This was the challenge facing Mainprize Offshore, who are always looking to increase efficiency. Therefore, improvements in propeller performance and vibration levels on their windfarm support vessels would lead to reduced maintenance levels, reduced docking, reduced failures and overall increase in efficiencies and cost savings.
This led Mainprize to approach Southampton’s CJR Propulsion, manufacturers of precision engineered propeller and sterngear packages. At the time, the vessel was fitted with the original set of propellers that were causing vibration when under load. The brief to CJR was simple; design, manufacture and supply a new set of propellers for its M01 Wind Farm Support Vessel that would reduce vibration and increase efficiency for a number of operational parameters.
In response, CJR Propulsion set about designing a bespoke set of propellers using its in-house advanced Computational Fluid Dynamic (CFD) department to define the optimal set up to the vessel’s hull form. The designs were tested in a virtual world using over 20 million data points to replicate real world conditions and to understand the flow of water around the propeller. The software provided accurate predictions of cavitation and an indication of the noise and vibration levels expected.
CJR Propulsion’s Mark Russell said: “Our ability to recreate real world conditions in a digital world, and to predict performance with incredible accuracy, dramatically impacts how our propulsion systems function. This ‘appliance of science’ does away with the traditional ‘made with experience’ approach so typical of the industry and ensures the products we produce match our designs to the millimetre. Unfortunately, many in the industry still don’t understand the long-term benefits CFD delivers, but as more owners and yards get on board, it’s only a matter of time before our approach is standard across the market.”
Following on from the design process, the propellers went into production, with patterns created using a 3D printer, before being cast in nickel aluminium bronze. The props were finished using a computer-driven five axis CNC machine, removing precisely the required amount of material to match the original design perfectly.
The propellers were dynamically balanced and MRI scanned to achieve the Class S standard required for optimum performance and smooth running. Mark Russell added: “The International Standards Organisation has four classes of propeller tolerances: 1) Class S, best, very high tolerance; 2) Class I, very good, high tolerance; 3) Class II, average tolerance; and 4) Class III, low tolerance. It is worth noting that not all propellers, even when brand new, are Class S.”
On the completion of the project Bob Mainprize, said: “Working with CJR has been a revelation - they have demonstrated how technology can dramatically improve the performance and overall costs by increasing efficiency, reducing fuel burn and vibration, and reducing service costs. Class S propellers are the only option for minimising vibration. The vessel is saving approximately 8% fuel. This is an incredible saving and demonstrates the value CJR provides its customers, it’s a win for our clients and our bottom line. We have ordered a second full stern gear set and are working closely with CJR for our new build programme.”
CJR Propulsion will be exhibiting at Seawork International on stand PO99.
