Other Engineering Fundamentals

Question 1

Who made the engines on Momsen?

Answer 1

General Electric LM2500 Gas Turbine Engines (GTE)

Question 2

How much power do the GTEs produce?

Answer 2

26,000 HP

Question 3

What are the four plant configurations?

Answer 3

1. Full Power = Four GTE online
2. Split Plant = One GTE on each shaft
3. Trail Shaft = One GTE on one shaft, idle shaft is windmilling
4. Locked shaft = MRG is locked due to a casualty

Question 4

What does GTM stand for?

Answer 4

Gas Turbine Module

Question 5

What does a GTM do?

Answer 5

Provides thermal and acoustic protection from the running Gas Turbine Engine for the crew

Question 6

Specs of the GTM

Answer 6

• Fire resistant for 2000* F for 15 min

- Sits on 32 shock mounts to allow movement between the engine and the ship’s hull

Question 7

What does MRG stand for?

Answer 7

Main Reduction Gear

Question 8

What does an MRG do?

Answer 8

Connects the turbines and shafts. Reduces the high RPM’s of the turbines to a working, more efficient speed. Reduces the speed to allow proper RPM at the propellors

Question 9

What are the six characteristics of an MRG?

Answer 9

1. Double input - Two GTMs as prime movers input to MRG
2. Double reduction - Reduction occurs over two stages to convert high speed, low torque to low speed, high torque
3. Double helical - Gear teeth are machine in a “V” pattern. Reduces noise and axial thrust
4. Articulated - The gears inside are connected to the pinion by a quill shaft
5. Single output - Each MRG drives a single shaft
6. Locked train - Refers to the gearing inside the MRG which is locked together to rotate in only one direction

Question 10

Characteristics of the ship’s shafts

Answer 10

Port - [168ft] Consists of 1 thrust bearing and 1 line shaft bearing located in shaft alley

STBD - [228ft] Consists of 1 thrust bearing in AUX 2, 1 line shaft bearing in MER 2 and a second line shaft bearing in shaft alley

Question 11

What are the Thrust Bearings?

Answer 11

Used to absorb the fore and aft thrust of the shaft as the torque is transmitted to the propellor. It is used to protect the gears inside of the MRG

Question 12

What are the Line Shaft Bearings?

Answer 12

Used to keep the shaft centered and true as it rotates and to support the weight of the shaft

Question 13

What are the Strut Bearings?

Answer 13

Mounted to the hull outside the skin of the ship. Used to support the weight of the propellor. Lubricated by seawater

Question 14

What are the Bulkhead Shaft Seals?

Answer 14

Used around the shaft where the shaft penetrates the ship’s bulkhead. Used to keep water from flooding out an adjacent space and keep it contained in the space that is flooding

Question 15

What are the Stern Tube Shaft Seals?

Answer 15

Located in shaft alley on port and stbd shafts. This seal is important as it prevents the ocean from flooding out shaft alley. In case of a leak, the seal can be inflated using LP air or two CO2 bottles mounted on the bulkhead. Once inflated the shaft cannot be rotated

Question 16

What are the four kinds of bleed air?

Answer 16

SPAM

Start Air
Prairie Air
Anti-icing
Masker Air

Question 17

What do each of the kinds of bleed air do?

Answer 17

Start Air - Used to start the GTMs and as an alternate source to start the GTGs

Prairie Air - Used to mask the noise of the propellor blades. Air travels down the shaft and exits through the small holes on the leading edge of each propeller blade creating bubbles in the water

Anti-icing - Used to warm up the intakes of the GTMs and GTGs in cold climates where the intakes may ice up by diverting warm bleed air to the intakes

Masker Air - Three emitter belts run around the hull of the ship in the vicinity of AUX 1, Main 1 and Main 2. Air exits through small holes out of the belts creating bubbles to mask the machinery noise

Question 18

What does CPP stand for?

Answer 18

Control Pitch Propeller

Question 19

What is the purpose of the CPP?

Answer 19

Used to vary the angle of attack of the propeller blades, otherwise known as PITCH. PITCH, when measured in feet, is the theoretical distance the ship will move through the water for each revolution of the shaft. Due to the MRG being Locked Train we are not able to go in reverse.

CPP helps us achieve reverse by rotating the propeller pitch to a negative percent resulting in a reverse movement of the ship

Question 20

Characteristics of the CPP

Answer 20

• Maximum CPP is -61 percent astern to +120 percent ahead
• Normal CPP range is -45 percent (full astern) to +100 percent (full ahead)
• Hand pump - Used for setting emergency ahead pitch and also if the CRP pumps fail

Question 21

How many blades are in each propeller?

Answer 21

5

Question 22

Characteristics of the blades

Answer 22

• Counter rotating
• STBD rotates clockwise viewed from the stern
• Nickel-Aluminum-Bronze
• 6200 LBs per blade

Question 23

What does HOPM stand for?

Answer 23

Hydraulic Oil Power Module [2]

Considered the heart of the CPP system

Question 24

What two divisions does the HOPM divide oil into?

Answer 24

1. Control Oil

2. Power Oil

Question 25

What do Control Oil and Power Oil do?

Answer 25

Control Oil

• Used to move the auxiliary servo piston located in the oil distribution box
• Regulated to 400 psi

Power Oil

• Used to move the main or hub servo located in the propeller hub assembly
• Normal Pressure: 500-800 psig
• Can get high as 1000 psig

Question 26

What is the Oil Distribution Box?

Answer 26

Control the position of the blades by positioning the valve rod, which in turn directs high-pressure hydraulic oil in the hub

Question 27

Where are the Oil Distribution Boxes located?

Answer 27

1. Port Shaft- located at the end of the MRG and the bulkhead
2. STBD Shaft- Located between 1A and 1B GTM