Fatal Electric Shock in a Workplace - Case Study Example

Fatal Electric Shock in a Workplace A REVIEW OF ACTUAL ELECTRICAL INCIDENT CASE-STUDY 18 May 2018 Prepared by: Table of Contents 1. Introduction 2 2. Summary 3 3. Description of the accident: 3 3.1 Place of the Incident 3 3.2 Accident in Detail 4 4. Investigation Stages 4 4.1 Primary Observations 4 4.2 Source Current Investigations 5 4.3 Investigating work status in the building at the time of accident 6 5. Discussion 7 5.1 The deceased and his co-worker 10 5.2 The employer 11 6. Mechanisms to Avoid Electrical Accidents in Workplaces in Future 11 7. Conclusion 12 Reference 13 1. Introduction Electrical accidents in workplaces are very common. Human errors are considered the major cause of electrical accidents in workplaces. Environmental conditions, such as flooding, also contribute to electrical accidents in organisations [1]. Statistics show that over 90% of all electrical accidents occurring at homes or workplaces are caused by human errors including carelessness, lack of knowledge and assumptions [2]. Therefore, addressing human errors goes a long way in preventing electrical accidents in workplaces. This report reviews a fatal electrocution incidence, which occurred when an employee was terminating electric cables to a column rose in a building under construction [3]. The incidence is presented in section 3 of the report and consequent investigations are reported in section 4. Section 5 presents a discussion of the accident and the investigations based on available literature and identifies who was to blame in this case. There is need to prevent future such incidences, which is presented in section 6 of this report. 2. Summary A worker received a fatal electrocution when terminating electric cables to a ceiling rose in one column of a building under construction. At the time of the accident, the deceased’s co-worker was working on another column. When he came back to see how his colleague was progressing, he found him sitting motionless on a steel column surrounding the column. The deceased did not show any burns on his body. Investigations revealed that the deceased was electrocuted as he was removing the casing of an energised cable because the MCB and isolator switch was “ON”. The current passed through the pair of shears that he was holding and flowed though his body. Lack of burns rule out the possibility of currents greater that 0.2A. Therefore, the deceased and his co-worker were to blame for failing to follow basic precautions prior to work. The employer was also to blame for failing to ensure workplace safety, particularly for failing to secure the switches. 3. Description of the accident: 3.1 Place of the Incident The accident occurred in Singapore in a building that was in construction. At the time of the accident, the deceased and his co-worker were shifting the location ceiling rose at some pillar columns of the house under construction. It is during the process of terminating cables to a ceiling rose at one column (column C2309) when the deceased was electrocuted to death. At the time, the deceased’s co-worker was working on another column, and he became aware of his workmate’s fate some time after when he went to look how his colleague was proceeding with work. 3.2 Accident in Detail According to the co-worker, the duo had been working on column C2309 before stopping for dinner. Before they stopped working, they removed the cables in the conduit from the ceiling rose terminals and consequently taped them using PVC insulation tape. After dinner, they decided that the deceased should complete work on column C2309 before joining his co-worker in another column. Therefore, after dinner, the deceased resumed work at column C2309 to terminate the cables into the ceiling rose where he received a fatal electric shock. However, the deceased took too long before joining his colleague at the other column, which prompted the co-worker to go to column C2309 to check how his workmate was proceeding. On arrival, he found the deceased sitting motionless on the steel frame adjacent to the column. The deceased was rushed to the hospital where he was pronounced dead on arrival. 4. Investigation Stages 4.1 Primary Observations Immediately after the accident, primary investigation was conducted. It was found that the column C2309 was covered with stone cladding. Steel brackets surrounded the column. The deceased’s co-worker confirmed that by the time he arrived at the scene of accident, the deceased was sitting motionless on the steel frame forming the bracket that was surrounding the column. After further observations, the investigators indentified 2 sets of three cables, which were housed in a PVC flexible conduit. The conduit was in turn terminated into the base of the ceiling rose and each cable was drawn beyond the ceiling rose. The deceased’s co-worker confirmed that the duo had drawn the cables awaiting to cut, fit and terminate them into the ceiling rose, a task that the deceased decided to complete alone while the co-worker proceeded to another point of work. The deceased did not show any signs of burns. An electrical engineer performing the investigations traced each of the two sets of wires, and he found out that one set was one of the circuits of DIM L1/CHI-GUTTER. The black cable of this set of wires was found to have been stripped off its insulation, which left about 15 mm of bare conductor exposed at the end. A jammed pair shears was also found hanging. The pair of shears had a piece of blue cable in between the cutting blades. The deceased’s co-worker confirmed that the pair of shears belonged to the deceased. 