[SML] Question about Safe Working Loads

[Bill Sapsis]

Ford.  I did not see your post but caught up with it in Steven’s response.

Working Load Limits (WLL)* in the US are determined by the manufacturer and are sometimes set by Standard, sometime not.  The typical WLL used by hardware manufacturers is 5:1 although the shackle folks, particularly those who sell to the entertainment industry, use 6:1, 7:1 and in some cases, 8:1.

Performer flying companies tend to hover (sorry) around 10:1 but not all the time.

Soooooo, the answer really is…it depends.  And what it depends on more often than not is your level of comfort.

Personally, I liked the old tried and true 7:1 simply because theatre folks deal in 1/4” Ø GAC and the breaking strength of 1/4” Ø GAC is always right around 7,000 pounds.  So using 7:1 means the math is real easy.  You’ll be hard pressed to find someone who tells you the WLL of 1/4” Ø GAC is something other than 1,000 pounds.

*most industries have moved away from SWL and are using WLL

zat help?

Bill S

bill at sapsis-rigging.com
http://www.sapsis-rigging.com
+1.267.278.4561   mobile
+1.215.228.0888   x206


On Apr 22, 2015, at 5:20 PM, Steven Hood via Stagecraft <stagecraft at theatrical.net> wrote:

> Me, of  German descent, vote at least 5:1, but would prefer 8:1 for WLL.
> Steven R Hood
> 310.756.3555
> 
> 
> 
> On April 22, 2015 2:12:55 PM Ford Sellers via Stagecraft <stagecraft at theatrical.net> wrote:
> 
>> Hi All,
>> I tried sending this message yesterday, twice.
>> I never saw it post, so I'm resending...
>> 
>> I am having some items destructively load tested, and have a question.
>> 
>> Once I discover the load at which the item breaks, what is the ratio I should use for SWL?
>> 
>> For instance, if the product is loaded to 2000kg before showing deformation, would I use a 3:1 or 5:1 or greater ratio to determine SWL?
>> 
>> Are there different standards for different markets?  I know the Germans (for instance) are extremely conservative in their ratings, whereas I have heard that in the USA and Canada, ratios of 3:1 and 5:1 are common.
>> 
>> Thanks in advance,
>> 
>> Ford Sellers
>> Senior Product Development Manager
>> Chauvet Professional Lighting & Iluminarc
>> 5200 NW 108th ave
>> Sunrise, FL 33351
>> Phone: 800-762-1084
>> Fax: 800-544-4898
>> 
>> 
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> 
> 
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