Extensive testing has been carried out by the NASC (National Association of Scaffolding Confederation) on tightening couplers with two popular types of impact wrenches and a wide range of drop forged couplers. The couplers were from different suppliers in various conditions, new, used, lubricated and unlubricated. Over 60 tests were completed.

The NASC analysed the data and found no concerns or adverse effects to the couplers resulting from the tests carried out with both impact wrenches and the traditional scaffold spanners. Subsequently the NASC has deemed the use of impact wrenches for scaffolding purposes is acceptable (https://nasc.org.uk/blog/article/nasc-position-on-the-use-of-impact-wrenches/).

FASET support this position when installing Edge Protection and Stair Towers. The following must be considered before selecting impact wrenches to be used by operatives:-

The recommended force required to tighten a fitting is 50 N/m as stated in EN 74. Most wrenches have stated torque settings (N/m) in excess of this recommended figure. During testing it was noted that settings published by the manufacturer can often differ greatly from what is achieved in practice. It is therefore recommended that any employer considering authorising the use of impact wrenches carries out testing to establish that the type of impact wrench which they intend to authorise for use by their employees is capable of applying the correct torque to scaffold fittings on a consistent and recurring basis. Further to completion of an adequate risk assessment by the employer the impact wrench may then be deemed fit for purpose for erection/dismantling and alterations to stair towers and edge protection by their employees.