Wheel chock placement for pumper and aerial apparatus
Wednesday, October 31, 2018
I remember when I first started going through the procedures for becoming a driver engineer in my former department, I do not recall being told about wheel chocks, or how to use them! Once assigned to a driver’s position, I don’t even recall having wheel chocks on my apparatus. That is probably because the geography of Miami is flat (boring). It was not until a few years later upon becoming the driver engineer instructor that I became educated on their use.
Most, if not all, fire apparatus come from the factory with wheel chocks. In general, the wheel chocks should be 25 percent of the measured diameter of the tire.
There are several types and different materials. Our department used aluminum wheel chocks. I preferred the one-piece casted type. Some of our aerial apparatus had the "collapsible" type. I was not a fan of these because they are "finger biters."
Great care and caution are needed when locking them into their open position — especially among new personnel unfamiliar with how they are deployed. I would always grab the newbies and show them how to place chocks in the open position.
Also, gloves are a must. The advantage to these is that they have a reduced profile when stored on the truck, whereas the one-piece cast would hang down further (closer to the ground) where they can get damaged from hitting something on the roadway.
When putting chocks in place, remember that during pumping operations the apparatus "vibrates" because it is obviously running. If you place the chocks right up against the tire on both sides (front and back of one tire), they can become lodged or wedged in.
Subsequently, you cannot get them out by hand. This is because they have dug their way into whatever type of surface you’re operating on. When you are on softer surfaces, i.e., asphalt or gravel/dirt roads, the likelihood of this occurring will be higher. The bottom of some wheel chocks are serrated, therefore making them even more difficult to remove.
I had one of our "not so bright" comrades tell me to hit them with a sledgehammer to get them out. I asked, "Why don’t we just try to avoid it in the first place and why does it have to get to that point?"
There have been times when the apparatus mechanics from our maintenance facility had to be called out to "lift" the axle where the affected tires/chocks were to get them out, so the truck could roll again. They were not very happy campers when that happened.
During aerial operations, the ladder/boom/bucket devices elevate, rotate, extend and lower. This causes the chassis and/or torque box to be put under stress, especially when operating over the side of the truck. When the truck "leans" to the side where the chocks are placed, it can cause the tires to "push down" on the wheel chocks, digging them into the surface.
Some manufacturer’s operational manuals state to have the wheels completely off the ground when using the out-riggers, or to just remove the bubble/bulge on the side of the tires to assure there is no weight on them but still be in contact with the ground. Always follow the manufacturer’s operational manual.
For a variety of wheel chock diagrams, please click here. (Image: Pierce Manufacturing Operational Manuals)
Close attention needs to be paid to "grade" or "slope." Are we operating uphill or downhill?
The solution is to abut one chock against the tire and leave a 2” to 4” space from the tire for the chock on the other side of the same tire. If you are in a situation, as in a downhill or uphill configuration, the manufacturer may want you to place the wheel chocks on the same side of another tire. (See linked pictures above.) In this case, all you would have to do is drive either forwards or backwards if the chocks become wedged into the ground and/or surface.
There are myriad training videos from outside the fire community, like professional drivers for trucking companies. There are also many types of wheel chocks made from different materials or having different functionality. Field test and explore the different types that work into the specific characteristics of your department’s functions and municipality features.
In hindsight, as far as I can remember, my department always used wheel chocks on aerial devices, but not on pumpers. It was not until later that we made it an SOP to place them whenever operations were occurring either during drill time or at emergency scenes.
There have been incidents where the trucks have "jumped" the chocks. It takes great inertia to drive over a wheel chock. This usually does not happen unless someone really messed up. If the truck moves or rolls from a stationary position, the wheel chock will do its job. Always err on the side of safety and put as many "back-ups" as possible in place to create redundancy in case the "OH S*%@" moment occurs.
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