Miko Marine AS has completed the delivery of four innovative sea chest covers and two cofferdams to be used during refurbishment of the Njord Bravo floating storage and off-loading vessel (FSO) owned and operated by Equinor. The covers have been delivered to the Aibel yard in Haugesund in Norway and will be used to ensure the watertight closure of sea chests when they are pumped dry for refurbishment work on the various ballast valves and pump systems inside.
Miko has developed specialised expertise in the design of hull closures and chooses from a range of design options according to the nature of the task. For this project, after the curvature of the hull had been precisely measured by laser scanner, covers were made for each of the four sea chests and two cofferdams were manufactured to provide additional security by covering each pair of hull seals.
Although Miko regularly uses magnetic fastenings for attaching hull closures, the Njord Bravo required the design of hull closures and cofferdams that could be quickly attached by ROV to a specially designed interface fixed permanently to the hull.
The covers and the cofferdams are all made from aluminium and incorporate a foam that makes them neutrally buoyant. This enables them to be easily deployed by an ROV (remotely operated vehicle) which benefits from an ingenious system of spring latches that enable it to lock the covers and cofferdams quickly into place against the interface and tighten the seal. Each component was subjected to detailed pressure and stress testing with the customer present to guarantee the integrity of the covers and their latches.
The closures will be deployed at a depth of 15 metres where divers would normally be required to undertake such work. Major cost and safety benefits may now be derived from being able to use ROVs for the complete installation of the system and by ensuring that in-water repairs can be carried-out inside the sea chests should an urgent need arise.
Miko Marine AS is based in Oslo, Norway, from where it also provides a range of unique salvage and support products for the marine industry. The company’s most recent innovation has been the Moskito oil recovery unit that was recently introduced as the first tool that can enable bunker fuels and other hydrocarbon cargoes to be quickly and easily extracted from the tanks of sunken vessels.