Forensics

Personal Injury

At times the facts surrounding a personal injury are unclear at first review - especially when it involves machinery controlled by computers. While only a few years ago, equipment was controlled and operated manually, factories in today's industry have a growing inventory of machinery controlled by hi-tech computers.




Accidents are sometimes caused by the physical and obvious failure of equipment ...or by the not-so-evident vital software controlling machinery. FSG can assist to determine and pinpoint if software was a liability issue.

Forensic Services Group (Hong Kong) has experience working with computers & specialized industrial computers called Programmed Logic Controllers (PLC's) in factory environments that manipulate various types of equipment including relays, solenoids, hydraulic servo valves, etc. which in turn operate cold rolling mills, motor controls, pinch-rolls & shears, coolant flow, coil cars, radiation & x-ray gauges, communication with other process control computers, etc.

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Below is an example of an accident resulting in personal injury along with several software programming issues that should be addressed.

... Machinery shears off workers' arm -


In the case of a machinery related accident, liability may not always be obvious. For example, consider a situation where a factory employee was performing maintenance on a shear that cuts paper rolls. Power supplied to the machine had been disconnected by turning off the main circuit breaker in the control room. While the maintenance worker was adjusting the shear, someone in the control room inadvertently turned on the main circuit breaker ....the shear plunged downward and severed the workers arm.

Could this accident have been prevented? The answer is yes, and for several reasons including the following:

  • Did the worker visibly tag the main circuit breaker indicating he was in a dangerous situation while working on the shear?
  • Was another worker physically standing by the main circuit breaker as added safety?
  • Did the worker chock the shear knife so that it would not move regardless of power?

The above are some of the steps that are normally taken into account when handling a personal injury case. However, there is another consideration that is often overlooked. An increasing proportion of factory machinery is now controlled by special purpose computers that is likely to be a Programmed Logic Controller (PLC).

While PLC's can be interconnected to other system computers, in most designs it the task of the PLC to be the last software controlled device to activate motors, solenoids & valves running machinery.

Technical issues - often overlooked :

  • Were the output states of the PLC programmed so that the shear would not move when power is applied?

    Potentially dangerous mechanical devices should be programmed with special considerations. For example: if the shear is up then leave it up ...if the shear is down then leave it down.

  • Is the primary initialization loop of the PLC programmed to look at the present state of the shear?

    Safely written software code insures that critical mechanical devices are carefully monitored before activation - especially at startup.

  • Were any safety features by-passed in the software code?

    Software is often modified during maintenance or troubleshooting in order to solve problems - sometimes in error and sometimes forgotten to return to its original state.

  • Has the PLC software code been modified by the factory technicians?

    In some cases, unauthorized factory technicians modify software code without the knowledge of the OEM.

  • Is the PLC software code written to operate the shear in a safe manner?

    Many technically skilled people can write/modify software code but it takes an experienced PLC programmer with many years of experience and training to write code that operates machinery in a safe manner.

Please contact Forensic Services Group (Hong Kong) as your next technical consultant !