Investigation of API 8 round casing connection performance Part one: Introduction and method of analysis

Journal Article · Sat Jan 01 04:00:00 EST 1983 · Am. Soc. Mech. Eng., (Pap.); (United States)

OSTI ID:5682899

Asbill, W T; Pattillo, P D; Rodgers, W M

The purpose of this investigation was to gain a better understanding into the mechanical behavior of the API 8 Round casing connection, when subjected to service loads of assembly interference, tension and internal pressure. The connection must provide both structural and sealing functions and these functions were evaluated by several methods. Part One discusses the methods of analysis, which include hand calculations using strength of materials, finite element method via unthreaded and threaded models, and experimental analysis using strain gages. Comparisons of all three methods are made for stresses and show that the finite element method accurately models connection behavior. Part Two is concerned with structural performance and the effects of different loadings on pin and coupling stresses. Accuracy of the hand equations is assessed and shows that they can be unconservatively low in the pin. Criteria for evaluating the finite element solutions is given and the maximum safe number of assembly turns is determined for several materials and thread taper fits. Part Three addresses sealability based on contact pressure in the threads. Hand calculations are shown to be reasonable in the middle of the engaged length, but not at the ends where geometric end effects are significant. The threaded model shows that tension decreases sealability by unloading the stab flanks. An equation for calculating torque based on test data and the threaded model is given. Effects of tension and pressure on torque are shown.

• Research Organization: Harry J. Sweet and Associates, Inc., Houston, Texas
• OSTI ID: 5682899
• Journal Information: Am. Soc. Mech. Eng., (Pap.); (United States), Journal Name: Am. Soc. Mech. Eng., (Pap.); (United States) Vol. 83-PET-16; ISSN ASMSA
• Country of Publication: United States
• Language: English

Related Subjects

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42 ENGINEERING
420206 -- Engineering-- Mining & Drilling Equipment & Facilities-- (1980-1989)
CALCULATION METHODS
COUPLINGS
DIMENSIONS
DRILL PIPES
DRILLING EQUIPMENT
EQUATIONS
EQUIPMENT
FINITE ELEMENT METHOD
GEOMETRY
JOINTS
LENGTH
LOADING
MATERIALS HANDLING
MATHEMATICS
NUMERICAL SOLUTION
PERFORMANCE
PERFORMANCE TESTING
PIPES
PRESSURE DEPENDENCE
SEALS
SIMULATION
STRAINS
STRESSES
SURFACE PROPERTIES
SURFACE TENSION
TESTING
THREADED JOINTS
TORQUE
WELL CASINGS