Page 22: of Marine Technology Magazine (Apr/May 2015)

Tech File gineering, operating and repair costs. There are built-in costs for subsea work that are unavoidable: operating equipment at

Subsea Industry Challenges a distance with remote devices, and dealing with external wa-

Several key industries already undertake signi? - ter pressure and corrosion conditions. Careful planning and cant subsea activities—here are some hydraulics- a willingness to integrate smart design principles into subsea related challenges they face: hydraulic systems make it possible to accomplish these goals cost-effectively.

Oil and gas production • The move to deep and ultra-deep water drilling is

Pressure Compensation forcing more process equipment from surface to subsea

Pressure compensation is useful in any system which oper- • Key requirements are ultra-high reliability, ability to ates below water. It is used to keep the pressure between ex- install and maintain utilizing ROVs/AUVs technology ternal environment (seawater) and reservoir constant, as seals • Expected operating lifetimes are for the life of the are typically designed for the pressure drop in one particular ? eld, typically covering 25 to 30 years direction and limited to a speci? ed amount.

• New techniques to accurately simulate the

Most components readily available on the market were de- performance of a hydraulic system across this signed for operation in normal surface environments. Almost timeframe becomes a key success factor all machines have sealing surfaces or parts which cannot with- stand high subsea external pressures or high pressure drops.

Subsea mining • Most mining occurs in shallow water using current One option—more dif? cult and expensive—is to seal pres- dredging technology sure-sensitive components inside a protective chamber. This • As mining moves to deep and ultra-deep water in is usually a container with rigid construction and heavy duty near future, ruggedness and long term durability seals to withstand the high external pressures. will be crucial

A more effective solution is called pressure compensation. • Several companies currently developing large Using this system a pressure is applied inside the component remotely operated mining vehicles.

equal and opposite to the ambient pressure outside. In a typi- • Transport of bulk materials over long distances cal hydraulic system, the standard reservoir is replaced with a while overcoming additional water weight is key sealed reservoir containing a ? exible medium separator. challenge In this way the external environment pressure is transferred to the reservoir, just as a normal surface system has the exter- nal air pressure on top of the oil in the reservoir. The difference

Communication & is the seawater is prevented from mixing with the oil. Through

Power Transmission this clever system any component used on the surface can be • Infrastructure facilities, such as communication used subsea as long as all volumes that normally contain air cable crossing the Atlantic Ocean, are subject to different underwater geography conditions,

Figure 3: including different water depths and complex deep ocean currents

HVOF Coating Technology for • Regular inspection and repair of power and communications cables in deep sea regions

Large Hydraulic Cylinders most signi? cant • Heavy dependence on ROV’s or AUV’s using hydraulics

Natural science • Special observations ROV’s and AUV’s are under development • Key capabilities include reliable operation of both moveable observation equipment—cameras and other sensors—and mobile sample-gathering tools • Research locations are widely varied in terms of depths, salinity, currents and other conditions • Reliability is ultra-crucial: failure of a ROV for even a day can drastically impact researchers with limited time and funding to complete projects

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