Spider lift accident

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Good points. I would think some cracking of the paint should be seen prior but a break that clean has to be sudden. That almost had to be a butt joint weld for it to be that clean. Very poor choice for the placement and very poor choice for that type of joint.
to the physics. Am I correct in saying that the pin location would see the most force ( the fulcrum) and the area of the break would see the second? I haven’t taken the time to actually look this up. I’m just thinking of how a pry bar bends and a general idea of forces applied
 
Tree09 said:
Oh i agree the whole thing sees a ton of stress, but you aren't gonna find that under paint. Honestly you wouldn't find that if it was bare polished steel. With a break that smooth it failed very suddenly, not slowly tearing leaving jagged bent ripped edges like a normal failure. Something looks very wrong there. You can't see small cracks with the naked eye, you either need to mag test them or die penetrant. I'm sorry, I've been fixing torn steel for over half of my life, there's a reason why they developed all these technical ways to find cracks non destructively. I've also prepared samples to test destructively, they would pull a part from the production line and i would cut it up and rip sections apart to make sure they were failing at the proper loads.
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Would a dye penetrant work on painted metal?
 
Mellow said:
I'd like to see some close up pics of that area.
I got this email from All Access Equipment earlier today:

​
Dear customers,

We are honored that you have placed your trust in CMC and All Access Equipment. Over the years, we have heard from so many of our customers who are very pleased with their lifts and our continuing service. We are always humbled to read those reviews and hope you too have been pleased with your lift.

Your lift is best-in-class and CMC is one of the World’s premier manufacturers of these machines.

Customer service and safety are paramount at CMC and All Access Equipment.
So too is transparency.

In the past several years, we have sold more than 1000 of these lifts. Unfortunately accidents can happen with these lifts just like any other equipment. We were very concerned to hear about two recent accidents. In both cases, we immediately sent our top technician to review the lift and circumstances of the accident. We also immediately contacted our manufacturer, CMC. As a result of those steps, we at All Access Equipment thought it would be important and helpful for you, our customers, to hear directly from CMC.

Here is a statement from them:
​
As specialists in the production of aerial platforms; we design, test and manufacture machines whose purpose is to preserve the safety and the life of the operators in every way possible.

Working on an elevated platform comes with some inherent risks, and we are working closely with the lift owners and OSHA to find out all we can about the two accidents. We are committed to assist with these investigations and learn as much as possible about what happened.

One thing we are sure of: If the lifts are used correctly and the safety protocols are followed, these machines are safe, effective and can remain in productive service for decades. Our years of design and testing procedures give us a great deal of confidence in the machine, its construction and performance characteristics.

In addition to our investigation, we have observed posts on social media of the lift being used improperly. To address this, All Access Equipment issued a warning communication in December 2020 to all CMC aerial lift owners in the United States reminding them to comply with safety regulations and procedures as indicated in the Owner’s Operating Manual.

To reiterate, it is important that all owners and operators are following the ANSI/SAIA A92.22 (OPERATORS RESPONSIBILITIES OF SAFE USE) and A92.24 (OPERATORS MANUAL OF RESPONSIBILITIES of TRAINING REQUIREMENTS). We must emphasize that the lift is designed to carry personnel and tools only. It should never be used in any other way. Doing so can subject the lift to extreme loads it is not designed to handle.

To address intentional or unintentional misuse of the equipment, we are immediately launching an awareness campaign to ensure that your equipment is safe and is being used properly.

Sincerely,

CMC
Click to expand...
Do you have a CMC lift? What model?
 
treebilly said:
Good points. I would think some cracking of the paint should be seen prior but a break that clean has to be sudden. That almost had to be a butt joint weld for it to be that clean. Very poor choice for the placement and very poor choice for that type of joint.
to the physics. Am I correct in saying that the pin location would see the most force ( the fulcrum) and the area of the break would see the second? I haven’t taken the time to actually look this up. I’m just thinking of how a pry bar bends and a general idea of forces applied
Click to expand...

Exactly, it would almost have to be a butt weld to be that clean. The cut even looks square, so I'm really thinking the company was welding drops together to try to save material. The pin location should be the most stressed, followed by the ram location. The middle of beam sees the large cantilever force, but the area between the pin and the ram is more highly stressed. The failure point should be right past the extra material (often called a repad) welds, in what's called the heat affected zone where the steel was heated and cooled at a different rate than the surrounding steel.

Die only works on bare steel, and so it's useless here. Mag checking would work, but would require tons of oxide dust. I suppose ut (ultrasonic) might work, but i was always taught to clean it down to bare steel first. X ray would want clean metal too, but once again it's not supposed to fail there so there's no reason to check there with such expensive and microscopic technologies. My guess is that they welded drops together, or added a piece on a length to have it fall like that. I would have thought a manufacturer of life support booms would be custom manufacturing their beams not using stock materials, but i guess i could see them using stock when possible.
 
While I understand the reasons behind that CYA email you received. That failure doesn't really look like an abuse problem. Looks more like a design issue. Either way hope that all hurt,
heal well.
 
Once is "One of those things". Even with one, I'd want to inspect the equipment if I were the manufacturer. Maybe the user did something stupid, but maybe not. Something like a lift is kinda important. It isn't a drill you just take back to homedepot whenever if you feel like it...
 
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  • #39
BlackSmith said:
The manufacturer’s first line of defense is to cry operator abuse but you’ll probably see that section redesigned in the future.
Click to expand...

Sounds about right. When I said above, 'sounds like manufacturer smells the lifts being use as cranes, or some such,' it is probably much more likely what Bob says, automatic suggestion of operator abuse even without any evidence
 
I tried to find a close-up pic of that area, but found nothing but mostly large views. There's one something special at this point of the boom though : it's the anchor underneath of the long tiny ram for the telescopic part and probably the hole to pass inside-out the hydraulic tubes for it. But it's hard to tell precisely with the pic's scale.
 
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It wasn’t welded ... The tube steel simply just sheared. Apparently this isn’t the first time this has occurred and in the exact same spot. Sometimes the bean counters/penny pinchers need to be kicked to the curb and a more robust design employed - especially when serious injury/death can occur.
 
I really would not want to be a crane/ manlift engineer. Cranes are allowed a certain robustness because they are supposed to be able to support loads many times greater than that of the boom. These spider lifts have design constraints that are very tight. They are supposed to be light and small and support up to 500 lbs at full extention and nearly any angle.
 
Was there a history if misuse with this lift? Like roping stuff of basket or such?
 
One thing that turned me off to this lift was the fact that the maximum basket capacity drops significantly from 507 lbs at 38' of side reach down to only 176 lbs at 46' of side reach. I'm over 200 lbs with no gear so I'd never be able to fully extend the boom safely.
 
  • Thread Starter Thread Starter
  • #45
I'm surprised the max basket cap in the weakest position is not rated as the max cap.
 
cory said:
I'm surprised the max basket cap in the weakest position is not rated as the max cap.
Click to expand...
The sales pitch is somewhat misleading. You have to read the fine print in the technical specs.

They wouldn't sell too many if they listed the max capacity at 176 pounds!
 
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