High Speed Coastguard Duties

Along with performance and maneuverability, one of the key factors affecting the choice of a vessel’s main propulsion is lifetime maintenance costs.

The target markets for most waterjet installations tend to be high performance defence and patrol applications or time-critical transportation. In these sectors reducing downtime and increasing MTBO (mean time between overhauls) is crucial for reducing lifetime costs.

In fast patrol craft, marine growth on the inlet surfaces, impeller housing, shaft pump blades and nozzle can have a very detrimental impact on efficiency and waterjet performance. Even relatively light fouling can drop top speed by 20% and create a corresponding spike in fuel consumption.

Surface fouling in the jet drive can also lead to increased vibration and accelerated mechanical wear in the engine, so antifouling is a key concern in waterjets.

It is awkward and time-consuming to access these internal surfaces for regular cleaning, so a solution that removes this requirement is a very attractive alternative.

Traditional self-polishing biocidal coatings struggle to perform in the waterjet environment where the coating has to be active while off-duty, but hard enough to polish away too quickly in the high-pressure and high-low environment when the waterjet is being used.

In recent coast guard waterjet installations, the time-consuming antifouling and cleaning regime has been avoided by mounting Sonihull systems inboard, onto the surface of the jet drive near the impeller housing inspection cover. This location ensures that all the surfaces that are in contact with water get a strong ultrasonic signal transmitted through them, even when the vessel is off duty.