Making Murene

The need to innovate, collaborate and standardize existed well before the downturn, and not least in Norway. Elaine Maslin sets out how Transmark Subsea has been doing all three.

Work on Murene at Transmark’s facility near Bergen. Images from Transmark Subsea.

Founded in 2009, Transmark Subsea set out three core business strands; cables and connection systems for ocean bottom seismic systems, internal connections on the ROVs, and subsea jumpers.

When the company found that a key component required for the subsea jumpers was only sold by one manufacturer – to two clients – and that new standards were also being drawn up by oil major Statoil for this part, it decided to take matters into its own hands.

Working with a specialist hose manufacturer the firm developed its Murene subsea oil-filled pressure compensated system, a hose and connector system design to be a conduit, barrier and protection for fiber optic and copper cables.

The system is used on subsea trees and transmits data to/from sensors to the control pods, if it’s an electric system. It would also be used on manifolds between subsea structures and as a jumper to the control umbilical.

The Murene system meets Statoil’s latest standard for electrical and optical wet mateable jumper assemblies, TR2390 Ver.2, which will be the base of a new international standard.

The clever thing is, the hose uses its own properties to act as a pressure compensator, and it can cope with the temperature and sunlight it would be exposed to on the back deck of a vessel offshore west Africa, as well as arctic temperatures, says Tore Diesen, sales and marketing director, Transmark, based at Rådal, near Bergen.“When the new [international] standard comes through, we are one of few, maybe the only one, that is qualified according to this standard,” Diesen says.

Tore Diesen

Transmark’s design is based on two layers of special rubber compounds, with an axial layer of aramid fiber in between, to absorb longitudinal pull load during handling, and a cross woven layer of nylon/polyester to provide the pressure compensation qualities of the hose.

“When you go deep subsea, it’s important to make sure water cannot penetrate electrical systems,” Diesen says. “The way they are doing it is to pressure compensate them – making the internal pressure the same as the external pressure. Murene is manufactured in a way so it acts like a spring, acting like a pressure compensator,” he says. The over pressure will be about 2-6 bar, but it will never be more than 10 bar differential pressure inside the hose, or less than 0 at +50°C or -10°C, he says.

“Not only can it withstand water depth, but also temperature differences, which is even harder to comply with,” he says. “The hose was developed to compensate for temperatures and pressure. In the Gulf of Mexico, for example, you will never have more than 10 bar over pressure, and at 3500m you will have slight over pressure of a couple of bars. It also has to tolerate hydrocarbons outside and inside, sea water and sunlight for six months in the likes of West Africa without losing its bright original color and mechanical properties. As it is supposed to be handled by an ROV system – with up to 250hp – it has to be strong as well,” Diesen says.

Working with a hose manufacturer, a special “recipe” for a rubber to meet these demands was created (NBR and NVC/SBR). Most use Natural Rubber, Nitrile or chloroprene/Hypalon, Diesen says, depending on the performance criteria needed.

Murene has also been designed so that it has an industry standard Mk2 interface, so it can connect with different types and brands of subsea connectors and different kinds of sensors, as well as being a modular system, comprising “split boxes” with multiple inlets and outlets. All metal components are made in Titanium as standard, other materials on request.

“We have sold several 1000m of Murene since late 2013,” Diesen says. “It’s good for the industry, now there are multiple suppliers and an upgraded version of this for the industry important product.”

Despite the current climate we are in, there’s still going to be a growing market, he says. “We are seeing more and more sensors being used to monitor and control what is going on subsea, and for this they [operators] need more hoses, so definitely the volume will grow.”