A direct comparison of water jets
Water jets from propulsion manufacturer Marine Jet Power (MJP) were recently used to solve "some significant propulsion issues" for a client, with the exchange of jet models helping the shipyard to achieve its project goals and deliver the vessels to the new owners.
The yard faced troubling circumstances. Three brand-new vessels could not be delivered, citing a "lack of performance". To remedy this, the decision was made to replace the existing mixed flow jets to MJP DRB mixed flow jets on one of the vessels.
MJP DRB jets with FRP intakes were installed. According to MJP, when comparing the two jet systems on paper, "they both claimed to deliver the same thrust,"
"In reality, however, the MJP jets consumed 8.5 per cent less power at the same operating speed. Power consumption was measured under the supervision of DNV, guaranteeing the accuracy of the measurements."
The FRP construction of the MJP water jet intake also provides a "smooth and efficient intake shape and eliminates any corrosion issues", and after measuring the noise level in the aft of the passenger compartment, it was also revealed that the noise level had halved following the installation of the MJP jets.
Following the successful exchange of the jets, the yard could deliver the ships to the owner, which is now successfully operating the vessels.
MJP is said to have removed a big burden from the shipyard and the operator is now counting on savings of approximately NOK 1.2 million (USD21,000) per year, with operating hours exceeding 3,500 annually.
In another case, MJP assisted the operator of a 10-year-old vessel that had decided to change to MJP DRB jets. Citing significant service and corrosion issues on the existing water jets, the vessels were originally equipped with axial flow jets.
MJP DRB mixed flow jets with FRP intakes were installed in the pre-existing hull of a vessel. The rest of the equipment, including the engine, remained unchanged.
Sea trials following the refit showed significant results: Ship speed instantly increased from 38 to 43 knots with a change of water jets. Originally, the vessel never exceeded more than 38 knots – with an overall efficiency increase from 57 per cent to 67 per cent.
"The difference in efficiency is an incredible 18 per cent, meaning that the vessel can obtain an 18 per cent lower fuel consumption. The engines can operate at lower load, giving less wear and longer service life," said MJP in a statement.
With the operator satisfied with both the installation and function of the control system, more vessels are now being rebuilt accordingly.
"The MJP DRB water jets are otherwise completely made of stainless steel and thus have unmatched strength, resulting in a full five-year warranty, which is unique in the marine market," said a MJP spokesperson.
In 2012, MJP Waterjets acquired Ultra Dynamics. The new group is named Marine Jet Power and has offices in Sweden, the United Kingdom, the United States, Italy and Singapore as well as sales and service representatives in over 30 countries. The company group product range comprises the MJP CSU, DRB and Ultrajet series.
