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MAN Diesel & Turbo has launched its new VBS Mk 5 range of propellers, which is said to lower fuel consumption and cut exhaust gas emissions.

The new VBS Mk 5 propellers consist of a complete range – a total of 20 new hub sizes which are able to handle outputs from 1,000 and up to 40,000 kW. The new range spans from hub diameters of 600 mm and up to 2,150 mm – distributed on three series designs: S (small, 600-940 mm), M (medium, 1,020-1,550 mm) and L (large, 1,640-2,150 mm).

Efficiency increase

The major benefit of the VBS Mk 5 propeller is said to be an increased efficiency of up to 2%. The operational advantages of increased propeller efficiency are then translated into savings via lower fuel consumption and reduced exhaust gas emissions. The increased efficiency may alternatively be exploited as higher thrust for increased ship speed or higher bollard pull for a given engine power.

Green propelling

"The flexibility of covering efficiently any propulsion power requirement and CP Propeller application is the overall product target for MAN Diesel & Turbo. Propeller and propulsion efficiency also carries the 'green aspect', as every gram of fuel saved by means of higher propulsive efficiency, results in a reduced impact on the environment," MAN Diesel said.

"Additionally, the new propellers have a green light for environmentally friendly lubes, as they are prepared for biodegradable servo and lube oils. The servo oil and lube oil systems are adapted to both biodegradable oils and ordinary mineral oils, and switching from one type to the other is possible without any requirements for component changes," the company added.

Hydrodynamic refinements

The shape of the new hub is flow-optimised at its afterpart and reduced in size, resulting in a lower hub/propeller diameter ratio and a reduced drag. The flow optimisation includes a new and more streamlined shape of the hub and blade foot integration, resulting in a blade foot, which is completely flush with the hub contour.

A design for demanding applications

The optimised hub/blade interface allows for higher propulsion power densities. Higher cavitation inception speed is allowed for the propelling of high-speed vessels. A reduced risk of root cavitation permits higher blade loading for demanding propulsion applications.

Compact, robust and lightweight

The new hub design is simplified with approximately 40 percent fewer parts. The material fatigue levels are calculated for a 30 year lifetime, considering all possible external loadings in service. Furthermore, the overall weight has been reduced for less impact on e.g. strut and stern tube bearing loads.

The new propellers have been developed with a number of inherent service, inspection and exchange features – including the unique possibility of inspecting/repairing all of the hub interior parts with the propellers placed in situ:

* The propeller blades can be exchanged inside a propeller nozzle – without pulling the shaft.

* The hub is completely serviceable with the propeller installed in the ship. No need for shaft/coupling flange dismantling, shaft pulling and removal of the rudder.

* Possibility of check/inspection and replacement of internal parts without removing the propeller blades.

* Hub bearing surfaces are exchangeable.

* The hub and shaft flange connection is designed for easy inspection during docking and survey.

* Maintenance concepts for hub wearing parts are available.

* Underwater exchange of propeller blades is possible.

Oil distribution unit for pitch control

A new compact ODF oil distribution unit – for gearbox mounting – has been developed for the VBS Mk 5 propellers. A short and very robust unit with 20% fewer parts compared with today's ordinary ODF designs. The installation length has been reduced by 15% – for the benefit of very short and compact engine-gear-propeller installations.