TANK SHELL Course Replacement

[saliths]

Hello,
Is there any calculations as per API 650/653 onto the cutout size of shell course for replacement purpose. We are planning to completely replace two complete shell course in between the other courses. A total of 8 course and the replacement has to be for 5th and 6th. Does API dictate on the biggest cutout which could be made in this respect.Request advice in this regard.
Regards

 

[lgwsaw]

Saliths,

Nothing that I am aware of in the code. This would really depend on things like-- Tank Access, any overhead obstructions, Will you make the repair on the exterior or interior?
I like to try to cut the sheets no longer than about 20 feet in length--- again if you have nozzles or some type of obstruction in the way you may need to reduce the length to What Ever Will Work Safety.
Remember the need for satisfactory stiffening.

Good Luck,
LGW

 

[saliths]

Hello,
Thank You for the information provided !
Regards

 

[gr2vessels]

Saliths,
The relevant code for your repair/alteration is API 579. Please read the Clause 1.1.1.
Cheers,
gr2vessels

 

[saliths]

gr2vessels,
I understand API 579 deals for FFS. Here the requirement is to replace 2 complete course of a tank of ID 18 Metres which we have already decided to. Now the thing is can we just replace the two course by dewelding on both the top and bottom joints, or should we remove each shell plate of a course and replace the new plate sequentially. Does any API standard deals with this precisely???Does it convey any thing on the cut out size ????? Please advice ! and thank you for the note provided.
Regards

 

[gr2vessels]

Unfortunately, no.
There is no (to my knowledge) any standard to make specific recommendations on how to remove particular courses of an existing tank for repair. I assume you intend to jack-up the upper part of the shell, cut off the shell courses by panel size and somehow to insert the new panels one by one to re-create the removed courses. I would contact a company like CBI or similar to ask advice.
Nevertheless, the inspection and review as per API 579 has to be performed by you or someone else qualified to do so, in order to highlight the current condition of the tank, before you start pulling it apart.
Cheers,
gr2vessels

 

[lgwsaw]

Again---you will need to have a Engineer tell you the recommended stiffening size needed to support the area you will be replacing. After you get the ok to proceed.
I would recommend to replace one (1) sheet at a time. New plates come in 6 mm in lengths, so if you can cut and replace a whole 6mm section safety Great.
Install a tank builders scaffold around the tank.
Install one (1) vertical I-Beam or channel of the proper size on the outside of each the marked out vertical CUT LINES. Cut out the sheet (2 vertical seams & 2 horizontals). Install the new sheet,Fit and tack weld the sheet in place.
The attached pic shows a tank with the interior stiffening installed (this is just another way of doing this but the entire idea is still the same....

cheers,

 

[saliths]

Hi !
Very gratefull for the guidance provided !
Regards

 

[IFRs]

Wind is your enemy here. Be very careful.