Fuel/Lube Oil Systems

- AND –

Propulsion Train & Shaft Line

Components

References

Required:•Introduction to Naval Engineering

(Ch. 6 pg. 81-84, Ch. 8 143-164).

ObjectivesA. Know the features of a standard shipboard lube oil system.

B. Know the standard safety considerations for both fuel and lube oil systems.

C Know the features of a standard shipboard fuel oil system.

D. Comprehend the theory of operation and key components of shipboard main propulsion power transmission from power source to propellers.

E. Comprehend the effects of cavitation.

Fuel Oil Systems

Tanks

• Storage tanks– Integral part of the ship’s bottom– Volume affects on list/trim of the ship

• Service tanks– 24 hour fuel supply– For immediate use

• Contaminated oil settling tanks– Contaminants pumped to oily waste

tanks– Good oil sent to service tanks

Piping System

• Fill and transfer system– On-loads, transfers, and off-loads fuel

oil– Emergency supply capability

• Stripping system– Used to discharge contaminated oil,

sludge, and water to the settling tank• Service system

– Must deliver oil at the proper temperature, pressure, and purity

Lube Oil System

• Provide lubrication and remove heat generated by bearings in overcoming friction

• Major components:– Sump– Pump– Strainer– Cooler– Bearings

Sump

PumpStrainer

Moving Parts

CoolerSW

Lube Oil System Components

• Storage tanks• Settling tanks• Cooler/heater• Pumps

– AC PLO Pump (Run)– DC PLO Pump (Stby)– Electrically redundant

Additional Components

• Strainers– Prevent passage of grit, scale, dirt,

and other foreign material• Filters• Purifiers

Propulsion Train & Shaft Line

Components

Introduction

• Reduction Gears - fast to slow• Lubrication System - minimize

friction• Shaft components - turbines to the

working medium (ocean)• Propeller - transform rotational

energy into thrust

Reduction Gears

• Purposes– Allow turbine

and propeller to operate at most efficient speeds

– Combine two turbines to common shaft

Reduction Gears• Gear Types

– Straight• excessive vibration• low power-transfer

ability– Helical

• Reduces vibration, quieter

• Higher power transfer ability

• Excessive axial thrust

– Double Helical• Two sets of teeth cut

at opposite angles• Eliminates axial

thrust

Reduction Gears• Reduction Process

– Pinion (small) gear drives reduction (large) gear

– Reduction ratio = turns of pinion : turns of reduction gear

– Double-reduction: reduction in 2 steps (more compact design)

– For naval reduction gears, normally 30:1

Reduction Gears• Articulated

– Shaft between the first reduction gear and second reduction pinion is shortened to reduce the size of the reduction gears

– To allow the shorter shaft to transfer more torque, a quill shaft is installed.

– A quill shaft is composed of two shafts, the outer shaft is hollow, coupled together on one end.

Quill Shaft

Reduction Gears• Locked Train

– Two sets of gears and shafts

– Torque transmitted equally

– Increases ability to transmit torque using smaller components

• Turbine shafts connected to reduction gears by flexible couplings to allow for thermal expansion

Shaft Turning/Jacking Gear

• Electric motor that rotates reduction gears, turbines, and shaft w/o using steam– Cool down turbines

after operation– Prior to startup for

even heating– Position for

maintenance• Can be used to lock

shaft in place– In event of casualty

(i.e., loss of lube oil)

Propulsion Shaft• Shaft is hollow: reduces weight &

increases resiliency• Consists of four sections

– Thrust shaft - from thrust bearing in reduction gears to end of engineroom

– Line shaft - located in shaft alley (supported by line shaft bearings)

– Stern shaft - part of shaft which penetrates hull (supported by Stern Tube bearings)

– Propeller shaft - shaft connected to propeller (supported by Strut Bearings)

Propulsion Shaft• Different sections needed for easy

installation, removal, & maintenance

Shaft Bearings• Designed to

support the moving parts of:– Shaft– Turbines

• Thrust bearings– Absorb axial forces

• Radial (Journal) bearings– Absorb radial forces– Line-shaft, stern

tube, and strut bearings

Propeller• Made of hub and blades & creates the

thrust necessary to propel the ship through the water

• Terms:– Pitch: axial

distance advanced during one complete revolution of screw

– Face: the pressure side

– Back: the suction side

Propeller Types• Constant vs. Variable

Pitch– Variable has the twisted

look– Adv: more efficient over

wide range of speeds• Fixed vs. Controllable

Pitch– In controllable, blades

can rotate on hub to change pitch (change direction)

• Right vs. Left Hand Screw– Viewed from aft of ship– Twin-screw ships have

one of each

Propeller

• Cavitation– Formation and subsequent collapse of

bubbles as propeller turns– Occurs at critical speed

• Effects– Excessive noise– Erosion of blades– Decreased efficiency

Propeller Power vs. Shaft RPM

• Flow a RPM; Thrust (head) a RPM2; Power a RPM3

• So, if 10% power yields 100 RPM, how much power will produce 200 RPM?

10% x%1003 2003

x = 10 * (200/100)3

= 80% power

Take aways

• Classify the main reduction gears• Describe the purpose of each

component in the propulsion train• Draw and label a one line diagram

of a simple lube oils system• Describe propeller cavitation.

What are the negative effects of cavitation.

Questions?