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_________________________________________ Midsouth Rescue Technologies

Bumper Struts

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The Dangers of Compressed Gas Bumper Struts

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In 1973, in an effort to absorb the impact of low speed crashes, manufacturers began to install nitrogen filled gas struts, which are much like shock absorbers, on their front and rear bumpers.
 
 
 
 

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The fire service soon learned that these struts would experience a very violent explosion when exposed to the heat of a vehicle fire, many times ripping the bumper off and throwing shrapnel as far as 150 feet. 
Nitrogen makes up 78% of the air that we breath, it is non-flammable and non-explosive, but it has a very high rate of expansion when exposed to very little heat causing its container to explode into shrapnel and shafts to be ejected like missiles, as seen in the picture.

As this became apparent, new training was developed in the early 1970s to protect firefighters from these projectiles. Firefighters are now taught to approach the vehicle at a 45 degree angle to one corner of the vehicle. Today this training is still being taught nationwide even in our largest academies.   

March 29, 2005
 
Salinas Rural Fire District responded to a vehicle fire involving a Volvo Station-wagon in which the engine compartment was fully involved. As they were taught, three firefighters approached the vehicle at a 45 degree angle from the driver's side of the front bumper. Just before water was applied to the fire, a loud explosion was heard and the fire in the engine compartment shifted. The three firefighters assumed that it was a tire that had exploded and continued the extinguishment.      

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After the fire was knocked down, an officer found the complete bumper and lift strut laying several feet from the vehicle. 
 
 
 
 

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The lift strut had exploded lunching the bumper away from the vehicle approximately 25 feet, penetrating a wooden fence.
 
The bumper weighting at lease 50 pounds, traveled fast enough that it was unnoticed by the three firefighters standing within ten feet of it at the time.
 
 

bumper4.jpg
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The bumper had departed from the vehicle at a 45 degree angle from the passenger's side. As seen in the picture, the driver's side strut failed. The bracket on the passenger's side secured the bumper long enough to change the flight path and cause the bumper to twist 180 degrees from its original shape. Because one of the brackets held the bumper in place, energy from the explosion was utilized to twist the bumper and to sheer three of the four bolts on the passenger's side of the car.
Had both of the struts failed simontaneously ,or the bracket on the passenger's side been further damaged from the fire, the bumper would have traveled at a much greater force, possibly damaging the engine park ahead of the fire or injuring the crew around it.

Notice the obvious?
If it had been the passenger's side strut that failed first, or if the firefighters had chosen to approached from the passengers side, there would be three seriously injured firefighters, injured because they were taught to be standing in this position.

Reality is!
Both struts must receive the same amount of heat for the same period of time in order for both to explode at the same time, which is the only way that a bumper can be lunched straight forward. The odds of that is nearly zero. The bumper is going to lead off in one direction or the other every time. The only variance depends on the amount of resistance the other side provides. 

Warning!
 
Never cross in front of the burning end of a vehicle

click here to play video

Did you notice again that the bumper swung to the right?
Looking real close at the end of the video, as he moves the hose, you can see the bumper lying beside the car and the strut is on the shoulder of the road in front of the car.

May 19, 2008
A Fla. crew responding to a vehicle fire experienced a bumper strut explosion first hand. It was reported that this video was the second strut to blow, the first blew out while they were exiting the truck.

May 1, 2008
An Oakland, Calf firefighter suffered two broken bones in her left leg, requiring surgery as a result of a bumper strut explosion.

 
March 25, 1990
Willis White's volunteer fire department was called to a structure fire, when they arrived the house was completely engulfed in flames. The blaze had already destroyed the entire house and its contents, including the 1988 Volvo that was parked in a carport adjoining the house. The Volvo's gas tank had exploded prior to their arrival.

While White was fighting the fire in the garage and carport area, the Volvo exploded again. White's legs were injured as a result of being struck by metal fragments that were propelled from the Volvo when the shock absorbers used to attach the bumpers to the car exploded.

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Feb 13, 2008
Firefighter received a broken leg.
 
 
 
 
 

As you can see, we are in drastic need of a change in our training. What is really scary though is that our currant training was developed in 1973 and some still do not understand it. Click on the video below and watch the fire over the right strut.  This is one of our largest academies.

Is it time to change our training yet?

This is a 1976 Buick Regal we know it is equipped with bumper struts both front and rear.

 

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Midsouth Rescue Technologies - PO Box 1830 Springtown, Texas 76082

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