Shock risk assessment in the workplace • Mike Doherty
March 14, 2017 - The source of risk assessment procedure best practices that you find in CSA Z462-15 “Workplace electrical safety” (Clause 184.108.40.206) is CAN/CSA-Z1002-12 “Occupational health and safety - Hazard identification and elimination and risk assessment and control”.
Z1002’s technical committee has done an outstanding job of compiling a common language for defining leading-edge job planning techniques. The resulting generic risk assessment procedure can be used for any hazard in any workplace, as the common language and well thought-out methodology are useful on any jobsite.
In the electrical workplace, a comprehensive electrical risk assessment procedure must be completed by safety-qualified personnel; that is, someone qualified to CSA Z462-15 “Qualified persons”. Specifically, look at Clause 220.127.116.11.1 (b)(iv), (1), (2), (3) and (4).
You may be a licensed electrician or professional electrical engineer, but that does not necessarily mean you are a qualified person when it comes to electrical safety. It is critical to ascertain whether your licensed electricians and electrical engineers are truly safety-qualified in alignment with Clause 18.104.22.168.1, as well as those you contract.
Only when due diligence requirements are met—and you’ve ensured safety-qualified personnel are truly in place—can comprehensive and effective electrical job planning begin.
Using the principles of the generic risk assessment procedure, the path for any electrical work splits into two sections: I always start with a comprehensive shock risk assessment. While a comprehensive arc flash risk assessment should also be completed as required), the rest of this column will deal primarily with the former. (My next column will address arc flash risk assessment.)
To execute a thorough shock or arc flash risk assessment, you need to be able to navigate CSA Z462 which, admittedly, is not laid out so as to provide a simple procedural walkthrough. No, you need to take time to make your way through the standard to ensure you have all the details, then document them in your own written electrical work procedures.
You cannot expect your supervisors and workers to use Z462 to execute efficient work without first transferring its risk assessment procedures to a logical flow for an electrical workplace.
Depending on how you break it down, there are about seven steps in Z462-15 for completing a good shock risk assessment. Specific details are in the standard but, on page 35, you will find Clause 22.214.171.124 “Shock risk assessment”, for which there are three basic determinations:
1. Voltage to which personnel will be exposed.
2. Boundary requirements.
3. PPE necessary to minimize the possibility of electric shock.
When they know the work at hand, a competent and qualified electrical person can usually quite easily determine the voltage(s) to which personnel could be exposed.
As for the second point, there are two boundary requirements in Z462-15 (the 3rd boundary requirement—Prohibited—was removed from the 2015 version). Clause 126.96.36.199 gives specific details for the Limited Approach Boundary, which applies to approach by unqualified persons, working at or close to the Limited Approach Boundary, and entering the Limited Approach Boundary.
Requirements for the second boundary—Restricted Approach—can be found in Clause 188.8.131.52, which also provides guidance for qualified and unqualified personnel. Tables 1A and 1B on pages 36 and 37 give the particulars for AC and DC equipment, which are, in fact, distances calculated from specific voltages.
The PPE requirements for the identified shock hazard can be found on page 130, Table H.3 “Summary of specific sections describing PPE for electrical hazards”. Your next source of guidance is found on page 42, Clause 184.108.40.206.7(a) “Shock protection”.
For the sake of due diligence, after you’ve transposed Z462’s shock risk assessment requirements into a simple, effective business-specific electrical procedure, have your efforts signed and dated by the accountable management team.
* This article also appears in the March 2017 edition of Electrical Business Magazine. Check out our ARCHIVE page for back issues.
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