Wire rope safety factor for horizontal life line 1

[tvar]

I am designing a horizontal life line and OSHA says to use a minimum safety factor of 2 for the system. My question is what safety factor would be appropriate to use on the breaking strength of the wire rope? A typical SF of 5 which is used for slings and lifts seems to be high. Thanks. TCV

 

[GregLocock]

What's your inspection regime for the system in service? What sort of environement is it in? Is it being rigged and used by qualified tall structure personnel, or brickies?

Frankly a factor of 5 sounds marginal.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Ussuri]

typically for offshore man riding a safety factor of 10 is used.

 

[Archie264]

You may want to check out this thread. (Or, you might not. Prepare to be disappointed.)

http://www.eng-tips.com/viewthread.cfm?qid=334794

 

[TXStructural]

Rigging for rescue uses a factor of 10-15. For instance, components carrying one person need a capacity of 4500 lbs, which agrees pretty well with OSHA's 5000 lb requirement for fall protection anchorages. The reason for this are many, including the unknowns, the effect of impact loads, and the aforementioned safety factor.

When you say "horizontal lifeline", what is the application? (i.e., between two fixed anchor points with one or more people tied off to it. In which case, is it to keep them away from an edge or could it be loaded with impact when they actually fall off something?)

 

[JStephen]

I would use at least the SF used for rigging.

 

[JStephen]

This is one of those "proof is in the pudding" issues, too, if it works, your reasoning (SF=2) is perfectly valid but if it fails, you'd have a hard time justifying it.

 

[tvar]

Thanks for the responses. The life line is for tie-off during maintenance. The cable is inspected prior to each use and replaced with a new cable if there is a fall. The tie off cables are maximum of 22' long connected to the structure through an anchor shackle to a lug at each end and there are spare cables made up for replacement. I did up size the cable to get a SF of ~ 5.0. Thanks again for the responses

 

[gwynn]

Provided that you follow all the way through the calculations regarding catenary action, specify the cable sag and/or pretension requirements and that anyone using the lifeline will be equipped with lanyard/shock absorbers etc. that meet ANSI/CSA requirements or the appropriate standards where you are, the factor of safety of 2 is the typical standard. Note, this is not a factor of safety of 2 on the 5000lb minimum anchorage requirement, as that is for a single point tie off and irrelevant for horizontal lifelines. A load factor of 5 could be high or low depending on what you are applying the factor to.

JStephen
This is not a "proof is in the pudding" issue. Every lifeline used in the construction industry is designed for a factor of safety of 2. A factor of safety of 2 is both the codified value and standard practice.

 

[chicopee]

Use a FS of 5; that's the number I used on bridge construction when the workers where placing formwork and form brackets for theconstruction of parapet walls.