Chaining through a D ring? Basket or Choke?

[Motorsports-X]

I am trying to address rigging safety in our plant. typically we use chains connected as an endless loop. the chain routed over the hook, through the d ring, and hooked to itself with a standard not supporting grab hook. It occurs to me that I am unsure how to de-rate this setup. I have 2 conditions, 1 is the D ring is 2.5 D/D of the chain, which in a basket scenario reduced the rating to 60%. But then you also have the chain hooked to itself. I'm not exactly sure how to measure this angle but its steeper than the typical choker pictures on the internet. Im aware that this isnt a true basket scenario so you dont get a doubling of capacity. could anyone help shed some light here.

 

[john.k]

According to some chain suppliers the spur type of grab hook is rated full chain capacity.........the old type claw ends were also rated full capacity.............you would have to go by the chain suppliers ratings ....and probably have the approval of your "risk assessment department"..............I had a nasty surprise with claw hooks when a kid "management trainee" hooked them upside down,and the sling suddenly came apart flipping the load. With grab hooks ,they cant be hooked upside down ,as they hold both ways.

 

[Tyrone Shoelaces]

According to some chain suppliers the spur type of grab hook is rated full chain capacity.........the old type claw ends were also rated full capacity.............you would have to go by the chain suppliers ratings ....and probably have the approval of your "risk assessment department"..............I had a nasty surprise with claw hooks when a kid "management trainee" hooked them upside down,and the sling suddenly came apart flipping the load. With grab hooks ,they cant be hooked upside down ,as they hold both ways.

As you mentioned there’s a right way and a wrong way to locate the lifting chain into the shortener.

Regards Tyrone

 

[Cole2534]

Do you have a budget? Thing seems like a good place to use something like a Crosby Eliminator with sling hooks. Consult with your local rigging house to select sizing based on your load and sling angles.

 

[Motorsports-X]

Do you have a budget? Thing seems like a good place to use something like a Crosby Eliminator with sling hooks. Consult with your local rigging house to select sizing based on your load and sling angles.

i really just need to know how to rate the endless loop. from what I can tell, endless loops are rated double and the same % drops apply for d/d and grab hook type.

 

[Cole2534]

i really just need to know how to rate the endless loop. from what I can tell, endless loops are rated double and the same % drops apply for d/d and grab hook type.

Call a rigging house and ask, you don't need to tell them you already own the slings. Just say-

'Hey, I wanna lift X load, it needs to use Y leg length at Z angle to meet space req's and it is for OH lift. Could you spec me a sling to meet those needs?'

I wish I could be more helpful, done some moderate sling spec stuff over the years, but I'm not fully grasping thr scenario.

 

[john.k]

The chain people hand out plastic cards with sling ratings and such .....I d have some ,somewhere ........I do have a crane drivers license ,so I should know all this stuff .....but I dont .

 

[Motorsports-X]

The chain people hand out plastic cards with sling ratings and such .....I d have some ,somewhere ........I do have a crane drivers license ,so I should know all this stuff .....but I dont .

the problem I have is that all of the endless chain slings I can find are rated without a grab hook. most of them are literally either endless chains (ie, the last link is put through the first and welded) or they are shackled to a master link.

i think the answer is pretty simple, I think you just take away 20% for the grab hook, and in our case you take away 40% for the small d/d. so we would rate the chain at (8800x2)-40%

I found an old document from OSHA that shows an endless chain as a double basket and Im not even sure you can do that anymore. (since the chain would go through the hook twice) i was always told never to double the chain through the hook.

 

[john.k]

Thats probably true,as the links would bite into each other in the hook ..On my old crane ,the hook was soft steel ,and any HT chain over the hook made a mess of it.............it was well worn anyway ,and had a groove where the sling rings bear .....anyhoo,not to worry ,I left the crane with the people who bought the property...........would have cost $2000 to shift it.

 

[m16ty]

I had a talk with a rigging supplier about this a couple years ago. The bottom is a chain hooked into a loop doesn’t double the capacity, it is over the straight pull but I don’t recall how much.
Now if you do have a length of chain attached to a lifting ring, and basket a item with enough d:d ratio, and you attach to a rated hook separately attached to the same lifting ring, it does double the capacity (providing the lifting ring is rated enough. We had some rigging made just like this, to double the chain sling capacity, they have a capacity tag attached to them saying as much.