Flush type opening in API 650 Tank

[nabeel3]

Dear All
Is it Mandatory to provide a Flush type shell Man way opening or a flush type clean out fitting in a API 650 tank? Also, what is the purpose of thermal stress relief in such a connection (Section 5.7.4)

 

[IFRs]

It is not required but if the purchaser wants one it shall be done in accordance with API 650 including the thermal stress relief which does exactly as it says - heating and cooling the assembly to appropriate temperature and durations to remove residual stressed from welding.