About the test temperature for CTOD test in warm water.

[liuyuxi]

We know that CTOD test can be used to waive the PWHT. For offshore platform in high latitude, we normally use DNV requirement to determine the CTOD test temperature:For members above water should be the lowest air temperature, For members below water should be zero(freeze point of water).

This time we are working on a platform in a warm area(lowest air temperature 20 Celsius degree, lowest water temperature about 10 Celsius degree). If we still use the DNV rules, then a zero degree test have to be performed, but it is unreasonable(too low).
So which one should be used:15,10 or zero?
Any other codes have relative requirements?a

 

[Carburize]

Will your proposed materials, welding processes etc meet the requirements at zero C? If so, do the CTOD tests at zero and avoid the conflict. If not,and a 10 or 15 degree temperature rise is necessary to meet the requirments, then they sound marginal for the application!

 

[liuyuxi]

Thank you Carburize!
The Fabricator have a CTOD test in the previous project(same material, same steel mill, same WPS) at 15 degree.
So they want to reuse the test result. I think it is not meet the DNV code requirement.

 

[TVP]

You should definitely qualify the work using 10 C, not 15 C.

 

[sayee1]

Using just CTOD tested PQRs for waiving PWHT is a crude method. The best method is to go for a fitness for purpose evaluation using ECA.
The latest rev of Total specs GS-STR-301 very nicely addresses the logic to be followed for impact tests, PWHt and/or CTOD.
A 0 Degree CTOD test is not unreasonable with the standard type(s) of consumables used in fabrication and erection of offshore jackets/platforms/pipelines. I feel "0" would be the most appropriate test temperature in your case, because you are not doing any fracture mechanics/fitness for purpose evaluations. If I were the client welding engineer, I would enforce a new procedure to be qualified- wouldn't accept a previously qualified procedure in the case that ECA not being performed, and ask for the testing @0 Degrees C.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[liuyuxi]

Thank you Mr. Sayee Prasad R! I have learn a lot from you.