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Log Truck vs 7200 V

Log Truck vs 7200 V

Log Truck vs 7200 V

(OP)
Log truck driver tried to throw a chain over his load and managed to throw it over a distribution line.  Apparently the ground fault detection was not overly sensitive.  

The driver was not injured (I assume the chain slipped out of his hands), otherwise he'd be in the running for this year's Darwin Awards.

My apologies if this has already made the rounds.

Cheers,

Dave

 

RE: Log Truck vs 7200 V

In the words of my mentor, Bugs Bunny; "What a maroon!"

You KNOW that the logging company will want to salvage those logs though...


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Log Truck vs 7200 V

(OP)
Maybe for making charcoal briquettes.  I have some other photos showing a nice red glow from the middle of the logs.  Of course, you're probably right - they'll just mill them down to 2 x 4 and sell the part that isn't charred too badly.  "Kiln-dried" looking around

Driver reported the tires caught on fire almost immediately.  

   

RE: Log Truck vs 7200 V

Quite a campfire!!!!  Also, I have thrown a few chains over loads, and all I have to say is to have reached those conductors, he must have eaten an extra helping of Wheaties that morning.

Jraef, I can't resist this one-maroon is a color close to purple.  This guy was a moron-but a danged lucky one.

rmw

RE: Log Truck vs 7200 V

It may be wire rope with a short section of chain on the end. That was common in this area many years ago.  

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Log Truck vs 7200 V

I really can't see how he would survive this?  You don't generally just heave the chain and step back do you?  Wouldn't some part of the chain still be touching you? Wouldn't the truck liven up and you'd be touching it or leaning on it, or be closer than the rubber tire distance?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Log Truck vs 7200 V

"Jraef, I can't resist this one-maroon is a color close to purple.  This guy was a moron-but a danged lucky one."

It was a malapropism, something Bugs Bunny was famous for...


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Log Truck vs 7200 V

I suspect that one end of the chain or cable was attached to a hand winch on the side of the truck, and the driver did just throw and step back. It looks like it may take a two handed throw to get that high.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Log Truck vs 7200 V

Or he did the swing trick where he spun it around and let it fly. I have seen loggers cast the cables that way, especially in old-growth areas where the logs are really big. Guess he didn't know his own strength.

More pictures:
http://tow411.yuku.com/topic/48827


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Log Truck vs 7200 V

Well I am going to call him "sir."  It is a cable with a chain and hook on the end.  I once owned flat beds and for those guys that did it all the time (I wasn't one-I just owned, not drove) some of them could send a chain pretty high in order to get it over the load and to the other side.

Still, I think this guy must be in a class of his own.

I agree with one of the posters on that thread that jraef just posted, think of what you say to your insurance adjuster.

Is there any news anywhere regarding what it did to the neighborhoods electrical service?  If it passed current long enough to set that much wood on fire, as well as burn the truck down, it must have really affected the voltage on that phase.

Notice the trailer tires aren't burnt.  Suspensions for log trailers are normally rubber mounted and/or rubber bushed.

rmw

RE: Log Truck vs 7200 V

I notice the trailer tires are completely gone!  You are looking at the bare rims.

I suspect the tires were the bulk fire energy used to get those logs up and running.

I can even see the red glow out of the core of that 'log reactor'!!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Log Truck vs 7200 V

I have to admit to an "oops" regarding the trailer tires after using getting up close to the screen and using the bifocals to get a better view, but the logs in the rear bolster don't appear to be burnt.  At least not on the drivers side.

I think the fire was started by one heck of a big charcoal lighter driven by 7200V.  Fires started by the tires would have shown evidence of burning from the outside in, not the inside out.

rmw

RE: Log Truck vs 7200 V

The oldsters here may remember when cars trailed static discharge straps to bleed of static charges. Static discharge straps haven't been required since the manufacturers started making tires fairly conductive. We had an embarrassing incident years ago. We were making up the connections to a 400 Hp motor. We were concerned  with the tight fit in the junction box so we used some inner tube rubber to separate the connections. That's when we found out about the conductivity of automotive rubber.
 

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Log Truck vs 7200 V

Explain that one to your insurance agent.  

RE: Log Truck vs 7200 V

Hi Keith;
You can see the end off the cable connected to the small hand winch on the front of the first bunk. The driver would have thrown and stepped back.That's how he survived.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Log Truck vs 7200 V

Yep yep! I see that now.  Makes sense.  Big old 'wing it over', "kaBLOWIE", run like hell.

Wish there'd been video..

Keith Cress
kcress - http://www.flaminsystems.com

RE: Log Truck vs 7200 V

A take on this that I hadn't thought of.....

I sent the link to an ex-employee of mine, a guy that is still in the trucking business and has been fairly successful at it.

His take was that the trucker had been scouting this parking place for some time while practicing his throw.  A way out in a bad economy with sky-high fuel prices.

rmw

RE: Log Truck vs 7200 V

What was the estimated operating time for this fault?
 

RE: Log Truck vs 7200 V

I found out about tire rubber conductivity a few years ago when working on a 2300V motor controller for a rubber mixer at a retreading plant. The ignorant workers in the plant were having trouble with the controller overheating on hot days, so they propped the door open and put a fan up to blow air into the cabinet. The carbon black of course followed the air, and although it was a vacuum starter so there was no immediate ignition source, eventually the dust built up on the conductive surfaces and KABOOM! The place lit up like a fireworks factory for a second or two. Luckily nobody was killed.

Still, the resistance across the tires must have been fairly high because the fault would have had to continue for a while it seems to cause that much damage. Unless a brief spark ignited dry grass or something else. It almost looks as though the fire started at the cab and worked backwards. Maybe a surge through the winch motor, igniting the wire insulation, then rubber hoses etc?


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Log Truck vs 7200 V

(OP)
cranky108,

I don't know, but I'm guessing several minutes, at least.  A 100 ohm fault impedance would be 72 amps, which probably isn't going to trip a distribution feeder ground relay.

72 A at 7200 V is about 500 kW just to put it in perspective.

I'd guess the fault impedance started pretty high, then went down as the fire progressed.  But there would still be the earth return to factor in.   

RE: Log Truck vs 7200 V

If dpc's 72A is in the right ball park, I would expect that the fault was cleared when enough smoke created a phase-phase flash over in the lines above.

RE: Log Truck vs 7200 V

There was a fuel fire. The fuel tanks are completely gone. They must have been aluminum.

RE: Log Truck vs 7200 V

I just wanted to know as I have a standard debate with the distribution guys. They want the ground set higher, and I say lower.
There isen't a best answer, just the debate.
 

RE: Log Truck vs 7200 V

Quote (cranky108):

There isen't a best answer...
That's the heart of a lot of protection work.  That's why the answer to all protection questions is "It depends."

RE: Log Truck vs 7200 V

When the truck melts, should have been lower. When the entire county gets cut off because a bird crapped on an insulator, should have been higher.

You're right, there is no answer, only the debate.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Log Truck vs 7200 V

Guys have you never seen a tire fire?  All you would need is a one inch section of a tire ignited and the rest will burn. It would probably take that current all of 1 second to have that one inch section burning.  And on all 14 tires.  Tire fires are hot.  Often fire departments cannot put out a pile of them at all.  So a few duals get cranking, the fuel tanks boil over, and that's it for Mr Truck.

 

Keith Cress
kcress - http://www.flaminsystems.com

RE: Log Truck vs 7200 V

Lest we've forgotten this is an image about 2 seconds into an incident.

Keith Cress
kcress - http://www.flaminsystems.com

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