pad lug Ring Girder Supports

[Aloni]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1574506301/tips/vessel_nlmi00.pdf[/url]Hi to all,

I need to design a stainless steel pressure vessel with carbon steel lugs Ring Girder (see att file).
Usually when design lug on a vessel it is possible to add a pad,
But in lugs Ring Girder I cannot find any guidance how to calculate the pad.
I have search Bednar
I use compress and pvelite, both of them doesn't have the option to add a pad to lugs Ring Girder.
Design condition -1+6 barg @200°C. Total weight include external loads is 35 ton
Ill appreciates some guidance how to calculate the pad.

Aloni

 

[RAJPT89]

Dear ALoni,

In PVElite you can input Pad parameters for Lug Supports. Refer image below:

Thanks,

Rajput

 

[Aloni]

hi rajout,
thanks .

if you choose in "lug type" the right image (lugs Ring Girder or gussets with continuoes top ring ), you can see that "optional pad parameters" is blocked.

aloni

 

[saplanti]

When you use the ring girders to support the vessel you can take the shell thickness into consideration. This is sufficient in most of the applications. I suggest you to look at "Design of Weldments" Section 4.7 for the calculation methodology.

In your case the materials are different and the area is subject to corrosion due to the cooling effect of the girder plates as well as the corrosion of dissimilar materials. So therefore you need to add intermediate plate to eliminate the corrosion on the shell of the vessel.

If there is no option for this application in the software that you are using, and I would suggest to do the calculation by hand. I would suggest to use the same thickness of material with same or higher strength as reinforcement for the start. However there is a catch in the application;

Sometimes split the reinforcement into two for upper and lower ring girders in case the distance between ring girders high, however it become costly due to additional two circumferential weld seams. The load on the localised reinforcement will be a lot better predictable and you can check the reinforcement plate thickness by hand.

Second; you may need to use single reinforcement plate due to the short distance between plates and economy so you need to check the reinforcement plate thickness by using the same reference.

Writing a spreadsheet may shorten your time on the decision making, I would say.

 

[Aloni]

hi saplanti,

thanks for the detail answer,
the picture is more clear now.
regards,
aloni