Fire Safety in Utility Manholes
Fires or explosions occur in manholes when CO, sewer gas, or natural gas ignites in the confined space of the underground system. A fire in a utility manhole can cause loss of life, extended system downtime, and equipment destruction.
Manhole fires are especially likely during the winter in areas where salt is used on roadways and sidewalks. The melting snow and salt filters into manholes and coating the underground electrical wiring and equipment. This salt-water mix is very corrosive and causes the wiring, transformers, and other elements of the underground electrical delivery system to deteriorate sometimes resulting in arcing exposed wires. The arcing, burning wire generates various toxic and combustible gases including high concentrations of carbon monoxide and neoprene gas, which are contained in the noxious smoke billowing out of the manhole during a manhole fire – a smoke that can itself ignite.
Because these are electrical fires and saltwater is an electrical conduit, water should not be used as an extinguishant. Flowing water into a burning manhole could result in electrocution of the firefighters on the line, and could cause an explosion. It could also force the CO in the hole through conduits to other manholes or structures.
One option for extinguishing manhole fires is an aerosol fire extinguishant such as Stat-X. There are several options for addressing manhole fires with Stat-X including first responder emergency fire suppressors and fixed systems.
Fixed Stat-X systems can be installed in manholes to activate by heat. The size of the Stat-X generators is determined by the cubic volume of the manhole. The generators are bracketed near or at the top of the manhole, aimed down to discharge and completely flood the space with the extinguishant. There are Stat-X systems which are capable of withstanding flooding that may occur in a manhole. These systems utilize a NEMA 6P rated enclosure and seal tight conduit to protect the panel from water intrusion due to occasional full submersion.
First Responder Stat-X systems are compact generators designed to be tossed into a burning manhole. The Stat-X fire suppressant is safe to be used in enclosed spaces with individuals present, so if a utility worker happens to be in the manhole when the fire ignites a Stat-X First Responder unit can be dropped into the manhole immediately. The First Responder unit will immediately suppress or extinguish the fire without harming the trapped worker.
Contact A1 to learn more about these life-saving options. A1 is a leading expert on the latest technology in life safety. To find out more information or to ask a question, click here or call us at 1-800-859-6198.
Posted on: April 25, 2017