1. #1
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    Default Wheel Chocks and Air Parking Brakes Question

    Hello everyone,
    I have a small issue that I'd like some input on. Our department has recently begun pressing our engineers to put out wheel chocks whenever we are outside of the station. Our pumpers are all relatively new and have modern air brake systems, including the air parking brake. Now first of all, there is no policy about this and I've not been ordered to do this, but it just keeps getting brought up because I do not chock the wheels unless a) I'm in pump gear, or b) the road is slippery. In these two situations the truck could in theory jump into drive (not that the chock would stop it anyway), or the truck could physically break friction with the ground and slide.
    I do not chock the wheels if I'm on a medical call or parked in a parking lot.
    We have had an incident where an engineer drove off with a wheel chock down and it shot off at a firefighter. There is a near miss incident on firehouse.com of a similar wheel chock event. I know that when the parking air brake is set that the rear wheel springs force the brakes into position and can not be released until 50psi of air goes back into the brakeline. There is no magical way of doing this except for pressing in the parking brake diamond.
    The system is specifically designed to stop the wheels when air pressure fails. Can the air brake system "fail"?
    So my question is: Why chock the wheels? Does anyone have an incident where the parking brake system somehow repressurized and the truck moved? Or where a wheel chock became a missle? I fear that this is another thing that we do on the fire department that we've done for decades but is no longer applicable. Just like feeding hay to the horses in the bay. A favorite story to drive the issue home:
    "You have five monkeys in a cage. A bunch of bananas is suspended from the ceiling, a ladder underneath it. One hungry monkey approaches the ladder with a clear intent to get a banana. As soon as it touches the ladder, you turn on the hose and douse all the monkeys with very cold water. In a little while, another monkey attempts to get a banana. Again, cold water for everybody. Turn off the water. When a third monkey, nearly faint with hunger, tries to get a banana, the others will grab it and hold it back, because they don't want another cold shower. Now, remove one monkey from the cage and replace it with a new one. As soon as it sees the bananas, it will try to go for them. The others will viciously attack it. After the third attempt, the rookie will realize that it cannot have a banana. Now, replace another one of the original monkeys with a new one. As soon as it reaches for a banana, it will get attacked by all the others, including the rapidly learning rookie #1, who will be as enthusiastic as the rest of them, if not more so. And so, after you have gradually replaced all the monkeys, the cage will contain five monkeys who have never had a cold shower but who will not allow anyone to get a banana. Why? Because that's the way things are done around here."

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    why take a chance.

    a few months ago some of the older guys on my vollie depts came up with this idea. needless to say it got shot down fairly quickly.
    Your a daisy if you do.

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    Well, I think that chocking the wheels every time is a good idea. I can't give any examples of an engine just taking off with the parking break set, but why take chances. At the same time I'll admit that I'm bad about using them, they're and afterthought on the fireground.

    As far as the safety aspect of accidently leaving them in place and driving off, that can be turned into an argument for doing it every time. By using the chocks every time, the operators get into the habit and routine of removing them and putting them away before they get back into the cab. A walk around is a good idea anyway and should catch the chocks under the tires.

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    The integrity of the system requires a few key elements to be in place for the system to work reliably.

    The biggest potential point of system failure for the spring brakes as well as the service brakes is of course the slack adjusters. Failure to keep them adjusted (or tested in the case of auto-slacks), can still cause a brake failure that the springs cannot compensate for. Not overly likely on a well maintained engine, but possible nonetheless. Un-noticed damage due to compounding, etc, is also a rare possibility in older units. On a single rear axle vehicle, there are only two rear springs for park. That also means that a damaged or broken spring results in 50% less parking brake. Not a problem on flat ground, but slopes...

    Next is an in-dash problem where the switch fails to seat properly, and doesn't fully dump the system, or allows air to leak by. Again, the operator should notice, but stuff happens.

