Evaluation of safety nets by experiment

1 Health and safety Executive Evaluation of safety nets by experiment Prepared by the Health and safety Laboratory for the Health and safety Executive 2011 RR835 Research Report Health and safety Executive Evaluation of safety nets by experiment Paul McCann BEng Health and safety Laboratory Harpur Hill Buxton Derbyshire SK17 9JN safety nets have become a common means of providing collective protection, particularly in construction, to mitigate the effects of falls where it is impractical to use temporary edge protection. The reason for carrying out the research was to explore issues where there was doubt/concern about the performance of safety nets and their attachments.

2 This research evaluated the effectiveness of safety nets , as used in the UK, to identify the risk (if any) of premature failure, in less than idea conditions that could occur in the use. A series of non-ideal loading conditions involving a range of variables were conducted. These included: n net type; n different impact locations (ie edge and corner); n attachment point spacing; n repeated dynamic loading at one position in the net; n multiple falls; n effect of sag in the net and industry practice to control sag; n presence of defects; n effect of differently shaped objects falling into net; and n effects of aging and degradation from ongoing service damage and the effectiveness of test meshes in monitoring degradation.

3 The UK safety net industry supported the research by providing nets . This report and the work it describes were funded by the Health and safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy. HSE Books Crown copyright 2011 First published 2011 You may reuse this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view the licence visit licence/, write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email Some images and illustrations may not be owned by the Crown so cannot be reproduced without permission of the copyright owner.

4 Enquiries should be sent to ACKNOWLEDGEMENTS The author would like to thank the following organisations for their support and assistance during this project. Fall Arrest safety Equipment and Training (FASET), for technical advice, free provision of training and acting as liaison between the safety net industry and Health and safety Laboratory (HSL). Boris nets , for supplying nets free of charge and inviting HSL to demonstrations of net testing. Higher safety , for supplying nets free of charge. Huck (UK), for supplying nets free of charge and arranging a HSL visit to the Huck factory in Dresden, Germany. Leon De Oro safety nets (UK), for supplying nets free of charge.

5 Rombull (UK), for the free provision of safety net inspection training. safety Net Services, for supplying nets free of charge and inviting HSL to demonstrations of net testing. safety Netting (UK), for supplying nets free of charge. Sta-Safe, for supplying nets free of charge. ii CONTENTS 1 1 2 3 European 3 Industry Guidance .. 4 3 VARIABLES INVESTIGATED .. 6 Phase 1 test variables .. 6 Phase 2 test variables .. 6 Phase 3 Test variables .. 7 4 nets TESTED .. 8 nets tested in Phase 8 nets tested in Phase 10 nets tested in Phase 10 5 TEST 11 Phase 1 and 2 11 Phase 3 19 6 RESULTS.

6 21 Phase 1 .. 21 Phase 2 .. 32 Phase 3 .. 43 7 45 8 49 9 RECOMMENDATIONS FOR FURTHER 51 10 REFERENCES .. 52 11 APPENDIX A PHASE 1 - LOAD ANALYSIS .. 53 12 APPENDIX B PHASE 2 - LOAD ANALYSIS .. 62 13 APPENDIX C PHASE 3 - LOAD ANALYSIS .. 68 14 APPENDIX D - MOTION ANALYSIS OF TESTING AT BORIS nets . 70 iii iv EXECUTIVE SUMMARY Objectives Falls from height are one of the most significant causes of death and major injury occurring while at work and workers in the construction industry are particularly at risk. safety nets are a preferred solution as they offer collective passive protection.

7 However, there is little historical information on the effectiveness of nets and an incident at Old Trafford, raised concerns about their performance in non-ideal loading situations (ie pre-existing damage, sharp or heavy material entering the net or variations in installation practices). Given the increased emphasis on safety nets as a result of new regulations for work at height, this work aimed to evaluate the effectiveness of safety nets , as used in the UK, and identify the risk (if any) of premature failure in the less than ideal situations that could occur in the workplace. The project was developed as a sampler for these non-ideal loading situations and included a range of variables.

8 These included: a) Net material and manufacture (knotted or knotless nets ). b) The effect of falling onto different positions in the net such as edges and corners. c) The spacing of the attachment points. d) The effect of repeated dynamic loading at one position (to simulate multiple falls). e) The effect of differently shaped items falling into the net. f) The effect of sag in the net. g) The use of alternative techniques to control sag in oversized nets . h) The presence of defects. i) The effects of ageing and degradation due to ongoing service damage and the effectiveness of test meshes in monitoring degradation To evaluate these variables a range of tests were carried out using a purpose built drop facility at HSL, Buxton.

9 The resulting loads were measured at various positions around the periphery of the net and damage to the net monitored. Main Findings This work identified the following: The safety nets used, generally withstood multiple tests, with penetration occurring only in unusual circumstances. No serious safety concerns were identified. The larger the attachment spacing, the higher the load at the attachment point and the greater the displacement of the net under load. The highest peak loads are generally recorded adjacent to the drop point. v Peak loads are generally higher for drops at centres of edges and lower for drops at corners.

10 Load is transmitted along linear axes from the point of drop, which is likely to be an effect of the square mesh configuration. Where damage to the net occurred, it was more likely to occur at attachment points than at drop points. There were no significant trends in performance differences between any of the net types. The highest load measured on a first drop was kN, well below the 6 kN characteristic limit. However, if the drop configuration had been changed (attachment spacing up to m, drop height up to 6 m) higher loading may have resulted. Loads measured at the attachment spacings are not necessarily the same as loads on the body falling into the net.