Experimental assessment of eye protection efficiency against high speed projectiles

Abstract

IntroductionWork in hazardous zones with the risk of mechanical injuries requires protection with safety spectacles. Mechanical eye injuries with metal foreign bodies are often caused by rotational material machining or production processes with high pressure or high velocity moving parts. Normative regulations restrict to tests with small and fast flying objects (e.g. 6mm ball). The literature does not provide any information about protection capabilities against larger objects with high mass and arbitrary shape.The purpose of this study was to test the protection efficiency of safety spectacles against flying objects. The scope of this paper is to present a new test setup for mechanical impact resistance testing of personal protective eyewear against objects with arbitrary shape and mass. Material and MethodsThe setup is based on a catapult platform, accelerating a sliding carriage on a rail. A pull rope system allows velocities up to 62±2 m·s-1. A photo sensor was used for velocity measurement. The carriage can be loaded with projectiles of up to 30mm×30mm×40mm in size with arbitrary orientation, depending on the carriage insert. Testing and validation was done with projectiles such as 7g metal chips and fragments with approximate dimensions of 10mm×15mm. Samples were standard occupational safety spectacles mounted on a test head. The projectile impact was captured with a monochrome high speed camera. ResultsThe aiming accuracy test showed deviations of approximately 1mm of two impacts on the same spectacle surface with a free flight distance of 150mm. All tests with slow, medium and high speed projectiles showed no contact with the eye medium. Objects with velocities from 10 m·s-1 to 62 m·s-1 fired the spectacle off from the test head. The medium speed test cut off one side of the spectacle frame. The high speed test with 62±2 m·s-1 cracked the polycarbonate shield. DiscussionWe describe a method for accelerating arbitrary objects up to 62 m·s-1 and for aiming these objects on safety eyewear, mounted on a test head. The setup allows a variety of projectile shapes, orientations and velocities. The accuracy of velocity measurement is ± 2 m·s-1 for high velocity (< ± 5%). Further studies will address optimization of this setup due to signs of wear and gliding properties of the carriage, wireless ignition and higher velocities.