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NEI > Main Propulsion and Shaftline > Flashcards

Main Propulsion and Shaftline Flashcards

1
Q

Purpose

A

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.

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2
Q

Gas Turbines

A

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.

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3
Q

PDE

A

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

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4
Q

Diesel Cycle

A

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

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5
Q

What are the aspects of the gearing?

A

Double Helical
Double Reduction
Dual Tandem
Articulated
Locked Train

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6
Q

Double Helical

A

Cut of the teeth

Allows smooth meshing
Eliminates axial thrust
Distributes load across teeth

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7
Q

Double Reduction

A

Refers to the number of reduction stages within each gearbox.

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

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8
Q

Dual Tandem

A

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.

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9
Q

Articulated

A

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.

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10
Q

Locked Train

A

Pre-loading of torque on gearing elements during assembly.

Load is distributed evenly across all gear teeth.

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11
Q

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

A

Turning Gear
Shaft Locking Device

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12
Q

Turning Gear

A

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.

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13
Q

Shaft Locking Device

A

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.

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14
Q

SSS Clutch

A

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.

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15
Q

Friction Clutches

A

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.

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16
Q

Modes of Operation:

A

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

17
Q

Flexible Coupling

A

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

18
Q

Combined Thrust and Plummer bearing

A

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.

19
Q

Solid couplings.

A

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.

20
Q

Bulkhead Seal

A

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.

21
Q

Torsion Meter

A

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.

22
Q

CRPP Actuating Unit

A

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

23
Q

CRPP Stand-By Pump Belts

A

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

24
Q

CRPP Hand pump

A

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.

25
Q

Loose Coupling

A

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.

26
Q

Plummer Bearing

A

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.

27
Q

Shaft Grounding Devices

A

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.

28
Q

Stern Seal

A

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.

29
Q

Draw the Stern Seal

A
30
Q

Eddy Plates

A

Limit turbulence where teh shaft line exits the ship.

For noise and for flow over the propellers.

31
Q

Loose Coupling (Stern Shaft)

A

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.

32
Q

A brackets

A

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.

33
Q

Propeller Hub

A

House the CRPP components that perform propeller pitch angle actuation.

Provide a base to mount the propeller blades.

34
Q

Propeller Blades

A

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.

35
Q

Explain Cavitation

A

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.

36
Q

Operational Description

A

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.

37
Q

System Interfaces

A

MLO
CRPP
EPG&D
ASWC
LP Air
FOS
IPMS
LOSCA

38
Q

Redundancy and Survivability

A

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

NEI (15 decks)

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