Expert Witness Forensic Engineer Industrial Controls Automation New Orleans
Arthur Zatarain
Project Profiles
Industrial Accidents: Electrical Shock and Electrocution
electrocution on offshore plaatform electrocution industrial electrician food cart electrocution

Industrial Accidents: Investigation of non-fatal electrical shock and fatal electrocution incidents on portable and permanent electrical power systems. The forensic work included equipment inspection, testing, and accident reconstruction. Various industrial standards and regulatory codes were also analyzed for relevance to each accident.

Sample expert witness engagements as a forensic engineer for electrical shock and electrocution include:

  • Construction worker operating an electrically driven pump

  • Offshore drilling rig worker with battery charger

  • Kitchen worker with rolling food cart

  • Electrical outlet embedded in a work table

  • Electrician testing instrumentation with digital volt meter

  • Portable tool connected with interconnected extension cords

  • Manufacturing equipment on temporary power

  • Living quarters (trailer) on utility power

Circumstances involving electrocution often include:

  • Electrical work performed by unskilled workers

  • Improper lockout-tagout (LOTO) procedures, process, and training

  • Misuse of electrical equipment in damp or wet locations

  • Improper modification or maintenance of electrical equipment

  • Damaged electrical power cords, receptacles, and storage devices

  • Inadequate ground fault circuit interrupter (GFCI) protection

  • Product design defect or manufacturing defect

  • Improper digging in areas subject to pre-approval permits and restrictions

  • Old, damaged, and overheated electrical insulation

Related information from Wikipedia, provided for reference only:

Electric shock occurs upon contact of a (human) body part with any source of electricity that causes a sufficient current through the skin, muscles, or hair. Typically, the expression is used to describe an injurious exposure to electricity. Very small currents can be imperceptible. Larger current passing through the body may make it impossible for a shock victim to let go of an energized object. Still larger currents can cause fibrillation of the heart and damage to tissues. Death caused by an electric shock is called electrocution.

The minimum current a human can feel depends on the current type (AC or DC) and frequency. A person can feel at least 1 mA (rms) of AC at 60 Hz, while at least 5 mA for DC. At around 10 milliamperes, AC current passing through the arm of a 68 kg (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object. This is known as the "let go threshold" and is a criterion for shock hazard in electrical regulations.

The current may, if it is high enough, cause tissue damage or fibrillation which leads to cardiac arrest; more than 30 mA of AC (rms, 60 Hz) or 300 – 500 mA of DC can cause fibrillation. A sustained electric shock from AC at 120 V, 60 Hz is an especially dangerous source of ventricular fibrillation because it usually exceeds the let-go threshold, while not delivering enough initial energy to propel the person away from the source.

However, the potential seriousness of the shock depends on paths through the body that the currents take. If the voltage is less than 200 V, then the human skin, more precisely the stratum corneum, is the main contributor to the impedance of the body in the case of a macroshock—the passing of current between two contact points on the skin. The characteristics of the skin are non-linear however. If the voltage is above 450–600 V, then dielectric breakdown of the skin occurs. The protection offered by the skin is lowered by perspiration, and this is accelerated if electricity causes muscles to contract above the let-go threshold for a sustained period of time.

If an electrical circuit is established by electrodes introduced in the body, bypassing the skin, then the potential for lethality is much higher if a circuit through the heart is established. This is known as a microshock. Currents of only 10 µA can be sufficient to cause fibrillation in this case. This is a concern in modern hospital settings when the patient is connected to multiple devices. This can actually have a very serious effect on the human body.

 



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