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Rigging Standards for Safety Factor

Discussion in 'Scenery, Props, and Rigging' started by chawalang, Mar 31, 2019.

  1. chawalang

    chawalang Active Member

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    Hi everyone,

    Can someone please tell me what the ESTA rigging standard is for safety factors? I'm having various people giving me number for ranging from 5:1, 7:1 and 10:1. I want to be able to have the standard so I can cite that if we are hanging a 1,000# load across a span the system needs to be designed correctly with the correct safety factor being put in. I am starting to run into this scenario with various clients and need to be able to cite this documentation to back up my claims. Also, if there is any other standards beyond ESTA I would love it if someone can point me in the right direction. Thanks!
     
    Last edited: Mar 31, 2019
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  2. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Calling @What Rigger? and @egilson1 and ?
     
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  3. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    It's not one factor for all parts. Suggest you just require they comply with ESTA standard and if they are not familiar, just say no.
     
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  4. egilson1

    egilson1 Well-Known Member Premium Member

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    Unfortunately as @BillConnerFASTC mentioned it’s not as black and white as a single design factor for the entertainment industry. Most but not all of the hardware we use is regulated by standards for industrial lifting applications, like ASME B30.26 which regulates shackles, turnbuckles, slings, etc. Truss on the other hand is not an industrial lifting device and is built according to building code.

    The reality is standards which prescribe a specific DF are not really intended for end users, but rather for manufacturers. Often you are not given the ultimate/breaking strength of the material, but a working load limit which is the maximum load you can apply to the piece of hardware based on the ultimate strength divided by the DF. It’s the manufacturers job to take on the liability to determine which DF to use and what the WLL should be.

    There are of course a few exceptions where the end user must apply a DF to the ultimate strength of the material, such as wire rope. Due to the flexibility of use by the end user (pun intended), we are given an ultimate strength and the user applies the appropriate DF. For wire rope used as a sling that’s 5:1. For running rigging its 8:1.

    So to answer the OPs question, i would suggest what you are actually trying to do is prove you are using hardware that is approved by the manufacturer for the application you are using it for. That means an engineered truss, hardware that conforms to B30.26, electric hoists that meet ANSI E1-6-2-2018, etc.

    I awaite the follow up questions.

    Ethan
     
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  5. EdSavoie

    EdSavoie Well-Known Member

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    10:1 for anything over the audience in Ontario.

    The people onstage can apparently just die though...

    Let's just call it 10:1
     
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  6. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Everything? So the structural framing which might be in the 2 to 3:1 range typically has to be 10:1?
     
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  7. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    2 words... snow load. The base requirement for structural steel is in the 4 to 6 range. Snow load factor multiplies that significantly for a flat roof.
     
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  8. EdSavoie

    EdSavoie Well-Known Member

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    The regulations get a little fuzzy because the 10:1 rule is applied sporadically in several overlapping regs, to the effect that 5:1 is the absolute minimum in all circumstances.

    According to various Ontario regs:

    Performer Flying: 10:1
    Over the audience: 10:1
    Temporary flown scenery: 8:1
    All other rigging: 5:1

    For the sake of calculations, safety, sleeping at night, and liability, it's best to stick to one number, so 10:1 for everything attached to whatever the engineer stamped as the WLL for a given point on a building.

    So everything I would hypothetically hang, is 1lb of load for 10lb of Ultimate strength, unless the manufacturer has an even more strict WLL.
     
    Last edited: Apr 14, 2019
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  9. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    I don't believe it's that simple. Such simple design factors don't account for impact loads and non vertical loads, among other issues. The need for high design factors for dynamic loads does not justify the same factors for static.

    This sort of discussion is no different than how-to-rig posts.
     
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  10. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    At some point it is an engineering issue and not a rigging issue that can be discussed in simplified terms like safety factor. The building code for structural steel has pages and pages of requirements for determining coefficients that take into account wind, earthquakes, vibration, variable loading, and other dynamic factors.
     
