Spherical Tank Shell Doesn't Fit Each Other/Any Gap Between One Plate to Another

This is very dangerous, and illegal in most places. Certified materials, procedures, and persons must be used. Inserting slivers of filler material into gaps is not permitted.

You say, "What references shall i use to fulfill safety consideration".

I say, What references can you use to justify such a dangerous patch?

Thanks gurus..

How is the solution then? Can i ask to subcontractor to apply R-stamp to make it more stringent? Is that a good idea?

Thanks a lot..

P.S: Inside diameter of tank is about 22 meter. The material is SA-537 Class 2. The gap between each plate is 25 mm!!!!

For a field fitup/repair like this on a pressure vessel, an R-stamp is the correct qualification (in the U.S. and other jurisdictions following the same Code). The holder of an R-stamp can meet the aforementioned standards.

An R-stamp is not something that one just "applies." Underlying it is a considerable body of skill, procedure, and verification.

I'm struggling to believe that this isn't a practical joke!

A 22m Dia LPG tank has a massive explosive potential if it fails - Google LPG BLEVE if you need convincing.

STOP WORK NOW and get some experts in!

Premium,

You say that this is a brand new tank. Is that true ? This tank is NOT part of some reclaimed rusted mess that has existed for 30 years.....is that correct ?

Where will this tank be located and what will be the contents ?

Is the tank installer the same company as those who fabricated and bent the plate ? If not, then this is yet another MBA management error.... !!

Common sense dictates that for a complex spherical tank YOU MUST ALWAYS make the plate fabricator and the installer the same party. CBI of the USA (and many, many others) only work under this arrangement.

Of course it is perfectly acceptable to put plate patches over joints with gaps. This is in conformance with all existing codes and standards. But, since you are constructing this tank in the third world and will probably perform a cheaper pneumatic pressure test, the results of your MBA errors will soon become obvious.

Good Luck !

Has a dialogue been opened with the company that is to supply burst indemnity insurance cover?

@anonymous: As you can see from my statement above, the spherical tank is a brand new vessel. The content of it is pressurized LPG with design pressure of 18 kg/cm2.

For your info, the company which done engineering of this spherical tank is different with the company which done the fabrication and construction.

@PWSlack: Will check it soon!

@Abdel Halim Galala: So the defect plates must be replaced by new plates? Sir, where can i find that the gap between plates must be 2 mm?

Thank you very much for all suggestions!

Go back to your contract and have an attorney with experience in this area of construction look at it. One or both of the design engineer and/or the contractor need to fix the problem and make it right BEFORE they get paid (or before you pay them any more). The problem is either a defective design, defective fabrication or both. I have been all sides of the aisle in construction activities, so turn to your contract for the remedies and do it soon, as it will only get worse with the passing of time. Good luck!

You are constructing a potential bomb, of some significance.

If not too late, you need to stop payment, and call your lawyers and registered consulting engineers. Consulting in this forum may give you an idea of your problem, but any engineering statements to "do this" or "do that" to rectify the problem is a little premature, to say the least.

Abdel Halim Galala's 2mm : if you are questioning this it tells me that you are not an engineer, or you know nothing about welding.

There is clearly a problem with the pre-fabrication which needs to be sorted out by the company who did the work, and any deviation from the original design must be properly approved.

@ Hilton,

In regards to the unprofessional comment regarding Mr. Abdel Halim Galala , I suggest you review his profile and some of his posts. He may possibly be one of the most highly respected Mechanical Engineers on this site, particularly in the Oil and Gas Industry, which obviously includes tanks, piping, pressure vessels, welding, etc. I know personally I have always found his comments both professional and informative. However, you will probably not receive a rebuttal from him, as I am sure he possesses far too much integrity to continue that particular thread. I however, do not sir !

You have completely misread Hilton's post.

Tuck your umbrage back in your pants

35point5,

You are absolutely right my friend. Way too much Chivas Regal. My humblest apologies to all.

