Dynamic Cut and Puncture – A Different Perspective on Safety

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Dynamic Impact Injuries; Nail Guns and Cut and Puncture Protection                                                                 

At TurtleSkin we design both safety equipment for the commercial market as well as body armor for law enforcement and military customers. These two product programs have significant shared technology and the learning goes back and forth between these disciplines. One of the engineering crossovers from body armor is dynamic cut and puncture. For characterization of the cut and puncture threats we look at the energy of the threat not the force of the threat.

The extended use of the nail guns, power staplers and related impact devices has broadly increased the rate of injury from dynamic treats in the workplace

In body armor testing  we have grouped threats into 3 energy levels, 35, 50, and 65 (E2)  joules of energy.  A joule is a watt-second or 0.74 ft-lbfs if that helps.  These levels were determined by measurement of the energy that young adult men could delivery with their arms. These energy levels are measured at impact when the mass and velocity of the hand and lower arm strikes. If the hand holds a tool or knife the energy at impact is delivered at the tip. In the workplace impact energy can be delivered without power tools.  Our estimates suggest these threats at 5-15 joules. However a 16 penny nail gun is more than capable of delivering nails at energies in the  35-65 joule range, the same as body armor requirements.

When tools slip, when product is dropped, when power tools are in use the threats to workers are dynamic.

The safety market has concentrated on testing equipment for cut and puncture at very slow speeds, by design these slow test speeds eliminate dynamic effects. PPE is measured in units of force to penetrate or cut. PPE tests like EN388 fall into this class.   These slow speed tests result in PPE that has real protection however the protection is not sufficient impact or for power fastening tools.

From the OSHA guide “Nail Gun Safety: A Guide for Construction Contractors”

“How likely are nail gun injuries? A study of apprentice carpenters found that:
• 2 out of 5 were injured using a nail gun during their 4 years of training.
• 1 out of 5 were injured twice.
• 1 out of 10 were injured three or more times.3
More than half of reported nail gun injuries are to the hand and fingers.4
One quarter of these hand injuries involve structural damage to tendons, joints,
nerves, and bones. After hands, the next most often injured are the leg, knee,
thigh, foot, and toes. Less common are injuries to the forearm or wrist, head
and neck, and trunk. Serious nail gun injuries to the spinal cord, head, neck,
eye, internal organs, and bones have been reported. Injuries have resulted in
paralysis, blindness, brain damage, bone fractures, and death”

At TurtleSkin we estimate impact energy threats at  5-15 joules of in construction and manufacturing occupations without power fastening. Nail guns are certainly increasing this threat.

Energy standards include NIJ, HOSDB, and VPAM

  1. Stab Resistance of Personal Body Armor
    NIJ Standard–0115.00
  2. HOSDB Body Armour Standards for UK Police (2007)
    Part 3: Knife and Spike Resistance Publication No. 39/07/C
  3.  VPAM – KDIW 2004 Schutzausstattungen Stich- und Schlagschutz
    – Anforderungen, Klassifizierung und Prüfverfahren

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