4.2 Source Current Investigations After conducting initial investigations and finding a naked blue wire and a jammed pair of shears, the inspectors suspected a case of electric shock. Consequently, further investigations we conducted to find the source of current. The investigators established that a 20A SPN MCB was used to control the source of supply for the circuit. The blue wire with a naked end was found to terminate to the 20A SPN MCB installed in the dimmer rack DIM L1/CHI-Gutter. The dimmer rack was in turn connected to a TPN 63A MCB through a 63A TPN isolator. Further investigations revealed that the circuit did not have an RCCB protection. It was possible that the blue cable was live at the time the deceased was attempting to terminate the cables to the ceiling rose. This prompted the investigators to determine whether the MCB and isolator were “ON” at the time of accident. A witnessed indicated that indeed he found that the MCB and the isolator were “ON” immediately after the deceased’s co-worker raised an alarm. This suggests that the MCB and the isolator were “ON” when the deceased was terminating the cables to the ceiling rose. When interviewed, the deceased’s co-worker indicated that he could not have suspected any live wire because when working independently, he did not interfere with any bare cable. 4.3 Investigating work status in the building at the time of accident Investigations made it clear that the deceased received an electric shock from the supply source through the MCB and isolator because they were “ON”. In this case, whose failure was it? Was it the failure by the duo to start working without having checked to ensure that the MCB and isolator were “OFF” before proceeding with work? Or was it the failure by the deceased to fail to check whether the wires were energised before removing the casing? Or were the MCB and isolator switched “ON” accidentally when the deceased was removing the casing? The investigators required answers to these questions. An interview with the deceased’s co-worker revealed that he (the co-worker) had personally switched “OFF” the MCB and isolator prior to start of work. However, this was before the duo retired for dinner. However, after dinner, when the two resumed work, neither of them remembered check the MCB and isolator giving the possibility that somebody else had switched “ON” the MCB and isolator when the deceased and his co worker were out for dinner or immediately after they were switched “OFF”. Consequently, there was need to understand the condition of work in the building during the day and at the time of the accident. Investigations revealed that a number of activities were running in the building during that day. Some construction work was underway including construction and installation of a metallic barrier at one side of the building and fixing of doors and windows in various parts of the building. This activity involved welding. Plumb work was also underway in one part of the building. Therefore, there were several people (about 10) working in the building. There were also some activities requiring electricity in the building. However, investigations revealed that all other activities requiring electricity were not powered via the same MCB and isolator as the cables that the deceased and his co-worker were terminating to the ceiling rose. However, the switches of all the circuits were located at the same place but in different racks. None of the racks was locked and/or secured. An eye witness indicated that immediately after the accident, all the switches were “ON” and all the racks were open. Further investigation revealed that the racks or switches were not labeled to differentiate switches for different circuits. 