Load Factor for OHSA Safety Loads 2

[dik]

I've seen load factors of 1.0 for live load on safety harness tie off for the 5K (22.2kN) load. The argument being that this is a maximum prescribed load. Has anyone else encountered this? Thanks, Dik

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[human909]

Absolutely I would use a factor of 1.0 for the live load on 22.2kN tie off point.

As per wiki or wiki or your more relevant code, live load factors are to do with the probability that the live load could exceed the number.

There is essentially zero probability of the Live load exceeding 22.2kN on an anchor point. Both the dynamics of a falling human body and the load rating of the attaching equipment will prevent this. Lots of the equipment will fail within a probabilistic over you get over 22.2kN.


The shock absorbers in a fall arrest system generally limit peak forces to 6kN and that is under extreme circumstances. Gross misuse of the system could see high loads but the person would probably be dead from the impact. If the fall is putting 22.2kN on the load point then it is putting 22.2kn on the person! You'd need a rigid cable (eg steel and no shock absorber) and a long fall (eg 20m) for a falling human to put 22.2kN on a tie off point. My knowledge base is broad on this topic due to being a rock climber. I've taken long 9m+ falls on equipment I've placed. I've fallen on 5kN rated equipment. You really need to try hard to exceed 20kN, though it can be done if there is gross misuse of the item. (AKA long falls without shock absorption)

 

[dik]

Thanks, I concur with his argument... to me the load is a prescribed maximum. I was just a little concerned that I might have been the only one to have heard of this.

I know all about the pain at the end of the stop. About 50 years back I went down about 100' on a 65 or 70 degree slope. The last few pitons kept me from going down a bunch more. Even my toenails hurt.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

dik - this has been debated pretty extensively here. If I remember correctly the 2018 IBC attempted to clarify things a bit, but they still left a few questions open. Even the wording is a bit ambiguous - I think the OSHA standard says something to the effect of "5,000lbs without failure". To some engineers, the only way to ensure you don't have failure at 5,000lbs is to apply an additional safety factor. I don't agree with that approach, but there are many out there who do.

 

[dik]

Thanks pham...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

Here's one of the more recent ones: thread507-469682

 

[dik]

again thanks... printed it out for my files.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[RPMG]

The maximum arresting force allowed by OSHA is 1,800 lb (300 lb worker + 10 lb tools). OSHA specifies a factor of safety of 2, so 3,600 lb maximum. In a working load stress check, the D-ring below should be around 20 ksi for the 3,600 lb. If a 900 lb lanyard is to be used, 900*2=1800 lb for say 36 ksi / 1.67 steel. Since you're a qualified person, that's how the OSHA codes should be used.

Now, the next person comes along, and buys a 5,000 lb shackle. An engineer could specify a 3,600 lb shackle. The shackle vendor could sell "OSHA-Compliant fall arrest" shackles, but random people just buy 5,000 lb shackles. Any product rated for 5,000 lb is ok to use in the fall arrest assembly.

I recommend tagging or labelling all fall arrest assemblies, such as "310 lb fall arrest" or "900 lb lanyard fall arrest". If its tagged "5,000 lb max", it can be used as fall arrest.

 

[dik]

Thanks, RPMG

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik