Q: Why does the selection of FR/AR clothing by PPE Category (or HRC) not work with the incident energy (IE) analysis?
A: In 2018 the PPE Categories are still for use with the Task Tables 130.7(C)(15)(a) and 130.7(C)(15)(b).
Using the Task Tables to pick PPE systems will overdress the worker for the energy since the Task Tables must meet the worst case energy in that equipment category within the fault current and clearing time parameters defined.
The PPE look up table for the Task Tables, Table 130.7(C)(15)(c) when used with the incident energy analysis would put people in more PPE than the standard requires. Many make this mistake because IEEE 1584-2002 used the PPE Categories (HRC, Hazard/Risk Categories at the time) to pick PPE as did most of the software companies making labels until about 2015. For example, if you have an 8.1 cal/cm² incident energy from your arc flash study, the categories would put you in an Category 3, which is minimum 25 cal/cm² because a PPE Category 2 has a minimum of 8.0 cal/cm² so it wouldn’t guarantee adequate protection.
When you do an Incident Energy Analysis or an Arc Flash Study, the PPE Level Table 130.5(G) “Selection of Arc-Rated Clothing and Other PPE When the Incident Energy Analysis Method Is Used,” gives you guidance. This table is NEW in NFPA 70E-2018 (but the same as H.3 in the non-mandatory annex for years), and would guide you to choose a face shield, balaclava, clothing and gloves meeting the minimum 8.1 cal/cm² and guides on other PPE for that level of arc flash hazard.
You may use the PPE categories as long as you understand the issues, but you will typically be overdressing your workers. So there is nothing wrong with using an HRC3 or ARC3 or CAT3 Arc Rated suit for an 8.1 cal/cm² exposure, but it isn’t mandatory.
The prohibition from using the categories was introduced when the PPE Categories (HRC’s at the time) would LOWER the PPE for some tasks. For instance, at one point voltage testing in a MCC with potentially 40 cal/cm² exposure would have only required HRC 2 or 8.0 cal/cm² protection while racking in a starter bucket in that same cabinet required a 40 cal/cm² flash suit or HRC4. This was removed in 2015 but in 2012, the committee did not feel that PPE should be lowered if the IE was known to be a certain level . This use of the “risk” component multiplier concept, was against OSHA’s perspective on risk assessment.
This is how the prohibition entered the standard, but now in the current versions of the Task Tables there is nothing to make the use of the PPE categories unsafe. However, you should choose what makes sense for your workplace. The PPE Levels for arc flash protection now required in Table 130.5(G) are the best ways to categorize your PPE, but using the categories would not cause an unsafe condition from an arc flash perspective. But if your calculations show 8.1 cal/cm², why would you want to use an old HRC 3 25 cal/cm² suit?