    Lastly, user error is perhaps the biggest issue. Somebody reaches across the dash in a hurry, and bumps the switch. A piece of equipment is knocked over, etc. Or perhaps someone just doesn't activate the brakes properly. All rare, but as we know, the biggest disasters are often the result of many small system failures.


    You mentioned the risk of forgetting to remove the chocks, but the whole point of a blanket policy such as "Always Chock" should reduce the possibility of wedged or thrown chocks. It is when you are selective with the practice that you increase the chance of "forgetting". If it is SOP and everyone does it consistently, it becomes habit. I don't think that the slight risk of a stuck or flying chock is a viable arguement NOT to chock.

    I don't necessarily think the overall safety factor is dramatically improved by carte-blanche chocking, but the uniformity has some value. Here in the sticks, we also use an "always chock" policy on air braked vehicles, primarily because the part-time volley driver is probably more prone to forget than a full-time trucker or operator who does it every day (at least IMHO).

    In the end, maybe it's a PITA, but what can it hurt?

    Last edited by mcaldwell; 07-11-2007 at 11:10 PM. Reason: Fixxed mi baad speeling
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    I don't know what style of chocks got thrown by the one truck, but most of the chocks I've seen and used, you get reminded of them as soon as you try to drive over them.
    All the trucks I've driven have been standards, so I don't know if having an auto makes it less noticable

    Also on the auto slack adjusters. Don't think that just because they adjust automatically, that they never have to be checked. The last trucking company I worked for had them, and we had the adjustment checked every six months.

    Matt.

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    I am guessing you launched rubber chocks.

    We are migrating to metal chocks. For the smaller trucks, they are one-piece units that you couldn't possibly drive over in blissful ignorance, and they have a lip around the base that works well for slip-out inverted track mounting so you don't have to fish around in a compartment for it.

    For the heavy apparatus we have collapsible metal chocks also mounted into exterior holders, that latch into an opn position with a locking mechanism. They are also called finger-biters by us, and they are noticeably larger than usual, with a curved surface against the tire and standing perhaps 12" high. I worry that sooner or later someone will be in too much of a rush and not ensure the chock opened all the way.

    But my real point... we had a rig roll away and get stopped by a parked car at the grocery store, because the driver failed to fully pull out the brake (and also failed to follow SOP and chock). I agree with the SOP rationale of "better safe than sorry so do it all the time", and I am betting that metal chocks are (a) harder to drive over - hence more likely to fulfill their mission, and (b) not susceptible to distortion through compression and thus not likely to get launched.

    But I don't fault you asking. Good discussion.
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    mcaldwell's points with respect to brake adjustment are important and well taken. Automatic slack adjusters as used today lull us into ignoring it. But if ASA's fail to operate (they can) or if someone does a manual adjustment incorrectly, the brakes will loosen up. You don't feel it in the pedal or treadle. You only find out when you're parked on a grade and the truck starts to roll. Personally, I dislike chocks. I find them to be a pain in my tail. I'm the person who tries to drive over them and has to back off, get back out of the cab and retrieve them. But I am trying to train myself to use them.

    Stay safe out there, everyone goes home!

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    Chock the wheels.

    I run the maintenence program for my department, so I can assure you the apparatus is in good working order.

    After all the hours spent keeping these trucks up to standard, operator error has reared it's ugly head. The operator failed to chock the wheels, and also failed to take the truck out of gear when he increased the rpms to run the pto generator.

    Our beautiful heavy squad ( black Peterbilt 379 w/ walk in rescue body ) proceeded to hit the rear of our neighboring FD's ladder truck. Damage done.

    Had anyone been walking behind the ladder truck, they would have been crushed.

    We have tested the truck in gear at the proper rpm's to operate the generator, and with all 4 wheel chocks in place, the truck doesn't move.

    Chock the wheels. Don't trust the mechanics of the vehicle to keep you safe, and don't trust that the operator of the vehicle is operating it correctly.

    If you don't see wheel chocks while the truck is parked and operating on scene, the truck is not safe.

