lugs 1

[Aloni]

Hi to all

I need some guidance or direct me to a literature calculating lugs that are not directly mounted on the reactor
Due the half pipe jacket as shown in the attached file

regards
Aloni

 

[DSB123]

I do not like that arrangement one bit. I think you need to perform a FEA to be certain of the stresses in the half pipe as it passes through the support.

 

[dhengr]

Aloni:
That certainly is a difficult location for support lugs. But, that is also a really crappy detail for the support lug, and FEA isn’t going to make it better or even prove that it will work well or fabricate well. The FEA will show a bunch of very high localized stresses. While you do provide a drawing which starts to explain things, it is pretty difficult to read; what with dimension lines and actual part lines being continuous, few dimension arrows or hash marks, lack of welds and weld sizes, etc. It would also be nice to know the loads on the lugs, the tank weight and C.G., the tank shell thickness, etc., since these are all important parts of the design. I would move the entire lug (lugs) above the top half-pipe, into the vert. 350mm, minus, space on the tank, if I could. I would move the four vert. shear transfer pls. to line up, either at 305mm or at (450 - 2[15]) 420mm, you can’t have those offset all over the place and make any sense out of the load paths. You also can’t (shouldn’t) take the canti. lug load and try to apply it to the 340x450x20mm pl., in pl. bending and then into the shear pls. btwn. it and the tank shell. This is really difficult, and will have many hard spots and high stress spots. I would much rather take the two lug, vert., shear pls. right back to the tank shell. I would also take the lug bearing/bolt pl. back to the tank wall, and add a similar, but narrower, top pl. over the two shear pls., again going back to the tank shell, and shaped to the tank i.d. Just get rid of the first layer (nearest the tank shell) of canti. structure. Obviously you want to minimize the lug load canti. length.

I would try to avoid the half pipes with my vert. shear pls., or at least cut the shear pls. with half circles with dias. greater than the o.d. of the half pipe, so they didn’t touch, can’t be welded, can move w.r.t. each other. Then, the damn half pipes slope as they move around the tank, so every vert. shear transfer pl. is going to be different. Where does the insul. stop above the top half pipe? I don’t know the ASME PV codes the way you should. You might run into the need for a reinforcing/doubler pl. on the tank shell to attach your lug to. I suspect that thinking influenced the shape of your 340x450x20mm pl. with 25mm radiused corners, but then you didn’t apply it at the tank shell. If the lugs are applied at the time of the tank fab., are these doubler pls. really needed. In this case, with proper design, welding and inspection, they are not really an improvement.

 

[Aloni]

Dhengr:

Thank you for the tips
Unfortunately I cannot change the geometric of the lug connecting to the vessel wall (this is the client demand)
The vertical shear plates is not connecting to the half pipe jacket there is a gap of ~ 5 mm
As for your question the total (working) weight of the vessel is 16 ton, Empty weight is 1.6 ton
Vessel wall thk is 5 mm hastelloy c-276
Thanks
aloni

 

[MJCronin]

Here are some pictures that may prove interesting:

http://www.westmetalworks.com/custom-fabrication-products

("Chemical half pipe jacket" photo)

Some fabricators seem to "skip" the half pipe coils at lugs located at the top of the shell.

http://www.bendelcorp.com/blog/heat-transfer-dimpled-half-pipe-jacket-fabricator/

http://www.ras-inc.com/assets/images/Stocktank.jpg

http://www.glattistgutgmbh.de/en/products/construction-of-vessels/half-pipe-coil-jacket-vessels/

Sometimes a "full supporting ring" is incorporated into the design...

http://www.rvii.com/chemical_literature.htm

http://www.wardtank.com/reactors.htm

Having fewer turns of half pipe simply means that the heatup/cooldown time increases very slightly....

Please respect us on this forum.....Let us know about your final decision and how you came to it...

Best Regards....

MJCronin
Sr. Process Engineer

 

[Duwe6]

"Having fewer turns of half pipe simply means that the heatup/cooldown time increases very slightly...."

Exactly; and that is just 'theoretical'. Very few, if any, process reactors are operated with liquid all the way up the shell. Skip the half-pipe on the top 2-feet of the shell. Conduction will keep 6 to 10 inches quite warm, and the remainder of the top of the shell should be unwetted headspace.

 

[dhengr]

Aloni:
This means no disrespect of the customer, but there are lots of times that the customer doesn’t know what he really needs, or wants, for lack of a deeper knowledge and more experienced engineering and engineering judgement. Explaining some of this is your job, that’s what we do lots of times. That’s kinda what I meant by the statement you should know the ASME code ‘and real design requirements’ better than I do. And, several of the other guys have indicated a pretty simple way of cleaning up this support detail, by eliminating the top ring or so of the half pipes. So, the statement, “Unfortunately I cannot change the geometric of the lug connecting to the vessel wall (this is the client demand),” might be a bunch of b.s. Because the clients says so, without knowing any better, are you willing to give him a crappy detail that you may have to go out and modify/fix, after installation, never an easier solution? Or, is the right time to fix it right now, before it becomes a problem?

Thanks for the support Duwe6.

 

[Aloni]

Hi to all
I will Let us know about my final decision
MJCronin thank you for the practical tips

Regards
Aloni