Fall Protection
Fall Protection
(OP)
In this thread, thread190-97369: fall arrest system anchor point , they state the 5000 is an ultimate load. When checking bending with this, we should use the tensile capacity and not the yield?
(Fy=50ksi, Fu=65ksi)
Is that correct?
(Fy=50ksi, Fu=65ksi)
Is that correct?
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke






RE: Fall Protection
RE: Fall Protection
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
RE: Fall Protection
We use a 6' lanyard with shock absorber, full body harness and approved D-ring or hook.
We have many "saves" over the last few years.
RE: Fall Protection
RE: Fall Protection
Is the 900# load the service/stress load case and the 5000# ultimate tensile strength load case?
If I am given a 1000# service and 4000# ultimate for a davit assembly, do I use the 1000# as a live load/impact load and design as normal?
This all seems to be so arbitrary.
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
RE: Fall Protection
Sounds like for your case you simply need to design for an 1800 lbs live load. .66Fy works for me. Or whatever it is in the new code.
Read the OSHA requiremnts at www.osha.gov. You'll want standard 1926.502.
RE: Fall Protection
If the system is engineered, I use 900# as a service live load and check accordingly. I'll have to look into the "Factor of Safety=2" thing. My initial thought is this would be the factor of safety built into the steel specification, and should not be applied to the live load, with that total being applied to the beam.
RE: Fall Protection
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This doesn't tell me to double the load, then do your design. I just need a FS of 2 against whatever I'm checking. AISC uses a FS of 2 against fracture, so that should be it.
OK. This wouldn't affect the 900# applied from the energy absorber. It just means that regardless of the energy absorber, you need a certain breaking strength for your lanyard and vertical lifeline.
Hmm, there's that pesky 1800 pounds.
RE: Fall Protection
We design to 1800 lbs. +/- and have the testing to prove it. We actaully took 250 lb "dummies" and threw them over the side. Worked great - fall arrest system that is. At 1800 lbs - it is my opinion that OSHA put in a 2:1 safety factor - but we design steel to say .66 or .6 which gives you another safety factor.
Still doesn't mean you won't get hurt - cuts, abrasions, concussion - because you will probably hit something on your way down - even at 6'length of lanyard. But at least you will go home that night..
and clean out your pants....
RE: Fall Protection
So, the test of the 250 lb person dropping 6 foot = x 2 (as safety factor) would tell you want load the hook (the tie-down point and tie-down structure) would need to be designed for.
I agree, their 5000 lb requirement is only applicable if you do NOT do an engineering (qualified person) review.
RE: Fall Protection
RE: Fall Protection
But the loads we are getting are 1250# service, 5000# ultimate. Also see comment above about the Davit assembly system.
How would you do use the provided loads?
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
RE: Fall Protection
Actually I might tend to disagree. We put the sensor in the lanyard near the hook. All it ever "saw" was about 900 lbs.
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Makes sense: 250 lb person dropping 6 ft with a "stretchable" lanyard in a harness would see 3.6 g's real load = the actual stopping force. (900lbs load)
Double that, and design the restraint point able to handle 1800 lbs. Probably how the "rules" were written to limit the force (from the restraint on the body) to 1800 lbs.
RE: Fall Protection
I would also like to point out that OSHA requires a 5000lb breaking strength on VERTICAL lifelines. The required breaking strength on a HORIZONTAL lifeline may be significantly more and as such is not specified by OSHA.
To make matters more confusing, at least to me, is the OSHA requirement that the ANCHORAGE POINT support at least 5,000lb. This is consistent with the requirement on a VERTICAL lifeline, but not necessarily for a HORIZONTAL one.
RE: Fall Protection
RE: Fall Protection
So: if you need to loop your restraint line around a pipe or a steel column, and that column can withstand 5000 lbs, it is OK - "by the book" - But seriously, how many pipes in the plant are labelled "This piece of steel has been tested and it can hold 5000 vertical load"?
Only a crane rail.
RE: Fall Protection
I have some reservation on "competent person", other than structural guys, who is competent to tell the strength of the pipes/columns that the lifeline is anchoraged to.
RE: Fall Protection
RE: Fall Protection
RE: Fall Protection
Correction: The resultant force argument is seemly only valid for horizontal lifeline using wire rope, not beams, or pipes.
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Your second comment is correct: The "load" (the person at the other end of the lanyard) is falling - by definition, so his lanyard MUST be vertical (or nearly so) then it would have to be wrapped over a rail, or steel, or pipe or something that might turn the vertical load into a side load of nearly equal amount.
The "worst case" would be a perfect inertial-less pully with no resistance: Any friction on the lanyard as the lanyard pulls down reduces the "final sideways" load on the lanyard hook.
Comes back to the [test results case] of a 900 lb load (3+ g's) on a 250 lb person's harness x 2 (factor of safety) = 1800 lb load on the hook.
RE: Fall Protection
You have to go back to a real support that can withstand the jerk
RE: Fall Protection
The wire rope is used in many industrial settings that have overhead cranes and runways. as long as I can remember, the suppliers claim the rope can sustain 10000# of ultimate load in tension, as well as the end fittings. Don't you think the near vertical pull of 900#/1800# will produce a tension in the rope several times higher than the applied load?
Also, I am not aware that lanyard is prohibit to hook to wire rope through the hooking device that comes with it. Can you point out where I can find info on this "prohibition"? Thanks ahead. (Instead, I am aware that the lanyard shouldn't wrap around a beam, or pipe, without using beam wrap with a D-Ring)
RE: Fall Protection
RE: Fall Protection
OSHA limits the maximum force on a body from a body harness to 1800#. In theory, the stiffest lanyard would allow this load. However, most lanyards in use will limit the impact to 900# because most employees don't like being hit with 1800#. If the lanyard is not provided with the system, I think you should design for the 1800# as a service load - applying the 2.0 FS to that. If a 900# lanyard is supplied with the lifeline system, apply the 2.0 FS to 900#.
RE: Fall Protection
Well tested....
RE: Fall Protection
RE: Fall Protection
RE: Fall Protection
We will typically have tensions on the order of 7000# (service level) for two men with 900# lanyards. Design the anchorages for an ultimate tensile load of around 14000#.
RE: Fall Protection