Forensic Engineers and Consultants

Archive: Electrical and Control Systems

Ready, Set, Fly! – Understanding Another Technology for Forensic Investigations

This is the first blog in a series on integrating new technologies into the process of forensic investigations.  Documenting the scene of an incident accurately, efficiently, and safely is a key step in every investigation.  Busy roadways and unstable structures present hazards to the investigator during the investigation process. The use of remote sensors can reduce these risks and provide data that otherwise could not safely be obtained. Read More

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Ground rod installed in the earth with clamp.

Grounding versus Bonding – Understanding the Difference in Building Electrical Systems

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While a teenager might be very familiar with being “grounded”, there is confusion over the meaning of the word in the electrical sense. In building electrical systems, “grounding” and “bonding” are two terms that are often misunderstood. Improper application of the concepts of grounding and bonding may create lethal shock and fire hazards. “Earthing” is a term which comes from the European International Electrotechnical Committee (IEC). Earthing is synonymous with grounding but often thought to have a different meaning. Read More

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Flood Damage to Electrical Equipment

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As a result of the recent weather, those of us in South Carolina have gained a renewed appreciation of the damage that can result from flooding. Even a few inches of flood water can result in property damage and a loss of services in addition to the immediate risk of physical harm. Read More

Figure 2: A view of a typical PLC.  The blue and red wiring to the right terminate at the PLC’s input / output wiring connections. The processor is to the left at the keyed switch.  This PLC has capacity to communicate over an Ethernet data link.

Forensic Examination of Losses that Include Programmable Logic Controllers (PLC’s)

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Many modern machines and processes are controlled by Programmable Logic Controllers (PLC’s).  PLC’s are essentially computers that have the ability, properly connected and programmed, to interface with the outside world and control the actions of a machine like a robot or conveyor.  The PLC has a processor for processing the user programmed logic, and also has input / output (I/O) wiring provisions for both analog (e.g. temperatures and pressure transducers) and digital (e.g. limit switches and indicator lights) devices.  Read More

Gas valves from a process furnace that experienced an explosion. The final gas safety shut off valve has its wiring cover partially open. This can be an indication that someone was directly powering the valve and bypassing the control system safety logic. Open wiring covers on controls should be fully investigated.

Stay in Control: Manipulation of Electrical Controls Can Lead to Fires and Explosions

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We have a saying at Warren, “When we go to work on a new case, usually someone else has had a very bad day.” If you are a plant manager at a factory, you know it’s a bad day when you hear the fire alarm or a loud explosion emanating from the back of the plant. Read More

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