Factors Influencing the Performance of Chain Saw Leg Protective Devices and Its Measurement

Abstract

Protective trousers and protective chaps are worn by chain saw operators to protect their legs. The protection is given by protective pads sewn on the clothing. These pads are an assembly of layers of fabrics made form high-strength fiber. Protective pads are tested using a gas powered chain saw according to the CAN/BNQ 1923-095 and the ASTM F1414-92a test methods which are similar. The threshold stopping speed is the performance criterion measured. The TSS is the largest motor or chain speed at which no cut through occurs. Since 1987, the CAN/BNQ 1923-095 test method has been used. From the test results, several observations are made and useful conclusions are drawn on the test method, on the mechanisms of protection and on the trousers and chaps. On the test method: the chain sharpness, the chain type, the angles of cutters, the condition of the clutch, the gasoline and oil mixture and its stability are factors that affect significantly the measurement. The most important one is the chain. The findings are useful for any cut resistance test method. The test method is reliable and gives repetitive results. Three main mechanisms of protection are observed. They are: cut resistant material, clogging (jamming) material and chain stop material. Description and examples of each are given. Test results on trousers and chaps were performed on North American and European products before implanting a certification program in Quebec and in Canada. The results show large variation in the performance of leg protective devices. Some are excellent, some are very bad offering nearly no protection even if labelled “safety trousers”. Tests and analysis of the textile show variation in the number of layers, in the fabrics and a lack of mechanical stability under washing. These facts support to need of third party certification program. In conclusion, the test method is reliable, sensitive to changes in the protective pads or changes in the chain conditions and giving always the same ranking. Three mechanisms of protection are identified and their use on specific clothing is suggested. End users are now able to find performing products that will protect adequately.