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).

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.

Fuel Oil Systems

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

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

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

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

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 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

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: 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 Effects 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?