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  1. #1

    Default Responding to Manhole Fires

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    Somthing you might want to review with local supervison and Fire Depts,

    This is the electric manhole fire season in those areas where cold weather, snow, and slippery roadways necessitate the placement of ice-melting salt onto roadways to make them safe. When the salt is put on top of slick roads, the result is a melting of the ice and snow that coats them. As a result, the roadway becomes safely passable but at a price. The mixture of salt and melted snow and ice filters into manholes, coating the underground electrical wiring and equipment. This salt-water cocktail 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. These gases are contained in the black noxious smoke billowing out of the manhole at a manhole fire.
    Firefighters and troubleshooters responding to these incidents should be aware of the many hazards that may accompany this phenomenon.
    1. The black smoke can at any moment suddenly ignite, exposing people and vehicles nearby. A person inside a car parked over such a manhole would be severely injured or killed should the smoke ignite as he tried to move the parked car away from the manhole.
    2. The ignition can be explosive, sending the 300-pound manhole cover flying into the air. Manhole covers have been blown onto the roofs of six-story buildings and have gone up in the air only to come crashing down through the roofs of passing vehicles.
    3. Manholes are connected underground to other manholes by electrical conduit through which wires pass. Fire in one manhole can spread to other nearby seemingly uninvolved manholes, which can suddenly start to smoke, erupt into flames, or blow their covers into the air.
    4. The explosive and toxic gases created at these incidents can pass through underground conduit into surrounding structures served by the underground electrical delivery system. The result can be overcome occupants and an explosive atmosphere in the electrical service box or the entire building. These explosive gases can also travel along underground conduit and enter and fill up hollow street light poles. A spark from a traffic light control box can ignite these gases, causing the lights' access panels to blow off the poles.
    5. Salt water is a good conductor of electricity and, as a result, manholes and grates covering underground electric equipment have become energized, resulting in the deaths of passing pedestrians, pets, and in one case a carriage horse. A metal bus stop shelter and metal curb strip became charged in one instance; in another, a nearby hydrant was charged.
    6. 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 into other manholes or structures.
    When responding to these incidents take the following actions and precautions:
    1. Notify your electric utility to respond.
    2. Stay clear of the trouble manhole.
    3. Stop any traffic that might be endangered by a flying manhole.
    4. Find and stay clear of the next manhole on either side of the trouble manhole.
    5. Check nearby structures for carbon monoxide and evacuate them, if necessary.
    6. Do not attempt to kill the power to a building, even if its lights are blinking; there could be an explosive atmosphere in the electric panel box. A spark created by opening the main cut-off could result in an explosion.
    7. Do not flow water into manholes until requested by your electric utility. When requested to flow water, do not flow it directly into the manhole from a hoseline. Bounce it off of the street and let it flow along the ground into the manhole or, better still, let water from an unmanned open butt flow into the manhole.
    8. Be aware that the danger area around a burning manhole may extend to other manholes, nearby street light poles, and traffic control boxes as well as the surrounding structures. If electric service is delivered by a combination of overhead and underground wiring, be aware that a manhole fire can extend up to the overhead wires via a connecting conduit. This would put the run of overhead wiring in the danger area.
    Manhole fires often do not have catastrophic results-they can often be concluded without explosions and without having to evacuate buildings. However, conditions can change without warning from lazy smoke seeping from a manhole to smoke billowing out under pressure. The smoke can suddenly erupt into flame or explode. Use caution and common sense when responding to these incidents. Seek and heed the advice of your utility representative and expect the unexpected. A manhole response is not a "routine" response. There are no "routine" responses

  2. Default I dont get it

    Why do you post all this. If you want to teach in a line school go ahead but most of us have been there and done that. You are just stating the obvious.

