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National Maritime Center Providing Credentials to Mariners

U.S.C.G. Merchant Marine Exam

DDE 1000/4000 HP

Q632 Gas Turbine Plants

(Sample Examination)

of 17 Q632 Gas Turbine Plants

8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5

Choose the best answer to the following Multiple Choice Questions.

1. The circle of turbine stationary vanes that convert pressure and thermal energy to velocity energy and direct the combustion gases in the direction of turbine wheel rotation is referred to as what?

o (A) Rotor assembly. o (B) Diffuser assembly. o (C) Compressor assembly. • (D) Nozzle assembly.

If choice D is selected set score to 1.

2. What type of starter is commonly used on smaller gas turbine engines?

o (A) Pneumatic o (B) Air turbine • (C) Electric o (D) Hydraulic

If choice C is selected set score to 1.

3. Which of the following is NOT a gas turbine auto shutdown parameter?

o (A) Module enclosure fire. o (B) Power turbine over speed. o (C) High exhaust gas temperature. • (D) High compressor discharge pressure.


4. Accelerometers are generally used on gas turbine engines to sense which of the following?

o (A) Rate of rotor speed changes. o (B) Gas generator speed with respect to power turbine speed. o (C) PLARA rate limited feedback to the FSEE. • (D) High frequency vibration.


5. The acronym FOD stands for which of the following?

• (A) Foreign object damage. o (B) Fuel override demand. o (C) Flow offset design. o (D) Fuel oil discharge.

If choice A is selected set score to 1.


8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 6. Borescope inspection of the combustor section requires which type of light source?

o (A) 150 watt o (B) 500 watt • (C) 1000 watt o (D) All of the above.


7. As shown in the illustration of a gas turbine fuel oil system, when the engine fuel oil valves are de-energized, the remaining fuel left in the system is recirculated back to which of the following? Illustration GT-0021

o (A) Day tank. o (B) High-pressure relief valve. o (C) Fuel purge manifold. • (D) Fuel pump inlet.


8. For the GE LM2500 gas turbine engine shown in the illustration, the 13th stage bleed air is used for which of the following? Illustration GT-0017

o (A) Sump pressurization and cooling. o (B) Power turbine balance piston cavity pressurization. o (C) Power turbine cooling. • (D) High-pressure turbine 2nd stage nozzle cooling.


9. To keep the exit pressures relatively constant across a HP turbine blade, which type of construction is generally utilized?

o (A) Curtis. • (B) Impulse-Reaction. o (C) Impulse. o (D) Rateau.

If choice B is selected set score to 1.

10. The term "lockout" on the synchronous self-shifting (SSS) clutch system means that the _________.

• (A) SSS clutch will not engage o (B) shaft will not rotate above 10 RPM's o (C) reduction gear will not rotate o (D) shaft will not rotate



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 11. What is the purpose of the air/oil separator shown in the illustration of the gas turbine lube oil

system? Illustration GT-0024

• (A) Minimize oil consumption by separating oily vapors being vented to the atmosphere. o (B) Reduce oil foaming. o (C) Maintain oil pressure in the sumps. o (D) All of the above.


12. For the GE LM2500 gas turbine shown in the illustration, the 9th stage bleed air is used for which of the following? Illustration GT-0017

o (A) High-pressure turbine second stage nozzle cooling. o (B) Compressor balance piston cavity pressurization. • (C) Power turbine cooling. o (D) Sump pressurization and cooling.


13. A centrifugal flow gas turbine uses what type of combustion chamber?

o (A) double-annular • (B) can o (C) can-annular o (D) annular


14. The three most common types of combustors used in gas turbine engines are which of the following?

• (A) can, annular, and can-annular. o (B) can, derivative, and can-derivative. o (C) can, vortex, and can-vortex. o (D) can, angular, and can-angular.


15. The lube oil scavenge pressure on the gas turbine engine shown in the illustration is sensed by which of the following? Illustration GT-0017

o (A) Manometer o (B) RTD • (C) Transducer o (D) Probe



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 16. Kelvin is the absolute temperature scale that corresponds to which of the following?

• (A) Absolute reading of a measured temperature in degrees Celsius. o (B) Absolute reading of a measured temperature in degrees Fahrenheit. o (C) Absolute reading of a measured temperature in degrees Rankine. o (D) None of the above.


17. Where are the carbon dioxide nozzles located in the GE LM2500 gas turbine enclosure?

o (A) Above and below the combustor section. o (B) On either side of the power turbine. o (C) Above the compressor. • (D) On the cross beam under the compressor front frame.


18. The lube oil system shown in the illustration, is designed to lubricate the main bearings by what principle? Illustration GT-0023

• (A) spray lubrication with dry sumps o (B) totally submerged oil bath o (C) splash lubrication o (D) self-contained partial oil bath


19. Thermal energy is the only form of energy that can be added to or removed from a substance. How is thermal energy that is added to a substance stored?

o (A) In the form of potential kinetic energy. o (B) In the form of heat. o (C) In the form of mechanical energy. • (D) In the form of internal energy.


