IRW Posted January 23, 2018 Share Posted January 23, 2018 Hi All,I was wondering if someone could point me in the direction of some official something or other that states advised safety factors for aerial dance work (silk-work if anyone is interested). Whilst I've got the knowledge, know-how and equipment to put together a safe system, I'm struggling to find something tangible to put in the risk assessment to back up various values I've been told, have in my head, or have dug up online. I realise this has potential to be a bit of a 'if you have to ask...' topic, so just to be clear, I'm not asking for advice on HOW to do this, just some direction towards any official published numbers that may exist! Thanks, Ian Link to comment Share on other sites More sharing options...
sandall Posted January 23, 2018 Share Posted January 23, 2018 Not strictly an answer to your question, but many years ago when I was involved in a show with a lot of trapeze work we called in Circus Space in Shoreditch (they now seem to be called the National Centre for Circus Arts), who gave a lot of advice on strengthening our fairly lightweight ironwork. I seem to recall safety factors of 10:1. Googling "safety factors for aerial performance" throws up a few possible leads. Link to comment Share on other sites More sharing options...
IRW Posted January 23, 2018 Author Share Posted January 23, 2018 Yep, 10:1 is one of the figures I’ve been working with. Would just be nice to know where that comes from! What google hasn’t thrown up for me thus far is anything officialish looking. Link to comment Share on other sites More sharing options...
ontoprigger Posted January 23, 2018 Share Posted January 23, 2018 In the UK there are no formal standards for Aerial performance, and it is indeed one of the grey areas within our industry that many people stay away from lack of understanding of what the regulations really say. If you look at the machinery Directive, which specifically excludes performer flying, but for lifting of persons says the SWL of any equipment used to suspend a person should be halved, then you end up with a safety factor of between 14:1 and 8:1 depending on what you are using. i.e. synthetic sling 2000kgs at 7:1 becomes 1000kgs at 14:1 Steel Wire Rope 1000kgs at 5:1 becomes 500Kgs at 10:1 and so on. Be careful if using climbing equipment or carabeners as this has a minimum breaking load usually in newtons, also be careful on the type of carabena you use as they are mostly only rated for direct pull and not to be used in a basket situation. BS 7905 & 6 lifting equipment for the entertainment industry recommends a minimum of 8:1 for loads lifting persons, this again is based on reducing the safe working load for normal lifting equipment and does not include synthetics. ICOPER is a new code of practice and while it covers entertainment rigging there are no formal calculations you can pull from it. there are a number of publications from ESTA in the USA that look at performer flying and has coverage of aerial work, http://tsp.esta.org/...yingSystems.pdf The main problem you will have with aerial work is to determine the load that will be imposed on the equipment to determine what size the equipment will be, for silks you will need to look at the length of the silk, height it is suspended, weight of the performer, type of silk used and its elasticity, the routine, any long drops with short stops in it. From this there is a calculation you can do to determine the maximum potential dynamic load imposed on the rigging. from experience the mathematical solution will yield a figure far above any real load you will see, we have fitted load monitoring to most of the aerial work we do and unless its an inexperienced performer or they are doing some really extreme falls the loadings are rarely double the dead weight . Strap acts on the other hand can load up a system, especially if it is a couple. As with anything like this Health and safety want to see that you have carried out a risk assessment and follow a method statement for the install, looking at all of the potential risks involved for the crew installing and the performer, which should be no big issue, the figures will be relatively low and if you work on a 1000kg SWL at 10:1 you are likely to be fine unless its multiple performers. Your biggest hurdle will be insurance, check you are covered specifically for this type of work and that your policy specifically mentions aerial performance or performer flying, because should you have any problems they will soon turn round and say you are not covered. Many of the health and safety myths out there about what you can and can't do are created by over zealous risk assessors protecting their clients, the insurer who contrary to popular belief are not looking after the best interests of the insured but their own profits..... I should also have mentioned its worth getting a Structural Engineer to look at the structure you are attaching to, I can put you in touch with someone who has a lot of experience with aerial performance and understands what involved. I find that a lot of engineers shy away from this type of work as the feel its a high liability situation or they don't understand all that's involved, and often they will charge a huge fee as they think it is high risk and therefore justifiable. Link to comment Share on other sites More sharing options...
kerry davies Posted January 23, 2018 Share Posted January 23, 2018 The only written down figure I can remember is from a German company specialising in trapeze and aerial performance which gives 14:1. Hopefully ImagineerTom will be along to talk about calculating dynamic human loads and the rest but OTR makes a really important point about what you are hanging from. Be warned. One biggish new venue was happily planning events when they were asked for the rigging points and load charts for their roof. They didn't have any so we had to engage a structural engineer familiar with our sector. They just hadn't catered for events in a specialist events venue. :blink: Link to comment Share on other sites More sharing options...
trussmonkey Posted January 24, 2018 Share Posted January 24, 2018 General rule of thumb is 10:1 . You wont go wrong with working to that factor of safety. All of the worlds biggest aerial shows work to that number. TM Link to comment Share on other sites More sharing options...
ImagineerTom Posted January 24, 2018 Share Posted January 24, 2018 //attempts to put lid back on can of worms// There's no specific set of regulations / ratios / protocols that define everything. Various rigging groups and circus organisations have developed their own internal standards and procedures but nothing is published in a referable way. You need tp speak to the specific performer themselves, they will have a specification of what they needs, the parameters they prefer to work to and be able to give you a run down of what they need to achieve what it is they're going to do. As a rule of thumb 10:1 ratio is common, but different performers require a "hard" (solid point that doesn't move at all) or "soft" (point that physically moves around a little, plus often with a rope or other /not steel/ element in it to provide some low-level shock/vibration absorption) and remember that pretty much every act will require a secondary point - either to use as a safety or to use to brail/swag their equipment out of sight during the rest of the show. Remember that shock loads and lateral loads can be quite significant - generally you want to ensure that performers are rigged off structures completely isolated from lighting/sound equipment otherwise you'll have moving lights that shouldn't be and will need to refocus every couple of performances. A good performer produces relatively low secondary forces but silks is one of those skills that dancers get taught in a night-classes and then get booked as "professional circus performers" even though they have relatively low skill so you will often find silks acts are the worse for over-loading and lack of precision so always assume the worst then be pleasantly surprised that stuff doesn't move. Courtesy note - don't touch the fabric unless the performer specifically invites you to; always let the performer clip their silks on to your hardwear - dirt/grease/grit that you think is nothing can alter the friction of silks or even instigate damage that dramatically shortens the life of the material. Link to comment Share on other sites More sharing options...
IRW Posted January 24, 2018 Author Share Posted January 24, 2018 Hi All,Thanks for replies. Seems I've got my answer, which is 'there isn't one'...! Most things mentioned in the thread have already been borne in mind to keep everyone's mind at rest ;) As a side note, with regards to rigging points in the roof, we're pretty good for that in this instance for the choreography being carried out...the RSJ's at grid level are somewhat overspecced for most of the things we do. Myth has it the original structural engineer got the decimal point in the wrong place...! http://www.blue-room.org.uk/public/style_emoticons/default/thumbup.gif If the mods see fit, I'd be happy for this thread to be closed, to prevent it turning into something it shouldn't? Link to comment Share on other sites More sharing options...
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