Main Propulsion and Shaftline

Question 1

Purpose

Answer 1

The purpose of the Main Propulsion and Shaftline system is to convert the rotational energy produced by the prime movers into thrust at the propellers, then transfer this thrust to the hull of the ship to propel the ship ahead or astern through the water.

Question 2

Gas Turbines

Answer 2

2x General Electric LM2500 Gas Turbines, both identicle and unidirectional, mounted in a raft assembly.

17.2 MW each
Gearing reduction ratio from GT output to shaftline input is 17.2:1.
GT aerodynamically coupled to the power turbine.

Located in the FER.

Question 3

PDE

Answer 3

1x 20-cylinder Pielstick Propulsion Diesel Engine, raft mounted.

6.47 MW
1050 rpm
Gearing reduction from PDE output to shaft line input is 8.9:1.

Located in the AER

Question 4

Diesel Cycle

Answer 4

Suck, Squeeze, Bang, Blow.
Intake, compression, power, exhaust.

Question 5

What are the aspects of the gearing?

Answer 5

Double Helical
Double Reduction
Dual Tandem
Articulated
Locked Train

Question 6

Double Helical

Answer 6

Cut of the teeth

Allows smooth meshing
Eliminates axial thrust
Distributes load across teeth

Question 7

Double Reduction

Answer 7

Refers to the number of reduction stages within each gearbox.

17:1 reduction achieved in two stages:
2.9:1 then 5.8:1

Question 8

Dual Tandem

Answer 8

GT’s load is transferred through each main gearbox along split power path (2 primary gearwheels to two secondary pinions and quill shafts.

Allows smaller gearing components.

Question 9

Articulated

Answer 9

Torsional flexibility tghrough the use of quill shafts and flexible couplings.

Achieves a torsional flexibility that would otherwise only be achieved using a longer shaft.

Question 10

Locked Train

Answer 10

Pre-loading of torque on gearing elements during assembly.

Load is distributed evenly across all gear teeth.

Question 11

What are the two miscellaneous components fitted to the reduction gearing assembly?

Answer 11

Turning Gear
Shaft Locking Device

Question 12

Turning Gear

Answer 12

Allow the reduction gearing assembly to be rotated without the use of the prime movers.

Initial lubrication
Prevents sagging.

Fitted to the after end of each main gearbox.

Question 13

Shaft Locking Device

Answer 13

A mechanical means of preventing the shaft from rotating. Consists of a turnbuckle.

Used in the event that rotation of the shaft line would cause further damage.

One device per ship.

490 kNm

Fitted at the FWD end of the Lower Main Quill Shafts.

Question 14

SSS Clutch

Answer 14

Synchronous Self-Shifting Clutch

Connect the Port and Stbd GTs to their respective main gearboxes.

Based on principle of over-riding torque. Like a bottlecap.

Question 15

Friction Clutches

Answer 15

Cross Connect Friction Clutches: Connect the Port and Stbd Main Gearboxes to the X-Conn Gearbox

Diesel Engine Friction Clutch: Connects the PDE to the X-Conn Gearbox

Use HP air to press a series of disk plates together, coupling the input and output members.

Fails to disengaged position.

Question 16

Modes of Operation:

Answer 16

Normal (both CCFCs engaged):

Port GT X-Conn (26kts ahead, 15 astern)
Stbd GT X-Conn (26 kts ahead, 15 astern)
2 GT X-Conn (30.8 kts ahead, 15 astern)
PDE X-Conn (17 kts ahead, 10 astern)

Abnormal (At least 1 CCFC disengaged):

Port GT Uni
Stbd GT Uni
2 GT Uni
PDE Uni Port
PDE Uni Stbd

Question 17

Flexible Coupling

Answer 17

Comprised of inner and outer members separated by rubber blocks and buffers.

Attenuates vibrations and accomodates misalignment between the raft mounted gearing assembly and solidly mounted shaft line.

Accomodates 15mm radial, 15mm axial, 0.633 degrees angular misalignment.

Located in the FER

Question 18

Combined Thrust and Plummer bearing

Answer 18

Thrust portion consists of a thrust collar on the shaftline and 8 tilted bearing pads.

Bearing portion consists of 5 tilted journal bearing pads.

Supports the weight of the shaft and transfers axial thrust to the hull of the ship.

Hydrodynamic lubrication ensures bearing to shaft contact does not occur.

Cooled and lubricated by MLO and radial cooling fins.

Located in the FER.

Question 19

Solid couplings.

Answer 19

Consist of two flanged faces bolted together.

Transfer torque and thrust between two shaft sections.

Torque is transferred across the surfaces of the flanges, not through the bolts.

