The ‘NPT’ propeller, or New Profile Technology propeller to give it its full title, is now well proven in service with over 150 installed.
The NPT has been installed on New builds where the high efficiency has been recognised, but it has also been retrofitted to existing ships for an improvement in propulsion efficiency. For instance, slow steaming is the “new normal” for container vessels, so a new NPT propeller optimised for lower power and rpm can make significant efficiency gains.
The NPT's high propulsion efficiency has been proven many times in model testing, and service experience now backs this up. A significant benefit is the smaller optimum diameter of the NPT. This gives more flexibility in selection of engine rpm at the design stage, and allows an even better efficiency gain because a more efficient, slower turning propeller is often possible without exceeding the maximum diameter. This benefit is also advantageous for retrofitting to a de-rated engine where the number of blades and blade surface area can be lower without an increase in propeller diameter – resulting in further efficiency gains.
The NPT also has a lower blade surface area than other types, which results in a significantly lower weight. This means the cost is very competitive and often significantly lower than other types.