Mechanical Engineer Case Study

Safety First on the Fire Truck

Posted by John R. Yannaccone, PE on with 0 Comment

In this case study, an Equipment Expert was requested to inspect the folding steps on a fire truck to determine if the folding steps were secured properly.

Case Synopsis: A firefighter needed to stow a piece of equipment in an open storage area on the top of a fire engine. As he was climbing the folding steps on the side of the engine, one of the steps shifted causing the firefighter to fall and strike his head on the concrete floor and sustain a serious head injury. Following the incident, one of the steps was found to be partially separated from the side of the vehicle with the top two mounting screws pulled out of their locations.

Expert Analysis: Inspection of the vehicle revealed the steps were mounted to the side of the engine with four bolts that extend through the sheet metal and into the storage compartments. The bolts were fastened to the sheet metal with large flat washers and nuts on the inside of the compartment. During the inspection, several different combinations of mounting hardware were found to be in use attaching the various steps to the engine. These included flat washers with non-locking and locking nuts. In some cases, in addition to the flat washers, there were lock washers also in place. These were used both with locking and non-locking nuts. The specific hardware used to secure the dislodged step could not be identified, as only the bolts were recovered. The nuts or washers used on the two dislodged screws were not found. It was hypothesized that the hardware for the dislodged screws did not incorporate any adequate locking features, and subsequently allowed the nuts to loosen over time and eventually separate from the bolt. When the step was loaded by the weight of the firefighter, it dislodged causing him to lose his footing and fall. Continue reading “Safety First on the Fire Truck” →

Chopping Machine Expert Witness

Be Careful Where You Put Your Hands!

Posted by John R. Yannaccone, PE on with 2 Comments

Case Synopsis: A worker was monitoring the flow of vegetables into a chopping machine. The machine’s inlet would occasionally clog, requiring the worker to clear out the jammed vegetables. The plant’s procedure to clear the clog was to shut down the chopper machine, thereby stopping the blades, and then use a plastic paddle to clear the clog in the inlet. On the day of the incident, the worker chose not to shut down the machine or use the plastic paddle to clear the jam. While reaching into the inlet, the worker extended their hand into the machine, placing their hand in the path of the rotating blades. The worker sustained amputation of all four fingers and part of their hand and thumb.

The plaintiff alleged the machine was defective because it allowed the worker to be exposed to the sharp, rotating blades. They indicated the machine should have been designed to automatically shut down in the event of a clog to prevent a worker from coming into contact with the blades when they were active. Continue reading “Be Careful Where You Put Your Hands!” →

Child Passenger Safety

A Potential Client Calls About A Child Injured in A Crash – What Should You Do?

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You just got a call from a parent that they were involved in a collision and, as a result, their young child was injured. What important steps should you take?

  1. Secure the evidence – both the vehicle and the child seat
  2. Get the make, model and date of manufacture of the child seat
  3. Photograph any marks on the child’s body
  4. Get accurate height and weight for the child

One of the most important steps to take is to immediately secure the evidence. In a case involving a child who was riding in a child seat, in addition to the vehicle, it is also very important to secure the child seat. If the child seat is still installed in the vehicle, take photographs to document how it is installed and how the harness is adjusted. If the child seat is no longer installed in the vehicle, it is best to secure the car seat by taking custody of it to prevent it from becoming separated from a vehicle you do not control. If the seat is not with the vehicle, check with the hospital or in other vehicles involved in the crash. In some cases, children are removed from a vehicle and transported to the hospital in the child seat. In these cases, the child seat will likely end up at the hospital and may be delivered to the parent’s or child’s hospital room or, if not secured quickly, discarded. If possible, have the client place the car seat in a safe location so that it remains available to be inspected. It is also very helpful to know the make and model of the child seat at the time of the initial call. This information, as well as the date of manufacture is always found on the car seat label. If possible, photograph the label.

In addition to preserving the child seat, it is also helpful to photograph any marks, i.e. bruising, on the child. The locations of these bruises will help to identify how the harness was positioned on the child at the time of the collision. Continue reading “A Potential Client Calls About A Child Injured in A Crash – What Should You Do?” →

lawn-mower-safety

Case Study: The Importance of Lawn Mower Safety

Posted by John R. Yannaccone, PE on with 0 Comment

Case Synopsis: A landscaper was operating a commercial riding mower at an industrial plant early one morning. The ground was covered in dew resulting in a slippery terrain. As the worker was cutting the lawn, he proceeded down a hill, was unable to stop, and slid into the side of a building. Due to the wet ground and the incline, he was unable to back the mower up from the building. At that point he dismounted the mower and attempted to pull it away from the wall so he would be able to drive again. While attempting to move the mower, the worker slipped, entangled his foot under the mower deck resulting in a partial amputation.

Expert Analysis: According to the operator’s manual for the mower, there were several interlocks, or safeties, which should have prevented the mower blades from operating after dismounting the mower. The system should turn off the mower’s engine if the blades were still engaged, or the parking brake was not set when the operator removed his weight from the seat. The manufacturer had performance requirements on how quickly the engine was required to stop after weight was removed from the seat. There was also a recommendation that the seat interlock be checked weekly to confirm it operated properly by shutting down the mower if weight was removed from the seat. Continue reading “Case Study: The Importance of Lawn Mower Safety” →