5. Discussion Carelessness and failure to follow basic procedures are quoted as significant sources of electrical accidents [4- 7]. An analysis of work related electrical accidents occurring in workplaces found that there are two main categories of accidents [8]. There are those accidents that occur because employees work in the vicinity of live cables without taking adequate precautions [8]. They fail to take adequate precautions either because they do not know the precautions they ought to take or because they are careless and fail to follow recommended work procedures [6]. The other category involves accidents that occur because employees work in the vicinity of live wires they think they are dead [8]. However, ignorance contributes to the second category of electrical accidents because employees ought to take necessary steps before working around electrical cables whose live status is not known yet they terminate to a power source [9]. Such steps include confirming the live status of the cables and disconnecting the cables from the power source before working in their vicinity [10]. Based on the investigation presented above and in conjunction with the aforementioned literature about electrical accidents in work places, it is possible to analyse the accident and determine who was to blame. From investigations, it is beyond doubt that the deceased was electrocuted; the series of investigations that were conducted consistently built on this theory. Firstly, a jammed pair of shears was found hanging in which a blue wire was found hanging in between the blades. This suggests that the deceased was electrocuted as he was removing the casing of the wire that was energised. This further suggests that the deceased was not aware that the wire was energised; if he knew that the cable was energised, he would most probably have avoided interfering with it. The fact that the MCB and isolator were “ON” immediately after the accident further strengthens the electrocution theory. The deceased’s co-worker admitted that they were aware that the cables were connected to the mains, and they had, therefore, switched “OFF” the isolator and MCB long before they started working. Therefore, the “ON” status of the MCB and isolator makes it clear that current was indeed flowing by the time the deceased was working. The investigations reported in [3], however, fail to determine the current that was passing through the cables. Nevertheless, since a 20A SPN MCB was used to control the source of supply for the circuit, it is clear that the current was below 20A. Giovinazzo [11] indicates that it is not possible to determine the amount of current that caused death by conducting post-mortem analysis of the body. However, Giovinazzo [11] provides a chart (figure 1) that can be used to suggest the current that caused death. Figure 1: A chart showing various current intensities and their impact in case of electrical accidents [11] As shown in figure 1, currents below 0.01A could not have caused death. The deceased would have felt mild sensation [11]. Currents between 0.01A and 0.1A would have caused muscular contractions and paralysis. Muscular contractions would be so intense that the victim would be unable to release the energised cable. The deceased would have had difficulties in breathing, which would result to unconsciousness [11]. At this current, the deceased would have good chances of survival if immediate first aid was given. Currents between 0.1A and 0.2A would have caused instant death due to ventricular fibrillation of the heart. Above 0.2A, chances of survival would be pretty good if the deceased was given immediate first aid. The deceased’s heart would be forcibly clamped owing to severe muscular contractions. The clamping would have prevented the occurrence of ventricular fibrillation thereby giving the deceased a chance to survive. However, severe burns would be seen at the point where current enters the body with severity of the burns depending on the current intensity [11]. Based on the above analysis, and considering the reported status of the deceased, it is arguable that the current passing through the circuit was below 0.2A. Most probably, the current was in the range of 0.1 and 0.2A, which caused instant death. However, it is not possible to completely rule out the possibility of currents between 0.01 and 0.1A because there might have been some considerable time between when deceased was electrocuted and when the co-worker arrived at the scene. In that case, the deceased might have died due to breathing problems arising from electrocution. Secondly, the health status of the deceased prior to electrocution might have exacerbated the situation especially if the deceased had history of heart problems. Nevertheless, the baseline is that the deceased died from electrocution and secondly because there was no one nearby to offer immediate intervention or to switch “OFF” the MCB and isolator or other switches immediately to save his life. Therefore, as to whether the employer or the employee was to blame for the accident, both parties were to blame due to the following reasons. 