Threaded connection limit state equations for use in LRFD tubular design
- Mobil E and P Technical Center, Dallas, TX (United States)
- Stress Engineering Services, Inc., Houston, TX (United States)
The purpose of the study was to identify and evaluate the variables that determine the leak resistance limit state functions of API 8-round and buttress connections. This work will be incorporated into Load and Resistance Factor Design (LRFD) equations. Connectors are an integral part any well design program. Therefore, it is vital that they be included in the LRFD design approach. Makeup, tension, internal pressure and dimensional data were among the variables in the evaluation, which was based on finite element analysis, testing and structural mechanics. The leak resistance limit state for round thread connections is defined by contact pressure, stab flank engaged length and coupling yield, while for buttress is defined by contact pressure, stab flank clearance and coupling yield. Leak pressure, as defined by API Bul. 5C3, is a function of makeup and dimensional data independent of thread type, tension, and pipe inside diameter and valid only in the elastic regime. Tension is detrimental in the leak resistance of 8-round connections, but does not compromise buttress leak resistance. Regression analysis was performed on structural mechanics results to produce the highest correlation to finite element results to account for end effects on round thread connections. It was determined by testing that stab flank contact over a minimum length of engagement is not sufficient to prevent 8-round leak, despite sufficient contact pressure level. Teflon impregnated thread compound should be the choice for API buttress. The indications are that optimized makeup should be considered in the leak resistance capacity of API connections.
- OSTI ID:
- 160700
- Report Number(s):
- CONF-950501-; TRN: IM9603%%282
- Resource Relation:
- Conference: 27. offshore technology conference, Houston, TX (United States), 1-4 May 1995; Other Information: PBD: 1995; Related Information: Is Part Of 27. Annual Offshore Technology Conference: 1995 Proceedings. Volume 4: Field drilling and development systems; PB: 688 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Results of Performance Tests Performed on the John Watts Casing Connection on 7" Pipe
Investigation of API 8 round casing connection performance Part one: Introduction and method of analysis