Shafting process

Engine Room

Shafting and etc.

Shafting

Shafting The thrust bearing and the thrust shaft (with thrust collar) transmit the

thrust, generated by the propeller, to the hull. The thrust bearing may

be independent of the engine, but mostly is integrated in the engine.

The shaft bearings support the weight of the shafts.

The propeller shaft connects the shafting system inside the ship with the

propeller.

The stern tube guides the propeller shaft through the hull. In the stern The stern tube guides the propeller shaft through the hull. In the stern

tube, the shaft is supported by one or two oil-lubricated bearings: the

aft and forward bearing. These bearings carry the shaft and propeller

weight, and also the transverse hydrodynamic load acting on the

propeller.

The forward stern tube seal assures that the lubrication oil stays within

the stern tube.

The aft stern tube seal has two functions: to keep the lubrication oil in

and to keep sea water out.

Shafting

Documents for approval (BKI Rules)

General drawings of the entire shafting, from themain engine coupling flange to the propeller, anddetail drawings of the shafts, couplings andother component parts transmitting theother component parts transmitting thepropelling engine torque, and in addition detaildrawings and the arrangement of the stern tubeseals and the cast resin mount for stern tube andshafts bearings are to be submitted intriplicatefor approval.

Propeller shaft

In general shaft are made of forged (mild steel).Sometimes high tensile steel, or alloys such asstainless steel are used and may be of compositematerials. Most often shafts are solid, but theymay also be hollow for example when light shaftsare required in passenger vessels or naval vesselsmay also be hollow for example when light shaftsare required in passenger vessels or naval vesselsor when CPPs are sed.

Propeller shaft

Minimum diameter (BKI Rules)

k [-] factor for the type of shaft

- Intermediate

- Thrust

- Propeller

Shaft bearings

Shaft bearings support the shafts. In general sleevebearings are used. In sleeve bearings the shaft issupported in a lubricating film in a bearing that isusually lined with white metal. The oil is added tothe bearing through a ring that is mounted on thethe bearing through a ring that is mounted on theshaft, and distributed by the rotation of the shaft.The bearing capacity of these bearings lies in therange of 0.3 to 0.5 N/mm2 on the projectedbearing surface. The length-diameter ratio ofsleeve bearings lies in the range of 0.8 to 1.

Shaft bearing

Shaft bearing

Maximum distance between bearings (BKI)

Thrust bearing

The thrust bearing converts the mechanical

energy in the rotating shaft into translating

mechanical energy to propel the ship. The

thrust bearing has to transfer thrust to thethrust bearing has to transfer thrust to the

hull while sailing both forward and astern.

Stern Tube

In general, two types of stern tube can be distinguished:

- Stern tube with oil lubricated bearings

- Stern tube with water lubricated bearings

Water lubricated bearings are rarely applied in Water lubricated bearings are rarely applied inmerchant vessels. In naval vessels the stern tubebearings and the A-bracket bearing are sometimeswater lubricated. In that case, the shaft is fitted with abronze sleeve for protection against corrosion by thesea water. The bearings will consist of a bronzebearing bush on which the bearing material, rubber orsynthetic material, will be mounted.

Stern Tube

In case of oil lubricated stern tube bearings, the shaftdoes not need to be protected against corrosionbecause the stern tube is filled with oil from a tank.This tank is located 3 to 5 m above the waterline andensures a slight overpressure relative to the sea waterpressure. The bearing bush is often of cast iron and thepressure. The bearing bush is often of cast iron and theinner surface of the bush is centrifugally cast withwhite metal.

Stern Tube

Stern Tube Lenght (BKI Rules)

Flexible Coupling

To reduce vibration in a system to an acceptablelevel, flexible couplings need to be fitted.

In a geared drive, these couplings are fittedbetween the engine and gearbox to allow somemisalignment and to control the torquemisalignment and to control the torquevariations within the system.

An elastic coupling introduces a low stiffness, thusreducing the natural frequencies of the system.Also, they may have good damping quality thusreducing the amplitude of the torsionalvibrations.

Flexible Coupling

Flexible Coupling

Limit shear stress (BKI Rules)

Gearbox

Marine gearboxes consist of meshing teeth on

pinions and wheels, which transfer power

from a drive shaft (primary) to a driven shaft

(secondary) andreduce speed: [i = nengine/n(secondary) andreduce speed: [i = nengine/n

propeller]. Three configurations; parallel, locked

train and epicyclic.

Gearbox

Gearbox

Minimum diameter (BKI Rules)

Propulsor