Lifting lugs on vertical vessel top head 2

[sivamech]

Hi,
Can anybody tell me how to design lifting lugs at the top of the head for vertical pressure vessel using ASME Div.1?
Regards
Siva

 

[metengr]

Here is a tip: Hire an experienced Engineer in PV design. Don't attempt to do this on your own!

 

[MJCronin]

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

 

[JStephen]

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.

 

[sivamech]

Thanks guys..!

The vessel is to be lifted vertically. I would like to design it in PV Elite itself. 3 nos. lifting lugs are required at 120° each on top dished head.
Is it possible to do the design in PV Elite on the top dished head?

 

[DSB123]

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.

 

[sivamech]

The above pic is a reference from old project.

 

[Bobfromoh]

To DSB123,
What do you mean by the "Mathcad Approach"
What edition of Bednar are you looking at?

 

[DSB123]

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.

 

[SnTMan]

If the vessel is to be lifted from horizontal and turned, trunnions & tailing lug is the way to go...

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[marty007]

Three lifting lugs on a head will not work when you are trying to turn the vessel from horizontal to vertical.

Unless you're into a special case, you would want to go with two lugs. These could be either ear-type lugs or trunnions.

 

[sivamech]

Thanks SnTman & marty007.

It is to be lifted from horizontal to vertical.