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Lifting lugs on vertical vessel top head 2
- Thread starter sivamech
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I agree with metengr .... The design of Lifting Lugs is far too important to be part on an "on the job" experience for the newbie.
What you can do that would be important is to decide upon a proven lifting device design that would best suit your particular vessel and its installation.
The proper lift for a huge process column is different than that of stubby vertical tank.
The location and design of lifting lugs must consider how the lug is loaded. this is PARTICULARLY IMPORTANT for lugs on vertical vessels, where the vessel must be rotated from the (typically) horizontal shipping position to the vertical lifting position.
Common proven designs include:
- Two lugs located 180 degrees apart on the top tangent line of head/shell -- coupled with a tailing lug
- Two lifting trunions located near the top head -- coupled with a tailing lug
- Lifting by a properly reinforced top mounted manway
Suggest that you google "lifting lug design" and read the articles/ look at the pictures
MJCronin
Sr. Process Engineer
What you can do that would be important is to decide upon a proven lifting device design that would best suit your particular vessel and its installation.
The proper lift for a huge process column is different than that of stubby vertical tank.
The location and design of lifting lugs must consider how the lug is loaded. this is PARTICULARLY IMPORTANT for lugs on vertical vessels, where the vessel must be rotated from the (typically) horizontal shipping position to the vertical lifting position.
Common proven designs include:
- Two lugs located 180 degrees apart on the top tangent line of head/shell -- coupled with a tailing lug
- Two lifting trunions located near the top head -- coupled with a tailing lug
- Lifting by a properly reinforced top mounted manway
Suggest that you google "lifting lug design" and read the articles/ look at the pictures
MJCronin
Sr. Process Engineer
I find some of the information in ASME BTH useful for design of the lug itself, specifically, the pinned connection details.
In addition to the above, also refer to the various pressure vessel handbooks (Bednar, for example).
In order to get reasonable designs, it may be necessary for you to specify exactly how it is to be lifted as well.
In addition to the above, also refer to the various pressure vessel handbooks (Bednar, for example).
In order to get reasonable designs, it may be necessary for you to specify exactly how it is to be lifted as well.
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- #5
JStephen
You quote Bednar which is a decent book but there are errors in it. I once had a fabrication Company design lifting lugs using Bednar and used the sectional properties in their Mathcad design approach. I told them that the equation for the sectional modulus was incorrect and the argued that it was not and that they had used the Mathcad approach for years. I told them that the lifting lugs bending stress was above yield and hence the lug would deform. They still argued with me until the designer went down to the workshop and asked the shop floor what happened when they lifted the vessels onto the wagon for delivery. The works said "oh the lugs bend and take up the natural angle to the single lift point - they said they thought the lugs were "designed to do that". Result was that the Mathcad calc was re-addressed. When they told me that I laughed. The Company must have many vessels out there where the lifting lugs should be vertical but are in fact bent inward depending on the length of the lifting slings.
You quote Bednar which is a decent book but there are errors in it. I once had a fabrication Company design lifting lugs using Bednar and used the sectional properties in their Mathcad design approach. I told them that the equation for the sectional modulus was incorrect and the argued that it was not and that they had used the Mathcad approach for years. I told them that the lifting lugs bending stress was above yield and hence the lug would deform. They still argued with me until the designer went down to the workshop and asked the shop floor what happened when they lifted the vessels onto the wagon for delivery. The works said "oh the lugs bend and take up the natural angle to the single lift point - they said they thought the lugs were "designed to do that". Result was that the Mathcad calc was re-addressed. When they told me that I laughed. The Company must have many vessels out there where the lifting lugs should be vertical but are in fact bent inward depending on the length of the lifting slings.
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Bobfromoh,
By "Mathcad approach" i meant they had been using a Mathcad calculation - developed in-house - for years.Of the top of my head I cannot remember the edition of Bednar they were referencing but the equation they extracted was wrong - hence the bending lifting lugs.
By "Mathcad approach" i meant they had been using a Mathcad calculation - developed in-house - for years.Of the top of my head I cannot remember the edition of Bednar they were referencing but the equation they extracted was wrong - hence the bending lifting lugs.
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