The effectiveness of stationary metal-to-metal seals is investigated with respect to contact pressure and length, load history, and the use of sealing compounds. Laboratory cup and cone tests were carried out, and experimental results were used to develop a sealability criterion. A sealability parameter is proposed and a critical value for it was obtained from experiments. The criterion was validated through full-scale tests of tubular connections and FEA. This criterion can be used for the comparison, qualification and future performance improvements of different metal-to-metal seals, in particular those used in the petroleum industry.

No abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractConventional sucker rods (working under torsion loads) are used nowadays to drive PCP pumping systems (Progressing Cavity Pumps). Conventional rods have been developed to work under alternating tensile stress, not under torsion stress. The use of these rods to drive PCP systems has several limitations and problems.These limitations result in high operative costs for artificial lift systems. Also, in many cases the high capacity pumps commonly used today cannot be driven, because of their high torque requirements.

A model based on elastic-plastic fracture mechanics (EPFM) and plasticity theory, was developed to study the effect of the Yield (Y) to Tensile (T) ratio, Y/T, on the structural reliability of linepipes with part through the thickness (PTT) circumferential defects subject to bend loading. The analysis allows for load or deformation control situations. The results are shown in terms of curves of critical defect size vs. the controlling variable, i.e. load or deformation. For each one of the materials studied, different cases with different Y/T values were considered. Even for the lower limits of experimental data, i.e. larger Y/T, the materials have adequate defect tolerance. A Leak Before Break Analysis was also conducted.

The effect of the yield (Y) to tensile (T) ratio Y∕T on the structural integrity of linepipes with part through the thickness longitudinal defects subject to internal pressure was studied in this work. A model based on elastic-plastic fracture mechanics and plasticity theory was developed for that purpose. The analysis allows for load or deformation control situations. The results are shown in terms of curves of critical defect size versus the controlling variable, i.e., load or deformation. For each one of the several materials studied, different cases with different Y∕T values were considered. Even for the lower limits of experimental data, i.e., larger Y∕T, the materials have adequate defect tolerance.