Electrical Safety Risk Assessment Page 3
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6assumed. “Very high” likelihood of occurrence of a hazardous event should be selected to reflect normal
workplace constraints and worst-case considerations. Positive reasons (e.g., well-defined application and a high
level of user competence are required for any lower values to be used.
Any required or assumed skills, knowledge, and so forth, should be stated in the information for use.
Select the appropriate value for Likelihood of Occurrence of Hazardous Event (Pr) from Table 3 below. Add
value to the Risk Register (Table 5).
Likelihood of a Hazardous Event
Pr Value
Very high
5
Likely
4
Possible
3
Rare
2
Negligible
1
Table 3
Listed below are examples of general questions to consider in determining the likelihood of an event (risk):
•
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®
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Has the equipment been installed in accordance with NFPA 70
, National Electrical Code
(NEC
)?
•
Has the equipment been maintained and tested in accordance with the manufacturer’s instructions?
•
How old is the equipment?
•
Is there any visual indication of overheating?
•
Is any component, device, or equipment loose or damaged?
The following are enclosure questions:
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Do all enclosure doors operate and latch properly?
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Does the enclosure have all of its bolts and screws installed?
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Does the equipment or enclosure have ventilation openings?
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Is the enclosure arc rated?
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Are there openings in the enclosure that rodents or other vermin could enter?
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Is there an indication of moisture in the equipment?
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Has the enclosure been examined for dust, dirt, soot, or grease?
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Is there any indication of overheating of the bus work, etc., in the enclosure, such as discoloration?
The following are circuit breaker (CB) condition questions:
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Has the CB periodically been operated in accordance with the manufacturer’s instructions?
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Has the CB been applied within its marked rating?
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Has the right type of CB been used?
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Have the proper conductor types and sizes been used to connect to the CB?
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Has the CB been checked for burn marks?
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Have the CB surfaces been examined for dust, dirt, soot, grease, or moisture? If any was found, have the CB
surfaces been appropriately cleaned?
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Has the CB been examined for cracks?
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Have all electrical connections to the CB been checked to be certain that they are clean and secure?
•
Is there any indication of discoloration of the CB’s molded case, discoloration or flaking of external metal parts,
or melting or blistering of adjacent wire insulation?
•
Is there any evidence of overheating or melting of the arc chute vent or area surrounding the vents?
•
Is there evidence of overheating or case blistering?
•
If the CB has interchangeable trip units, have the trip units been visually checked for overheating or looseness?
•
Have mechanical operation tests been performed on the CB and proper contact operation verified?
•
Have insulation resistance and/or individual pole resistance (millivolt drop) tests been performed on the CB?
•
Have inverse-time and/or instantaneous overcurrent trip tests been conducted on the CB?
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