Write short notes on following
Thrust Block, Intermediate Shaft, Incinerator, Bow Thruster
The main thrust block transfers forward or astern propeller thrust to the hull and limits axial movement of the shaft. Some axial clearance is essential to allow formation of an oil film in the wedge shape between the collar and the thrust pads. This clearance is also needed to allow for expansion as parts warm up to operating temperature. The actual clearance required depends on dimensions of pads, speed, thrust load and the type of oil employed. High bearing temperature, power loss and failure can result if axial clearance is too small.
The shaft installed between the thrust shaft and tailshaft. It has flange at both ends. It can be more than one section depending upon the machinery space location. It is supported by intermediate or tunnel bearings.
Burning of waste oil, sludge, cotton waste is carried out using the incinerator. The waste oil which is obtained from the scavenge drain tank, sludge from the purifier and oil water separator cannot be disposed overboard so the incinerator is used to burn this oil. Plastic is not burnt in it because it would cause air pollution.
The bow thruster is a propulsion device fitted to certain types of ships to improve manceuvrability. The thrust unit consists of a propeller mounted in an athwartships tunnel and provided with some auxiliary drive such as an electric or hydraulic motor. During operation water is forced through the tunnel to push the ship sideways either to port or starboard as required. The unit is normally bridge controlled and is most effective when the vessel is stationary.
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