Forensic Engineers and Consultants

Archive: Machinery and Equipment

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

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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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Should I Trust My Nail Gun?

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Can you imagine framing a house with the tools of our forefathers, using hand saws and hammers, rather than power saws and pneumatic nail guns? Power tools have made the job much easier and faster, that even the amateur is well equipped for this kind of work. Read More

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

Improper Design Leads to Fatigue Failure In Blower Shaft

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A blower used to exhaust air from an industrial process stopped functioning when the blower wheel drive shaft fractured.  The process, and thereby most of the plant, had to operate at a reduced volume until the blower wheel could be replaced.  The blower wheel had been installed during a shutdown a week before the incident.  The blower wheel was a spare installed when the existing blower wheel was sent for scheduled remanufacturing. Read More

Injury Involving a Capstan Winch

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A capstan winch uses a mechanically powered rotating cylinder, called a capstan, to apply pulling force through a rope. When the rope is looped around the rotating capstan and tightened, friction between the rope and capstan allows the winch to apply force to pull a load. A typical capstan winch is shown in Figure 1 below. Read More

Are You Prepared for Emergencies? Your Generator Set Should Be!

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Emergency generators are often called into service during catastrophic events like hurricanes, floods, tornadoes or fires, but also during more mundane events like thunderstorms and other things that may temporarily interrupt the public power grid. Can you rely on your generator to perform at those critical times? Read More

Case Study of an Injury Involving a Soil Mixer

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In May, 2014, a plant farm worker was seriously injured when he fell into the hopper of an electrically powered soil mixer.  The mixer in question used a rotating steel ribbon powered by a 7-1/2 hp electric motor to mix batches of materials such as sand, mulch, wood shavings, fertilizers and other landscaping materials to create potting soil. At the top of the hopper sidewalls, within 6 inches of the ribbon, was a steel grate. Read More

A Case Study in a Coal Mine: What are a Machine Rebuilder’s Responsibilities?

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In November of 2010, a miner was injured by a roof bolting machine (roof bolter) in an Alabama underground coal mine. The roof bolter in question had undergone a complete rebuild intended to return the machine to the original equipment manufacturer’s (OEM’s) specifications. Warren was hired to analyze both the design of the roof bolter and the actions of the rebuilder to determine if either contributed to the unfortunate coal miner’s serious injury. Background information on coal mining and roof bolters, as well as an analysis of the roof bolter and the actions of the rebuilder are included. Read More

Flood Damage to Electrical Equipment

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As a result of the recent weather, those of us in South Carolina have gained a renewed appreciation of the damage that can result from flooding. Even a few inches of flood water can result in property damage and a loss of services in addition to the immediate risk of physical harm. Read More

Manufacturer Settles with Operator Injured by a Flying Tool Fragment from Milling Machine

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In my June 2015 blog, I discussed a personal injury case where the jury decided that the lack of interlocks on the covers of a swamp cooler did not render it defective, even though it was technologically feasible to do so and their existence would have prevented the amputation.  Conversely, in another interesting personal injury case involving a computer numerically controlled (CNC) milling machine, a large settlement was made by the manufacturer with the injured operator because the machine did not have adequate interlocks on its enclosure doors. Read More

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