Forensic Engineering Investigation of Electrical and Electronic Causes of an Industrial Equipment Failure

This case involved industrial equipment whose repeated, seemingly random failures resulted in the buyer of that equipment suing the seller. The failures had been isolated to a group of several transistors within electro-mechanical modules within the equipment, but the root cause of those transistors failing had not been determined. The equipment seller had more than 1,000 units in the field with no similar failures. And the electro-mechanical module manufacturer had more than 20,000 units in the field with no similar failures. Electrical contractors hired by the buyer had measured power quality, and reported no faults found in the three-phase power at the equipment terminals. This paper presents circuit analyses of the failing electro-mechanical module, basics of electrostatic discharge damage and protection, and the root cause of these failures — an electrical code-violating extraneous neutral-to-ground bond in a secondary power cabinet.

pH Measurement of Cement-Based Materials: The Effect of Particle Size

Healthy reinforced concrete should be highly alkaline to safeguard the passive protective film for reinforcement of steel bars against corrosion. pH measurement is gaining importance in research of cement-based materials (CBMs), such as paste, mortar and concrete, as well as in structural health monitoring and forensic engineering applications. However, insufficient information is available regarding the most practical, economical and applicable quantitative pH measurement method for CBMs from the sampling to measurement stage. Existing recommended methods for measuring pH have many variables that need to be investigated to determine how they influence the pH value. Samples were recommended to be ground into very fine particles for pH measurement. Preparing very fine particles of CBMs is costly and time consuming, while larger particles, with sizes similar to sand particles, are easier to obtain, without needing special equipment. This study aims to investigate the effect of different particle sizes on the pH of cement mortar. Mortar specimens were crushed and sieved to obtain different ranges of particle sizes to measure the pH values. Results showed that specimens with large particle sizes (between 600 µm and 4.75 mm) can produce similar results to specimens with very fine particle sizes (<600 µm) by increasing the solid-to-solvent ratio or the leaching time.

Forensic Engineering Analysis Of Golf Course Cart Club And Ball Accidents

With Over 27.8 Million Golfers And More Than 16,000 Golf Facilities In The United States, Golf Is A Non-Contact Sport With Statistically Low Risk For Injury. However, Research Has Documented Golf Related Injuries Can Be Disproportionally Serious Or Even Fatal. Federal Regulations And Countermeasures To Improve Golf Safety Are Outlined. A Spectrum Of Forensic Engineering Analysis Of Golf-Related Incidents Illustrates The Broad Range Of Resulting Trauma. Categories Of Golf Incidents Include: Cart Collisions With Other Vehicles Resulting From Mixed Use On Automotive Roadways, Cart Solo Incidents Including Ejection With And Without Rollover, Errant Golf Ball Impacts, Inadvertent Golf Club Impacts, Trip And Fall Incidents As Well As Golf Cart Fires.

Ergonomics and Forensic Engineering

In disputes, forensic engineers routinely investigate available hardware and software and may examine other engineering attributes and activities. Human factors and ergonomic (HF&E) aspects may be considered, but these tend to be more limited or overlooked. This paper discusses an HF&E framework for forensic analysis, including its four major subdisciplines (micro-, meso-, macro-, and mega-ergonomics), the role each plays throughout the product life cycle, and examines their relationship to known and foreseeable use and misuse of a product or system. A taxonomy of errors, including distinguishing features of individual user errors versus system use errors, is presented and then used in a diagnostic rubric developed for forensic engineers to help identify HF&E issues as part of a forensic analysis. A health care setting case study is offered to demonstrate rubric use, but the rubric is generalizable to other domains.