Question 20

Bulkhead Seal

Answer 20

Consists of a housing and an axially sliding block tension mounted to the shaft.

Maintains watertight and airtight integrity as the shaft line penetrates the bulkhead.

Seals at 0.05 bar pressure differential.

Question 21

Torsion Meter

Answer 21

30 equally spaced magnets on a collar on the shaftline. Magentic pickup in the housing measures shaft rpm.

Strain guage on the shaft line measures torque and transmits via FM telemetry to the housing.

Question 22

CRPP Actuating Unit

Answer 22

Admits hydraulic oil from the CRPP pumps to the hollow shaft line for propeller pitch angle actuation.

Question 23

CRPP Stand-By Pump Belts

Answer 23

7 belts looped around the shaftline are coupled to standby pumps.

Deliver hydraulic oil to the CRPP Actuating Unit in the event that electrical power is lost.

7 belts to a pulley wheel.
4 belts to Pump No. 1 clutch.
2 belts from No. 1 output to No. 2 input clutch.

6 bar - Pump No. 1 engages
92 - 98 rpm - Pump No. 2 engages

Question 24

CRPP Hand pump

Answer 24

Hand pump can be used if all other pumps fail.

Used to set pitch angle to full ahead (32 degrees), then 4 steel locking pints are inserted to hold the propeller pitch.

Question 25

Loose Coupling

Answer 25

2 flanged faces are bolted together with one side of the coupling sleeve-mounted to the shaft line, which allows a gap between shaft line sections. Transfers torwue and thrust and the gap allows a maintainer to place additional sets of CRPP Standby Pump drive belts around the shaft.

Question 26

Plummer Bearing

Answer 26

Supports the weight of the shaft and aligns its rotation. 5 tilted journal bearing pads ensure hydrodynamic lubrication. Has its own dedicated sump. An oil disk picks up oil and a scraper ring scarpes it off and directs it onto the bearing pads. Cooled by ASWC and radial cooling fins.

Question 27

Shaft Grounding Devices

Answer 27

Remove electrical potential from the shaft line. Reduces the magnetic signature and prevents corossion (electrons leave the hull (anode) to build up on the shaft (cathode). Active grounding: DC voltage supplied. Used where there is threat of mines. Passive grounding: Prevents corrosion.

Question 28

Stern Seal

Answer 28

Prevents ingress of water into the ship. A stationary sealing face is pressed against a rotating sealing face hard-mounted to the shaft line. Tension is provided by an Omega Spring. Back up seal inflated by LP air. With seal inflated, rpm restricted to 50 rpm and a leakage rate of 25 - 50 L/min required for cooling.

Question 29

Draw the Stern Seal

Answer 29

Question 30

Eddy Plates

Answer 30

Limit turbulence where teh shaft line exits the ship. For noise and for flow over the propellers.

Question 31

Loose Coupling (Stern Shaft)

Answer 31

Both sides are press fit into a sleeve. Allows the shaft to be taken apart for easier maintenance. Hood fairings ensure laminar flow of seawater across coupling into A bracket.

Question 32

A brackets

Answer 32

Support the weight of the shaft and aline its rotation. Uses elastomer polymer phenolic resin bearings. Lower portion is solid. Upper portion is staved to assist in cooling and hydrodynamic lubrication using seawater. Surrounded by a fairing with slots which ensure laminar flow of seawater.

Question 33

Propeller Hub

Answer 33

House the CRPP components that perform propeller pitch angle actuation. Provide a base to mount the propeller blades.

Question 34

Propeller Blades

Answer 34

5 variable pitch propeller blades mounted to the Propeller Hub. 4.34m dia Full Ahead Pitch: 32.2 degrees. Zero-Thrust Pitch: 4 degrees ahead. Full Astern Pitch: -19.5 degrees.

Question 35

Explain Cavitation

Answer 35

Low pressure zones develop on the propeller blade at the boundary layer. Water vapourizes into steam bubbles which then collapse and create shock waves which damage the propeller and create noise.

Question 36

Operational Description

Answer 36

PRIME MOVERS generate high speed low torque rotational energy. GEARBOXES convert this into low speed high torque rotational energy and couple it to the shaftline. SHAFTLINE carries the rotational energy to the propellers. PROPELLERS convert the rotational energy into thrust. Pitch angle constant above 10.7 kts. SHAFTLINE carries the thrust to the CTPB. CTPB transfers the thrust to the hull.

Question 37

System Interfaces

Answer 37

MLO CRPP EPG&D ASWC LP Air FOS IPMS LOSCA

Question 38

Redundancy and Survivability

Answer 38

Multiple Prime Movers Mutltiple shaftlines Multiple drive mode configurations Multiple propulsion control modes Standby CRPP Pumps Inflatable stern seal BHS