Pod Propulsion

Pods are devices which combine both propulsive and steering functions in one device. They are usually located below the stern of a ship, making use of the following internal components: a fix pitch propeller, shaft, thrust and support bearings, brake, and shaft seals; exciter; AC motor (synchronous); bilge pump; and appropriate monitoring and control equipment. The steering unit uses slewing gears and is located in the hull above the pod itself. Lubrication equipment and ventilation/cooling units are usually located externally, as sub systems. Propulsion pods are not a new product, but a new configuration of traditional marine systems and components.

As yet, studies have not shown whether pods are more efficient than conventional shaft lines. There has been much research on the subject, but most studies have been aimed at a specific aspect of pod performance instead of an overall efficiency review. Several advantages have been attributed to pod propulsion systems, such as: reduced emissions, lower noise and vibration levels and emissions; improved steering maneuvering, and braking capabilities. The reduced number of component parts also allows for more flexibility in arranging system machinery, more efficient construction and improved shipyard logistics. On the opposite end of the argument, pods require a greater capital investment, have a 30MW power limitation (per screw), and have been known to suffer losses in power due to electric propulsion.