  3. #3

    Default

    what may be obvious to you might not be so ppl with less experience or apprentices, so it does help some people, b/c i have learned a few things by reading it
    Hemingray Insulators
    work smart, go home every night

  4. Default Really

    You are right Brian but you know how boring this is to the old hands on here. I do see your point though. A little less of the line school though would be nice. I personally get bored with it. Its all new to you so you like it. I don't. I wish you the best Brian good luck. Always think first then do cause I don't want to read on here you got hurt. On the other hand don't let it scare you. A healthy respect is what you need. Thanks for posting.

  5. #5

    Default

    I thought it was a good post. I'm also a volunteer firefighter, and the only thing that we are ever taught is that 99% of the time if it is anything involving power lines we just go there and keep everybody away and wait for the power company to show up. Good post though, I wish there were more like this. Forums are a great place to learn things and not just shoot the sh!t. You old timers should post stuff like this and other things you know or have learned over the years. What you might think is "useless knowledge" just might save somebody's life some day, or at least a world of hurt.

  6. #6

    Thumbs up Good post

    We have 3 phase primary manholes with large heavy lids on them in the middle of streets. It would be good for fire depts to know that the lid could fly off at any time. Most of the time the fire dept. gets on seen before linecrews do.

  7. #7

    Default Talk about it with your FD before it happens

    Quote Originally Posted by PA BEN View Post
    We have 3 phase primary manholes with large heavy lids on them in the middle of streets. It would be good for fire depts to know that the lid could fly off at any time. Most of the time the fire dept. gets on seen before linecrews do.
    It does take balls to lift the cover off a a smoking MH. The inrush of O2 can cause flashover.

    Some of this is old hat to us all but even an old dog can learn a few new tricks. It's always better to have a plan than to fly by the seat of the pants. Trouble Shooters are first responders much like Fire Dept and/or Police. How many of us have seen Cops wandering around down conductors at P-Hits. I sure have. Countless times. Have heard about fire departmens refusing to flood Manholes at Elec Utility request. It happens. Foam works best I believe, not readily available, but again, you do not want to discuss it on the fly..........Have a planned response in place.

    Ground rules on electrical hazzards for first responders are best established prior to an emergency response. Agreed? Plan the work. Work the plan. Sure it's a cliché but if your not working from the same page things go to shit quickly.

    Just check out these links to reacent manhole fires.
    http://www.wtoctv.com/Global/story.a...2&nav=menu89_2
    http://www.google.com/hostednews/ap/...-0KqQD959JV280
    http://gothamist.com/2008/12/22/if_i...be_manhole.php

    Does your company have a planed response?

    SEAPOPE Electrical Consulting LLc
    CPONEIL@Charter.net
    JOURNEYMAN #E31316
    PE REGISTRATION #37843
    Last edited by CPOPE; 01-02-2009 at 02:29 PM.

  8. #8

    Question I don't buy the salt water

    I know of URD Manholes on the waterfront w/600 hammer heads, that are subject to ocean tidal water. And salt water doesn't effect them. I think the URD was getting ready to go anyway and the salty water put it over the edge. In any event manhole fires are Dangerous.

  9. #9

    Default

    I'm guessing the ones that get ocean water in them will be suitably designed and spaced internally to limit the risk of fires.

    The ones getting salty road water washed into them sound like they are an old system that was never really designed for that scenario, and aren't being subject to suitable modernisation. Maybe when they go on fire that's the cue to modernise.

    The use of modern chemical "salt" for ice removal is definitely causing more issues than plain grit alone did. The road spray coats insulators and causes tracking, so it may be that modern ice removal chemicals are the main issue with manhole fires.
    Portable defibrillators were first invented to save the lives of linemen. Where's yours?

    www.bigclive.com

  10. Default

    Featured Sponsorr

    Not living in a climate that has snow or ice in winter we dont have any salt issues in my area.
    I used to work for a company with a extensive underground system of substations and infrastructure , had a few problems mainly with gas entering street ducts and heavy rain flooding vaults, these days you need a confined space permit , gas test ,full rescue team with tripod and rescue equipment set up before entering these areas can take hours to gain access for a five minute job.

    Years ago we worked in them with no safety equipment or training .. times sure have changed.

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