Mooring systems on floating production systems with a design life of 15 years can still be in service two decades later. So, how do industry operators balance the costs of maintenance and downtime against the risk of failure?<\/p>\n
It\u2019s an issue that is gaining in importance because advances in drilling and production technologies are leading operators to deeper and more remote locations. This in turn is creating a greater demand for older facilities such as FPSOs.<\/p>\n
\u201cWe deploy imaging technologies to identify a problem before it becomes a problem,\u201d said Richard Hall of Welaptega Marine, the Halifax-Nova Scotia based inspection company.<\/p>\n
The evaluation tools include an optical, \u2018caliper\u2019 unit that measures the chain link length and diameter taking pictures that can be modeled in 3D to determine its strength using finite element analysis.<\/p>\n
However, the company is also developing a magnetic tool that will travel the length of wire ropes and pick up corroded regions or damaged sections, even on sheathed wire ropes, giving the inside story on their state.<\/p>\n
\u201cThese inspections are complicated and have to be done over a period of time in order to get a good assessment of the asset\u2019s condition,\u201d explains Mr Hall, adding that \u201cspot checks\u201d simply can\u2019t give the whole picture.<\/p>\n
\u201cThe point is, sometimes there are mooring systems failures that come as a surprise because the deterioration has taken place at a much faster rate than you\u2019d expect,\u201d he says.<\/p>\n
Inspections start with the baseline data which captures the condition of mooring systems \u2018as new\u2019. Periodic inspections give a timeline of wear that can be recorded as part of the asset\u2019s maintenance history.<\/p>\n
\u201cLooked at over time like this operators might find a few surprises that don\u2019t show up with a simple \u2018snapshot\u2019,\u201d explains Mr Hall.<\/p>\n
The best inspections, according to Mr Hall, are those carried out by engineers who understand the way mooring systems deteriorate: although experience might lead an investigation on the areas where problems are known to occur, inspections must also identify anomalies \u201cwhich have not been associated with failure in the past but that could lead to failure in the future\u201d.<\/p>\n
It\u2019s all a bit of a moving target as there are a number of factors that come into play which bear on a mooring system\u2019s lifespan. Microbiologically-influenced corrosion for example tends to occur more in warmer waters and this can accelerate issues.<\/p>\n
Other deteriorative mechanisms include heavy wear and corrosion at the turret or anywhere else the chain might be rubbing. The splash zone close to the asset itself can be problematic: \u201cThere are usually some issues wherever movement and corrosion intersect, for instance shackled connections can give trouble,\u201d he adds.<\/p>\n
But there are also a number of less obvious points that can cause difficulties, such as the touchdown area where the chains bounce off the ocean floor. \u201cWhen chains interface with the seabed, surface corrosion is knocked off, exposing the chain to bacteria and salt water which speeds up the process,\u201d explains Mr Hall.<\/p>\n
Despite the multitude of corrosion issues, the surprises aren\u2019t always bad: \u201cSometimes these links can look like they are in a really terrible state, but \u2013 and it does happen \u2013 if the links have been over-specified in the first place, the system can still have more life left in it,\u201d explains Mr Hall.<\/p>\n
However, there can still be some resistance on the part of owners and operators to a regular assessment regime, and \u2018old-school attitudes\u2019 are part of the barrier to getting these checks done. Mr Hall says: \u201cTo be blunt, this kind of old-school thought can be summed up as \u2018if you are not on the revenue generation side, you are a cost\u2019, and as such to be avoided where possible.\u201d<\/p>\n
\u201cHowever it is changing and although jobs still get cancelled at the last minute because a ROV asset is wanted somewhere else, more and more people are realising that the state of these mooring systems is critical,\u201d he concludes.<\/p>\n
\u201cAfter all, if you lose and FPSO because you haven\u2019t looked at the moorings, it\u2019s a very, very expensive business loss.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
The offshore oil and gas industry is facing a major challenge as facilities age beyond their design life, writes Stevie Knight.<\/p>\n","protected":false},"author":8,"featured_media":3473,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[11],"tags":[],"sponsor":[],"class_list":["post-3472","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-vessels-shipyards"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts\/3472","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/comments?post=3472"}],"version-history":[{"count":0,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts\/3472\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/media\/3473"}],"wp:attachment":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/media?parent=3472"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/categories?post=3472"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/tags?post=3472"},{"taxonomy":"sponsor","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/sponsor?post=3472"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}