Heavy machinery is regularly in use in industrial plants. In most cases, the “standard” configuration of the equipment is bought from a local distributor. Quite often, this “standard" equipment needs some modification to fit into the specific application.
I was called in as an expert on a case where the piece of equipment was a 6-ton scissor lift. This “standard” lift was designed for a floor-mounted application where there would be access on all sides for the operator and service personnel. The lift was designed with flip over “maintenance” devices, similar to door hinges, on the base frame that could be flipped into position to hold the lift up in the air. The lift was powered by a hydraulic system that was nested in the base frame under the lift table. The hydraulic system included a pump, a motor, the oil reservoir and the control valves and plumbing.
In the case I investigated, the “standard” lift, designed for an open-sided floor mounting, was installed in a five-foot deep pit made of concrete. The lift was part of a panel door assembly process where veneer “door skins” and wood struts and blocks were glued together.
The lift deck was used as the assembly platform. As doors were assembled, one atop another, the stack of doors grew higher. As the stack grew higher, the lift was lowered to keep the work deck at an easy working height.
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On occasion, small pieces of wood would be dropped and they would fall into the lift pit. Sometimes they would become entangled in the scissor lift mechanism. At the end of each workday shift, someone had to raise the lift deck and climb down into the pit to clean out the wood debris.
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One night, a worker who had been employed in the plant for only 16 days, climbed into the pit to clean it out. While he was in the pit, something went wrong and the lift lowered on top of him crushing him to death. Although they tried, his co-workers could not stop the lift from going down.
What did I find when I investigated the incident? Here are just a few of the things.
The hydraulic pump and motor assembly included a check valve that was supposed to prevent the hydraulic oil from flowing out of the lifting cylinders if a hydraulic hose failed. If this valve worked as planned, it would hold the lift deck up and keep it from descending.
One problem occurred as the “standard” installation was changed from a floor mount to a pit mounting. To make maintenance of the pump and motor easier, the hydraulic system was taken out from under the deck and relocated to a second, shallow pit next to the main pit. A longer, rubber hydraulic hose was used to reconnect the unit to the lifting cylinders.
Since putting the pump in a separate pit was not a “standard” installation configuration, the lift was not designed to route and protect a long hydraulic hose. The hose was just laid in place so that it ran up and over the bottom frame. In the “over the frame” location, the hose was exposed to cutting, crushing and pinching.
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The lift had been bought with a beveled “toe guard” safety guard that extended below the lift deck. The toe guard pushed workers’ feet out from under the descending deck to prevent foot injuries. However, the toe guard projected far enough below the deck that it also could and did crush fallen scrap wood pieces into the base frame as it came all the way down. In addition, due to the pit mounting, the safety latches that were located on the bottom frame, were out of sight and difficult to use.
During my investigation, I concluded that as the lift was operated to its fully lowered position, it repeatedly pushed wood pieces down on top of the exposed hose crushing it against the base frame. The repeated crushing finally chewed through the protective covering of the hose. When the employee climbed into the pit and moved about picking up the wood scraps, he most likely stepped on the hose where it went over the frame, which caused the hose to fully rupture.
The check valve, which should have been mounted directly to the base of the cylinders to stop the oil from flowing out when the hose ruptured, was now remotely mounted eight feet away with the hydraulic pump and motor. In this location, the check valve no longer helped. Instead of holding the oil in the cylinders and keeping the lift in the air, the ruptured hose allowed the oil to flow out of the ruptured hose and into the pit.
As the lift came down and the lift deck passed the floor level, it closed the pit completely and eliminated any exit path for the employee. The lift deck was too heavy to grab and hold, and so it lowered down into the pit. It took one and a half minutes for the lift to lower all the way down. Moreover, the whole time it was lowering, it was crushing the employee trapped underneath the lift deck.
This death did not need to happen. I testified that the product defects could have been easily and inexpensively eliminated. The jury agreed and returned a verdict in favor of the plaintiff and an award of $2.5 million to the widow.
The Warren Group can help you analyze personal injury claims involving machinery, equipment, and vehicles. Please call us toll free at 888-827-7823 to discuss your case.
