Feature 8 | WATERJETS
Vibrant product development gives buyers more scope
Vigorous development and improvement in the field of waterjets has seen competition sharpen in the multifarious small-ship market, benefiting users in terms of choice and performance. David Tinsley looks at the ever important factors shaping design progression.
H
amiltonJet’s new generation of HT-series waterjets made its seagoing debut in 2008 by way of
the twin installation of powerful HT1000 propulsors in the first of four patrol ships to be built for the Korean Coast Guard. The second model in the range, the smaller HT810, has now been completed at the company’s Christchurch factory in New Zealand, where manufacture of a further addition to the series, the HT900, has been set in train. Developed from the HM family, the
new HT offering incorporates improved efficiency and cavitation properties. It strengthens HamiltonJet’s hand considerably in providing propulsion solutions in unit power applications up to 5500kW, in the case of the HT1000, and to 4000kW and 5000kW, respectively, as regards the HT810 and the nascent HT900. With its new reverse duct design,
the HT810 has a reduced transom footprint for a jet of its size. It is also supplied with a factory-built transition duct, obviating the need for this element to be fabricated by the vessel builder and better ensuring accurate geometry for the intake flow. Another refinement hosted by the
HT810 model is a new arrangement for the positioning and attachment of the anti-corrosion sacrificial anodes. A cartridge system enables internal anodes to be inspected and replaced without the need for jet disassembly, simplifying maintenance and reducing downtime. A further new feature is the integrated tailpipe and nozzle housing, eliminating a bolted flange and reducing the overall length of the waterjet. The opening contract entails two HT810s for a 34m vessel in Taiwan, with
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HamiltonJet’s HT810 design is suited to power inputs up to 4000kW and has a reduced transom footprint for a waterjet of its size (Credit: HamiltonJet).
power delivery by MTU 16V4000 M90 main engines promising a speed in excess of 30kts. Assembly of the larger HT900 model has recently been implemented, and the first installation involves a Gulf of Mexico crewboat. Te new series features a mixed flow
pump with a greater nozzle inlet ratio than axial flow waterjets of comparable size, conferring high efficiency over a vessel’s full speed range. An optimised, compact astern deflector retains the performance of HM series-type ducts, but at reduced weight and width for installation in narrow hulls. In the case of the two larger models, the
HT1000 and HT900, the front transition is supplied by the customer’s yard of build, and the transition duct extends from the flat surface aſt of the intake opening to an area forward of the front intake screen mount. For an aluminium hull,
the transition duct casting is surrounded by a section of 5083 aluminium plate so as to obviate the need for the shipyard to undertake plate-to-casting welds. Te use of a relatively short transition
in the case of the HT1000 and HT900 types makes these waterjets easier to adapt to warped hull shapes common in larger monohull vessels, and avoids interference with hull wedges and other appendages. Knowledge gained from the HT1000
design project was brought to bear on the HT810, making it easier to both manufacture and service in the field. “Trough the development of the HT series, we have been able to advance several new features of our waterjets, including one-piece casting of large impellers, compact and efficient reverse duct designs, and improved servicing features,” confirmed HamiltonJet’s
Ship & Boat International July/August 2010
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