International Symposium on Mitigative Measures against Snow ...
International Symposium on Mitigative Measures against Snow ...
International Symposium on Mitigative Measures against Snow ...
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<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>Symposium</str<strong>on</strong>g> <strong>on</strong> <strong>Mitigative</strong> <strong>Measures</strong> <strong>against</strong> <strong>Snow</strong> Avalanches<br />
Egilsstaðir, Iceland, March 11–14, 2008<br />
Figure 3 Typical drawing of the Daisy Bell® system<br />
Two plugs, placed <strong>on</strong> the top of the system, launch the explosi<strong>on</strong>, where the mixture<br />
accumulates. C<strong>on</strong>cerning the injecti<strong>on</strong>, systems of check valves prevent the explosi<strong>on</strong> from<br />
going to the gas reserves.<br />
The c<strong>on</strong>trol system is placed in a protected box, remotely c<strong>on</strong>trolled by an operator from the<br />
helicopter. The firing procedure is semi-automatic because the operator just needs to remain<br />
pressing <strong>on</strong> two butt<strong>on</strong>s to automatically start the operati<strong>on</strong>s: simultaneous injecti<strong>on</strong> of both<br />
gases during 7 sec<strong>on</strong>ds and igniti<strong>on</strong> of the sparks. In case of trouble and to exploit human<br />
reflexes, the simple release of at least <strong>on</strong>e butt<strong>on</strong> stops the procedure. It can be started again<br />
within 30 sec<strong>on</strong>ds or the system will start the draining of the volume. It c<strong>on</strong>sists in saturating<br />
the volume with oxygen to make the injected mixture n<strong>on</strong>-explosive: it can be activated to<br />
secure the system in case of problem.<br />
A system of distance measurement with the snow cover surface has been added to well place<br />
the system above snow from the helicopter: an about 2-meter distance is in principle<br />
desirable. All in all, the system weighs about 600 kilos.<br />
With the gas reserves fixed <strong>on</strong> the main c<strong>on</strong>e, about fifty fires can be made before refilling<br />
with new bottles. It takes about ten minutes with two people.<br />
94 A new helicopter gas device for avalanche preventive release