BSEE has received the draft Argonne National Laboratory report, “Evaluation of Pressure Rating Methods Recommended by API RP 17TR8,” and pending a peer review of the report is making available an advance draft report. The peer review of this report will be conducted according to BSEE’s scientific integrity procedures.
Recently, industry has begun to design equipment for high pressure and or high temperature service using the methodologies described in API’s Technical Report 17TR8, “HPHT Design Guidelines”. Two of these methodologies are new to the oil and gas community and the modeling method(s) above a certain threshold are of greater concern. Therefore, two special test bodies were designed and manufactured then hydro-tested to failure; and, they were examined under both elastic-plastic and linear-elastic FEA using ASME procedures. Pressure ratings were based on methods allowed by 17TR8. The margins of safety from all the rating methods were calculated and compared.
The study raises questions concerning the validity of the criteria and assumptions that are currently being used in the design of HPHT subsea equipment. The report concludes that the Division 3 elastic-plastic method is not recommended for HPHT subsea equipment as published with a 1.8 design-load factor. However, additional tests and/or validation data could still be used to provide justification for the 1.8 factor provided the data supports it. The Division 2 elastic-plastic method with a design-load factor of 2.1 is more in line with historically successful equipment for calculating load ratings for HPHT subsea equipment. For a Division 2 linear-elastic analysis, it is recommended that stress intensities and not von Mises stresses be compared with allowable stresses. Additional recommendations for future research are also suggested.