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Plumbness & Roundness(API 620)

Plumbness & Roundness(API 620)

I am looking for complete Procedure of measuring Plumbness & Roundness setforth in API 620 with details preferably with photos.
Thanks in advance,

RE: Plumbness & Roundness(API 620)

What is it that you are asking for?

Steve Braune
Tank Industry Consultants

RE: Plumbness & Roundness(API 620)

Actually, there are some 60 m3 Bulk tanks of drilling plant, and i'd like to calculate their permissible plumbness and roundness of them as per API 620.
If there is any further information you require about mentioned tanks, let me know.

RE: Plumbness & Roundness(API 620)

Are these tanks under construction or are they existing tanks that are being inspected?

Steve Braune
Tank Industry Consultants

RE: Plumbness & Roundness(API 620)

These tanks were constucted before,but due to lack of inspection over them,poor quality of workmanship and making the mistake of choosing some improper materials and filler metal in some parts,the company decided to repair everything such as welding and replacing proper materials and finally checking of their Plumbness and Roundness.


RE: Plumbness & Roundness(API 620)

I can't help you with a specific procedure, but I would advise caution before jumping into something like this.  If the tanks have been built and hyrotested, it might be better to leave them as is than to repair them.  You could spend a lot of time and money with no real improvement in safety.

If you take a new "perfect" tank, and start cutting out seams and rewelding them, or removing plates and rewelding them, you'll induce a lot more distortion than was done in the initial building of the tank.  When the tank is being built, and you weld one seam, other edges of that plate are free to move somewhat, but not so when it's all welded out.  This makes it difficult to improve a tank by additional work.

One of the common ways to round up a tank is to weld stiffeners in it.  But the API-650 interpretation of Nov. 9, 1994 prohibits this as a means of achieving tolerances.

If I remember correctly, API-653 allows higher tolerances for tanks that have been cut down and re-erected, and you might want to consider applying these tolerances.

RE: Plumbness & Roundness(API 620)

Thanks very much JStephen for your comments,Tanks have been repaired and as you mentioned,decidedly distortion is inevitable,for this reason ,we would like to report the amount of distorion to the client so as to ask him whether this amount is acceptable to him or not.Therefore,i am looking for complete procedure for calculating this distortion.

RE: Plumbness & Roundness(API 620)

I'm confused.  Is it 620 or 650 or 653 you are using?  Your initial post said 620.  Later posts referred to 650 and 653.  Is the tank cylindrical or some other shape?  Do you want to measure from the inside or outside?  Distortion is better measured rather than calculated in my opinion.  Measuring the distortion in a tank is fairly straightforward and the equipment can be inexpensive.  Where are the tanks located?  I may be able to set you up, or at least show you one way that I have done it many times.

RE: Plumbness & Roundness(API 620)

As i mentioned in my first message, I want to measure Roundness and Plumbness of Cylindrical storage tanks as per API 620.Measurments can be carried out either inside or outside. Tanks are located inside columns of Drilling plant.I know the equipment such as thread is inexpensive but i want to know how to measure Plumbness and Roundness.
It would be highly appreciated to show me How.
Thanks in advance!

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