What is the Frequent Use Factor?
What is it?
The frequent use factor is a down rating of the loading capacity that is applied to truss used in the entertainment industry for damage and general wear and tear resulting from its day to day use.
All those times you are throwing a truss module on the back of a van to load it and dragging it back off the van whilst unloading it with the owner looking on in horror as his shiny new aluminium truss is getting scratched and battered is doing the product structural harm. All those scratches and dings are removing material from the truss. Less material means less strength, so think about it the next time you are handling those pieces of truss.
BS and DIN Standards
A frequent use factor was originally bought in with the British Standard, BS 7905-2:2000 Lifting equipment for performance, broadcast and similar applications – Part 2: Specification for the design and manufacture of aluminium and steel trusses and towers, and reduces the calculated loading by 15%. At the time, this was reflected in the Truss Load Charts issued by all UK manufacturers conforming to this British Standard. However, as time went on, and more truss manufacturers appeared on mainland Europe these manufactures opted to conform to German DIN standards. These standards do NOT have a reduction factor for frequent use in them as they were primarily aimed at structural products within the construction industry. As a result, the manufactures could display loading data that seemed higher and better for similar sized products. The fact is that on equal terms their truss is not stronger.
Over recent years some discrepancies between national standards have been harmonised and with the advent of the new EN standard for manufacturing steel and aluminium trusses in the entertainment industry this 15% reduction as a frequent use factor has been included. Now all truss manufacturer’s adhering to this new EN standard should include this factor if they foresee that their product is to be used frequently. Otherwise the onus could well be on manufacturers to prove their product is used without incurring day to day damage.
It should be noted, and has already been discussed in a previous post regarding truss inspection criteria [LINK], that without this frequent use factor included in the published load capacity then it is impossible for any manufacture to publish pass / fail guidelines for inspecting their product as any damage would potentially take the product outside the manufacturers specification, according to their structural report.
For your own peace of mind check the load data for your truss includes a frequent use factor in the calculations or structural report.