API TR 6AM
Technical Report on Material Toughness
|Publication Date:||1 January 1995|
INITIAL TASK GROUP CHARGE
The July 30, 1986, API Subcommittee Meeting Minutes contained the Material Toughness Task Group Charge. It comprised Attachment 6. The charge(s) were:
Evaluate the material toughness requirements for API Specification 6A materials, for acceptance worldwide.
Perform a survey of the industry and review literature for material toughness values based on technical data and design requirements.
Devise a method or action to resolve difference between the European and U.S. opinions on material toughness.
Establish work groups to prepare appropriate revisions to API Specification 6A for ballot by June 1987.
AMENDED TASK GROUP CHARGE
The Task Group came to several conclusions based on the charges:
Charge 1 : The Task Group could not evaluate worldwide parameters necessary for acceptance of API Specification 6A materials toughness requirements. The justification for other groups' requirements was not readily obvious.
Charge 2: The members of the Task Group comprised a cross section of industry users and manufacturers which have worldwide exposure. The Task Group could not document any materials related failures on equipment whose materials had met the API Specification 6A requirement of 15 ft-lb. Ali documentable failures did not meet the existing requirements. A literature survey revealed no technical data or design requirements which are relatable to API Specification 6A equipment design or usage.
Charge 3: The differences between U.S. and European opinions on material toughness relate directly to a difference in philosophy. There are several differences, but the major difference is that the Europeans feel that the Charpy value relates to design while the U.S. opinion is that the Charpy test is a quality assurance exercise in sorting out "rogue materials." All other differences stem from that major premise.
Unfortunately, the technical justification of either of the requirements is unclear. The historical evidence indicates that both approaches are conservative since no API Specification 6A equipment failures have been attributed to brittle materials which met the requirements of the existing standards.
Therefore, the Task Group decided to start with a clean sheet and adopted the charge to "Determine what is necessary to prevent brittle fracture in the field."
Charge 4: With this charge in mind, the Task Group established work groups for:
a. Literature survey.
b. Literature evaluation.
c. Correlations and calculations.
d. Position paper containing proposed changes.