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Canmore Ab. Canada | I'm going to show my ignorance here.
Why do some truckdrivers say you need to dump the airride suspension air before unloading. They are talking about when a B-Train unloads fast or a Hay trailer is unloaded fast.
I can't see the need but correct me. What could it damage?
Dan... |
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NE SD | It takes X PSI to inflate the air bags to a certain level with a certain amount of weight on the trailer. If you remove the weight very fast, all of the sudden X PSI is able to inflate the bags out to a longer length. Regular leveling valves are not able to release the pressure fast enough in some situations. The risk is that you can stretch the bags, make them burst, etc. Some here will think it's a joke to dump them, but IMO when you're doing something such as unloading hay, unloading grain over a large pit where you can dump in terms of seconds instead of minutes, it is a good idea to dump them. I don't bother when unloading in the swing away auger that takes 10 minutes, but I do when I'm at the ethanol plant where I can dump in under a minute. Not worth risking it for being too lazy to flip a switch IMO.
Edited by Chad H 2/15/2009 19:23
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Slicker than a Yes album. | Have never dumped them on the trucks (trailers never had airride.) No damage in 20+ years. |
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America | Think its more of a myth than fact but some think that it is hard on airbags to expand suddenly. My experience is with a hopper that was not even originally equipped with a dump valve. I added one because I saw others dumping air but rarely used it. Replaced airbags when they were 15 years old because the bases were rusting out. Talked to a rep for an airbag company and he said just to dump if you need the stability. |
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Southeastern, IL | it dont take much time to flip the switch so wy not do it to be on the safe side. |
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Near-north Ontario, French River | I always dump the air when dumping my end dump, but thats for stability more then anything. I have the dump valve wired into the pto valve, so if I engage the PTO to dump the load the trailer suspension dumps automatically, I also have a manual switch on the trailer . I dont know many guys that dump the air on hopper trailers as it takes a couple minutes( even when dumping at ADM ) to unload them, plenty enough time for the suspension to adjust. I cant see a hay trailer being dumped anywhere near fast enough to warrant the hassle, unless of course hay is unloading differently 'here", here its done with forks ( tractor mounted usually) so the process is relatively slow ( 10-15 minutes), again plenty of time for the suspension. |
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NE ND | As far as the bags expanding too much and bursting, i dont believe it. the pressure in the bag stays the same, it just expands, no problem there as far as the bag is concered. HOWERER, on some trucks the bags can expand beyond the travel of the shocks. this can break shocks or shock mounts. it seems to me more of a problem for strait trucks. just my .02. |
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| I usually dump both tractor and grain trailer unless really slow unloading. The other day I noticed trailer unloading next to me with the trailer air bags (it looked to me) inflated 2-2 1/2 times their normal length. Flipping a switch isn't that hard to do.
I heard a air bag blow one time. It was very loud, louder than a large rifle blast. I don't need that blast hurting my ears while in a tin shed unloading at a ethanol plant because you were too lazy to flip a switch. I don't care what you do at your yard. |
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Manitoba, Canada | This is in reply to all of you that say "how hard is it to flip a switch" well its not so much the flipping the switch thats hard, because your right it is very easy. But its more so the remembering to flip the switch again once you are done unloading. I have a couple trailers that when the bags are dumped the tires touch the fenders. Guess how many miles till you get to buy new tires... not many. |
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| I dump every time at a fast pit. Easier on bags and shocks. If you do it every time you don't forget. My tractor doesn't have a dump and on occasion I end up with a leaky shock. (bent I assume, because it dents the cover) |
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Central Iowa | When dumping in a pit I always dump truck and trailer very easy to do and I dont want to take a chance of one blowing |
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| How many times you forget to crank the door shut?
Same difference you just get in a habbit. Do it often enough and you'll ge to the point that it is second nature. |
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Mather, Manitoba | that switch is all the way over on the other side of the dashboard! LOL
The air bags don't look too healthy if you don't dump the air beforehand. Looks like the ends are going to blow apart. |
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SW Ohio | Like Pinto said, it is not so much damaging the bags as something else. On an older KW with the small air lines it will rip the shocks right out of the mounts, BTDT
If your fenders rub when air is dumped you need to redo your fenders, nothing should touch. |
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South Plains of Texas | I am not a "seasoned" trucker but when I bought my truck this year a friend advised me to dump the air when dumping grain at the local ethanol plant. I asked why and he said that he had a truck that dumped so fast that it actually flipped the sensor rod on the leveling valve or at least that is what I understood. He said it was a real job to fix. I don't really claim to understand how it happened but this guy don't lie about things so I do like he advised. He said it was on his grain trailer. |
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Manitoba, Canada | The trailers come from the factory that the fenders are really close to the tires, especially if there is a layer of mud under the fender to begin with. There is no adjust ment, trailers arnt ment to move without air in the bags. |
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NE SD | If they can rub at all they should be moved. If they rub when the bags are dumped they'll rub when they're aired up and it's loaded while leaning etc. |
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Manitoba, Canada | they just hardley touch when bags are dumped, they sit 4 inches up when when the air is in them. They arnt supposed to move with the bags dumped |
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Brazilton KS | For those of you who think that reducing the load on the suspension is somehow going to 'burst' the bag, do you dump the air bags every time you drive through a low spot? I guarantee that driving across a small ditch is going to unload the axle a hundred times faster then unloading a hopper every would. If REMOVING load was somehow going to 'burst the bag' that should be what would do it.
Reality is that with both trucks and tractors, what really does burst the bag is COMPRESSING it to the stop suddenly when it is fully pressurized. Extending the bag will inevitably REDUCE the pressure in the bag. Compressing it, on the other hand, will INCREASE the pressure....if it is mostly extended and at 80PSI to begin with and you suddenly compress it to the stop, it is going to go to somewhere close to 300 psi and it will go BOOOM really loudly. That's why it is always wise to make sure it is not sitting with the midwheels in a low spot when you add air to the bags on a Challenger or grain cart. |
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Brazilton KS | So do you never drive over uneven ground? If there is enough suspension travel for it to hit, you should assume it is going to hit, and therefore correct the problem somehow!
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Flandreau, SD | You should also leave the park brake off on either the truck or trailer as to not bend an axle and stuff.
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Dumping Air Ride Suspension before Unloading??
