API 650 RT CRITERIA FOR BUTTWELDS

[Muza33]

As per API 650 CLAUSE 8.1.2.2 b

For thinner shell plate greater than 10 mm but less than 25 mm

“In the lowest shell course, two spot radiography in each vertical joints shall be taken”


Now for our tank, shell plate thickness are 10 mm,10mm,15 mm,21 mm,and 30 mm in this case we are already taking 100 % radiography of 30 mm joints ,which is lowest shell course in tank


My concern is for fulfilling “In the lowest shell course ,two spot radiography in each vertical joints shall be taken” for 21 mm shell plate requirement,shall we take two additional radiography in existing 21 mm shell which is not actual lowest clause,or ignore the clause as we are taking 100% radiography of our 30 mm which is actual lowest shell course of tank,


Please share your expert opinions

 

[Muza33]

ALSO

FOR 15 MM AND 21 MM ,30 MM one RT shall be taken in first 3 meter of welds as per clause 8.1.2.2 ? because RT is mentioned for each thickness

,even though already we have done RT done in first 3 meter of 10 mm itself

 

[JStephen]

You do the full RT on the 30mm and omit the 2-shots in lowest course.
Not sure I understand the second question- but each thickness gets the RT in first 3m by each welder.

 

[Muza33]

Jstephen,


Thanks a lot for clarification especially the second answer,

i was not sure whether to take first 3 meter of each thickness of each welder (and even initially didn't consider in my RT scope),as clause 8.1.2 b says to follow clause 8.1.2 a(which applicable for below 10 mm) and not for above 10 mm,so i initially considered RT per 3 m /per welder only below 10 mm