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Fixed Industrial Ladder Width

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smb4050

Structural
Jul 19, 2006
89
Is there a maximum width between ladder rails for fixed ladders? Background for the question is I designed a steel platform to support a new equipment installation. The new platform is to be accessed from an existing platform that is 24" lower. A ladder was shown for access with a flared 24" top for a step through application with the railings narrowing for a 16" clear rung distance length. The steel fabricator showed straight rails with 24" clear rung length. I question if that was acceptable per OSHA, but accepted it after I was unable to find any reference to a maximum length of rung after spending a fair amount of time looking for it.

What I showed is a common ladder detail that I've seen and used for years, but I can't find the basis for it. Any references or insight will be appreciated.

Thanks,

smb
 
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I think 16'' is minimum - no maximum shown or I couldn't find it. Also must support 250 lbs on any rung with 4:1 Safety Factor

Try OSHA 1926.451(e)(3)(iii) Look over this area becasue there is a difference between "attachable" (11'') versus "fixed" (16'')
 
Thanks for the reply. So the limiting factor on rung length is a strength consideration which is the conclusion I was coming to also. It seemed to me there would be a maximum width which is why I posted the thread.

However your recommended design load of 250lbs and FS of 4 caused me to pause because they seem high. I've been using 200lbs for the load and FS of 1.67. Am I missing a revised standard?
 
When it comes to scaffolding and the associated parts - OSHA deems that the average man weighs 250 lbs with tools. I actaully think this is kind of light in today's world. We have guys that stand 6'-6'' and weigh 325 lbs. Even Hulk Hogan though on steroids - had no body fat and was 6-6 and 350 lbs.

OSHA says you must use a 4:1 SF aganst all known live loads. This is generally figured against the ultimate capactiy of the steel or by actual testing.
 
I personally feel that the dimensions for shell man-ways recently suggested by OSHA of around 24" if correctly recalled in connection with storage tanks and vessels.

Similar width should serve as benchmark for the fixed ladders under normal circumstance ensuring quick and safe getting-on and coming-off.

Moreover the wight considerationmay and possibly should vary from area to area however 300 ponds and with tools,extra loads around 350 ponds seems considerable indeed!

OSHA people or those on OSHA's panels/committees may further enlighten us.

Best Regards
Qalander(Chem)
 
Thanks for taking time to reply. I find the responses interesting and indicative of my efforts to track down OSHA structural requirements. Qalander, with a petroleum perspective, cites standards from that industry, MiketheEngineer cites standards for scaffold from the Construction Industry Standard, and I come from a manufacturing industry cite General Industry standards. I don't know if I agree with using a FS of 4 and ultimate strength for a manufactured, fixed ladder, or even a design load over 200 pounds. However, to avoid being liable, I'll probably start checking designs using those values.

My point is OSHA provides no definitive values or methods for structural design, and has contradicting information. I'd appreciate a discussion from them on the basis of their standards. For me the biggest knock against OSHA is that they are strictly an enforcement agency. You fear their involvement after an injury/tragedy occurs and they are not seen or heard being proactive to avoid it.
 
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