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Trunnion design...Your Suggestions?
3

Trunnion design...Your Suggestions?

Trunnion design...Your Suggestions?

(OP)
We plan to release a trunnion design feature in the next build of COMPRESS. Most of the work has been completed.

However, I am interested in any suggestions users may have regarding preferences, special details, etc. Please post or e-mail any suggestions you may have for trunnion design. Thank you.

  Tom Barsh
  Codeware Technical Support

RE: Trunnion design...Your Suggestions?

(OP)
We are 'locking down' this new feature for trunnions. Useful comments would be appreciated.

The trunnion analysis is based on method where a tear-drop-shaped plate is attached to the end of the trunnion; a pin-hole in the plate is provided to attach the lifting clevis. Thus the lifting occurs at the pin-hole in the plate.

Two options are provided: (1) the tear-drop plate is welded to the trunnion "pipe" (thus a rigid connection), and (2) the tear-drop plate is free to rotate on the pipe.

Some references describe a third type of trunnion where the lifting cable is slung directly around the "pipe" (rolled plate, or whatever). This is the only type that I personally have any experience with (and I fail to see the utility of the first two types of trunnions, other than that they may be preferable to top ear-type lugs and probably provide a construction detail that provides for better quality assurance on the welding than the flat lugs do).

I would like to request anyone who has actual experience with lifting of vessels to add any pertinent comments or suggestions/requests. Thank you.


  Tom Barsh
  Codeware Technical Support

RE: Trunnion design...Your Suggestions?

(OP)
Well, let me retract part of my comment, I can see the utility of the trunnion with the rotating plate. But not the construction with "fixed plate". But I digress...

RE: Trunnion design...Your Suggestions?

Tom, I have been designing lifting trunnions for over 25 years, and, like you, have only dealt with the 3rd type (cable around neck). I am familar with the 1st two, and know that they are covered in DuPont standards. The advantages of the those would be safety, I imagine, due to the fact that shackles are more secure. If improperly rigged (say by using a spreader bar length not matching trunnion spread), the 3rd type presents some danger of the cable slipping off the end. Here are some points to keep in mind:

(1) Watch out for torsion. Even for the 3rd type, cable friction induces torsional stress in the trunnion-to-shell weld(s) which is proportional to the coefficient of friction between the cable and the trunnion neck.

(2) Beware lamellar tearing, which is always a danger with high loadings normal to plate surfaces. I have always tried to keep stresses at the neck-to-shell weld(s) below 20% of allowable by increasing neck thickness and/or diameter as necessary.

(3) When pads are added, depending on thickness and/or diameter of the pad, it may be advisable to weld the neck thru the pad directly to the shell instead of welding onto the pad surface. A fundamental assumption in the WRC-107 method of calculating shell stresses is attachment rigidity.

(4) Trunnion end plates serve two purposes: (a) to keep the cable from slipping off the end and (2) to keep the end of the neck round under load.

(5) Trunnions are relatively inexpensive compared to the consequences of failure. I always figured a little conservatism on them to be cheap insurance.

RE: Trunnion design...Your Suggestions?

Please go into following engineering website
http://www.pes21.com

you may calculate trunnion lifting lug .

RE: Trunnion design...Your Suggestions?

Hi Tom
I would like to add that it would be nice by COMPRESS to include another type of Lifting Arrangement by Lifting Blind on Top Nozzle for Vertical Vessels. Due you intend to think in this way or some one has any analysis how to do this in safe but in economical way.
Regards
irfan

RE: Trunnion design...Your Suggestions?

Tom, we see users request all three types of trunnions mentioned.  Cable between two plates being most common and the fixed/rotating tear drop falling way behind.

I'd really like to see some enhancements on tailing lug and skirt stiffening

RE: Trunnion design...Your Suggestions?

(OP)
khanirfan:   The lifting procedure you describe is addressed in several pressure vessel design texts. I believe the 3rd Edition of "Pressure Vessel Design Manual" by Dennis Moss addresses this method. At this time Codeware has no plan to provide for this type of lifting as an option in COMPRESS. However, you can check the nozzle neck and shell for the applied loads using COMPRESS.


vesselfab:   I believe the cable wrapped directly on the trunnion is the most common configuration. I was very surprised not to see this in the initial release of the COMPRESS trunnion feature (our programmers...who are also engineers...were equally surprised to learn that such a trunnion type was greatly used).

   There has been some tweaking made to tailing lugs in the latest build of COMPRESS (and there will likely always be some tweaking to these). COMPRESS is still limited to only a single stiffener beam; this may not be suitable for extremely heavy refinery vessels.


LSThill:   Thank you Leonard. This information may be useful to others. Can you provide some reference as to where documents like these were obtained and if they may be used without fear of legal 'reprimand'?




  Tom Barsh
  Codeware Technical Support

RE: Trunnion design...Your Suggestions?

Tom

Did you Take the SOUTH TEXAS SECTIN OF ASME PRESSURE VESSEL ENGINEERING SEMINAR 1998:

SESSIN 1 Interduction and Desing Philosophy Pressure Vessel Code, Section VIII, Div 1, 2, and 3 by James R. Farr, PE Pressur Vessel Consultant, Wadsworth, Ohio.

Section 2 Pressure Vessel Design per ASME Code; Desing of Support and Lifting and Tailing Lugs Gerry Gravin, P.E. Bechtel Corporatin Houston, Texas.

Section P. Design of Lifting and Tailing Lugs Page 208.

The above was given to LES in 2004 for the project requirements.

Also, is LIFTING_LUG_&_TAILING_LUG_CALCCULATION.pdf
This was given to Les in 2004 for the project requirements.

Tom, I hope this will be included in CODEWARE COMPRESS TO NEET THE CLIENT REQUIREMENTS and CODEWARE COMPRESS USERS.

Regards

Leonard Stephen  Thill





RE: Trunnion design...Your Suggestions?

Leonard,

thanks a lot for such a useful information on lifting lugs and tailing lugs. but some of the files are not opening properly. thanks a lot for your information on that topic. one more request is there can u please provide some info regarding the book whose link u've provided.

thanks again
Narvirsinh

RE: Trunnion design...Your Suggestions?

I couldnot download the attached file. Is there any problems with the attachments ?

RE: Trunnion design...Your Suggestions?

I do not have experience in pressure vessel design, but I am involved in the heavy lifting industry. In my experience, the "fixed plate" trunnions with the non-rotating teardrop plate are mainly for flare stacks and other tall columns.

From a lifting standpoint, the benefit over rotating plates is that they do not need to be lubricated before the lift. This is especially important for removal of old equipment because the trunnion may be hundreds of feet above the ground where re-lubricating a seized plate presents additional difficulty.

RE: Trunnion design...Your Suggestions?

(OP)
TW,   Thank you for your insight. It is nice to get this from someone who is directly involved in the lifting jobs.

  Tom Barsh
  Codeware Technical Support

RE: Trunnion design...Your Suggestions?

we use the 3rd type.

I'd really like to see some enhancements on tailing lug and skirt stiffening(cross or triangle stiffening beams).  

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