Het is zelfs een wereldwijde ontwikkeling met onderzoek in GB, NZL en USA...
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Un-Shielded Fires
Michael Dunn - University of Canterbury - Christchurch, New Zealand. (Report 1998/2)
A comparison is made between CAFS (compressed air Foam), HPD (High Pressure Discharge) and HPD with Class A Solution on unshielded post flashover compartment fires. Extinguishment was carried out by trained fire fighters using hand held lines, whilst the method of attack was carried out following New Zealand Fire Service operating procedures. The effectiveness of each method was determined, by recording the heat release rate using the method of Oxygen Calorimetry. Knockdown effectiveness was also evaluated by recording internal compartment temperatures with the use of themrocouples. In addition comments from firefighters have been recorded and video footage reviewed so that a qualitative assessment could also be made. It was found that CAFS performed more effectively than HPD or Class A solution, in that less water was needed to obtain a similar knockdown performance. No noticeable benefit was obtained when Class A solution was added to the unmodified HPD line. The biggest advantage of CAFS over the other methods was the ability in being able to attack the compartment indirectly from a distance, which has additional benefits with respect to tire fighter safety.
For these three firefighting methods agent was applied at a constant rate of 170 litres per minute to a post flashover, wood crib fire in a standard 2.4m x 2.4m x 3.6m unshielded enclosure. A mix of 0.3% foam solution was used for the CAFS and Class A runs which provided an average expansion ratio of 5.0 for the CAFS runs and 2.3 for the Class A runs. In all 10 experimental runs were carried out, which provided a minimum of three runs for each method. All experiments had identical fuel loads with the measured peak Heat release rate varying between 3 and 5 MW.
It was found that in order to achieve total suppression CAFS required on average 12 litres of agent whilst HPD and Class A required 19 and 21 litres respectively. In terms of the time taken for the compartment to reach tenable conditions and the heat release rate to be knocked down to 30%, 20%, and 10% of its initial value no clear difference was found between either three of the methods. When the application for the latter two methods was reduced to 12 litres for one set of runs it was found that compartment conditions at termination of suppression were more tenable for the CAFS run, and re-ignition of the cribs was less likely using CAFS. The use of plain water in fog form (HPD) was found to cool temperatures in the overhead more effectively than with CAFS. The main advantage of CAFS over HPD and Class 'A' Solution found during these tests is the benefit it has regarding the ability to indirectly attack the compartment fire from a distance.
Shielded (by Partition) Fires
Neil Gravestock - University of Canterbury - Christchurch, New Zealand. (Report 1998/3)
A research project by Gravestock looks at the effect of the three firefighting methods discussed above when held in comparison for extinguishing a shielded post-flashover fire. A partition prevented any direct impingement on the fire located towards the rear of the test-rig. The indirect applications of 170 LPM for 10 seconds achieved compartmental temperature reductions from 820 deg C to 200 deg C within 80 seconds. However, the report stated that cooling rates were similar for all three methods although plain water was again seen to be the most effective of the three agents. It was noted that the CAFS stream passed through the flames and only had any real cooling effect when it came into contact with superheated surfaces towards the rear of the test-rig. This caused an amount of steam to 'push' the flames out of the test-rig doorway to a distance of 2-3 metres on initial applications.
The conclusion of the Gravestock research was similar to that of Dunn in that very little difference was found in the suppressive effectiveness of the three firefighting methods although it was suggested that additional research using these agents on larger compartment fires may prove worthwhile.
USA Experience of CAFS
In a range of field trials the operational capabilities of fire-fighting streams have been compared for structural firefighting effectiveness. In most cases the comparisons were made in straight-stream or smooth-bore form only. The cooling effectiveness of water-fog applications were rarely evaluated.
A series of controlled room and contents fires were performed at Wallops Island, Virginia and Salem, Connecticut by Hale Fire Pump, the Atlantic Virginia Fire Department, Ansul Fire Protection, the International Society of Fire Service Instructors, Elkhart Brass, the National Aeronautic and Space Administration-Goddard Flight Center Fire Department, the Charlotte North Carolina Fire Department, the Fairfax County Virginia Fire Department and F.l.E.R.O. (Fire Industry Equipment Research Organization) and the Salem Connecticut Fire Department.
