As a rescue instructor, I always have the participants stabilize a vehicle that is resting on its' roof. More times than not, what they come up with is a secure vehicle held up by some well-placed struts. That's what I should see.
There is usually one team however that tries to stabilize a roof-resting vehicle with just cribbing. So what that usually results in is a failure to understand the safety height limitations of a box crib.
FEMA Urban Search & Rescue teams will build box cribbing up to a height equal to THREE times the length of the individual cribbing blocks. That's their protocol. But, they might nail it all together. I believe working with a roof-resting car is different than working with a damaged structure or building.
So, over the years of seeing the successes and failures of box cribbing used to support a vehicle, I have come up with the recommendation that in vehicle rescue, the maximum height of a box crib should NOT exceed TWO times the length of the cribbing being used. In other words, with 18 inch long cribbing, the box crib should not be more than 36 inches tall. Actually, the lower the better.
Besides my height recommendation, make sure that when you build each layer of the crib, the blocks sit in from the end of the block below it a distance about equal to their width. If your cribbing is a 4"x4"x18" block, then each layer sits in about 3 or 4 inches from the end of the blocks below it. That locks the cribbing together when under a load.
Also, all wood blocks used in a box crib should have the grain of the wood running horizontally; not vertically. Vertical grain can fail a wood cribbing block by splitting or splintering when under a serious load.
First is a photo of a box crib, using wood blocks, that clearly shows that its' total height is equal to the length of the blocks being used.
The second image shows a tall box crib that is about as high as I would like to see one built at an incident scene. Any higher than two times the length of the cribbing and it begins to get a lot unstable!
What guidelines or protocols does your department use when establishing the construction of box cribbing at a vehicle rescue incident? Let's share ideas...
There is usually one team however that tries to stabilize a roof-resting vehicle with just cribbing. So what that usually results in is a failure to understand the safety height limitations of a box crib.
FEMA Urban Search & Rescue teams will build box cribbing up to a height equal to THREE times the length of the individual cribbing blocks. That's their protocol. But, they might nail it all together. I believe working with a roof-resting car is different than working with a damaged structure or building.
So, over the years of seeing the successes and failures of box cribbing used to support a vehicle, I have come up with the recommendation that in vehicle rescue, the maximum height of a box crib should NOT exceed TWO times the length of the cribbing being used. In other words, with 18 inch long cribbing, the box crib should not be more than 36 inches tall. Actually, the lower the better.
Besides my height recommendation, make sure that when you build each layer of the crib, the blocks sit in from the end of the block below it a distance about equal to their width. If your cribbing is a 4"x4"x18" block, then each layer sits in about 3 or 4 inches from the end of the blocks below it. That locks the cribbing together when under a load.
Also, all wood blocks used in a box crib should have the grain of the wood running horizontally; not vertically. Vertical grain can fail a wood cribbing block by splitting or splintering when under a serious load.
First is a photo of a box crib, using wood blocks, that clearly shows that its' total height is equal to the length of the blocks being used.
The second image shows a tall box crib that is about as high as I would like to see one built at an incident scene. Any higher than two times the length of the cribbing and it begins to get a lot unstable!
What guidelines or protocols does your department use when establishing the construction of box cribbing at a vehicle rescue incident? Let's share ideas...
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