Getty Fleet Orders Lips Speed-Adapted Propellers To Increase Efficiency

—Literature Available Cognizant of the efficiencies achieved through modern propeller designs, Getty Fleet (Texaco) ordered a Lips speed-adapted propeller to meet the revised operational specifications of the M/T Getty Fleet.

The new four-blade propeller has a maximum diameter of 7,400 millimeters (24.27 feet) and an expanded area ratio of .527. Cast from Lips "Cunial" alloy (ABS Grade IV/nickel aluminum bronze) material and manufactured to ISO Class 1 standards, the finished propeller weighed approximately 62,800 pounds.

Speed-adapted propellers become a viable consideration when vessels are continually operated at lower ship speeds than they were originally designed for. It pays to exchange the propeller for a speed adapted one, designed for a new operating point. In this point the number of revolutions is lower than in the original one. Optimization of the propeller diameter now leads to a larger propeller. As a consequence of the resulting larger diameter, thrust loading coefficient is reduced, axial and rotational losses are reduced and the open water efficiency is increased. Note that the propulsive efficiency is not improved as much as the open water efficiency due to hull propeller interaction. Due to the reduced propeller load, cavitational properties will be better and an additional increase in efficiency can be obtained by reduction of blade area ratio.

For additional information, including a listing of vessels retrofitted with Lips speed-adapted propellers, Circle 51 on Reader Service Card

Maritime Reporter Magazine, page 6,  Dec 1985 Charles Burrell

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