The experts at Alpine Engineering and Design, Inc. (AED) provided Mechanical Expert Witness services on a case involving an auger conveyor. It is our understanding that this case was resolved outside of court. AED has multiple offices in the intermountain west, and provides services throughout the United States.
I recently investigated an incident involving an auger conveyor. While an operator, who we will call Mr. Jones in this article, was cleaning the conveyor at the end of that day’s work, something caught while he was scrubbing and his arm was pulled into the conveyor. When the conveyor couldn’t pull it in any further, it cut through his arm just below his elbow, amputating his lower arm. A tragic situation that never should have happened.
Auger conveyors (also called screw conveyors) are essentially large screws, that are often placed inside of a tube or housing to move material from one place to another. Auger conveyors have certain advantages when compared to belt or other types of conveyors. They are extremely versatile and can effectively move materials ranging from viscous sludgy material like concrete, to free flowing bulk materials like grains and even liquids. There can also be multiple inlets and discharge points allowing material to be distributed to various locations as required. Because of their versatility, auger conveyors and screw conveyors are widely used in many industries. They can and often are used safely. However, there are certain hazards that, if not controlled properly, can lead to terrible consequences.
Over the years, the best practices for designing, using and safeguarding auger and screw conveyors have been documented in various standards and guide books including OSHA 1926.555, OSHA 1910.212, OSHA 3067, CEMA-ANSI 350, and ISO Technical Report 9172. Following these best practices greatly increases the probability that the auger conveyor can be used safely and effectively. However, each conveyor and each installation is unique and the people that wrote the standards could not possibly foresee possible implementation and potential hazard. Accordingly, users of auger conveyors should have a hazard analysis done by a competent professional to help determine what controls, warnings and training are necessary to keep their people safe.
In this particular incident, the auger conveyor was only part of a much larger machine. The auger was used to move materials from part of the machine in one room, through a small window, to part of the machine in a second room. The hatch for cleaning the auger was in the second room, away from and out of sight of the main control panel where the E-stop and the lock out tag out equipment was located.
The expected users were also an important consideration. Multiple people worked in conjunction with the machine at different stations. While the supervisors were trained employees, many of the workers were day laborers or temporary employees who would work for a few days or may be a few weeks at a time. Mr. Jones was completing his first day with the equipment when he was injured.
When the cleanup began, the supervisor opened the hatch to the conveyor and instructed Mr. Jones to clean it. He was given a hose, a putty knife and a green scrub brush. The auger was not moving when Mr. Jones started to clean it, but while he was working on it, someone started the machine up and the auger started to spin, catching Mr. Jones arm and pulling it into the machine and eventually amputating it.
The supervisor knew that the machine should have been locked out and tagged out before any of the cleaning was done, but found that it was easier and faster to clean the auger when it was still rotating slowly. Mr. Jones didn’t know any of the rules for washing the auger conveyor, and was simply following his supervisor’s instructions. The only warning on the auger itself was on top of the hatch, which wasn’t visible to Mr. Jones since the supervisor had opened the hatch for him. The warning was very basic and only instructed to stay clear of moving components.
Injuries like Mr. Jones’ are completely unnecessary and could have been avoided if simple actions were taken. As a result of our investigation and analysis, we generated the following opinions:
In this case, the accident occurred because the auger was not properly safeguarded and allowed Mr. Jones’ arm to come into contact with a moving auger, independent of whether the machine was running the whole time, or whether it was off then then started back up while he was cleaning it.
The manufacturer and the company that operated the auger conveyor should have known the hazards associated with auger conveyors, including the configuration found in this piece of equipment. Those hazards include nip points, shearing, crushing, or pulling body parts into the auger. Steps should have been taken appropriate steps to ameliorate them.
The shearing hazard could have been safeguarded against by including interlocks on the auger hatch doors that would prevent the auger from turning while the hatch was open. Such interlocks were well known and could have easily been included.
Such interlocks would have been both technologically and economically feasible at the time the equipment was manufactured.
The manufacturer had a responsibility to provide equipment that is safe for its intended uses and foreseeable misuses. Cleaning an auger without locking out/tagging out the machine is a foreseeable misuse. In this case, it may not even have been a misuse according to the manufacturer, as no such requirements are found on the auger or in the manual.
The manufacturer failed to sufficiently warn against the shearing hazard that was a known hazard for auger conveyors.
The manufacturer failed to specify what training was necessary for using their equipment with the shearing hazard that was a known hazard for auger conveyors.
If this auger had been designed, built and operated in accordance with the best practices for auger conveyors, this accident would never have happened. If a risk assessment had been done in the equipment, the risk associated with shear point when the auger hatch is opened would likely have been found to be high and would likely have been safeguarded by the inclusion of interlocks.
It is my understanding that this incident was resolved outside of court.
About Alpine Engineering and Design, Inc.
AED is a mechanical engineering consulting firm that focuses on industrial equipment design and forensic analysis. We have six experts on staff. All of our experts are licensed professional engineers and certified safety professionals. Between us, we have over 110 years of mechanical engineering consulting experience, we have consulted on thousands of projects and are listed as inventors on well over 100 patents. We have provided expert opinions on over 500 product liability, personal injury and patent cases. We have expertise in a wide variety of areas including aerial lifts, garbage trucks, forklifts, ziplines and thrill rides, construction equipment, oil and gas equipment, exercise equipment, consumer products and manufacturing equipment. If you would like AED to help you with your next project, please reach out to David. Contact information can be found at www.alpineeng.com