Lifting using Shell Flange Lug (Dennis Moss)

[lmacallndong]

One of the lift options in the Pressure Vessel Design Manual 3rd edition by Dennis Moss is the Shell Flange Lug shown on pages 391 and 397. Has anybody used a shell flange lug in lifting a vertical vessel? How is it possible to lift a vessel in the vertical position?

 

[marty007]

lmacallndong,

I'm actually working on a vessel right now that will use a top flange lug. This works for vertical vessels because the whole vessel hangs off the top flange. If you keep going to page 422, it discusses the design a little further.

For vertical vessels, I think the shell flange lug is more suited to be used to replace a tailing lug. The only way I could see using shell flanges to erect a vertical vessel otherwise is if you had two opposing flanges and essentially used them like trunions. This design would be different however from a standard Moss shell flange lug.

Cheers,

 

[dineshakabari]

In my opinion, Lifting lugs on nozzle flanges shall not be applied. If applied then further analysis of nozzle, shell/head local stress needs to analyze. The real practice different client's specifications are in favor to apply lugs on head or shell (as a lifting trunion incase of heavy loads). I have curiosity what is the special reason/motivation to apply lugs on flange although it is creating much more complications. As a short cut some people are uses nozzle necks to fix lifting chain hook, but as per good practice this is also restricted to safe guard equipment since stresses are concentrated at the roots of nozzle.

 

[marty007]

dineshakabari,

Yes, extra analysis is certainly required, but in some cases it is justified. Depending on the size of the vessel and location and orientation of nozzles, the use of lifting blinds can be a simple and smart solution.

In our case, due to fatigue cycling, the client would prefer to keep the number of attachments to a minimum. So trunions or lifting lugs are not preferred. We also have the benefit of a heavy forged manway on the top head that provides more than adequate strength. Add to that, we are building multiple vessels of the same geometry, and a single lifting blind can be used for multiple lifts.

 

[dineshakabari]

Considering the situation & proper care is taken for the induced stress, the proposed solution looks smarter. In case of some specification the client is also asking to remove the lifting lugs after finish of installation. This solution will become a good development in the practice.