Glove Impact Testing
Hand impact protection is an issue that deserves serious attention when it comes to choosing the right gloves for your employees. Currently, there are no industry-wide standards for measuring hand impact reduction. This creates numerous problems for HSE managers when it comes to properly evaluating or comparing impact protection provided by various glove models. Glove manufacturers are not required to test the impact protection of their gloves, and this can lead to false claims and minimal protection for the user, which may lead to higher recordable injuries. Pinching, bruising blows, and broken bones are the three main recordables when it comes to impact related hand injuries.
What To Look For
There are many things that an HSE manager can look for to help him or her make his hand safety decisions:
- 1) Make sure the impact protection extends all the way to the finger tips. This reduces pinching fractures and bruises to the finger tips.
- 2) Make sure the Impact protective TPR’s are long, with wide cross-sections. Small TPR’s and narrow cross-sections don’t maintain lateral stability during impact.
- 3) TPR coverage specifically needs to protect and cover all bones, joints, and fingers. For example, having only three TPR’s on the back of the hand to cover four metacarpal bones will not be sufficient protection.
- 4) Make sure that flex-points are built into the TPR design. The TPR still needs to protect and absorb impact, but integrated flex-points allow the hand to fully open and close without “puffing” away from the hand or exposing bones. This also allows for increased comfort and dexterity which allows the worker to maintain a high level of work-efficiency.
Although there are no industry-wide testing standards for impact force reduction, true hand impact testing does exist. Note that ASTM does not have a test for reduction in hand impact force, and the ASTM rebound test should not be used as a substitute. The rebound test does not measure impact forces to the hand from heavy objects it only measures the rebound height of a small steel ball on a flat surface. Rebound height has no correlation to the impact force delivered to the “object” beneath the protective piece, and the test is not performed on a hand. This data can be misleading and can leave the worker vulnerable to real-world impact hazards.
Peak Impact Performance
True hand impact testing provided by glove manufacturers must evaluate the reduction of peak impact force, as this is the leading cause of fractures and severe bruising to the bones in the human hand. Measurement of peak impact force reduction can be made with the gloves being worn on a Ballistic Mannequin Hand, while the force measurements should be taken on the surface of the hand beneath the protective glove. The Ballistic Mannequin Hand must mimic the soft tissue and hard structure (bones) of the human hand, as well as the three dimensional shape of the hand. A wooden or plastic hand, or a flat surface test will not give accurate readings of real-world hazards. The impact measurements can then be taken from three different regions: the metacarpal region, the fingers, and the knuckles, and must be presented as a percentage of reduction in peak impact force at each region of the hand.
No Glove Is Invincible
HSE managers can utilize this information to make better decisions. For example, an 80% reduction in peak impact force equates to a 200 lb impact (which will cause serious injury) being reduced to a 40 lb impact (likely to cause bruising only). Caution should be taken however, as thresholds for injuries vary widely from person to person and between different types of injuries (pinching, bruising, and fractures). Finally, glove impact protection should be viewed as a last line of defense. The first line is always safety training and behavior modification. The second line is work place hazard reduction. No glove is invincible and must be viewed as a complimentary piece of the safety training puzzle. There are great gloves in the market place that can help reduce recordable injuries, and knowing what to look for can make all the difference in the world.