1. Fuel/Lube Oil Systems - AND – Propulsion Train & Shaft Line Components

2. References Required: Introduction to Naval Engineering
(Ch. 6 pg , Ch ).

3. Objectives
A. 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.

4. Fuel Oil Systems

6. Tanks Storage tanks Service tanks Contaminated oil settling 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

7. Piping System Fill and transfer system Stripping system Service 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

9. Lube Oil System
Provide lubrication and remove heat generated by bearings in overcoming friction
Major components:
Sump
Pump
Strainer
Cooler
Bearings
Cooler SW
Moving Parts
Strainer
Pump
Sump

10. Lube Oil System Components
Storage tanks
Settling tanks
Cooler/heater
Pumps
AC PLO Pump (Run)
DC PLO Pump (Stby)
Electrically redundant
Components of System:
Storage and Settling Tanks- see above
Cooler/ Heater- Lube oil removes heat from bearings and gears so it must be kept cool. However, if it is too cold, it is too thick and will not flow or coat properly. Sometimes, for rapid startup, it is necessary to heat the oil prior to operation. Once operating, the balance of the cooler and the heat generated from friction keeps the oil temperature within a narrow band.
Pumps- pumps are all positive displacement pumps
1. Attached- driven by the reduction gears- regular service pump
2. Standby- driven by electric motor
3. Emergency- driven by steam turbine

11. Additional Components
Strainers
Prevent passage of grit, scale, dirt, and other foreign material
Filters
Purifiers

12. Propulsion Train & Shaft Line Components

13. Introduction Reduction Gears - fast to slow
Lubrication System - minimize friction
Shaft components - turbines to the working medium (ocean)
Propeller - transform rotational energy into thrust

14. Reduction Gears Purposes
Allow turbine and propeller to operate at most efficient speeds
Combine two turbines to common shaft

15. Reduction Gears Gear Types Straight Helical Double Helical
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

16. 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

17. 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.

18. Quill Shaft

19. 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

20. 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)

21. 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)

22. Propulsion Shaft
Different sections needed for easy installation, removal, & maintenance

23. Shaft Bearings Designed to support the moving parts of:
Turbines
Thrust bearings
Absorb axial forces
Radial (Journal) bearings
Absorb radial forces
Line-shaft, stern tube, and strut bearings

24. 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

25. 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

26. Propeller Cavitation Effects
Formation and subsequent collapse of bubbles as propeller turns
Occurs at critical speed
Effects
Excessive noise
Erosion of blades
Decreased efficiency

27. 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%
x = 10 * (200/100)3
= 80% power

28. 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.

29. Questions?