Forensic Engineering Analysis of Video Screens for a Dispute Over Requirements and Specifications

This case was about LCD video screens intended to become components of medical equipment requiring an ultra-wide viewing angle. The seller was a wholesaler of various types of video screens from multiple manufacturers. The buyer was a distributor of multiple electrical components for various industries. The OEM, not involved in the case, was a manufacturer of medical instruments and equipment. Claiming that multiple units did not meet the requirements specified in the purchase agreement, the OEM refused a shipment of 1,000 LCD video screens. The buyer had already paid the seller, who refused to take back the shipment and issue a refund or credit. As a result, the buyer sued seller, and the author investigated and submitted expert opinions regarding the following questions: Did performance differ between examined samples? Did each sample meet data sheet specification for viewing angle? And was each sample adequate for its intended application as advertised in the datasheet (that is, for industrial settings requiring ultra-wide viewing angle)?

Chemical Incident Analysis Involving Storage of Fertilizer Product

A forensic engineering analyses of a chemical incident is presented that was classified as a self-sustaining decomposition (SSD) event, which occurred in a load of 10,000 tons of NK 21-00-21 fertilizer bulk stored inside a warehouse in the city of São Francisco do Sul in Brazil. The chemical reaction developed within the fertilizer mass and took several days to be controlled, resulting in the evacuation of thousands of residents. The water used to fight against the reaction, after having contact with the load of fertilizer material, promoted changes in adjacent water bodies, causing the death of animals (fish, crustaceans, and amphibians). The smoke from the chemical reaction products damaged the incident’s surrounding vegetation. Large SSD events are rare, with an average worldwide frequency of one every three years. Therefore, in addition to presenting a case study of this type of phenomenon, the main objective of this work is to discuss the causes that led to SSD reaction at this event, evaluate its consequences, and motivate future studies.

Forensic Engineering Analysis of a Commercial Dry Storage Marina Reinforced Concrete Runway Slab

An important element of a commercial marina is the landside site work behind the bulkhead. At many dry storage marinas, boats are launched, retrieved, and handled by large forklifts with axle loads up to 100 tons. In this case, the owner of a commercial marina sued the general contractor, alleging numerous design and construction defects in the reinforced concrete “runway” between the dry storage buildings and the bulkhead. This auger cast pile supported structure served as a relieving platform carrying vertical loads below the depth of the adjacent bulkhead. Some of the observed deficiencies were random cracking, joint damage, excessive edge settlement, and readily visible live load deflections. This paper presents the methods used to investigate the design and construction of this specialized structure. A finite element model (FEM) was used to review the original design intent and help establish the cost to cure. The original design of the runway and pile foundations was found to be inadequate.

Computational Fluid Dynamics Modeling of a Commercial Diving Incident

A commercial diver using surface-supplied air was “jetting” a trench, which was using high-pressure water via an industrial “jetting hose” connected to a pressure-compensated tool to cut trenches in silty sea bottoms. This tool used high-pressure water pumped from the tender boat down to the diver. It was reported that man-made objects in the area cut the jetting hose, resulting in uncontrolled diver movement and subsequent injury. There were no direct witnesses available. The subsequent forensic engineering investigation used traditional calculations, laboratory testing, ergonomics, biomechanics, and computational fluid dynamics (CFDs) to determine the limits of the physics involved in order to assess the feasibility of the reported scenario. Specifically, CFD modeled the mass flow exiting the tool’s two ends and the cut in the hose as well as modeled the diver’s flow resistance while propelled through the water. The results indicated the applicable physics precluded the events as described.

Forensic Engineering Analysis of a Swimming Pool Electric Shock Injury

This case involves a minor who received an electric shock while swimming in a membership swimming pool. Her family sued the pool association, its president, the electric utility, and others. At some time, tree trimmers had accidentally severed the service drop’s neutral return wire. The electric utility made a temporary splice repair, but did not permanently replace the wire until several years later (after the incident). The forensic engineer (FE) was retained by counsel for the pool and its president to opine on electrical aspects of the plaintiff’s complaints. The FE inspected the pool premises, reviewed documents, and examined the spliced service wires in storage. The FE opined that the pool association and its president were not negligent or careless — and that the electric utility failed its responsibility to maintain the service drop. This report discusses three-phase electric power, current flow, and how a severed neutral can cause a shock.