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    Quote Originally Posted by GhostRider73 View Post
    I don't know what style of chocks got thrown by the one truck, but most of the chocks I've seen and used, you get reminded of them as soon as you try to drive over them.
    All the trucks I've driven have been standards, so I don't know if having an auto makes it less noticable.

    We have a perfectly flat large aluminum chock in the hall from an incident with our new engine. The guys didn't even feel it as they pulled away, but another FF just happened to see it.

    The manufacturer was surprised that it failed so easily, but these trucks are getting heavier and more powerful every year.

    And I have spent an hour or two in the past prying an old steel chock out from between the duals on our 79. That same truck has a bent rear step from a careless FF who tripped the brake while reaching in the cab, and didn't have the chocks down. He is a big proponent of chocks now.
    Never argue with an Idiot. They drag you down to their level, and then beat you with experience!

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    Default Wheel chocks and Parking Brake

    Hi everyone, thanks for the great responses, I've enjoyed reading them. Here is some follow up.
    * Many of my fellow engineers have similar positions. The most common is the "why take the chance". Of course with that train of thought we should chock the wheels when the truck is in the station. Or I should see wheel chocks under their personal vehicles out in the parking lot because why take the chance of their cars suddenly rolling away. Perhaps we could remove the battery cables in order to prevent the vehicle suddenly starting up on it's own, etc. etc.
    * As far as someone accidentally releasing the parking brake, for us I guess that is about as likely as someone accidentally starting the engine. The start switch is much easier to depress than the Parking brake diamond.
    * The chocks we fired were metal, but not the folding kind.
    * All of our trucks have a pump gear that cannot be engaged until the parking brake is set, nor does the pump panel throttle work until the pump gear is engaged. No PTO's.
    * We too have a very vigilant maintenance officer. The brakes are meticulously maintained. All of the brakes or all of the slack adjusters would have to be mis-adjusted for the brakes to slip.

    At the core of this issue is that we have had an incident where a chock almost injured a firefighter, and we can not find any incident where a fire engine with a parking brake engaged suddenly rolled away on it's own. Not when someone disengages the brake, not when it's pumping, not went it's on a slick road, but simply sitting in a parking lot or on the street. I'm wondering if we just do it because we used to have a different type of parking brake system decades ago and haven't re-evaluated our procedures.

    Again, love the discussion, I think this is the most beneficial aspect of firehouse.com is the ability to discuss topics.

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    Quote Originally Posted by gobigorstayhome View Post
    "You have five monkeys in a cage. ...... And so, after you have gradually replaced all the monkeys, the cage will contain five monkeys who have never had a cold shower but who will not allow anyone to get a banana."
    What this story failed to point out was that no one ever said the cold showers were canceled. You have evolutionary survival here. The monkeys don't know why they are doing it, but it is a good thing, because it is preventing cold showers. Like Dad always said, "Sometimes you don't know what's good for you".
    Last edited by ElectricHoser; 07-12-2007 at 10:34 AM.
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    Exclamation Wheel Chocks

    I have often wondered the same thing as your original post states, however, on the side of caution I alway use the chocks on the engines & tankers.

    What I do not use the wheel chocks on is the brush truck - this has stirred debate in the firehouse. It is a F-350 pickup. I ask those who think we should use them if they chock their personally owned trucks ??? - or should we also be chocking the chiefs car then ??

    I have personally seen 1 metal chock fire like a missle and 1 metal chock explode into fragments. The missle was with the heavy rescue on a medical assist call (the BLS crew needed a ladder). The chock flew about 15 to 20 feet forcefully and luckily no one was in the way. (BTW, I was not the driver that day, I was the officer). The explosion incident was with the tanker at the station, the driver moved the truck and when the weight of the tanker was on the chock it violently became pieces. Again, thankfully no one was in the way.

    Moral of the story......use the chocks and REMEMBER TO PUT THEM AWAY BEFORE MOVING THE TRUCK !

