Risk management calls for OHS, electrical professional expertise
Written by Daniel Roberts 01 August 2012
Table of contents
On the other hand, electrical professionals would have significant education and experience on electrical installations, but that education typically does not include OHS theory and practice.
Electrical safety can be advanced through a co-operative effort between the two professions using OHS risk management principles.
Risk management process
The purpose of the iterative risk management process (Figure 1) is to identify hazards, assess the risk deriving from those hazards and identify and implement risk controls, either alone or in combination, to achieve a level of risk that is “as low as reasonably practicable” (ALARP).
Using definitions under CSA Z1002, a “hazard” is a potential source of harm to a worker, while “risk” is the combination of the likelihood of the occurrence of harm and the severity of that harm. We will focus on the aspect of identifying risk criteria when establishing the context, and applying risk assessment and risk control methods to electrical hazards.
Risk criteria
Employers are required by law to exercise due diligence and create a workplace free of reasonably foreseeable harm. Shock and arc flash injuries are a reasonably foreseeable harm.
There are now many technological solutions for each risk control method in the hierarchy of risk controls that, when used individually or in combination, facilitate the avoidance of harm from electrical hazards.
The risk associated with electrical hazards can be managed by applying the hierarchy of risk controls to achieve a level of risk that is ALARP.
Risk analysis for electric shock
The likelihood of occurrence of a shock incident relates to whether an electrical conductor is exposed; and whether or not a person is closer than a “safe” distance. CSA Z462-12 defines the “safe” distance as the “limited approach boundary.”
The severity of the effect of electricity on human tissue correlates to the amount of electric current flowing through the tissue and duration of the current flow. According to Ohms Law, the flow of electric current is a function of the voltage applied. Therefore, to a limited degree, the severity of an electric shock incident can be correlated to the level of voltage. CSA Z462-12 clause 6.5.3.4 indicates the threshold below which voltage would not be considered hazardous is 30 Vac (rms) and 60 Vdc.
Risk analysis for arc flash
The likelihood of an arc flash incident correlates to the likelihood that the insulation or isolation of an energized conductor can be compromised. Factors affecting this likelihood can be grouped into two broad, but interrelated categories: activities or tasks that involve interacting with energized electrical equipment; and, the condition of the electrical equipment.
CSA Z462 describes some interactions with electrical equipment as normal — that is, they have a likelihood that is ALARP of initiating an arc flash incident. An example of a normal interaction is the operation of a circuit breaker or fused switch with the enclosure door closed.
CSA Z462 describes the condition of electrical equipment as normal if it is properly installed and properly maintained. Codes and standards should be used to determine if equipment is properly installed and maintained. Factors affecting equipment condition include the application, the state of the equipment (for example, doors closed and covers in place), the state of maintenance, the frequency of operation and the environment the equipment is located in.
If both the planned activity and the equipment condition can be characterized as normal, then the likelihood an arc flash event might occur can be described as ALARP.
In occupational health and safety, severity of harm is usually proportional to the dose or magnitude of exposure. In arc flash terms, the magnitude of thermal exposure is called incident energy. Incident energy is an estimate of the thermal energy density (in calories/cm2) that could occur at a specific distance from the electric arc. The distance is the linear distance from the electric arc to the expected location of a worker’s torso, typically 18 inches for electrical equipment rated less than 750 volts.
Last modified on Wednesday, 01 August 2012 09:28
Electrical safety can be advanced through a co-operative effort between the two professions using OHS risk management principles.
Risk management process
The purpose of the iterative risk management process (Figure 1) is to identify hazards, assess the risk deriving from those hazards and identify and implement risk controls, either alone or in combination, to achieve a level of risk that is “as low as reasonably practicable” (ALARP).
Using definitions under CSA Z1002, a “hazard” is a potential source of harm to a worker, while “risk” is the combination of the likelihood of the occurrence of harm and the severity of that harm. We will focus on the aspect of identifying risk criteria when establishing the context, and applying risk assessment and risk control methods to electrical hazards.
Risk criteria
Employers are required by law to exercise due diligence and create a workplace free of reasonably foreseeable harm. Shock and arc flash injuries are a reasonably foreseeable harm.
There are now many technological solutions for each risk control method in the hierarchy of risk controls that, when used individually or in combination, facilitate the avoidance of harm from electrical hazards.
The risk associated with electrical hazards can be managed by applying the hierarchy of risk controls to achieve a level of risk that is ALARP.
Risk analysis for electric shock
The likelihood of occurrence of a shock incident relates to whether an electrical conductor is exposed; and whether or not a person is closer than a “safe” distance. CSA Z462-12 defines the “safe” distance as the “limited approach boundary.”
The severity of the effect of electricity on human tissue correlates to the amount of electric current flowing through the tissue and duration of the current flow. According to Ohms Law, the flow of electric current is a function of the voltage applied. Therefore, to a limited degree, the severity of an electric shock incident can be correlated to the level of voltage. CSA Z462-12 clause 6.5.3.4 indicates the threshold below which voltage would not be considered hazardous is 30 Vac (rms) and 60 Vdc.
Risk analysis for arc flash
The likelihood of an arc flash incident correlates to the likelihood that the insulation or isolation of an energized conductor can be compromised. Factors affecting this likelihood can be grouped into two broad, but interrelated categories: activities or tasks that involve interacting with energized electrical equipment; and, the condition of the electrical equipment.
CSA Z462 describes some interactions with electrical equipment as normal — that is, they have a likelihood that is ALARP of initiating an arc flash incident. An example of a normal interaction is the operation of a circuit breaker or fused switch with the enclosure door closed.
CSA Z462 describes the condition of electrical equipment as normal if it is properly installed and properly maintained. Codes and standards should be used to determine if equipment is properly installed and maintained. Factors affecting equipment condition include the application, the state of the equipment (for example, doors closed and covers in place), the state of maintenance, the frequency of operation and the environment the equipment is located in.
If both the planned activity and the equipment condition can be characterized as normal, then the likelihood an arc flash event might occur can be described as ALARP.
In occupational health and safety, severity of harm is usually proportional to the dose or magnitude of exposure. In arc flash terms, the magnitude of thermal exposure is called incident energy. Incident energy is an estimate of the thermal energy density (in calories/cm2) that could occur at a specific distance from the electric arc. The distance is the linear distance from the electric arc to the expected location of a worker’s torso, typically 18 inches for electrical equipment rated less than 750 volts.
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