply in reserve.
The systems we install hold a supply of water in a pressurised accumulator, with the pipework holding stored pressure all the way up to the discharge nozzle, where there is a high speed solenoid. This ensures that the system begins discharge the instant a fire is detected.
As pumped water mist systems have a larger water supply available, they are more suitable for protecting the processes taking place on your premises. We would recommend protecting risk areas such as your shredders (hopper and outfeed conveyor), conveyors and dust extract systems. The system is automatically refilling the break tank etc while the system is in use which means that there is no extra cost incurred whenever the system activates and there is no system downtime after activation.
Although pumped systems will typically cost a little more to install, they are a much better long term investment for protecting high risk processes where a fire is very likely and the cost or replacing cylinders is unsustainable.
Pro’s and Con’s of Water Mist Fire Suppression Systems