Lift Oopsie At Work....

[torquepower85]

~12k lb truck on a 15k rated lift????

even if it worked out to be 15k or just above...

how many people tell you to get an ALI certified lift? >.< they test it 150% past the rated capacity.

plus third party engineers ensure a 3-to-1 safety factor

i mean if you dont get ALI certified lift... get good insurance for your company... not to mention life insurance for your family


http://www.autolift.org/members.php

 

[pmiranda]

If you assume that the lift has a working safety valve, 4700's weigh in under the rated load of the lift when empty, and that the lift cylinders have a 2:1 safety factor or better, there's still something unseen going on. A damaged lift rod would make sense.
A carriage that's binding could have contributed, as would lifting the truck too far away from center of mass, but I don't think either completely fit the facts.

One random comment: having a lift force gauge would be a great thing to watch as you raise a load, so that if there are any points where it's binding you'd see a pressure spike. You might see something that's too subtle to hear in the motor effort, especially in a noisy shop.

I've learned alot from this thread and I'm thankful nobody was hurt!

 

[bobadame]

I suspect that the load rating on the cylinders requires that the cylinders be clamped to a structure to prevent column buckling of the rod which is what happened in this case. So my question to the original poster and to Mr. Worth deserves an answer. I'll ask it again. Was the top of the cylinder secured to the frame of the machine?

 

[neel2008]

I have been doing my best to keep this thread civil. I have not been back here in a little while and don't mean to bump an "old" thread. But I wanted to clear a few things up.... The thread was not a slam on Worth. It was really just a "hey I look what happened at work today" thread. We use this lift EVERY DAY and my boss bought it sometime back in 04 and it has served the shop well. I would not steer anyone away from purchasing a Worth lift. I have concluded what actually happened, was the cables were not set correctly.....The locks were not engaging at the same time. It has been that way since I started working there. I brought it up to my boss and he said he has messed with the cables before and could not get the locks to "clunk" at the same time. After studying things more closely, I realized what needed to be done and got the locks to engage at the same time and got the cables so they have the same amount of "tautness" (which they were not before). Now the two carriages stay in sync throughout the range of motion no matter if there is a car on them or not and if they are on the locks or not. Now there is no "one side, than the other side" movement when coming off or going down on the locks like it kind of did before. This shows how it is imperative to have your lift adjusted perfectly. With the cables uneven/not set correctly, It will allow one side (the side that became damaged) to "work harder" when coming off the locks because it will raise that side and any difference out of the cables before it will move the other cylinder.....So for a short moment in time, once cylinder would receive pretty much all of the hydraulic pressure capacity of the pump, hence the reason any kind of relief valve would not help unless the lift is adjusted properly.

I suspect that the load rating on the cylinders requires that the cylinders be clamped to a structure to prevent column buckling of the rod which is what happened in this case. So my question to the original poster and to Mr. Worth deserves an answer. I'll ask it again. Was the top of the cylinder secured to the frame of the machine?

I responded to your pm but I will also do it here. I don't mean to speak on Mr. Worth's behalf, but the cylinder actually "floats" where it is mounted. It sits in a "hole" in the base plate of the column and the top of the ram has a "yoke" that sits on it with a roller that the chain travels over. The chain and the lip on the roller is what holds the top of the ram. I assume this is to allow a small amount of movement of the cylinder to keep the lift mechanism from binding. Our older Challenger lift is also designed in a similar fashion.

We have tested these lifts to extremes. It appears to have been overloaded and mis loaded as well. Unfortunately short of getting sworn testimony we will never know. The factory has STILL Not been contacted.

I apologize for not contacting you directly. That was my original intention but I did not really have access to this thread to get the info you posted while I was at work when I wanted to call. I ended up calling the regular 800 number for Worth in Texas and ordering a new roller and pin for the cylinder on that side of the lift. The lip on the roller had also became damaged when the cylinder bent and the chain tried to slide off of the roller because of the change of direction of the ram. The cylinder was sent to a hydraulic shop where they dissembled the cylinder, inspected the cylinder body and replaced the ram, piston, seals, etc. Again, this thread was not meant to be a slam or complaint against worth. Our Worth lift is great lift that has served the shop well on a daily basis, despite spending an (unknown to me) amount of time being not properly adjusted. Let this be a lesson to all, MAKE SURE YOUR LIFTS ARE ADJUSTED PROPERLY! And if you don't know how to do it, ask someone who does....

/thread

 

[pstnbly]

The one thing I did not see discussed (although I may have missed it) is if the hydraulic power pack relief pressure was checked. If the relief was set properly the cylinder rod probably would not have bent. I'm not saying there was not some fatigue issue, but do have the relief pressure checked if that has not been done.

 

[bobadame]

Re: Lift Oopsie At Work.........

With the cables uneven/not set correctly, It will allow one side (the side that became damaged) to "work harder" when coming off the locks because it will raise that side and any difference out of the cables before it will move the other cylinder.....So for a short moment in time, once cylinder would receive pretty much all of the hydraulic pressure capacity of the pump, hence the reason any kind of relief valve would not help unless the lift is adjusted properly.


I don't agree with this statement. The side that moves first does so because there is less load on it. Whether that load is due to weight or friction doesn't matter to the hydraulic system. The oil pressure at the bottom of the pistons in the cylinders in a 2 post lift is exactly the same whether the piston is moving or not.

Hydraulic cylinders are often times mounted as they are in the Worth lift. Look at a cherry picker type engine lift. In that case there really isn't a better option. On the other side of the scale is the trunnion mount at the top of the cylinder. These are often used in heavy duty construction equipment. A simple compromise between these 2 examples would be to strap the top of the cylinder to the frame of the lift. The reason you do this is that columns fail "catastrophically". Which means that they work really well right up until the point where they suddenly fail. So, given the cost of failure, possibly loss of human life, a couple of heavy duty hose clamps at the tops of the cylinders would seem to be cheap effective insurance.



/thread

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[neel2008]

Took me a minute to realize you responded in the quote there. But yes I see what you are saying about how the one with the less of a load would work first. The way I meant it was if the cables are not set right, when you are down on the locks, one cable becomes tighter than the other....when the pump starts running, it is going to make the cables equal in tightness before both sides will raise together. The side that bent was the "low side" and when the pump began to run, it started to raise that side while the "high side" was not moving. This is not speculation, it is what I witnessed happening. That's why I said it like that. The load is going to be leaning towards the low side......which would have to have more weight on it than the high side right? In that situation, the lift has to raise the low side to equal the tightness of the cables so that both cylinders can than work together again. The other thing is that while the cylinder does push up on the chain that in turn raises the carriage....it also pulls up on the cable that is connected to the other carriage and vise versa, so if the cables are set incorrectly to where when you sit the lift on the locks, one cable is taught while the other has slack, the lift will make them the same no matter what (move one side and not the other) before it will move both carriages at the same time .....It's also 1 am here so I could be way out in left field somewhere. lol.....either way, the lift is now operational and correctly adjusted now to where it lifts evenly, sets on the locks evenly, raises back up off the locks evenly, and lowers evenly as it should.

Also, come to think of it, what would you "clamp" the top of the cylinder too anyway? The carriage assembly is a square "tube" that slides up and down.....so the column is on the outside of the "tube" and the cylinder is on the inside of the "tube", so there is no fixed point you could fasten the cylinder to anyway.