Hi,

This problem may be related to either improper fabrication or installation which is more common. Normally good manufacturers provide sending specialists to perform such a job and issue a certification after installation, testing and commissioning depending on the contract between parties. Others provide detailed complete installation manuals and issue certification after testing by them or by third agreed party.

I prefer to contact the manufacturer for such a problem,normally curved plates deform under its weights that is why you get such gaps. So, special supports should be provided during erection.You must aware of sequence of installation.

Note:The filler material and method of welding is of great importance.

Good luck

Eng. Azat A. Rifat

"You waited until the gap grew to 25mm before figuring that something isn't right???!!!![

Dare I ask how you were bridging this gap when it was still "only" 5, 10, 15 or 20mm?

I hope, for your sake,it has only been tacked so far

Refer to the designers, check the fabricated components for dimensional conformity to design, check the method of alignment....

Delegate this to someone who knows what they are doing. Please.

General engineering practice allows a double/single bevel groove butt joint (depending upon the plate thickness or design) with a root gap of 2 to 2.50 mm throughout the length of the weld, let it be a horizontal (or) vertical weld.The process being used is SAW or SMAW / MMAW.

In your case the fabricator has not done a proper job, leaving an uneven/excessive cutting gap in between the matting edges. It happens because of poor planning or due to lack of skill on part of the gas cutter.

Each segment of plate prepared for welding will be app. 2.0 mt in length and 0.6 mts in width. This can vary again as per the design. Each row of plates are staggered to provide "T" type joints so as to avoid stress concentration at junctions.

Hence, yours being a new tank under fabrication, you can think of re-cutting all the plates using a skilled gas cutter, under supervision and as per the weld joint design. Maintain an even width for all the plates again. Use a semi-auto gas cutting machine instead of hand cutting the plates, to get a straight line cutting and also to provide even gap throughout the weld length.

This will help to remove the excessive 25 mm or so gap existing presently. Re-bevel and carry out the welding in normal way. The resulting weld will be strong and acceptable as per the code of fabrication.

May be, you may require one extra row of welding, but It will help you to fabricate the tank in normal way to maintain the tank height and volume.

All the best,

Sridhar.

I agree. It seems that the cuts may have been made on the inside of the marked dimensions, AND the width of the cut itself was not allowed for in the first place.

That's why I advised to stop payment and deploy a registered professional to the problem. If the weld quality matches the cut quality, I don't think the patches previously suggested are appropriate in this case.

I don't aim to belittle 'third world' manufacturing here...just helping to avoid the inevitable disaster if this job is botched.

Are you sure that the geomery of the segments are correct? Check the inner radial dimensions of each equatorial segment. I believe the sphere is in erected position and you have scaffolding in the inner side. If the dimensions of each segment are not the same there is a fabrication mistake. The welding gap must be given in your WPS. It means that you have to erect the segments by leaving the necessary welding gap between the bevels (most probably you have X type bevels). You must adjust the contour of the edges of the adjacent segments by lock and wedge devices (in necessary numbers along the whole lenght of the edge).

I recommend that the manufacturer checks the dimensions of the segments as per the fabrication drawings. If the dimensions are correct you can adjust the contours of the edges by wedges as explained above.

Don't forget that after finishing of the vertical seams of the eqatorial segments, there shall be a shrinkage due to welding. This may affect the gaps between the upper and bottom segments with the eqatorial ones.

This thread suffers from a common CR4 problem: the OP is not giving enough detailed information for competent comments to be made. What has been done to determine the cause of the problem? What is the nature of the support structure? Is it a golf ball on a tee? Is it a web? Is it internal? external? both? What is the shape of the plates, with sizes? We have guesses on all these subjects, with the correct knowledge dramatically varying the correct answers. It sounds like this could be a serious complex engineering problem, or someone tinkering in their backyard. Only the cost and size gives us a clue. The idea that someone admitting that they misread a post and wants to retract a comment should be considered to be off-topic on a subject this serious is truly mind-boggling. I there a way for serious issues to allow for more information in the OP?

All True - & it could be just a local area due to poor tacking practice.

Seems that the OP has left the building.