794 KB21 KB199920252016Chibueze, Nnamdi OnochieOkoli, John UmunnaOssia, Chinwuba Victorletnik:62številka:nr. 12str. 751-756ISSN:0039-2480COBISSID_HOST:15164955URN:URN:NBN:SI:doc-YDCF8GWNenZveza strojnih inženirjev in tehnikov Slovenije etc.Strojniški vestnikGvinejski zalivjeklene viseče dvižne ceviJONSWAPOchi-Hubbletočka stika z morskim dnomutrujanjeOn the fatigue of steel catenary risers|Steel catenary risers (SCR), though an appropriate and cost effective tool for deepwater development, are fraught with difficult fatigue challenges derived from loads due to the actions of wind, wave and current. In this study, a model SCR-AB with end-A attached to floating production, storage and offloading vessels (FPSO) and end-B anchored to the seabed was created using OrcaFlex © finite element software. Also attached to this model is a 10 4 kg 6D buoy of 6 m height and volume 20 m%, which was fixed to the SCR at 900 m of the riser length. The various sections of the homogenous 2200 m long SCR pipe include 50 m flex joint section, 350 m strake length, 1300 m riser pipe length, and 500 m flowline section. Metrological ocean data, geotechnical data and SCR data were input into the model which was subjected to the Ochi-Hubble and Joint North Sea Wave Project (JONSWAP) wave spectra. Analyses to determine the influence of fatigue damage on the model was made using system simulation under both static and dynamic modes. The results for JONSWAP wave spectra showed the fatigue life of the SCR to be 1.8 years at the touch-down-point (TDP) while that of Ochi-Hubble wave spectra showed a fatigue life of 13.6 years at SCR TDP, differing by a factor of 7.5. Furthermore, the S-N curves obtained from both wave spectra corroborated an inverse relationship between Stress values S and the number of stress cycles to failure N on a log-log scaleObstoječa črpališča se počasi praznijo in iskanje nafte ter plina se zato seli v globoke vode in v zahtevnejša okolja. Vse večje potrebe po energiji tudi spodbujajo razvoj naprednejših tehnologij. Jeklene viseče dvižne cevi (SCR) so se uveljavile kot rešitev za globoka in ultragloboka črpališča predvsem zaradi svoje ekonomičnosti, obstojnosti proti tlaku, tehnično preproste montaže in možnosti priključitve na različne gostiteljske ploščadi. Zato obstaja potreba po raziskavah utrujenostne trajnostne dobe SCR v Gvinejskem zalivu, kjer uvajajo te cevi na osnovi zbranih podatkov iz Severnega morja in iz Mehiškega zaliva. Jeklene viseče povezovalne cevi so občutljive na dinamiko gostiteljske ploščadi in so podvržene utrujanju. Uporaba SCR pri polpotopljivih ploščadih v globokih vodah prinaša posebne konstrukcijske izzive zaradi velikih amplitud gibanja ploščadi pod vplivom valov in velikih odmikov ploščadi, ki jih povzročajo vibracije zaradi vrtincev (VIV), gibanja zaradi vrtincev (VIM), veter in počasni tokovi. Močno zibanje ploščadi tako povzroča uklon in utrujanje v območju stika dvižne cevi z morskim dnom (TDP). Pri načrtovanju SCR je izjemno pomembna izbira ustreznega spektra valovanjaTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Ljubljani, Fakulteta za strojništvo