Forensic Engineers and Consultants

Tag Archive: engineering analysis

  1. T is for Temporary – Issues with Extension Cords and Other Temporary Wiring Applications

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    Temporary wiring is just that….temporary, and is typically used for repair and maintenance projects.  In this blog I am going to discuss guidance offered by Article 590 of the National Electric Code (NEC), as well as some points to consider when using temporary wiring, including extension cords and holiday lighting.

    Before each use, extension cords need to be inspected for visual damage.  Cords with cuts or splits to the insulation need to be discarded.  Cords with damage to the connectors, including those that feel loose when connected, need to be taken out of service.   Failure to properly select and use extension cords can have a catastrophic result.  (more…)

  2. TVSS or SPD … Can I Buy a Vowel? Understanding Surge Protection and the Changing Requirements

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    Surge Protective Devices (SPD), formerly known as Transient Voltage Surge Suppressors (TVSS) have been around for a long time.   The most recognized version is integrated into outlet strips and used to protect sensitive electronics from surges, or higher than expected voltages on the power line.  Early versions of these surge strips were known to have problems where internal components could overheat and cause a fire.  Thermal protection was added to the designs to greatly reduce the potential for a fire hazard.  Such an implementation in an outlet strip is considered a Type 3 SPD. (more…)

  3. In a Flash – The Transfer of Energies in Our Global Electrical System

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    According to published weather data for the year 2019, 2.35 billion lightning strikes were recorded across the world, with 223 million of these in the United States.  The movement of atmosphere causes electrical charges to build up between clouds.  A tipping point is reached where the insulating properties of the air cannot withstand the level of energy and a discharge occurs.

    Image Credit: Charleston Post and Courier. A lightning strike over Charleston, SC on July 3, 2019.

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  4. Major Causes of Wood Truss Failures

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    Wood truss failures can vary and identifying the cause requires visual inspection as well as a working knowledge of the structural loads and building codes. These truss systems must transfer the gravity and lateral loads to the foundations. Consequently, the framing system and the foundation provide strength and stability for a structure. The most common type of wood-framed construction uses roof trusses, exterior and interior load-bearing walls, beams, girders, posts, and floor framing to resist the gravity and vertical loads. This type of wood-framed construction engages a system of horizontal diaphragms (roof and floors) and shear walls (vertical exterior sheathed walls) to resist the lateral loads. (more…)

  5. The Demise of Insulation on Electrical Wiring

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    Unlike fine wines and some types of cheeses, not everything ages well.  Such is the case with the materials used as insulation of electrical wiring.  While the copper metal used as the conductor in many wire types will last virtually forever, the cladding used to protect and insulate the wire allowing electrons to flow to their final destination does not. (more…)

  6. Hidden Heat: The Unseen Hazard of a High Resistance Connection

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    A typical residence can have upwards of 10,000 feet of electrical conductors installed, most of which are buried in the walls, attics and crawlspaces.  A commercial building can have 100,000 to upwards of 1 million feet of electrical conductors.  At each device such as a switch or a receptacle are at least three, and typically six or more connections of these conductors within a junction box.  The connections can be in the form of twisted connectors, screw terminals, push in terminals and crimped connectors.

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  7. OSHA’s Process Safety Management – Is This Process Covered?

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    In February of 1992, the OSHA Process Safety Management (PSM) standard was issued. The official title is: ‘Process Safety Management of Highly Hazardous Chemicals.’ As its title implies, not every facility is covered by this rigorous standard. A process must contain highly hazardous, as defined by OSHA, chemicals above a certain weight threshold, again defined by OSHA. Notice that this is a process by process determination, so there could be certain processes at a manufacturing facility that are not covered by this standard situated beside other processes that are.
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  8. Boiler Blowdown – It’s Not a Dance Move

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    When thinking about the safe operation of boilers (and don’t we all?), several systems can readily be named; flame control, fuel/air ratio; steam pressure control, levels in the vessel, etc. What about the water? It seems so passive, as long as there is enough for level control, what’s the big deal? Well, it turns out, that as the steam produced by a boiler is used in the process, the condensate from that steam is returned to the boiler as feedwater. However, since 100% of the condensate is not returned, whatever solids had been in that water before it evaporated to form steam are left in the remaining water.  Fresh feedwater is added to maintain levels, but even fresh water contains some dissolved solids. So over time, the water in the boiler system gets saturated with all sorts of dissolved minerals.
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  9. Testing…testing… Is this thing on?

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    Many people just take for granted that something is just going to work, and in many cases assume that it will work forever.  One such device that does not get enough attention is the Ground Fault Circuit Interrupter (GFCI).   Simply put, a GFCI is a protective device that compares the current flowing on the hot and neutral wires of the circuit and will “trip” to disconnect power to the circuit if a small imbalance of current is detected.  The imbalance of current is an indication of a dangerous alternate path for the current to flow from a damaged line cord or a fault inside an appliance and constitutes a shock hazard to a person. (more…)

  10. How a Central Indian Town Changed the United States Code of Federal Regulations

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    On December 3, 1984, at a pesticide ingredient manufacturing facility owned by Union Carbide, a leak occurred in the Methyl Isocyanate (MIC) plant. Due to the toxic nature of the gases released and the plant’s proximity to local residences, the death toll was in the thousands; both plant workers and nearby residents.  The first recorded public meeting in response to this incident was on December 9th, in Institute, WV, the site of Union Carbide’s only US MIC production unit.  Full disclosure: my father was a research & development chemist for Union Carbide and Institute is about 10 miles down the Kanawha River from my hometown of Charleston, WV. (more…)

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