national maritime center - dco.uscg.mil · which of the following conditions will not be the result...

National Maritime Center Providing Credentials to Mariners

U.S.C.G. Merchant Marine Exam

First Assistant Engineer, Unlimited

Q515 Gas Turbine Plants

(Sample Examination)

of 25 Q515 Gas Turbine Plants

8/30/2017

U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9

Choose the best answer to the following Multiple Choice Questions.

1. You are conducting a borescope inspection of the compressor section of a GE LM2500 gas turbine. In stage four, you see a slight tilt to one blade and the blade platform is raised higher than the other blades. What could be a cause of this condition and what would be your course of action?

• (A) Condition could be the result of blade root failure. Engine should be taken out of service until condition can be evaluated.

o (B) FOD damage could cause this condition. Engine can be operated at full load until next scheduled maintenance.

o (C) Metal fatigue could cause this condition. Engine can be operated but gas generator speed should be reduced.

o (D) Ice damage could cause this condition. Blade tilt should be corrected using special tool provided, then engine will be safe to operate.

If choice A is selected set score to 1.

2. What type of seal is used in the gearbox of a gas turbine engine?

o (A) Fishmouth o (B) Labyrinth-Windback • (C) Carbon ring o (D) Lip-type

If choice C is selected set score to 1.

3. A fuel analysis report for a gas turbine propelled vessel indicates a calcium level in excess of 0.5 ppm. High calcium levels in distillate fuels for gas turbines can cause which of the following?

o (A) Corrosion in the combustor section of the turbine. o (B) Clogged fuel filters in the fuel service system. • (C) Calcium deposits which can clog cooling holes in the turbine section. o (D) Abrasive wear in the compressor section of the turbine.


4. What design feature is incorporated into the main propulsion gas turbine to eliminate compressor surge?

o (A) The governor adjusts the fuel to maintain the turbine inlet temperature constant. • (B) Variable compressor stator vanes are used. o (C) Fuel modulating function is incorporated into the governor control system. o (D) The governor maintains the compressor turbine speed constant.

If choice B is selected set score to 1.


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5. The two basic types of compressors used in gas turbine engines are which of the following?

• (A) Centrifugal and axial. o (B) Centrifugal and reciprocating. o (C) Axial and lobe. o (D) Axial and reciprocating.


6. While air is being compressed in a centrifugal flow gas turbine, what happens to the direction of air flow?

• (A) Changes at each separate component. o (B) Changes only at the compressor inlet. o (C) Changes only once from inlet to outlet. o (D) Changes only at the compressor discharge.


7. What type of metallurgical failure does Item A represent in the illustration? Illustration GT-0014

• (A) Radial cracking. o (B) Rupture. o (C) Axial cracking. o (D) Creep.


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

If choice D is selected set score to 1.

9. The fuel purge valve on the marine gas turbine shown in the illustration is opened _________. Illustration GT-0017

o (A) automatically with auto sequencing o (B) prior to starting o (C) manually by the operator • (D) all of the above



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 10. What does the term "lock-out" of a synchro-self-shifting (SSS) clutch system mean? Illustration GT-

0018

o (A) Shaft will not rotate. o (B) Reduction gear will not rotate. • (C) SSS clutch will not engage. o (D) Shaft will not rotate above 10 RPM.


11. On the marine gas turbine engine shown in the illustration, what temperature should be carefully monitored following a shutdown for an engine fire? Illustration GT-0016

o (A) combustor liner o (B) fuel manifold • (C) power turbine inlet o (D) compressor discharge


12. The electrostatic vent fog precipitator removes oil mist from which of the following areas?

o (A) Synchronous self-shifting clutch o (B) Gas turbine engine • (C) Main reduction gear o (D) Lube oil storage tank


13. Aboard ship, single-shaft gas turbines are used mostly as prime movers for which of the following applications?

o (A) Multi-screw ships o (B) Auxiliary power units o (C) Single-screw ships • (D) Generators


14. Which of the following is true concerning the main engine lube oil system of the marine gas turbine shown in the illustration? Illustration GT-0024

• (A) The system includes a single combined lube oil supply and scavenge pump. o (B) The line shaft bearing lubrication system is provided for by the LOSCA. o (C) Lubrication is provided for the main reduction gears through the transfer gearbox. o (D) All of the above.



