Electrical hazards are generally a result of a short, fault, or the opening or closing of an energized circuit.
A "short" occurs when a low-resistance path exists between a live wire and the ground, or between wires at different voltages. When the current is unintended, a "fault" results. Damaged insulation could cause a short, leading to arching or a fire. (see Electrical Safety: Safety and Health for Electrical Trades--Student Manual).
Electric Shock is the physical stimulation or trauma caused by the flow of electricity through the human body. It can occur during contact with or by being near live (energized) electrical parts. An electric shock can occur without direct contact with electricity. Electrocution results when death occurs from an electric shock. The most common shock-related injury is a burn.
Electrical shock hazards can be created by:
|Defective electrical tools||Untrained or unqualified personnel attempting electrical power connections|
|Improper electrical phasing||Damaged wire insulation as a result of hot work processes|
|Inaccurate schematic drawings||Corroded connectors due to saltwater intrusion or contact|
|Worn or frayed electric cables||Inadequate electrical isolation, failure to test for deenergization, and improper lockout/tags-plus application|
|Electric cables pinched in hatches/doors||Tools and equipment not properly grounded|
|Electric cables struck by grinders/saws||Blind-side drilling into electrical conductors|
Electric Arc is the luminous electrical discharge that occurs when high voltages exist across a gap between conductors and current travels through the air. This situation is often caused by equipment failure as a result of poor maintenance or overuse.
Arc Flash is the release of heat and bright intense light from an electric arc. Temperatures have been recorded as high as 35,000°F. Exposure to these extreme temperatures both burns the skin directly and causes ignition of clothing (see National Fire Protection Association Standard, NFPA 70E, 2012). An arc flash can be spontaneous or result from bridging the gap between electrical contacts with a conductive object such as a tool or jewelry. Other causes may include dropped tools on energized conductors which create sparks, breaks or gaps in insulation, as well as the buildup of dust, corrosion, or other impurities on the surface of an insulator, creating a fault path.
Arc Blast is the explosive release of molten material from equipment caused by high amperage arcs. The pressure waves produced by an arc blast are powerful enough that workers can be knocked off, onto, or into objects. The high pressure can cause injuries such as falls, exposure to being struck by molten metal and loose materials or equipment, ruptured eardrums, and memory loss as a result of a concussion.
Before electrical work is performed, employers need to conduct an arc flash hazard analysis, which will help to determine safe work practices for preventing injuries, the arc flash boundary, and the appropriate level of protective clothing and other PPE for workers to use.
Some examples of safe work practices are discussed in this document and include assigning responsibility and ensuring workers are only assigned to tasks that they have been trained on; the testing of electrical equipment and circuits to verify deenergization; the implementation of an effective lockout/tags-plus system; and the use of appropriate tools.
The arc flash boundary must be determined for each arc flash hazard analysis done for a specific task. The arc flash boundary marks the point at which arc-rated (AR) protective clothing and other PPE are necessary to avoid second-degree burns. AR clothing or equipment are necessary for protection against arc flash hazards, as they are specifically designed and tested for protection against the thermal effects of an arc flash. The arc rating can be expressed in cal/cm2.
A hazard assessment is necessary for determining the hazards present, or likely to be present, at each worksite (29 CFR 1915.152(b)). Employers must provide and ensure that workers use personal protective equipment (PPE) appropriate for protecting them against these hazards (29 CFR 1915.152(a)). For example, non-conductive goggles should be worn instead of glasses with metal frames when performing electrical work. In addition, workers should avoid wearing jewelry, including metal watches, metal fasteners on clothing, or any other conductive material when working on equipment with high amperage. The selection of PPE must be communicated to each affected employee and training provided to ensure they understand the hazards associated with the work activity and the use of the PPE determined necessary (29 CFR 1915.152(b)(2) and (e)(1)).
Protective clothing and other PPE can be determined by either calculating an incident energy analysis (which predict the amount of energy that will be generated during an electrical arc incident) or by using the tables in NFPA 70E. NFPA 70E tables are used to determine the hazard/risk category for a specific task. The hazard/risk category is assigned a number from 0 to 4 and is used to identify the required protective clothing and other PPE for the specific task (see pages D6 and D7). While NFPA 70E does not cover shipboard electrical work, protective clothing and other PPE consistent with the standard's requirements is recommended.
For more detailed information, see Chapter 1, Article 130 of NFPA 70E, 2012.
Electrical work done during the construction of vessels involves the installation of conductive cables, wires, circuit boards, and equipment, which at some point must be activated and tested. Repair work often requires isolating and deenergizing single or multiple systems while work is done, as well as the use of electric power supplied to the vessel from an outside source (shore power). Electric shock injuries or injuries from arc flash or arc blast incidents such as burns, caused by the uncontrolled release of electrical energy, can be life-threatening. Every precaution must be taken to avoid these incidents (e.g., voltage testing).
The following OSHA standards specify safety measures that must be followed to protect workers from electrical hazards in ship repairing, shipbuilding, or shipbreaking activities:
D-4, D-5 and D8
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