“Electrical control” is a specialized discipline of electrical engineering where, to put it simply, electrical circuits and programmable electronics are engineered to turn machines and consumer products on and off. That is an over simplification but after all the engineering design, functional requirements, safety requirements, testing, and many other required activities are completed, the product or machine will turn on and off in accordance with desired parameters.
In this article, Electrical Engineer Jeffrey Kobilka explains what some of those devices are, how they can fail, and how an electrical controls engineer could be beneficial to your case.
Is Your Product Liability Case Really an Electrical Controls Case? - Expert Article
Electrical control systems are commonly found in both industrial settings and consumer products. In fact, by the time you complete your morning routine, you have interacted with multiple machinery control systems. As you shower and hot water is depleted from your water heater, a temperature sensor signals to the electrical controller to ignite the gas burner. The water pressure in your home may be maintained by a municipal water utility that employs a Supervisory, Control, and Data Acquisition (SCADA) system to control water pumps and maintain tank levels throughout your town.
The consumer product you use to provide your morning pick me up, the coffee maker, is a machine with electrically controlled heating elements and pumps. Electrical control systems provide many benefits, but failures in these relied upon systems can cause personal injury and property loss.
Unexpected/Unintended Start up
Unexpected start up occurs when a machine activates without an intentional action from the operator. When the equipment in question is a massive industrial machine, this can cause severe injury.
A hydraulic press brake is an industrial machine that is used for bending and forming sheet metal. Often the operator must place his hands within the hazardous area of the machine. Machine activation at this time can result in severe injury to the hands and arms. While the operator should perform the work in accordance with safe work practices, the electrical control system should provide an additional layer of safety and guard against an unintended activation. Failure to protect the operator from unintended operation may indicate lack of required safety equipment or incorrect integration and installation of the control system.
Vehicle barriers are used to control access to roadways and parking lots. These systems often use electric motors controlled by a programmable logic controller (PLC) with input from keypads, vehicle loop detectors, and optical sensors to control the barrier. A failure in the programming of the system can manifest as unintended gate operations which can lead to barrier collisions with vehicles or pedestrians. Analysis of the Programmable Logic Controller (PLC) code can be instrumental in understanding the cause of these collisions.
Failure to stop
Another type of unintended motion is a failure to stop. This failure mode occurs when the user commands the equipment to stop or deactivate, but equipment operation continues.
Patient lifts found in healthcare facilities are used to assist staff in moving patients with mobility issues. These lifts can be electrically controlled by a wired remote control to raise, lower, or otherwise reposition the patient. In normal operation, the lift raises when the raise button is pressed, and stops when the button is released. In the event of a failure to stop, the button is released and the lift and patient continue to rise. The unexpected nature of the motion and increased height of the patient can cause instability and patient fall injuries. In this case, the control systems engineer can analyze the incident controller for a local failure such as failed button contacts. Beyond the local failure, the entire design lifecycle of the product (which includes risk analysis and hardware design) is relevant to the cause of the incident, and can be investigated by a control systems engineer.
Failure to warn/alarm
Modern process control systems in industries such as Food and Beverage and Pharmaceutical utilize a wide array of sensors to provide feedback to the process controller (the control system) and to the system operators. The information provided by these sensors is vital for decision making. The information can come in the form of alarms on a Human Machine Interface (HMI), a flashing light, or a siren. A system that fails to present this information properly can lead to property damage.
For example, an industrial bakery could have a cookie producing line that utilizes a control system to maintain temperature while baking. The system has a temperature sensor which is used to control a heating element. This temperature sensor could fail. Without that sensor, the control system does not know how to control the heater and could under-heat resulting in dough instead of cookies, or overheat resulting in burned cookies or fire. Either way, the product is ruined and not salable. This type of alarm should be reported to the operator and/or shut down the production line. If it does not, that may indicate a failure in the design of the control system.
Control Systems Engineer/Discovery questions
When safety incidents and property loss occur, the control systems engineer has a wide array of tools to investigate. Each stage of the product life cycle can be analyzed to determine liability. This includes:
- Systems engineering – Were critical activities such as risk analysis and the development of safety requirements performed? Was the analysis thorough? Did it include reasonably foreseeable failure modes and hazards?
- Hardware selection and design – Were appropriate sensors and safety interlocks included in the design?
- Software implementation – Was the failure a result of defective programming? Analysis of Programmable Logic Controller (PLC) or microprocessor code can uncover defective programming.
- Installation – Were the design documents followed? Are appropriate instructions for installation included from the manufacturer?
- System Testing – Was testing performed in the factory? What testing is required by the manufacturer to be performed after installation? Do the manufacturer’s test instructions test all required safety functions?
- Operation – Did the manufacturer provide instruction for safe operation? Were the manufacturer’s operation instructions followed?
- Maintenance – Does the manufacturer recommend appropriate maintenance? Was maintenance performed by the equipment owner?
- Modification – Was the machine or system modified after installation? By whom? Did that party perform system testing to verify operation and safety function?
When electrically controlled equipment and consumer products fail to start, stop, or behave as desired, the cause of this failure often lies within the discipline of control systems engineering.
ELECTRICAL CONTROLS INVESTIGATIONS
When determining what experts should be included on your team, consider whether the equipment involved in the incident underwent unintended motion, failing to start or stop at the appropriate time, or failed to provide needed information to the user to prevent the incident. If so, the technical matters of your case may fall within the discipline of a control systems engineer.
For more information, contact the author of this article or submit an inquiry.
Electrical Engineer & Industrial Controls Expert
Jeff Kobilka is an electrical engineer with more than a decade of professional experience in plants and manufacturing environments that produce advanced, technical products. Jeff was the Lead Systems Engineer and Software Lead at the Naval Surface Warfare Center, Philadelphia Division for machinery control systems aboard the LCS Freedom class of US Navy ships. These controls developed by Jeff managed critical vessel operations, including propulsion, electrical plant, damage control, and auxiliary systems. Jeff’s hands-on experience extends onto dry land, where he worked for an electrical engineering and systems integration firm. In this role, he designed and implemented control systems with a wide array of industry technologies. Jeff applies his expertise to forensic casework involving electrical burn and shock injuries, fires of electrical origin, and machinery mishaps involving software or automation malfunctions.