ARCHIVED - New Water-Mist Fire-Suppression System Now Available For Industrial Oil Cooker Protection

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December 05, 2005— Ottawa, Ontario

Mock-up used to test effectiveness of water-mist in extinguishing large-scale cooking oil fires.
Mock-up used to test effectiveness of water-mist in extinguishing large-scale cooking oil fires.

Not long ago, researchers in the Fire Research Program at the NRC Institute for Research in Construction (NRC-IRC) successfully developed a water-mist fire-suppression system to protect industrial oil cookers with industry partner CAFS Unit Inc. Now they have two more successes to celebrate connected with that system, which has been named MistShield. These include the construction of a new test facility for use in studying and approving water-mist systems for industrial oil cooker protection and the product's successful completion of FM Global approval - the first time this type of technology has received such approval for use in the market.

This stems from a collaborative research project with CAFS Unit Inc. and researchers in NRC-IRC's Fire Research Program undertaken in 2003 that demonstrated the effectiveness of water-mist fire-suppression technology in extinguishing fires in large industrial oil cookers.

"This is the first time a water-mist system has been made available for industrial oil cooker protection, and it's good news for the industry," says NRC-IRC's Dr. Zhigang Liu, who led the project.

Industrial oil cookers are essential equipment used in food processing plants for processing chicken, fish, potato products, doughnuts and other food products. When fires occur in these cookers, they are challenging to extinguish. With oil varying in quantity from hundreds to tens of thousands of litres, the fire can spread rapidly over the oil surface to form a large fire. The oil becomes very hot (up to 407°C) after ignition, and if the oil is not cooled sufficiently as the fire is being extinguished, the fire can re-ignite.

Until now, carbon dioxide has been the most commonly used fire-control agent for industrial oil cookers. Although it works well in extinguishing flames over the oil surface, it does not have sufficient cooling capacity to bring the oil below its auto-ignition temperature and prevent it from re-igniting. Chemical extinguishing agents are not an alternative because they are not allowed in food-processing plants due to food safety considerations.

IRC researchers came up with a viable option: they found that a mist of fine water droplets was very effective in extinguishing commercial cooking oil fires and preventing re-ignition. Researchers developed two water-mist systems for extinguishing these large cooking oil fires. Using a simulated industrial oil cooker 2.44 m wide and 3 m long, and holding up to 1000 litres of canola oil, they studied both the characteristics of water mist and the required design parameters for use of water mist in extinguishing such fires.

The MistShield water-mist system developed by NRC-IRC and CAFS units is able to effectively extinguish large-scale cooking oil fires.
The MistShield water-mist system developed by NRC-IRC and CAFS units is able to effectively extinguish large-scale cooking oil fires.

Both of the water-mist systems they had developed were effective in extinguishing the cooking oil fires with short extinguishing times. The fine water droplets penetrated the fire plume and reached the oil surface. Oil temperature quickly decreased with water-mist discharge. No burning oil was splashed outside the cooker, and no cooking oil re-ignited in the pan. The effectiveness of water mist in fighting large cooking oil fires was influenced by the spray pattern and coverage, water density distribution, and water spray momentum.

More recently, the system underwent testing protocols with FM Global, a leading commercial and industrial property insurance and risk management organization. The water-mist system demonstrated its excellent performance in extinguishing very large cooking oil fires in less than 12 seconds (the test standard requirement is 60 seconds).

Constructed specifically for MistShield's FM fire testing approval, NRC-IRC's new test facility includes five large industrial oil cooker mock-ups built in NRC-IRC's burn hall. During the FM approval fire tests, the system also cooled large quantities of very hot cooking oil to below 200°C from its burning temperature in less than two minutes of water-mist discharge, without causing oil splashing outside the cooker, thus preventing re-ignition.

This outstanding performance secured FM fire testing approval for MistShield, which is an essential step for a product to gain acceptance in the food processing industry. The system has also recently passed other approving requirements for use in the market. FM is the only organization that has such approval standards for factories.

"This is the first time a water-mist system has been made available for industrial oil cooker protection, and it's good news for the industry," says NRC-IRC's Dr. Zhigang Liu, who led the project.


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