Forensic Engineers and Consultants

Category Archive: Case Studies

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.

Electric Hazard Guardrail photo

Hazards Can Lurk Anywhere … Watch Your Step …

Author

While on a lunch stop during a recent vacation trip through Tennessee, I happened across a safety hazard that required immediate attention.  The establishment had a raised concrete patio at the front with a steel railing around the perimeter.  At one edge of the patio was a set of stairs with a continuation of the steel railing used as a handrail.  The top edge of the patio had light strings wrapping the top metal bar as accent lighting for the perimeter.  The light string continued down the stair handrail wrapped in the same manner as the rest of the patio.

Electric Hazard Guardrail photo

FIGURE 1 – A view of the subject patio

While walking down the stairs, it was noted that two bulbs were missing from the sockets on the portion of the light string that wrapped the handrail.  The sockets, a common Edison-style base, were open to the weather.  More significantly, the open sockets were in the path of a person’s hand (adult or child) sliding down the handrail while traversing the stairs.  The damaged condition of the light strings due to the missing bulbs presented an electrocution hazard.  While the risk of electrocution may be mitigated if the light strings are supplied by the required National Electric Code (NEC) Article 527.5, Ground Fault Circuit Interrupter (GFCI) protected circuit, the condition of the light string presented a hazard.

Closeup photo of one of the open lamp sockets

FIGURE 2 – Closeup photo of one of the two open lamp sockets

Further, the wrapping of the light string around the handrail violates the International Building Code (IBC) requirements.  Section 1012.4 Continuity states that “Handrail gripping surfaces shall be continuous, without interruption by newel posts or other obstructions.”  The random placement of the cable from the light string randomly interferes with the continuous profile of the handrail.

View of the cord wrapping the handrail interfering with usability

FIGURE 3 – View of the cord wrapping the handrail interfering with usability

While there was likely good intent with the placement of the light string to add light to the stairs, the method that was used impeded the use of the handrail.   Further, lack of maintenance by not replacing the missing bulbs crated a shock or electrocution hazard.   Beware of these lurking hazards, if things don’t look right, they probably aren’t.

Tom Kelly has a Bachelor of Science in Electrical Engineering and a Master of Science in Electrical Engineering from Florida Atlantic University, Boca Raton, Florida, along with a Master of Business Administration with emphasis in strategic leadership from Winthrop University, Rock Hill, South Carolina. Tom’s 25-year career in electrical engineering includes forensic engineering investigations involving industrial electrical accidents, electrical equipment failure analysis, control system failures, robotics and automation components, and scope of damage assessments.  He has conducted investigations for fires, arc flash incidents, electrocution and electric shock accidents and lightning strike evaluations.

Orange mini excavator

Case Study: Fatality Servicing Unsupported Excavator Boom

A mini-excavator at a job site developed a leak at a hydraulic fitting at the base of the cylinder that raises and lowers the boom. A subcontractor foreman at the site raised the boom to search for the leak. The foreman found and attempted to tighten the leaking fitting. When he did, the fitting separated from the base of the cylinder, releasing the hydraulic pressure that held the boom aloft. The boom fell and the bucket struck a nearby superintendent for the general contractor.

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box bailer

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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Figure 1: A view of a playground with impact absorbing surfacing. The brightly colored surfacing beneath the play equipment is a poured-in-place rubber and polyurethane material.

Children Will Fall At Playgrounds. What Shall We Do To Protect Them? A Multipart Blog Series – Part III: An Overview of Selected Playground Safety Technologies

Co-Authored with Aron Olson, PE

Welcome to the third and final post in our multipart series of blog posts about a young boy’s fall and serious injury at a public playground. In our first post we gave a brief overview of the incident and our investigation. In the second post we discussed some of the safety standards applicable to public playgrounds. In this post, we will examine some of the impact-absorbing playground surfaces available to protect children at playgrounds from injury. If you would like to read the first two posts, they are available here and here.
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Figure 1: A view from a vendor's website of a material known as engineered wood fiber that is designed for use as a playground surface.

Children Will Fall At Playgrounds. What Shall We Do To Protect Them? A Multipart Blog Series – Part II: A Brief Summary of Playground Safety Standards

Co-Authored with Aron Olson, PE   

Welcome to the second part in our multipart blog series examining a young boy’s fall and injury at a public playground. If you missed the first part in this series, click www.warrenforensics.com/2017/10/11/children-will-fall-at-playgrounds-what-shall-we-do-to-protect-them-a-multipart-blog-series-part-i/ to read it. In this post, we will highlight some resources that designers of public playgrounds can use to help ensure their designs are reasonably safe. Read More

Figure 1: A typical warning found on a confined space.

Permit-Required Confined Spaces – What You Need to Know to Safely Enter (and Exit!)

According to the OSHA regulations, a confined space is anyplace that meets the following criteria:

(1)   Is large enough and so configured that an employee can bodily enter and perform assigned work; and
(2)  Has limited or restricted means for entry or exit; and
(3)  Is not designed for continuous employee occupancy. Read More

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Children Will Fall At Playgrounds. What Shall We Do To Protect Them? A Multipart Blog Series – Part I

Co-Authored with Aron Olson, PE   

In 2011, a 5-year old boy was severely injured at a public playground when he fell through a second floor opening around a fireman’s pole in a playhouse. He fell more than seven feet and struck a bare concrete floor. We are thankful that he eventually recovered from his injuries. The person who designed and built the playground was accused of negligence. A lawsuit ensued, and eventually settled in favor of the boy. Read More

Cooker - Figure 2

Commercial Gas-Fired Cookers Can Do More Than Burn

The first hazard that comes to mind when thinking about large scale ovens and steam kettles is burning or scalding injury. Carbon monoxide poisoning is just as dangerous but less understood, so oftentimes proper prevention methods are not followed. In the United States, this results in over 20,000 emergency room visits and over 400 deaths a year. Before we get to the case study and poisoning prevention methods, we need to know what CO is, where it comes from, and why it is poisonous. Read More

Fig-1-Chem-E-Intro

Chemical Engineers: More than Glorified Plumbers – Really!

As a senior at Virginia Tech, I was told that ChemE’s were little more than glorified plumbers.  Looking back, I’m pretty sure it was to keep our geek-egos in check. It was an effective tool! However, as I grew and traveled as a professional, it became an effective descriptor; applying to a larger scale and using a modifier or two for specific applications.  So, if you have a loss that falls into one of the categories below, a ChemE could be the expert you need. Read More

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