“How can you be sure your seabed equipment won’t be damaged by overtrawling? There’s only one sure way”, claims Martin East , Head of Analysis at Jee, “…and that’s by tank testing.”
A recent project commissioned by Allseas drew Martin away from his office base and took him to Denmark where he could see his recommendations come to life in a 30 metre by 8 metre flume tank.
“ There are no comprehensive guidelines for designing overtrawl protection. There is some guidance on design loads in one of the Norsok standards, but it’s based on fishing in Norwegian waters and really isn’t applicable in many parts of the world.
“Also, the guidance on structure geometry is really inadequate, so the designer may think that he has come up with something overtrawlable when in fact it’s nothing of the sort ,” said Martin .
“It’s one thing designing the structure from your computer, but it’s quite another to see a scale model react to the different nets and trawl gear it may come into contact with. This really is the only way to come up with accurate design loads.”
At SINTEF’s hydrodynamic laboratory, Martin worked on the overtrawlability of two structures:
• A flowline end termination (FLET) protection structure approximately 35 metres long and 20 metres wide
• An in-line tee (ILT) protection structure, approximately 47 metres long and 16 metres wide
Both of these structures are in about 600m water depth on the West of Shetlands continental shelf.
Recommendations made as a result of the research mean Allseas’ subsea equipment and fishing vessels in the Laggan-Tormore field will be able to interact safely.
“ Tank tests cost money, but the amount they save in protecting subsea kit from damage can be millions of pounds ,” said Martin . “ Like insurance, tests like these make good commercial sense.”
[mappress] Source: jee ,June 09, 2011;