In the first two parts of this series, I explained how to determine an arc-flash boundary to comply with the National Fire Protection Association standard for Electrical Safety in the Workplace (NFPA 70E). Today, I'll explain how to determine PPE requirements for persons working within that boundary.

Determining PPE Requirements

NFPA 70E requires the employer to provide and employees to wear appropriate flame resistant (FR) clothing and other PPE when they're within the arc-flash boundary. Which FR clothing to use depends on the level of incident energy the individual will be exposed to in the event of an arc-flash.

The level of incident energy is determined by the distance of the person from the arc-flash (incident energy increases rapidly as the individual moves closer to the arc-flash). Generally, 18 inches is assumed to be the distance between a worker's face/chest and the arc-flash.

Using the information collected to establish the arc-flash boundary, the engineer can calculate the incident energy in cal/cm² at 18 inches. FR clothing is rated in cal/cm². This enables you to select appropriate clothing to protect against the incident energy of exposure.

It's not uncommon for calculated results at 18 inches to show an arc-flash incident energy of less than 1.2 cal/cm². In these circumstances, no FR clothing is required for the face/chest area; all that's needed is clothing that won't melt, such as cotton. However, additional PPE may be required for parts of the body that are closer than the18-inch basis.

It's also not uncommon to find at least one location in a facility where the calculated incident energy at 18 inches exceeds 40 cal/cm², the highest level that 70E recognizes as being practical to protect (some clothing manufacturers offer clothing with higher ratings). In these circumstances, the employer should either make changes to the electrical system to reduce the incident energy or prohibit work within the arc-flash boundary.

PPE for the Default Boundary

Small facilities that choose to use the 4-foot default boundary instead of using the formula won't have the incident energy results needed to select the proper level of PPE for the arc-flash hazard.

For these facilities, 70E provides two tables to use in selecting PPE. The first table matches a "Hazard/Risk Category" to a specific task by voltage level and type of equipment. (See Table 1 in Tools.) The second table describes the FR clothing and corresponding incident energy for each of five Hazard/Risk Categories. (See Table 2 in Tools.)

Limitations of the NFPA 70E Tables

Using the 70E tables to select PPE has its limitations. The first table that matches the category to the task is limited to electrical systems that don't exceed specified levels of available short circuit current and fault clearing times as described in the table footnotes.

Also, 70E states that for tasks not included in the table and for electrical systems that exceed the footnote limitations, the tables cannot be used and the incident energy must be calculated for PPE selection.

Using the tables when the electrical system exceeds the levels described may expose individuals to hazardous energies beyond the protection of their FR clothing, potentially resulting in serious injury or death. On the other hand, when the footnotes are met, the level of protection can be overly conservative, which may increase hazards to the individual by limiting vision, mobility and dexterity.

In other words, it's always better to select the proper PPE based on the calculated incident energy of exposure. Selecting PPE based on incident energy may also result in substantial savings over the cost of selecting PPE based on the tables.

Next week, Mr. Klingler describes labelling and other requirements under NFPA 70E.

ALL-STAR SPECIAL

MAYBE THERE SHOULD BE CRYING IN BASEBALL

In honor of tonight's Major League Baseball All-Star Game, we look at the occupational hazards of baseball's most physically demanding and hazardous position: Catcher.

Even if you didn't know a thing about baseball, you could tell that catchers are the ones who face the greatest physical risks by all the PPE they wear. But masks, helmets, shin guards, chest protectors and the padded mitt are still only partial protection. That's why they call the stuff "the tools of ignorance."

Don't try this at home -- or behind it.

Pounding on the Glove Hand

One hazard of the catching profession is the pounding on the glove hand. According to a study from Wake Forest University's Department of Orthopaedic Surgery, most pitches are caught in an area of the hand where nerves and blood vessels are located. Although the design of the catcher's mitt has been modified repeatedly over the years, today's mitts are still inadequate to protect against repetitive hand trauma. Even while resting, most of the catchers studied experienced pain, weakness, tingling or numbness in their glove hand. And only the catchers on a baseball team experienced hypertrophy (an increase in finger circumference) -- with increase averaging 5mm, or 1.89 ring sizes.

Catch these statistics

• Pitched balls often travel at speeds exceeding 90mph
• Catchers receive as many as 300 impacts to the gloved hand per day (150 pitches per game + 150 pitches warming up scheduled and potential pitchers)
• Catchers play at least 162 scheduled games over a nine-month period.

So, mammas and papas, don't let your babies grow up to be catchers.

Source: American Academy of Orthopaedic Surgeons

CATCHERS' QUIZ

Continuing the theme, and at the risk of beating a dead horse -- or horse hide, here's a quiz to test your knowledge of baseball's all-time great catchers.

1. Which catcher is famous for the lines: "It aint over 'til it's over"; "Baseball is 95 percent half-mental"; and "Nobody eats there any more. It's too crowded."
2. Which Boston Red Sox catcher hit a famous home run in the 12 th inning to win Game 6 of the 1975 World Series?
3. Who holds the record for the most games caught (and thus, the greatest hand poundage)?
4. Which catcher has hit the most home runs as a catcher?
5. Name the only catcher to steal home in a World Series game. Hint: He played for the St. Louis Cardinals and is now a nationally known baseball analyst.
6. Which Hall of Fame catcher never played a single game in the Major Leagues?
7. Bonus Question: There are 14 catchers in the Baseball Hall of Fame. How many can you name?

Answers

1. Yogi Berra
2. Carlton Fisk
3. Carlton Fisk
4. Mike Piazza
5. Tim McCarver
6. Josh Gibson who spent his whole career in the Negro Leagues
7. Johnny Bench, Reds (elected 89); Yogi Berra, Yankees (72); Roger Bresnahan, Cards (45); Roy Campanella, Dodgers (69); Gary Carter, Expos (03); Mickey Cochrane, Athletics (47); Bill Dickey, Yankees (54); Buck Ewing, Reds (36); Rick Ferrell, Red Sox (84); Carlton Fisk, Red Sox (00); Josh Gibson, Homestead Grays, Negro Leagues (72); Gabby Hartnett, Cubs (55); Ernie Lombardi, Reds (86); Ray Schalk, White Sox (55).

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