The full scale testing of two elastomer components of the Snorre TLP tether system, the radial bearing and the conduit seal, is presented. The tests verify that the design requirements specified to ensure proper functioning during the 30 years service life are met.
Elastomers play a key role in the design of tether systems for Tension Leg Platforms (TLP's). Figure 1 illustrates the main load bearing components of the tether system for the Snorre TLP, which will be installed in 1992 on the Saga Petroleum a.s operated Snorre Field in the Norwegian sector of the North Sea. The anchor latch and the cross load bearing (CLB) both incorporates a flexjoint which accommodates for angular displacements due to TLP offset. The CLB shown in Figure 2 also incorporates two other elastomer components: the radial bearing which transfers the horizontal component of the tether tension into the TLP hull, and; the conduit seal which allows the tether conduits to be dry during operation. McIntosh and Stevenson (1988) report good in service performance of the similar elastomer components of the Hutton TLP. The only exception has been the conduit tube seal for which a number of in service failures are reported. This problem has recently been solved by installing new conduit seals of a modified design. This paper presents the full scale testing of the Snorre CLB radial bearing and conduit seal. The test programs were designed to provide the necessary data to validate essential functional and strength aspects of the designs. Design data of the two elastomer components are presented in paragraphs below. For descriptions of the Snorre TLP platform and tether system, references are made to Gaul and Pettersen (1989) and Hannus et. al. (1990). Conclusions are presented in section 4.