Replacement jets improve performance

The first case involved a 10-year-old vessel which was suffering significant service and corrosion issues with its existing axial flow waterjets from another maker. The operator decided to change to MJP DRB mixed flow jets, while the rest of the equipment, including the engine, remained unchanged. MJP says that the DRB jets are made of stainless steel while the intakes are moulded in GRP to give a smooth and efficient intake shape and eliminate corrosion issues. As a result, the DRB jets are offered with a five-year warranty.

Following the waterjet exchange, sea trials showed that ship speed increased from 38 to 43 knots and overall efficiency increased from 57% to 67%, as a result of an 18% improvement in fuel consumption. The engines can thus operate at lower load, giving less wear and longer service life. According to the operator, even when new, this vessel could not manage more than 38 knots maximum. MJP says that other vessels are now receiving similar modifications.

In the second case, a yard was unable to deliver three brand-new vessels because they were unable to perform to specification. It was decided to try MJP DRB jets on one of the ships in place of the installed mixed-flow jets from another manufacturer. Although both jets claimed, on paper, to deliver similar thrust, it was found that with the MJP jets with GRP intakes 8,5% less power was consumed at the same operating speed. Measurements were taken under DNV supervision as a guarantee of accuracy.

Another benefit of the MJP jets was a 50% reduction in noise levels in the aft passenger compartment. After the exchange of water jets, the yard could finally deliver the ships and they are now in successful operation. According to MJP, operator Norled can expect annual savings of around NOK 1.2million, while the yard was relieved of a large burden.

According to Norled MD Ivan Fossan: “Norled is very satisfied that Oma Baatbygeri has been able to find the reason why our new vessels didn’t reach the agreed speed. Oma Baatbyggeri builds high-speed vessels with an important comfort-factor and thanks to the MJP waterjets we do not only reach our desired speed, but save a substantial amount of fuel oil at the same time.”

MJP Waterjets is now part of Marine Jet Power, following the 2012 acquisition of Ultra Dynamics. The new group product range comprises the MJP CSU, DRB and Ultrajet series.