The market for these vessels is forecast to increase rapidly between now and the end of the century. It is estimated that expenditure for such vessels operating on the U.K. Continental Shelf could reach about US $ 1.5 billion by that time. Norway is also at the forefront of this technology and possibly has similar expenditure planned. Petrobras of Brazil is reported to be planning to deploy at least 8 such vessels and Australian companies, such as BHP and Woodside Petroleum are also considering additional vessels.
5. The_Requirement for_Compressed_Air
The most common requirement for compressed air on ocean going vessels is to start the diesel engines, with lesser needs for instrumentation, control and general service. On FPSO vessels the position is reversed with the starting air requirement being relatively small (mainly for generator prime movers).
The big requirement is for service, instrumentation and control applications, associated with the equipment on deck. Turbines may require large volumes of medium pressure starting air whilst Nitrogen generator systems and pneumatic controls call for significant amounts of oil-free air.
Broadly speaking, machinery below decks belongs to the marine industry whereas the equipment on deck is oil industry territory. Compressors installed below decks must comply to marine class society regulations whilst the compressed air is used mainly for the processing side. The compressors are relatively high volume rotary screw type and class rules apply to both internal components and the complete machines. Electric motors, pressure vessels (separator tanks / heat exchangers), air screw ends & gear drives must all be individually tested and certified. The compressor is finally tested for performance and compliance, prior to a class certificate being issued.
Unlike standard industrial compressors, marine compressors must be designed to operate in a non-horizontal plane; to allow for the pitch and roll of the vessel. Potentially hazardous materials must be eliminated, such as plastics which could generate heavy smoke or noxious fumes in the event of a fire. Individual components must be restricted to minimum weights in view of the limited maintenance access on board ship.