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  11. EdSavoie

    EdSavoie Well-Known Member

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    As far as rigging goes, of course you still need to account for things like non-vertical, dynamic loads, etc.

    I should also point out what I'm talking about is from a reference of "Here are your points, rated for x WLL, now make a plan to rig from them" as given by an engineer.

    I have no, and don't pretend to have knowledge in complex temporary structures such as an outdoor stage assembly.
     
    Last edited: Apr 15, 2019
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  12. TimMc

    TimMc Well-Known Member

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    As designer, you have the right and obligation to set your own high standards. If clients demand justification, turn the table and tell them you'll design it any way they want, but you won't put your name on it and the contract will include explicit release of liability for you, and require full indemnification for you and your company. When you put an unlimited price tag of damage recovery for victims of injury or wrongful death versus the cost of build it *might* put things in perspective.
     
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  13. RickR

    RickR Well-Known Member

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  14. What Rigger?

    What Rigger? I'm so fly....I Neverland.

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    Bill is correct. Safety (or design) factors are not so much about how much is being lifted, but rather what and how.

    In other words, I would probably have no issue flying muslin flats at 5:1. But I'll never put a human in the air at less than 10:1.
     
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  15. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    And how and where applied. For example, on a motorized set is the factor used for the wire rope based on the maximum load the set us designed to lift or the worst case impact load - like when the car takes out the utility pole while max load is descending at max speed and hits the category 0 stop? That impact can easily be 3-4 times the normal load. 2000 pounds x 10 or 8000 pounds x 10?
     
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  16. DavidJones

    DavidJones Active Member

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    I think its a little fuzzy, but Design Factor and safety factor are somewhat different things. Design factors are published by equipment manufacturers and determine the WLL. The safety factor is determined by the equipment application. A Chicago Hardware shackle has a stamped WLL on it, and if you read the manufactures spec, they use a 6:1 design factor to come up with WLL. Now I can half that number if I require a 12:1 safety factor. So an item can have a design factor of 6:1, and be implemented with a safety factor of 12:1 at the same time.

    To the OP. Most entertainment specific rigging gear is manufactured using a 5:1 design factor minimum. In the case of a working piece or flying a person, It is up to the end user to add additional safety factor on top of the manufactures design factor. i.e. 8:1 for working hardware(like a wire rope over a pulley) and 10:1 for flying people. I cannot cite a source, but I'm pretty certain that was what Jay Glerum taught me years ago.
     
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  17. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Design factor is application and designer specific, not a value assigned by a manufacturer.
     
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  18. DavidJones

    DavidJones Active Member

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    I may have further muddied the waters. My point was that the manufacturer puts a working load limit on a product, and this is based on a design factor of their choosing(possibly dictated by a standard or regulation). My example was shackles, where Chicago hardware uses a 6:1 design factor. This is published by the manufacturer as such.


    **Edit** to your point Bill, all of the individual items should have some rating. WLL, or MBS, but in designing a functioning system with various parts, the overall design factor would be determined by that designer, along with a lot of math and probably an engineering firm. I was more speaking to just how the ratings are figured for a single component that is found in a typical rental house. Given the ambiguity of the original post, I think both are worth talking about, to make sure we are not leading people in the wrong direction.
     
    Last edited: Apr 24, 2019
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  19. DavidJones

    DavidJones Active Member

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    Alternatively, some products like wire rope as mentioned in a post above, or hardware meant for climbing like carabiners and pulleys that are often used by entertainment riggers, are only rated at minimum breaking strength, and it is up to the user to apply an appropriate safety factor when used.
     
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  20. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    You might want to keep in mind that the safety factor is for safety, and generally is as stated a ratio of ultimate strength to a working load. Design factors account for aging, unexpected conditions and events, and other conditions, and may also apply to other than safety issues, showing regard for maintenance, inconvenience, and comfort for instance.
     
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