OSHA 5 to 1 factor of safey 2

[precast78]

Let's say you design a basket that is being used to lift a heavy product that has wheels. The product will be rolled into this basket. Then the basket will be lifted by a crane. It is pretty clear to me that I need to make sure I have 5 F.S. on the cable, shackle, connection to the cable (most lifting assembly already has this 5:1 factor of safety) etc.

But how about the rafters of the basket and the plate on the top of the rafters? Do I need to apply this 5:1 factor of safety? Or shall I just put 1.2 DL, 1.6 LL and use phi per AISC LRFD.

Thanks folks!

 

[CTW]

This qualifies as a below-the-hook lifting device and should follow the design recommendations in ASME BTH-1 Design of Below-the-Hook Lifting Devices. This document gives guidance on selecting the appropriate safety factor or design factor as it is referred to in BTH-1.

 

[dvd]

Also, don't assume that you can just stamp the drawing for this -

an excerpt from a previous version (ASME B30.20-2003) reads:

(a) Prior to initial use, all new, altered, modified, or
repaired lifting devices should be tested and inspected
by, or under the direction of, a qualified person and a
written report be furnished by such a person, confirming
the load rating of the lifter. The load rating should not
be more than 80% of the maximum load sustained dur-
ing the test. Test loads shall not be more than 125% of
the rated load unless otherwise recommended by the
manufacturer. Test reports should be available....
​

 

[dhengr]

Precast78:
I’m not so sure that OSHA has much to do with your problem here, but ASME BTH-1, “Design of Below-the-Hook Lifting Devices” is a real good place to start. You should get a copy, as CTW suggests. The 5:1 FoS for wire ropes, slings, shackles and the like was briefly explained in your earlier thread. You should read that thread, do a little more research on your own on the matter, and digest some of that. Not all codes and standards require the 5:1 FoS on all items in the lifting process. If this new design problem relates to your previous thread on the 4 legged lifting slings, why not put four lifting points on your load, and lift it? This would eliminate the lifting basket which could be fraught with potential difficulties. Your load has to be loaded into and out of the basket; and, on wheels, it must be locked into the basket before lifting, so it can’t move during the lift. As much as concern about exact FoS is important, why would you intentionally add another layer/level of lifting equipment into the process if you could avoid it. This is just another layer/item which could go wrong and needs inspection and maintenance before each lift. Is your load a grout bucket or buggy? Put lifting eyes on the corners, shackles on these eyes and use slings with hooks on them. These 4 legged sling arrangements usually have to be designed so that two of the legs, in a line/plane will carry the full load, and the other two legs just keep the load stable.

 

[Sawbux]

The specified 5:1 safety factor applies to items that are subject to wear - cables, sheaves, etc. You should apply this factor to anything subject to wear, shackles, lifting eyes, etc.

The deisgn of the basket itself is subject to engineering judgement, but should be designed for the typical working stress or load factors. Do not forget to include dynamic loads from the lifting process - impact and acceleration. Also deflection, which many times may govern over strength considerations.