Why PWHT can be replaced CTOD test

[xuanthien]

when i read some project structure spec, they require CTOD test for thickness above 60mm but we no need to do that, if you replace PWHT.
pls explain to me understand why PWHT can be replaced CTOD test

 

[metengr]

Something is lost in translation. Post weld heat treatment cannot substitute for crack tip opening displacement test (CTOD). Possibly you meant the CTOD test can be avoided by performing PWHT. This depsneds on the specification, code or standard you are using.

 

[xuanthien]

Dear Metengr,

Why CTOD test can be avoided when we performing PWHT, What is root case.

 

[metengr]

I can provide one situation where credit is given in pressure vessel design (ASME Section VIII, Div 1) when PWHT is performed where it is not required by Code. The application of PWHT provides a reduction in minimum design temperature of 30 deg F where Charpy impact testing is unnecessary. Again, this is an example you might understand. The credit for PWHT is because it reduces harmful residual tensile stresses from welding and fabrication and reduces hardness in weld heat affected zones, thus increasing the tolerance for defects (toughness).

 

[Guest102023]

Help yourself by retaining a specialist consultant. Most metallurgists and even many welding engineers have no experience with CTOD testing.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"