seismic design of subsea jumper per iso: part i- preliminaries

Subsea rigid steel spools (spool) are used to connect subsea equipment using diver-less connectors. spools must meet functional requirements such as pressure, temperature, thermal expansion, environmental load, installation loads, lack of fit (misalignments), etc., yielding numerous loading conditions. the installation accuracy that the installation contractor can achieve is another issue. thus, it is inevitable that numerous geometries to be investigated and perform several iterations in search of a suitable configuration. the no-burst concept, in conjunction with a high integrity pressure protection (hipp) system, leads to heavier spool wall thickness, hence less structural flexibility which in turn increases reactions on the subsea connectors, which in turn is transferred to the adjoining equipment. add to this complexity, the seismic qualification requirement if a jumper is in an earthquake-prone area. this is the first part of a three-part paper that discusses experiences gained in designing spools in 500m of water. the primary focus of the paper is on seismic design, but other issues are discussed including loading & load combinations, increasing the structural flexibility without lowering the natural frequencies; limitation imposed by the subsea connectors, the neighboring equipment loads, and tolerances. generally, the capacity envelope of connectors will govern most of the time. these papers build on the existing literature and liberally draws from them. the objective is to summarise and bring together existing research data needed to design subsea rigid spools.