ASME Section VIII Impact test in UCS 67 1

[andrespastor1987]

Hello

I need your help to solve a discussion. I am working in the fabrication of a pressure vessel under ASME VIII Division 1. The cylindrical shell have a thickness (1/2 in.) and material that not require impact test by UCS-66. However the hemispherical head have a thickness (1 in.) that require impact test by UCS-66. The two parts are welded by a tapered joint, where the weld thickness is 1/2 in. In this case, the governing thickness is 1/2 in.. Do the rules of UCS-67 require qualification with impact testing of the WPS to be used for welding of two parts if neither material require impact test in this governing thickness (1/2 in.)? Many thanks and excuse me by my english. It is not my native idiom.

 

[weldstan]

Why would a hemi-head be 2" thick? They would normally be 1/2 the thickness of the shell?

 

[andrespastor1987]

I am sorry, it was a mistake. The head thickness is 1 in. Thanks¡¡¡

 

[weldstan]

Again why 1-inch? The required thickness would normally be 1/4". Or is there some other reason for the overly thick hemi-head?

If the base materials do not require impact testing, it is not required that the WPS be impact test qualified.

 

[andrespastor1987]

The answer is easy. The thickness are defined by design. The ASME requirements are minimum requirements. However, this is not the main question. I can see that you dont understand the question, which is regarding to the impact test in the WPS qualification. Moreover, your answer about impact test in the WPS is incorrect. Please check UCS-67(a)(3) to see a example. Many thanks

 

[david339933]

The governing thickness is 1/2" as per UCS-66.3(a). WPS impact testing is not required, based on the information given. Of course if MDMT is below -20F, UCS-67(a)(3) is applicable.

 

[andrespastor1987]

david339933, Is true that, based in the governing thickness, the impact test are not required in the WPS qualification. However, the shell require impact test by design and UCS-67(a)(1) say that "impact test are required when either base metal is required to be impact tested by the rules of this Division (ASME VIII Div. 1)". In this point is my problem.

 

[david339933]

I don't understand in your OP you say that the 1/2" shell does not require impact testing. If it requires impact testing by client requirement...the code does not address such issues.

 

[andrespastor1987]

david339933, The shell (1/2") does not require impact by UCS-66. However, the head (1") does require impact test by UCS-66, but does not require impact test to the governing thickness (1/2"). In this case, is it necessary the impact test in the WPS qualification?
Perhaps the problem is my english. Please check this information to understand better my question:
MDMT:-40ºC
Head: SA-516 Gr.70N, thickness = 1" (25 mm).
Shell: SA-516 Gr.70N, thickness = 1/2" (13 mm).
Governing Thicness (weld): 1/2" (13 mm).

Does head-to-shell WPS require impact test?

 

[david339933]

The basis for impact testing is stated in UCS-66. "Each component shall be evaluated for impact test requirements based on its individual material classification (SA-516-70N which is Curve D), governing thickness as defined in {1}{2}{3} below and the minimum design metal temperature (-40C/-40F)." So with this material and MDMT, you can have a governing thickness of approximately 3/4" based on Table UCS-66 without impact testing. Straight line interpolation would give an exact value, but in this case an approximate of 3/4" is sufficient.

So the remaining item is to establish the governing thickness based on UCS-66 {1}{2}{3} as stated above.

{1}(a) refers you to UCS-66.3(a) as I stated in a previous post, giving a governing thickness of 1/2".
{2} deals with castings, so not applicable.
{3} deals with flat non-welded parts such as bolted flanges and flat heads, so not applicable.

Therefore {1} rules your governing thickness (1/2") and it is below the thickness required for impact testing (3/4"). Therefore impact testing of the material is not required, and subsequently not required for WPS qualification as well.

 

[andrespastor1987]

Many thanks david339933 for your answer.