[MW:16792] Re: Difference between 100% RADIOGRAPHY & Full RADIOGRAPHY

Item 1: All butt welds in vessels used to contain a lethal substance (UW-11(a)).Lethal substances have specific definitions in ASME Code in UW-2 and it is the responsibility of the end user to determine if they ordered a vessel that contains lethal substances.

Item 2: All butt welds in vessels in which the nominal thickness exceeds specified values (UW-11(a). You can find these values in subsection C, in UCS-57, UNF-57, etc. For example, this value for P-No.1 in UCS-57 is 1 ¼ inch.

Item 3: All butt welds in an unfired steam boiler with design pressure > 50 psi (UW-11(a)).

Item 4: All category A and D butt welds in vessel when "Full Radiography" optionally selected from table UW-12(column (a) in this table is selected); and categories B and C which intersect Category A shall meet the spot radiography requirement (UW-11(a) (5) (b)).

The point is this: items 1, 2 and 3 are similar, but item 4 is completely different. In items 1, 2 and 3 it is mandated by code; to do full radiography in all butt welds in vessel so it means it is mandatory for designer to select column (a) in UW-12 table.

But in item 4, there is no mandating rule. A manufacturer with its own decision has chosen to use column (a) in table UW-12 for full radiography.

So here there is a concession or bonus to manufacturers for categories B and C.

On Saturday, February 16, 2013 10:41:36 AM UTC+5:30, Ashay Kadam wrote:

Full radiography is equivalent to RT-1 stamping as defined in UG-116. As you can see, butt welds in small (not exceeding 10"), thin wall nozzles are not required to be RTed.

100% RT means all butt welds, including those in small nozzles will have radiography examination in full length. This is not a code requirement. It is usually a service requirement. Vessels in wet H2S service often require 100% RT.

Full radiography need not be 100%  See UW 11(a)(5)(b). 

If you review item 1, 2 and 3 one more time, you will see that the pressure vessel RT tests are related to the type of welds and services.

You can see the pressure vessels in these items are critical from a safety point of view, one contains a lethal substance, the other one has a high thickness, which implicates high pressure, and the last one is an unfired steam boiler. But item 4 has no criticality like the other items have.

But you should note all 4 items have been categorized in full radiography clause( U-11(a)), so to differentiate item 1, 2 and 3 from item 4, the RT symbols are used in Code (UG-116).

RT 1: Full radiography mandate as per Items 1, 2 and 3, (E=1), All butt welds-100% radiography

RT 2: Full radiography nonmandate Item 4 (E=1), Category A and D butt welds full length radiography and category B and C butt welds spot Radiography- Full radiography

RT 3: (E=0.85), Spot radiography butt welds

RT 4: (E=0.7), Partial / No radiography 

 

On Wednesday, October 13, 2010 10:56:24 AM UTC+5:30, hemant solanki wrote:

Dear All,

Could you please tell me what is the difference between 100% radiography & fully radiography? Is it clarified in ASME code?

Thanks,
Hemant Solanki

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