20. A gas turbine engine in which exhaust gas heat energy is added to the compressor air charge before entering the combustor, is classified as which of the following?

o (A) Reheat cycle. • (B) Regenerative cycle. o (C) Combined cycle. o (D) ICR cycle.



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 21. The thermal energy added to the gas as it flows through the combustion section has what effect on

the gas?

o (A) Increases pressure. o (B) Decreases volume. o (C) Decreases pressure. • (D) Increases volume.


22. The bleed air surge relief valve differs from a normal relief valve in which of the following ways?

o (A) Opens completely at a specified lift pressure and closes immediately as soon as the pressure begins to drop.

o (B) Gradually opens at a specified lift pressure and remains open until the pressure drops to a specified preset pressure.

• (C) Opens completely at a specified lift pressure and remains open until the pressure drops to a specified preset pressure.

o (D) Gradually opens at a specified lift pressure and closes immediately as soon as the pressure begins to drop.


23. What is the term given to the condition in which cyclic pressure changes result in a repetitive failure and recovery of compressor air flow?

o (A) Laminar. o (B) Turbulence. o (C) Stall. • (D) Surge.


24. What are the two primary sources of deposits that build up on compressor blades?

o (A) Salt spray and carbon residue. o (B) Lube oil mist and carbon residue. • (C) Salt spray and lube oil mist. o (D) Lube oil mist and dry particulate matter.


25. Potential energy is defined as which of the following?

o (A) The energy a body possesses due to its motion. o (B) A measurement in feet per second. o (C) A total pressure measurement. • (D) The energy a body possesses due to its position.



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 26. What is the purpose of the spring in a lip-type oil seal?

o (A) To remove burrs and dirt from the shaft • (B) To keep the neoprene snugly fit around the shaft o (C) To seal against maximum fluid pressure o (D) To prevent air from entering the sump


27. The struts of the GE LM2500 compressor front frame provide passages for all of the following mediums EXCEPT which of the following?

o (A) Scavenge oil • (B) Fuel oil o (C) Seal-pressurization air o (D) Lube oil


28. Routine water washing of the gas turbine compressor shown in the illustration, is usually performed while operating under which of the following conditions? Illustration GT-0017

o (A) At 25% power. o (B) At 75% power. o (C) At 100% power. • (D) With the starter motor drive.


29. In the operation of a marine propulsion gas turbine, kinetic and thermal energy required to drive the main propeller shaft are extracted by which of the following?

o (A) Multi-stage compressor. o (B) Combustor. o (C) Exhaust gas. • (D) Power turbine.


30. The term "divergent" is best described as which of the following?

o (A) Maintaining an equal distance between edges. • (B) Moving away from each other, as the inner walls of a tube that flare outward. o (C) Approaching nearer together, as the inner walls of a tube that is constricted. o (D)

Thermal and kinetic energy being converted to mechanical energy.



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 31. An axial compressor stator vane that is mechanically adjusted to provide optimum compressor

performance over a wide operating range is referred to as which of the following?

o (A) Variable Guide Vane (VGV) o (B) Static Guide Vane (SGV) • (C) Variable Stator Vane (VSV) o (D) Inlet Guide Vane (IGV)


32. In a single shaft, cold-end drive gas turbine, the power output speed has what relationship to the speed of the compressor?

o (A) It varies independently of compressor speed. • (B) It is the same or in a direct relationship through reduction gears. o (C) It is in an inverse relationship through reduction gears. o (D) None of the above.


33. What are the two principle functions of the turbine nozzle guide vanes?

• (A) Convert the heat energy of the hot gases into kinetic energy and direct the flow of gases to the turbine rotor blades.

o (B) Convert the potential energy of the hot gases into heat energy and direct the flow of gases to the turbine rotor blades.

o (C) Convert the heat energy of the hot gases into potential energy and direct the flow of gases to the compressor rotor blades.

o (D) Convert the heat energy of the hot gases into potential energy and direct the flow of gases to the turbine rotor blades.


34. Rotation of the controllable-pitch propeller (CPP) blades is achieved through axial movement of what component in the hub body assembly?

• (A) Crosshead o (B) Sliding block o (C) Crank pin ring o (D) Servomotor piston



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 35. A gas turbine engine's main lube oil system pump check valve serves to maintain system prime and

perform what other function?

o (A) To increase system pressure • (B) To prevent reverse flow of oil through a secured pump o (C) To return oil to the main reduction gear sump o (D) None of the above


36. According to the gas turbine engine illustration shown, the areas labeled "14 thru 29" are locations for _______. Illustration GT-0006

o (A) fuel nozzles o (B) bell mouth strut cones o (C) thermocouples • (D) inspection ports


37. While standing watch underway on a ship with the gas turbine shown in the illustration, a fire emergency stop is initiated when which of the following occurs? Illustration GT-0017

o (A) Either the primary or reserve gas turbine module CO2 system activates. o (B) The fire emergency shutdown switch located on the gas turbine module is activated. o (C) One of the UV flame detectors is activated. • (D) All of the above.


