Load factor in two opposite slings lift
Load factor in two opposite slings lift
(OP)
A static load is lifted by two opposite slings. Please advise on appropriate load factors to cover the case
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Load factor in two opposite slings lift
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RE: Load factor in two opposite slings lift
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Load factor in two opposite slings lift
RE: Load factor in two opposite slings lift
RE: Load factor in two opposite slings lift
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Load factor in two opposite slings lift
RE: Load factor in two opposite slings lift
You really should provide a good sketch of what you are trying to do, a free body diagram (FBD), becuase you word description is not very good/complete in detail. Since this is only a temporary loading you might be able to take some well founder liberties, based on good sound engineering judgment. But, at the same time, with this kind of rigging you can end up in a situation where one of the slings takes much more than its assumed share of the loading, and you should pay attention to that prospect.
RE: Load factor in two opposite slings lift
The worst case is on the Pic 3. This is a low probability however, once the chain block C is attached to master-link 2 a rigger can loosen the chain block B which effectively puts all loads to chain blocks A and C.
However on Pic 4 I am saying maybe the chain block B is still kept tensioned in contrast to pic 3 and takes the loads while the valve bypasses across.
Am I being here over-conservative? Please revert back and let me know your thoughts.
RE: Load factor in two opposite slings lift
In addition, in the very beginning a consequence factor is introduced. This will cover any friction related issues as well.
The reason is a hard pipe spool is attached to the valve with a flange connection on each side. Once the line is broken and lifting started, instantly, one of the slings may take much in respect to the another one. Once the slings are balanced a friction can come up between the valve and the hard pipe flange.
RE: Load factor in two opposite slings lift
Thaidavid
RE: Load factor in two opposite slings lift
It really seems that what you are thinking of doing is dangerous and quite precarious. It seems pretty darn complicated, something that a couple inexperienced millwrights had dreamed up after a couple too many beers, using the left over lifting junk in the back of their pick-up truck. You’ve got the potential of the valve kinda swinging and rolling to some extent because with each move you are picking it from different angles and locations w.r.t. its C.G. You may be using some beam clamps which may not be as secure as you might wish given the various angles and sling forces being applied. You should probably take a look at the way your clamps and slings load the bottom flanges of the beams laterally and torsionally.
I can’t read your sketches very well, they are too light. When you scan to pdf’s increase the contrast and darkness of your scans before you send them to the pdf files. As I understand it, you have to lift the valve, straight up, about 1m (3.3') to get it out from btwn. two flanges in a pipe spool, on a skid, or some such. Then you have to move it laterally 4 or 5m (13' - 17') to get it over the piping and the skid, to finally get it out in the open, and set it down. I also understand that the valve and misc. lifting equip. weigh about 5.8 - 6kips (6000lbs.); the weight you will be lifting, whatever the load factors you apply. I’m also not particularly found of the hinged temporary beam connectors (beam clamps) which you appear to propose. I would have to see their load and safety literature to confirm their use. I think they are generally intended to be loaded vertically, not at some considerable angle and loading.
I would hang a trolley beam from the underside of the upper deck beams, with a better type of beam clamp, so that you could lift the valve straight up in the first place, and then just push it down the beam until you could lower it.
RE: Load factor in two opposite slings lift
The lifting plan was proposed by lifting authority. My role is to check capacity of the upperdeck beams. By the way, I have already rejected the proposal as the flange local and lateral bending failed for a code check.
I am exactly in the same opinion concerning with the way that the lifting is planned and the trolley solution has already been put forward which is safest solution to the problem.
Going back to the first question do you think any other safety factors have to be included in this sort of lifts?
RE: Load factor in two opposite slings lift
Concerning other safety factors; the analysis assumes the load is supported by at least 2 beams at all times. Although that sounds reasonable, I would never rely on a 2-beam support requirement for the analysis. IMHO, at a minimum there should be a (vertical) load requirement on each of the 5 beams of 32.5 KN (Load, including the weight contingency factor). This is not unreasonable since the maximum actual (best case) load calculated for an IPE 200 is 23.7 KN... and that load is applied at an angle.
Also, the 1.25 consequence factor for separating the valve from the pipeline seems low. I would consider a consequence factor of 2 as a minimum value.
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