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    Our policy is when out of the station chock the airbrake vehicles.All smaller vehicles (brush truck,med unit) are to have parking brakes applied and actually have chocks in compartments that could be put down.We have the one piece metal chocks that ride in inverted racks under the body in front of the wheels,so there is a visual reminder to put them down,and you have to do a walk around before driving so you will see them down.We have never thrown one and to my knowledge the only time they were driven over was on soft dirt and that was due to them being pushed into the ground.Dang near impossible on hard top to drive over one,the truck wont go and you have to get out and see why.
    Firefighter/Paramedic Seven Hills Fire Rescue Mobile,AL

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    Default Wheel Chock's

    Both Martian and Sam hit the nail on the head along with some of the other posts.

    We had an incident in our county a couple of months ago where a driver was knocked over and run over by the engine he was driving. Parking Brake was set, however some how the truck jump into gear and ran him over.

    Things happen! Therefore you should always Chock your wheels.

    How ever like Sam I too am retraining myself to use wheel Chocks.

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    Thumbs up

    Quote Originally Posted by gobigorstayhome
    At the core of this issue is that we have had an incident where a chock almost injured a firefighter, and we can not find any incident where a fire engine with a parking brake engaged suddenly rolled away on it's own.
    Quote Originally Posted by mcaldwell View Post
    You mentioned the risk of forgetting to remove the chocks, but the whole point of a blanket policy such as "Always Chock" should reduce the possibility of wedged or thrown chocks. It is when you are selective with the practice that you increase the chance of "forgetting". If it is SOP and everyone does it consistently, it becomes habit. I don't think that the slight risk of a stuck or flying chock is a viable arguement NOT to chock.
    Mcaldwell, You are one smart son of a gun! You hit every reason on the head! (but the one I quoted from you above is my favorite because it is what is at the heart of every SOP)

    I would only add a couple things for the aerial users.

    1.) Always chock your aerial trucks BEFORE setting the stabilizers and remember which wheels come of the ground easiest – then chock the opposite set which means usually chock the front wheels.
    2.) I have seen so many departments with the awesome folding / locking chocks, drop them behind the wheel without “locking them” in deployed position (so they are easy to pick up later) – Never do this TL

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    Quote Originally Posted by SSIaerialmanTIM View Post
    [u]

    I would only add a couple things for the aerial users.

    1.) Always chock your aerial trucks BEFORE setting the stabilizers and remember which wheels come of the ground easiest – then chock the opposite set which means usually chock the front wheels.
    TL
    can you elaborate on this point? I'm confused, and interested...if you chaulk the wheels before setting the stabilizers, then why would you be chaulking them again after you checked which wheels came off the ground easiest (does that make sense?) Also, once the weight of the unit has been taken up by the outriggers, is there really any chance that the rig can move on the wheels? I know you have talked about sliding resistance alot in your posts, but I'm really not familiar with the term.

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    Hey Canuck,

    I am saying to chock the wheels on an aerial truck at the scene (the set that will not come off the ground which is usually the front wheels) before even touching stabilizers. That way when setting the stabilizers and some tires come up, the truck won’t slide.

    After setting the chocks and then setting the stabilizers – reposition chocks as needed. (which usually isn’t necessary if you chocked right in the first place)

    I see so many guys try to completely setup the truck stabilizers before they even drop a chock. Their thinking is that way they won’t “pinch the chocks” I suppose. ( Also note these same people generally use this line of reasoning to pick up the chocks FIRST and then stow the stabilizers when they are done – again so they don’t “pinch” a chock ).

    This is wrong because it is duing set up and teardown that the truck is likely to slide on a slope. Yes, I probably talk too much about sliding resistance – but I have seen several severe slopes cause trucks to start sliding during stabilizer set ups because the operator forgets he is raising the parking brake off the ground right along with the tires.

    Fortunately more trucks are coming out with front “service brakes” and they should be used at every aerial scene too, but this feature should never allow the operator to become too confident at an actual set up and not set the chocks first anyway.