38. In a gas turbine propulsion installation, the typical control system is designed to perform which of the following three functions?

o (A) Operational control, speed control, and braking. • (B) Operational control, safety control, and monitoring. o (C) Pneumatic, hydraulic, and electric control. o (D) Pneumatic control, electric control and monitoring.


39. What type of main reduction gear arrangement prevents independent axial and rotational movement of the pinions?

o (A) Independent suspension • (B) Locked train o (C) Unlocked train o (D) Hydraulic suspension



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 40. An axial compressor stage is represented by which of the following components and in which order?

• (A) One set of rotating blades, one set of stationary vanes. o (B) One set of stationary vanes, one set of rotating blades. o (C) One set of rotating blades, two sets of stationary vanes. o (D) One set of rotating vanes, one set of stationary blades.


41. What are the two common forms of axial compressor rotor blade roots?

o (A) Grub and bulb. o (B) Fir tree and key. o (C) Sawtooth and knob. • (D) Fir tree and bulb.


42. How is the HP turbine rotor of the GE LM2500 gas turbine cooled?

o (A) By synthetic lube oil o (B) By the ship's service sea water cooling system • (C) By a continuous flow of compressor discharge air o (D) By an air to air heat exchanger


43. Newton's Second Law of Motion states which of the following?

• (A) An unbalancing force on a body tends to produce an acceleration in the same direction of the force applied.

o (B) The acceleration of a body is inversely proportional to the applied force. o (C) An unbalancing force on a body tends to produce an acceleration in the opposite direction of

the force applied. o (D) The acceleration of a body is directly proportional to the mass.


44. The purpose of the metal spray rub coating on the rotor and stator casing of an axial type compressor is which of the following?

o (A) control air flow through the compressor • (B) provide close vane to rotor and blade to stator case clearances o (C) seal the circumferential dovetails o (D) ensure protection for the gearbox adapter when removing or replacing the bearings



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 45. All clock positions, engine references, and enclosure references apply to viewing the gas turbine

engine shown in the illustration, from which of the following locations? Illustration GT-0017

o (A) Right side of the compressor to the left side. o (B) Left side of the power turbine to the right side. o (C) Intake end, looking toward the exhaust end. • (D) Rear (exhaust end), looking toward the intake end.


46. Which of the following statements is true regarding centrifugal compressors?

o (A) The impeller of a centrifugal compressor has a radial inlet and axial discharge. o (B) The efficiency of a centrifugal compressor is greater than that of an axial compressor. • (C) The centrifugal compressor is frequently used on small, low power turbines. o (D) Centrifugal compressors are complicated in design and heavy.


47. Which of the following is the principle that a magnetic speed sensor/pickup operates on?

• (A) Voltage is produced when a ferrous material moves through a magnetic field. o (B) Vibration caused by shaft rotation can determine the speed of rotation. o (C) Force is the product of mass and acceleration. o (D) Variations in the earth’s magnetic field are caused by ferrous materials.


48. What is the power source for the ignition exciter of a gas turbine engine?

o (A) Ship's 400 Hz system • (B) Ship's 115 volt AC system o (C) Ship's 28 volt DC system o (D) Four lead-acid batteries


49. You are on watch on a gas turbine propelled vessel as shown in the illustration. After reducing power in response to a high lube oil supply temperature alarm, the temperature continues to increase. Your next step should be which of the following? Illustration GT-0017

o (A) Continue to reduce power. • (B) Shutdown the engine. o (C) Water wash the engine. o (D) Check oil consumption.



8/30/2017

U.S.C.G. Merchant Marine Exam DDE 1000/4000 HP Q632 Gas Turbine Plants Illustrations: 5 50. As shown in the illustration, what is the purpose of pressurizing the main bearing lube oil sumps on a

typical marine gas turbine? Illustration GT-0023

o (A) Provides uniform lube oil distribution around the bearing. • (B) Minimizes oil leakage from the rotor shaft. o (C) Increases lube oil penetration. o (D) Assists in cooling the lube oil.



8/30/2017


6/10/2015

GT-0006

Adapted for testing purposes only from Gas Turbine Systems Supervisor

NAVEDTRA 14111

Further reproduction prohibited without permission. of 17 Q632 Gas Turbine Plants


6/26/2015

GT-0017

Adapted for testing purposes only from Gas Turbine Systems Technician (Electrical) 3/

Gas Turbine Systems Technician (Mechanical) 3, Volume 2

NAVEDTRA 14114

Further reproduction prohibited without permission.

EE DD

FF

CC

BB AA



7/7/2015

GT-0021



NAVEDTRA 14114

Further reproduction prohibited without permission.

A

B 1 2

3

5

4 6



7/14/2015

GT-0024



NAVEDTRA 14114


national maritime center - dco.uscg.mil€¢ (a) sss clutch will not engage o (b) ... • (b)...

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