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API Standard 6X: Design Calculations for Pressure-Containing Equipment

API Standard 6X: Design Calculations for Pressure-Containing Equipment. New Draft Standard under Subcommittee 6. Task Group Membership. John Fowler – On-Line Resources - Chairman Jim Britton – Cameron – 17D and 16C Paul Bunch – Cameron – 16A and 17D Jean Brunjes – GE – 6A

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API Standard 6X: Design Calculations for Pressure-Containing Equipment

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  1. API Standard 6X: Design Calculations for Pressure-Containing Equipment New Draft Standard under Subcommittee 6

  2. Task Group Membership • John Fowler – On-Line Resources - Chairman • Jim Britton – Cameron – 17D and 16C • Paul Bunch – Cameron – 16A and 17D • Jean Brunjes – GE – 6A • Bill Carbaugh – GE – 16A • Maynard Chance – West Engineering – All specs • Chris Johnson - NOV – 16A • Jim Kaculi – DrilQuip – 17D • Chris Kocurek – Cameron – 17D • John McCaskill - Expro – 16C • Nigel McKie – FMC – 17D • Mark Miser – DNV – All specs • Ramon San Pedro – Stress Engineering – all specs • AlirezaShirani – Cameron – All specs

  3. History and Objective • API 6A, 16A, and 16C referenced the ASME Code Section VIII Division 2, 2004 Edition, Appendix 4. • Since referencing an obsolete spec is awkward, an Annex (Annex I) was prepared for 16A capturing the method from that ASME Appendix. • Subcommittee 6 proposed that the method be put in a separate document to assure uniformity.

  4. Task Group Charge • Create a new API standard documenting the rules of the ASME Code, based on Annex I. • Problem: 16A and 6A used different allowable stresses.

  5. Resolution • The task group consensus was to use the rules of 16A, since going to the slightly more conservative 6A rules would penalize 16A/16C users who had designed to higher allowable stresses. • The 90% of Sy used in 16A and 16C is the same as the limit in the 2004 ASME Code Section VIII Division 2 • Using only the yield strength as a basis follows Section VIII Division 3 practice.

  6. Changes to Annex I • Several revisions were made to the Annex I document to clarify the requirements, including several changes to the wording.. • The uses of limit analysis and elastic/plastic analysis were clarified. • The requirement on the sum of the three principal stresses was clarified as to the calculation basis.

  7. Status of the draft Standard • The TG finalized the draft and agreed it was ready for ballot. • API edited the document into standard API format and returned it to the TG for review. • After review the draft standard was be sent out for ballot by SC6, with an April 30 deadline. • SC 16 and SC 17 solicited comments from their member companies, which will be considered along with those from SC6 members.

  8. Status of the ballot • The ballot passed, with four negative votes. • Over 150 comments were made, which the TG has resolved. • A TG meeting was held May 14 and the negative voters were invited to attend. • Three of the negative voters agreed to withdraw their negatives, and the fourth was unable to attend. • Another TG meeting was held June 13, and all negative ballots have been resolved.

  9. Revisions resulting from resolution of the ballot comments • Numerous editorial changes have been made, including moving material around to clarify requirements and follow the API Style Guide more closely. • An introduction was added to give background of the standard. • Definitions, abbreviations, and symbols were added, as well as equations showing requirements. • Stress components may be combined using vonMises equivalent stress (vs. stress intensity) if permitted by the product specification.

  10. Revisions, cont. • Removed the note that if the material has a high yield/tensile ratio a lower Sm value may be used. This makes the Sm determination exactly like in 16A and 16C. • “Shall” substituted for more vague language several places to clarify that requirements are required. • Title changed to “Design Calculations for Pressure-containing Equipment.” • An “Extreme Conditions” paragraph will be added providing the “k” factor from ASME code.

  11. Next Steps • After agreeing on disposition of all comments, the edited document and comment matrix are being returned to API. API can then, depending on the extent of the changes: • Accept the changes and publish the document • Recirculate the document for further comment • Re-ballot the document • Hopefully a new standard will be ready to be referenced by the new editions of 6A, 16A, and 16C.

  12. Follow-on actions after publication of the new Standard • Specifications 6A, 16A and 16C should revise their design section to direct the designer to this new standard instead of the 2004 Code. • This may require several changes in the body of the specifications. • Since 17D refers to 6A for design requirements, no change is needed. • The 2004 ASME Code Section VIII Division 2 can be removed as a referenced standard, and Standard 6X added.

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