HamiltonJet HT Series Waterjets off to a Fast Start

By Edward Lundquist at November 24, 2010 20:46
Filed Under: Navy insights, Navy News

HamiltonJet HT Series Waterjets off to a Fast Start

By Edward Lundquist

Waterjet propulsion is well suited for small combatants and large patrol craft, according to Christian Walsh of HamiltonJet.

Walsh says New Zealand-based HamiltonJet has sold 60 units of its new HT series of waterjets since the first introduced less than two years ago.

The HamiltonJet HT range is very well suited to large patrol boats as it provides vessels with high performance, excellent control and high lifecycle durability all of which are highly desirable attributes for patrol boats,” Walsh says.  “For a patrol boat high performance translates as high top speeds for a given power and also rapid acceleration. Excellent control translates to exceptional maneuverability at both high speed for pursuit and also at low speeds for operations such as coming alongside another vessel or installation.  Lifecycle durability translates to the ability for the unit to take all manner of conditions that patrol boats have to experience and keep working to 100% of its capability. 

Walsh says 18 HamiltonJet HT1000 jets have been delivered to South Korea for coast guard patrol boats, with ten more on order; Taiwan has ordered seven HT810 twin shipsets for patrol boats; projects, with the first of these vessels recently exceeding expectations at sea trial; and, he says, a new large RiverHawk Advanced Multi-Mission Platform AMP-137 patrol boats under construction in the U.S. will feature twin HT1000s.  He also says HamiltonJet is providing 16 HT900s for four fast supply vessels for the oil industry.

The Republic of Korea’s KCG 300TCoast Guard Patrol Boat uses a pair of twin HT1000 fully controllable ‘wing jets,” with a pair of HM811 central boost jets.  The patrol boats are powered by four MTU 16V 4000 diesels.  Walsh says the patrol boats can operate at over 20 knots on the wing jets alone.

I asked Walsh about the materials used in the HamiltonJet HT series waterjets.

“The HT range and all HamiltonJet waterjets for that matter are constructed from a range of materials and a great deal of research and development work goes into the material selection. Aluminium is selected for the body of the jet, yes because it is lighter, and also because it is easier to cast more complex fine shapes allowing for further reduction in the size and weight of the jet body and allows us to integrate elements such as oil coolers in to the jet intake,” Walsh says.  “ Stainless steel is selected for the impeller, shaft, wear ring and leading edges of the stator for its durability for these highly stressed parts of the unit, not corrosion resistance.”

Waterjets have some problems with corrosion caused by cavitation, so I asked Walsh for his point of view.

“Whereas propellers experience cavitation at high speeds waterjet cavitation is a low speed phenomenon. The hydrodynamic design of a HamiltonJet ensures the widest cavitation margin in the market today and this has been maintained in the HT range. In a practical sense this means that full power can be applied at lower speeds and so faster acceleration is possible and generally the units can be used more aggressively without experiencing cavitation.,” he says. 

Because of the tunnels and geometry of waterjets, it can be tricky to ensure cathodic protection.  I asked Walsh how HamiltonJet deals with it.

We utilize sacrificial anode protection throughout the unit to control galvanic corrosion along with electrical isolation of some of the stainless steel elements,” Walsh says.  “Years of experience and optimization of the anode placement and anode material itself (HamiltonJet use a specific Aluminium alloy with better properties than traditional zinc anodes) have ensured excellent results from this protection scheme, and this has been well proven in the field.”

According to Walsh, the new anode system that is in place on the HT units is a cartridge system so that some of the internal anodes can be more easily accessed, checked and if necessary removed from outside the unit and this clearly makes for easier maintenance and checking of the anodes.

 (Author Lundquist notes the spelling of “Aluminium,” which is the accepted spelling in New Zealand.  Captain Edward Lundquist, U.S. Navy (Ret.) is a principal science writer for MCR Federal in Arlington, VA.  Views expressed in this article are not necessarily those of his employer.)






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