Incident energy analysis calculation: value for dollars spent? • Mike Doherty
July 7, 2016 - To ensure electrical safety is being observed on the jobsite, it is imperative for supervisors and managers to regularly get in the field and make comprehensive observations and perform audits.
Many organizations have made the right decision to get incident energy analysis calculations completed for the electrical equipment at their facilities, as it enables them to select appropriate arc flash PPE for workers who may be exposed to potential arc flash energies in their work tasks.
For example, CSA Z462-15 Clause 220.127.116.11.2 “Incident Energy Analysis Method” states:
The incident energy exposure level shall be based on the working distance of the workers’ face and chest areas from a prospective arc source for the task to be performed. Arc-rated clothing and PPE shall be used by the worker and selected on the basis of the incident energy exposure associated with the specific task. Because incident energy increases as the distance from the arc flash decreases, additional PPE shall be used for any parts of the body that are closer than the distance at which the incident energy was determined.
This can be determined manually using Annex D in CSA Z462-15 to perform the calculations, but this is a tedious and time-consuming process. Short-circuit coordination study software (wielded by a professional electrical engineer) takes the required parameters and inputs them into an IEEE 1584 module, which has the ability to calculate—when used correctly—the incident energy at any node within the electrical distribution system of a given organization.
It is critical to note, as per Clause 18.104.22.168.1 General,
One of the methods described in Clauses 22.214.171.124.2 and 126.96.36.199.3 shall be used for the selection of PPE. Either, but not both, methods may be used on the same piece of equipment. The results of an incident energy analysis to specify an arc flash PPE Category in Table 5 shall be prohibited.
Once the arc flash incident energy values are determined, one of the normal requirements is to have shock and arc flash warning labels printed and installed in the appropriate locations on the electrical equipment in the field, which is required under CE Code 2-306 and explained in CSA Z462-15 Annex Q.
Whenever I am in the field performing electrical safety audits, or delivering training on this subject, one of the first things I do is ask the electrical tradespeople to explain exactly what the shock and arc flash warning label actually means.
Not always, but far too often, the people doing the work—including the electrical supervision—cannot interpret the information on these labels, nor understand what actions to take to ensure safer electrical work.
The next time you’re out in the field, ask the electrical workers (whether they’re yours or your contractor’s) a few simple questions to gauge whether they are on the right path for planning safe electrical work:
• What actions do you take at the Limited and Restricted Approach boundaries?
• What Class of rubber insulating gloves would be worn?
• What does the Working Distance mean?
• What is the Incident Energy value on the label and does that correlate to the PPE being used to execute work in that location?
• Define the Arc Flash Boundary, and how will it be respected?
These questions will help you determine whether the electrical workers are knowledgeable, competent and qualified. If not, you need to take action.
Companies are doing the right thing when they carry out expensive arc flash studies; however, when workers in the field cannot answer the simple questions above, then you have to question your ROI for the cash you spent.
* This article also appears in the June 2016 edition of Electrical Business Magazine. Check out our ARCHIVE page for back issues.
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