| 摘要 |
<p>The system is applicable where cables are laid in armoured steel conduits in locations where there is a fire hazard. It is particularly advantageous where telephone or control cables are concerned whose circuits must be maintained for as long as possible in the event of a fire. The inner surface of the conduit is treated with a proprietary varnish which produces a foam when its temp. reaches a certain value thereby pushing the cables towards the centre of the tube and surrounding them with a thermal barrier to delay the decomposition of the cable insulation. A typical varnish applied in a layer 1 mm thick will bulk up to between 30 to 40mm when heated. It is advantageous to apply a rust proofing coating before the varnish.</p> |
