Pressure Vessels and Thickness Measurements

Please tell us what exactly you are planning on doing. Are you in the design stage of a vessel? Is this an already inservice vessel that you are inspecting? Are you a material supplier?

Article 23 gives the specifications for testing new material supply and is not strictly thickness measurement, but also testing for discontinuities such as delaminations; usually as a supplementary requirement between the purchaser and manufacturer specified in the order. If this is what you are intending to use the Article 23 standards as - I would suggest (re)reading each individual specification because it is all spelled out in them.

In general ASME Section V tells you HOW to do things, while the other sections tell you WHAT you have to do.

Xmech, thank you for replay

it is in service pressure vessel, please try to read article 5 T-544 thickness measurement: then see a) SE-114 and b) SE-797

please correct me if wrong.

by the way, I am the client

regards

ASME codes are for new construction only (except for FFS below), for inservice inspection you should look to:

• National Board NB-23
• API 510
• API RP 579-1 / ASME FFS-1

(I can't find T-544, I think it must be a typo, even in the Index; it should be T-574)

Hello, First I would suggest hiring a specialized NDT company to calculate the minimum wall thickness allowed for each vessel, take vessel thickness readings and to produce inspection reports. It should be a company that is used to working with ASME and API codes and standards. I use a company that has in house engineering department so a PE does the min. wall calculations and signs off off on all work. If you only have a few vessels you can do it yourself but I would stress having a certified ASME/API inspector and a PE review and sign off on all inspection reports as being correct.

The way you pick the places to scan are varied and it is according to the wear and corrosion characteristics and history of the particular vessel or what it is used for. As a general rule you will pick a certain sized grid and take UTT readings at equal spaces to get a general wear pattern for a particular vessel. Once you have identified high wear areas then I would suggest that you narrow up the grid in these areas so you can get more detailed information there. Also if you get a reading below your flag point (the min wall thickness plus what ever safety margin you decide on) I would start at the thin point and tighten up the scan grid to determine how big an area you are dealing with. After you build a little history on your vessels you can determine at what intervals to do UTT on each vessel. I have some "high wear" vessels that I do a UTT every year and I also have some tanks that I do only every 5 years. All together I look over the inspection of 630 tanks and vessels where I work and I record everything in a computerized vessel inspection data base so that I can pull up any information on any particular tank/vessel very easily.

Thnaks Xmech and Pipe Welder

Mr. Xmech, could you please tell me Why we can't use ASME for Inservice vessels??

it is not mention in the ASME BPV that it is for new vessels( i have ASME PBV section V 2001) and T-544 it is on page 115 as follow:

Artical 5 Ulterasonic Examination Method

T-544 Thickness Measurment

see the picture

Mr. pipe welder, I am just responsible to submit a request to the NDT company (i will not calculat anything) just to tell the NDT comapny which code they have to follow( it is about 22 Vessels need to be check)

http://www.up07.com/up8/download.php?filename=268065a3c1.jpg

what I wrote to them that, the inspection must be according to ASME BPV section V and API 510

and I ask for location where the thickness to be measure just to know either they will measure total surface area or part of the vessel.

Ahhh ....... there is T-544, I was looking in 2004 editions and newer (when they changed the chapter they didn't change the Index - it is still wrong in the newer editions )

You can look to the scopes of the various ASME codes to determine that they are for new construction, even in the titles: VIII Division 1 Rules for Construction of Pressure Vessels.

And from the scope of ASME Sec V:

-----------------------------------

T-110 SCOPE

(a) This Section of the Code contains requirements and methods for nondestructive examination (NDE), which are Code requirements to the extent they are specifically referenced and required by other Code Sections or referencing document ..............

-----------------------------------

And this is where we get into the 'trap' of inspection codes where they often refer to the "original code of construction"

As PipeWelder stated there are no blind rules for inspections - it depends on each particular vessel, operations, and service - determined by experience, and often upon initial inspection (if a large pitted area is spotted by inspectors, it is prudent to look into it, even if not in the original scope of work).

From API 572:

--------------------------

All areas of the vessel should be inspected for corrosion, erosion, hydrogen blistering, deformation, cracking, and laminations. A careful record should be made of the types and locations of all deterioration found.

Thickness measurements should be taken at those locations that show the most deterioration. When deterioration appears to be widespread, enough readings should be taken to assure an accurate determination of the remaining thickness. When deterioration is slight, one thickness measurement on each head and each shell course may be sufficient on small vessels
but more measurements should be taken on large vessels. Ultrasonic instruments can be used to obtain the necessary measurements. Other special methods of measuring wall thickness are discussed in 10.5.

Thanks alot Xmech,

Now I got confused, what is the difference between API 510 And API 572?

They are similar, but API 510 is a "code", and API 572 is a "Recommended Practice"

API 510

API 572

i think that the most important thing is to understand the type of service of the vessel and the types of damagae mechanisms that you've to expect: corrosion, erosion, stress corrosion, blistering.....

then you can decide where, what typs, how much and how to make your NDT..

S

corrosion prevention

Dear All, Thank you very much for help, but i ahve already told the NDT company , that inspection will be according to ASME BPV section V and API 510

now, I can't change but i will wait his reponse regarding this