volunteera
Structural
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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TehMightyEngineer
Structural
Depends on what is being lifting and what jurisdiction you're under.
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
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- #4
volunteera
Structural
It is a valve and i am working to AISC standards. The valve will be cross hauled through the numbers of beams located on upper deck. Lifting authority confirms that the load will always be at least on two beams and their lifting plan says the same. My assumption is 0.67 of the load for vertical down and along the most severe sling angle separately. I am adding 1.25 for weight contingency factor.
TehMightyEngineer
Structural
What are you designing? The slings, the valve, below the hook lifting devices, or the supporting steel frame? Your required factor of safety varies depending on what is actually being designed.
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
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- #6
volunteera
Structural
Sorry for not making it enough clear. I am checking upper deck beams. Beam clamps will be used to transfer the weight transverse to the beams. I have no issues with lifting appliances.
Volunteera:
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.
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.
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volunteera
Structural
Now we have got sketches as well. They will start with lifting the valve 1m up to clear the spools (pic 1). Once lifted (Pic 2) chain block C is connected to master link 2 (Pic 3), the valve is cross hauled between B & C (Pic 4), once the cross hauled is complete block B is released for master-link 2 then attached to master-link 1 (Pic 5), the valve is then hauled from chain block A onto chain block B. The rest is just repeat of the same procedure.
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.
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.
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volunteera
Structural
Concerning with the safety margins i have got weight contingency factor in all cases.
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.
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.
thaidavid40
Structural
If the valve itself is particularly valuable, or if the property below the lifted valve is particularly valuable, or could cause great damage if the valve fell on it, or if the lift activities themselves are very complicated, then you should probably look at "critical lift" requirements to ensure that you have covered all the bases you should with regard to safety. NASA has some open-source specifications on critical lift planning, if you want to search for them on the web, to use a a guide.
Thaidavid
Thaidavid
Volunteera:
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.
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.
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- #12
volunteera
Structural
Thanks to all for repling back. I appreciate it.
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?
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?
SlideRuleEra
Structural
volunteera - I see that Beam "A" is fairly large, but that Beams "B", "C", "D" and "E" are much smaller, IPE 200 (W8 x 15). Not surprising that lateral loading (up to 10.33 KN) applied to those beams fails.
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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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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