5.1 The deceased and his co-worker Firstly, the duo was supposed to work together, but they decided to split after dinner most probably to finish work earlier than required. If the two stack together, the deceased’s co-worker would have saved his colleague by switching OFF the switches immediately and/or offer necessary first aid. Secondly, the duo was to blame due to failure to observe basic safety precautions and work procedures. They were supposed to have checked that the isolator and MCP were “OFF” before resuming work and secure the rack to ensure nobody interfered with it. Further blame is placed on the deceased for failing to check whether the wire was energised before removing the casing. About 50% of blame for the accident is placed to the deceased and his co-worker in which 90% of this lies on the deceased. 5.2 The employer The rest 50% of the accident’s blame is placed on the employer for improper management of the workplace. Firstly, the employer knew that there were several activities going on in the building and workers might have interfered with the MCB and isolator switch. The employer ought to have secured every switch so that only respective workers would have authorised access to the switches. 6. Mechanisms to Avoid Electrical Accidents in Workplaces in Future The following practices can help in avoiding similar accidents in the future: firstly, all work places should have a well established and communicated good practice on electrical circuits and components. The practice should include basic safety steps and procedures that workers should follow when carrying out electrical installations and repair. Workplaces should also have a policy that ensures no employee works alone; every employee must be accompanied by a co-worker who should stay close or work close to the employee and in such a way that the two can constantly observe and communicate with each other. Secondly, all switches must be labeled and provided with a means of securing them. When work is underway on a circuit, its respective switch must be switched “OFF” and the switch box closed. The keys to the switch box must only be in the possession of the work’s supervisor, employee or the manager. The box must not be opened unless the supervisor or worker gives the go ahead. Finally, organisations should provide frequent training sessions about safety in the workplaces and the basic safety procedures that workers should follow before commencing on various works. Workers should also be reminded of these safety procedures before they commence working on various assignments. This way, workers will be reminded of the various safety precautions that they should observe when working. 7. Conclusion Failure to observe basic safety precautions, by the deceased, his co-worker and the employer, was the main cause of the fatal electric accident. It seems that the deceased’s hands came into contact with the lethal current that flowed through his body thereby causing electrocution. This happened as the deceased was uncasing an energised wire. Three lessons are learnt from this cases study: it is always crucial to check whether electric cables are energised before working on them. It is highly advisable to have a person accompany another person working on electrical cables or in remote areas. The co-worker is supposed to take immediate and appropriate actions in case of accidents. Finally, proper work safety management is required by the employer to ensure that the workplace is safe before workers commence on any work. Therefore, similar accidents can be prevented by observing basic safety precautions when working on electrical circuits. Reference [1] R. B. Whittingham, The Blame Machine: Why Human Error Causes Accidents, Burlington, MA: Elsevier Butterworth-Heinemann, 2004. [2] T. Linsley, Basic Electrical Installation Works, 6th edition, Oxford, UK: Elsevier Ltd, 2011. [3] C. Seow, Electrical Accident Investigations Case Studies, Energy Market Authority (EMA). [4] A. S. Dent, Health and Safety Accidents: The Causes Analysis within the Construction Industry, Aberdeen University Press Services, 2007. [5] C. Shelton, Electrical Installations, 3rd edition, London, UK: Nelson Thornes Ltd, 2004. [6] EHS Safety Training. Electrical Safety: What are the Leading Causes of Electrical Accidents? Accessed 1st September, 2013. Available http://ehs.okstate.edu/modules/electric/accidents.htm [7] L. A. Geddes & R.A. Roeder, Handbook of Electrical Hazards and Accidents, 2nd edition, Lawyers & Judges Publishing Company, Inc. 2006. [8] J. H. Wiggins, Managing Electrical Safety, Government Institutes. 2001 [9] Z. Xu., Y. Lu & N. Han, Causes and Solutions of Electrical Circuit Fire of the Residential Basements in Beijing City, China. In; J. Lee, Ed, Advanced Electrical and Electronics Engineering, volume 2. Springer. 2011. [10] P. E. Batra, “Electric Accidents in the Production, Transmission, and Distribution of Electric Energy: A Review of Literature”, International Journal of Occupational Safety and Ergonomics, vol. 7, no. 3, pp. 285-307, 2001. [11] P. Geovinazzo, The Fatal Current. New Jersey State Council of Electrical Contractors Association. Accessed 2nd September, 2013, Available http://www.physics.ohio-state.edu/~p616/safety/fatal_current.html Read More