CVN Impact Test
CVN Impact Test
(OP)
Why do we need to do CVN impact test at –46 degrees Celsius to qualify a WPS?
Is it a contractor requirement or ASME Code or AWS D1.1?
Is it a contractor requirement or ASME Code or AWS D1.1?
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RE: CVN Impact Test
RE: CVN Impact Test
My question is just a general one. I mean, is there anywhere at AWS D1.1 or ASME Code, refering to CVN impact test at -46 degress Celsius?
Or it's just a contractor/design requirement? and why -46 degrees?
Thanks in advance for your help.
RE: CVN Impact Test
RE: CVN Impact Test
This is probably a really stupid question (what I'm best at), but why not just ask the specifier why they specified that?
Hg
RE: CVN Impact Test
If you design a structure for climatic area of -46°C and up it might be a reason for that requirement.
ASME VIII (and AWS D1.1 too) being an imperial units code uses specific temperature values in °F.
Some materials are prequalified for use at -50°F (-45.5°C) as per ASME VIII Div 1 UCS 66. The impact exemption curves are also based on round °F values. These temperature values are customary thresholds for impact testing temperatures.
Your -45 or -46°C comes directly from calculation from °F.
As HgTX rightly says "if in doubt - ask".
And by the way: couldn't you use prequalified procedures?
RE: CVN Impact Test
RE: CVN Impact Test
JacekM is right on with regard to the -46C CVN test origins that you have described; however, the minimum design metal temperature (MDMT)is specified by the Engineer/Owner. When the Engineer/Owner defines an MDMT of -46C for items fabricated from ferritic steels, ASME Section VIII, B31.3, etc. requires the welding procedure to be impact test qualified at that temperature.
RE: CVN Impact Test
Andy