Page 34 - OHS, July/August 2020

PPE: HAND PROTECTION
Interpreting ANSI/ISEA 138:2019 Glove Impact Results
One question often asked by end-users is: what performance level is appropriate for dorsal impact glove application needs?
BY RODNEY TAYLOR
The ANSI/ISEA 138:2019 standard fills a criti- cal gap in the industrial glove standards in- frastructure. One question often asked by end-users is: what performance level is ap- propriate for application needs? This question is not unique to the dorsal impact glove standard. This ar- ticle will discuss how impact is measured to provide context for end-users to determine the appropriate impact performance per the ANSI/ISEA 138:2019 dorsal impact glove standard.
When assessing the appropriate dorsal impact glove, is it critical to conduct a hazard assessment and obtain guidance from a certified industrial hygienist or safety engineer.
Impact Considerations
Consider this example: shoot an armor piercing bullet at a brick wall and it will likely pass through. If a base- ball were hurled at the same wall with the same kinetic energy of the bullet it would bounce off. The differ- ence in outcomes in these two examples is due to the
The ANSI/ISEA 138: 2019 dorsal glove impact standard can be a powerful tool to improve hand safety performance.
significant difference in impact areas of the ball vs. the bullet—where a smaller contact area translates into a much higher concentration of energy. Plus, the bul- let is several orders of magnitude harder than the ball.
This example highlights that, when evaluating impact forces, it is important to consider two impor- tant factors:
1. Contact area
2. Hardness of the materials involved in the impact Not only do we need to consider the total energy
of the projectile (5 Joules for the ANSI/ISEA 138:2019 impact test method) but also the concentration of en- ergy at the contact area.
In other example, a professional player can throw a football (about 0.88 lbs.) at about 70 mph generat- ing about 190 joules of energy. That is about the same amount of energy from the firing of a .22 caliber round (0.006 lbs. at 850 mph). But, would you rather be hit by the football or the bullet? Keep in mind that the ANSI/ISEA 138:2019 test method calls for a solid metal striker that has a 2.5kg (5.5 lb) mass (“weight”) with a contact area of 3.15 inches in diameter.
Impact Measurement Units
Another challenge in interpreting impact force results from the ANSI/ISEA 138:2019 impact standard is the often-unfamiliar terms used. The SI system (Interna- tional System of Units)—the modern metric system of measurement—is the dominant system of interna- tional commerce, trade and science. The ANSI/ISEA 138:2019 impact standard utilizes SI system units for force and energy.
The force unit in the SI system is the newton (sym- bol: N). One newton (N) is equal to 0.22481 pounds- force. Typical impact forces encountered in ANSI/ISEA 138: 2019 compliant testing are over 1,000 newtons. To simplify, in the SI system, a thousand is abbreviated as “kilo” such that 1,000 newtons = 1 kilo newton (1 kN).
The corresponding energy unit in the SI system is the joule. It is an expression of the mechanical work done by pushing an object through a distance against a force. The English unit of energy is the foot-pound. One joule is equal to 0.737562 foot-pounds. The test method utilized in ANSI/ISEA 138:2019 is designed to generate 5 joules of energy.
28 Occupational Health & Safety | JULY/AUGUST 2020
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