    I always say “Chocks – first thing down and the VERY last thing up” I hope this clarifies it, let me know, TL

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    At the Massachusetts Fire Academy, chocking the wheels is part of the procedure taught in pump and aerial ops.

    Failure to chock the wheels during any training evolution gets the student 5 deficiency points.
    ‎"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
    Lt. Ray McCormack, FDNY

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    ...we always chock every time we stop anywhere......... ...so far no one has tried to drive over them just due to the habit of always chocking i think........... this has worked well for us...........

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    Default Wheel Chocks

    Just an additional bit of information for comparison purposes. My brother is in the propane business and he says that it is a government mandate that the drive wheels of the propane truck must be chocked every time the driver gets out of the cab. This could be 30 times a day when the driver is making deliveries. They get a hefty fine if the DOT people catch an unchocked truck.

    I think the two biggest risks when not chocking trucks is if someone forgets to set the parking brake on a very slight slope and if the engineer leaves the transmission in drive when shifting the pump and then opens the throttle with the truck still in road gear. We've seen both occurances. Not pretty!

    Always Chock Wheels And Wear Seat Belts!

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    Smile why ??? why wear seat belts why do anything safe?

    I have been a career FF 19 years, was a volly operator for 16 years before that , and I got my Class 1 license the week I turned 18 drove straight and tractor trailers until 2001 full time or on the side, I've seen apparatus and commercial trucks roll with the maxi brakes on, I've actually jumped back in the cab to stop the truck from getting away, on a grade with the brakes applied , I've also had "brake fade" happen , believe me driving a 22 foot straight truck loaded legally down an off ramp into three lanes of traffic stopped at the stop light,, steering into the curb and coming to a low speed stop, 12 feet past thecar I would have struck had I not steered right.... makes you open your eyes.... wheel chocks down when you get out of the cab is the safest thing you can do.... with boomed or ladders , the shifting of weight is enough to get it moving, hence using front and rear chocks.....to hopefully give you enough time to get to the controls if nessisary...

    My Career job, and one of my former volly departments Both had pumps that at one time or another either drove across the street or began to drive away when the "ump" was throttled up ,but the pump shift was not fully engaged... at least if the chocks are crushed they can say you should have ... so its your fault .... dont be lazy, chocks take 3 seconds to deploy use em... for your and yourbrothers sake as well as anyone else within a distance of 100 feet if its to hard , dont drive, just stretch and pack hose....

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    Chock the driver side front tire. That way the driver becomes the responsible party and can easily see if the the chock is down or not. It really doesn't matter which wheel gets chocked, as long as it happens.
    FTM-PTB DTRT

    Everything I state on here is to support and aid my fellow firefighters. Everything I post is my opinion only, and in no way should be taken as an official opinion of any Company, Department, or Municipality I represent... oh and this includes Pierce Mfg, as so their legal department has advised me; since they apparently also invented the right to control "Free Speech".

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    Have you ever driven away and left your wheel chock at the scene? Put a small chock or piece of cribbing on the other side of the tire as a reminder bump.
    METZ AERIALS: "SO EASY A CAVEMAN CAN USE THEM"

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    I've been in the back of a brand new ambulance(less than 6 months old) where the parking brakes let loose and the only thing that stopped us was the chocks that are always put down. Granted we were on a semi-steep driveway, but the outcome would have been much worse had it not been for our department policy. Had there been no chocks down we would have been in the dining room of the house across the street at suppertime...

    I don't know why the brakes failed, the switch was fully engaged and no one was in the front to touch anything, but I do know that I always chock the wheels.

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    After reading both sides of this
    And being on both sides of this coin so to speak

    I guess the best way this could be put is simply this

    Unless you are one of the rare people the only see other people have accidents as it won't possibly happen to you
    I would Use wheel chocks just as the are designed for safety
    Just my opinion
    Stay safe
    Ray

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