Forensic Engineers and Consultants

Archive: Subrogation

Grounding versus Bonding – Understanding the Difference in Building Electrical Systems

While a teenager might be very familiar with being “grounded”, there is confusion over the meaning of the word in the electrical sense. In building electrical systems, “grounding” and “bonding” are two terms that are often misunderstood. Improper application of the concepts of grounding and bonding may create lethal shock and fire hazards. “Earthing” is a term which comes from the European International Electrotechnical Committee (IEC). Earthing is synonymous with grounding but often thought to have a different meaning. Read More

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Figure 1:  A view of the blower machinery.

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

Figure 2: A close view of the opening of the heat sealer. A person’s hand will fit in the opening below the guard to the left. Two "Danger" stickers are visible.

Injury Involving Packaging Machinery

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From time to time, I and other engineers here at Warren are asked to evaluate a case involving an injury that has been caused by machinery designed to produce or fill packaging. The hazards associated with packaging machinery are often similar to other commonly-used industrial machinery, but packaging machinery has its own voluntary consensus standard for machine safety. Read More

Figure 2: A view of some of the undersize anchors used to secure the capstan winch. The anchors at the upper right failed by pulling out of the concrete slab. The one at the lower left failed by bending and pulling out.

Injury Involving a Capstan Winch

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Co-Authored with Jeff Warren, PE   

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

A close-up view of the steel column.

Timber – Falling Beam Strikes Worker

As an experienced safety consultant, I have investigated many serious injuries and deaths at construction sites over the past 39 years. The United States Department of Labor reports that the fatal injury rate for the construction industry is highest of all industries in the nation. Out of 4,386 worker fatalities in private industry in calendar year 2014, 899 or 20.5% were in construction i.e., one in five worker deaths were in construction. Read More

Figure 1:  A view of the improperly constructed fireplace alleged to have caused the subject fire. 
 The hearth extension has been largely consumed in the fire.

Improper Fireplace Construction: Testing the Impact of Non-Compliant Clearance to Combustibles

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As the weather turns cold, many people use fireplaces to provide supplemental heat. The warmth from a fireplace is a comfort and the aesthetics of a glowing fire are a pleasure.  However, there is nothing pleasurable about a residential house fire that results from an improperly built or used fireplace or chimney. Read More

A clevis pin with the spring clip attached.

Defective Clevis Pin Culprit in Runaway Trailer

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A large agricultural trailer had been connected to a truck using a clevis pin with a spring locking clip.  The trailer became disconnected from the truck and collided with an oncoming vehicle.  The trailer was in poor condition, did not have safety chains, and had substantial recent modifications by the owner. Read More

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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

Figure 2.  A view looking into the mixer. The grate and ribbon are visible. The grate openings are large enough to admit a worker's leg.

Case Study of an Injury Involving a Soil Mixer

Co-Authored with Aron Olson, P.E.

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

Figure 2: A self-propelled roof bolter similar to the one described in this post. The canopy is on the extreme left of the image.

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

Co-Authored with Aron Olson, P.E.

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

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