Forensic Engineers and Consultants

Archive: Mechanical and Electrical Systems

Unguarded Shear Point on Force Tester Amputates Worker’s Finger

A worker was injured while testing gas springs similar to the type that hold the hatchback of an SUV open. The hazard that injured the worker was an unguarded shear point. The tester contained a mounting plate that was raised and lowered by a pneumatic cylinder.

The pneumatic cylinder lowered the mounting plate while the worker’s fingers were in the hazardous, unguarded shear point. The force testing machine violated applicable safety standards including ASME B15.1-2000 Safety Standard for Mechanical Power Transmission Apparatus sections 1.3 and 3.1.

Unguarded Shear point 1 white

The force tester. 

It was technologically and economically feasible for the manufacturer to have guarded the hazardous shear point at the time they designed and built the force testing machine by installing a fixed guard to prevent a worker from getting too close to the hazard. The hazardous, unguarded shear point on the force testing machine was capable of producing serious injury, including amputating fingers.

The risk of injury associated with the hazardous shear point was high because the hazard was unguarded, workers were exposed to the hazard every time the force testing machine cycled, and serious injury would occur every time a worker’s body part became trapped in the rapidly closing shear point. The high risk of injury associated with the hazardous, unguarded shear point was not tolerable because it was feasible to control the hazard using a fixed guard with no effect on the utility of the force tester.

It was or should have been foreseeable to the manufacturer at the time they designed and manufactured the force testing machine that the hazardous, unguarded pinch point would cause serious harm any time an operator got too close to the hazard.

Unguarded Shear Point Img 2

A shear point was created between the fixed frame and the movable mounting plate when the pneumatic cylinder lowered the mounting plate.

The force testing machine was unreasonably dangerous and defective.  It contained an uncontrolled hazard with a high, foreseeable and intolerable risk of serious injury with a certain probability of occurrence any time a worker’s body part is caught in the shear point.  There were technologically and economically feasible means that existed to control the hazard at the time of the machine’s design and manufacture. The unreasonably dangerous and defective condition of the force tester was a cause of the worker’s injury.

Unguarded Shear Point IMG 3 whiteA simple Lexan guard was all that was required to protect a worker from the hazardous shear point.

If you have a case involving personal injury involving a worker injured on a machine in an industrial setting, please give us a call. We are happy to consult with you.

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Author

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Defective Vertical Baler Causes Serious Crush Injury to Operator’s Arm

I recently worked on an interesting case involving a box baler. An employee of a butcher shop put some empty cardboard boxes in a vertical box baler and pushed the control switch to compact the boxes. After the 30 by 60 inch platen weighing 851 pounds returned to its raised position, the employee reached into the open space above the bottom door on the baler and began to clear cardboard from the bale tie slots in the bottom of the raised platen. Suddenly, and without warning, the steel pin attaching the platen to the raised hydraulic cylinder rod failed. The heavy steel platen fell and crushed his arm which was outstretched over the baler door into the compaction space.

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Graphitic Corrosion – Difficult to determine before a failure!

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Graphitic corrosion is a process that may happen in equipment made of iron, particularly grey cast iron, but also ductile cast iron. Graphitic corrosion can lead to unexpected catastrophic failure of the affected part because the cast iron can lose its strength without a visible warning such as a change in size, shape, or appearance. Read More

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