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 15. You are conducting a borescope inspection of the combustor section of a GE LM2500 gas turbine

engine. You observe a one square inch hole in the combustor dome where burn through has removed the metal. What would be your course of action?

• (A) Record the damage and continue to operate the engine while monitoring the high-pressure turbine temperatures and nozzle condition.

o (B) Immediately take the engine out of service. o (C) Operate the engine only in an emergency and at reduced load. o (D) Make temporary repairs with onboard repair kit to patch hole.


16. Which of the following is the most probable cause if, while underway, the main propulsion gas turbine air intake blow-in doors open?

o (A) Air inlet pressures to the compressor are higher than normal. o (B) Exhaust pressures are higher than normal. o (C) Air inlet temperatures to the compressor are higher than normal. • (D) Ice has formed on the air intakes.


17. Gear backlash is best described as which of the following?

o (A) Radial play between the pinion teeth and bearings. o (B) Clearance of the gears that do not mesh. o (C) Clearance of the gears operating in parallel. • (D) Play between the surfaces of the teeth in mesh.


18. Boyle's law can best be defined as _________.

• (A) the volume of an enclosed gas varies inversely with the applied pressure, provided the temperature remains constant

o (B) if the pressure is constant, the volume of an enclosed gas varies indirectly with absolute temperature

o (C) a body at rest tends to remain at rest o (D) none of the above


19. How do you gain access to the burner units of a can-annular combustor to perform maintenance?

o (A) By removing the power turbine • (B) By sliding the can-annular case aside o (C) By removing the annular case o (D) By disassembling the engine



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 20. In order to get a ready indication for a normal start with a GE LM2500 marine gas turbine, what

permissive(s) must be met?

o (A) Bleed air valve must be closed. o (B) Gas generator speed must be less than 1200 RPM and all engine trips reset. o (C) Fuel supply pressure must be greater than 8 psig. • (D) All of the above.


21. You are preparing for a borescope inspection of an LM2500 gas turbine engine. You are reviewing the correct geometric orientation nomenclature which includes which of the following?

• (A) All references left, right, and radial are orientated as viewed from aft looking forward on the engine.

o (B) All references left, right, and radial are orientated as viewed from forward looking aft on the engine.

o (C) All references are made from the combustor section, forward to the HP turbine and aft to the power turbine.

o (D) All references are made from the combustor section, aft to the HP turbine and forward to the power turbine.


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

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


23. Which of the following conditions will NOT be the result of a build-up of deposits in a gas turbine compressor?

o (A) Turbine blade corrosion. o (B) Increased combustion gas temperatures. • (C) Reduced fuel consumption. o (D) Restricted air flow.



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24. Which of the following designs is the most satisfactory method for attaching turbine blades to the rotor disk?

• (A) Fir-tree design. o (B) Pinning design. o (C) Retaining ring design. o (D) Locking tab design.


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

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


26. The main fuel control module used on a marine gas turbine engine as shown in the illustration, is responsible for managing which function(s)? Illustration GT-0021

o (A) acceleration schedule o (B) variable stator vane feedback lever o (C) deceleration schedule • (D) all of the above


27. Most GTE fuel nozzles have passages for all of the following except ____________.

o (A) compressed air o (B) primary fuel flow • (C) cooling water o (D) secondary fuel flow


28. What is the purpose of the GE LM2500 gas turbine enclosure heater?

o (A) To ensure enclosure temperature is maintained at 145 degrees F • (B) To ensure fuel viscosity is maintained while the GTE is secured o (C) To warm up the enclosure for maintenance personnel o (D) To increase inlet air temperature



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 29. Which of the following is the most probable cause for the sump oil to be excessively aerated on an

aero derivative main propulsion gas turbine engine?

o (A) The compressor discharge pressure is lower than normal. o (B) Exhaust pressures are lower than normal. o (C) Air inlet temperatures to the compressor are higher than normal. • (D) The air oil separator is not functioning properly.


30. Assuming that the turbine inlet temperature of a gas turbine engine remains constant, which of the following operating parameter changes would be noted with an increase in the compressor inlet air temperature?

o (A) The power turbine output increases due to hot inlet air requiring less fuel to be heated to the same turbine inlet temperature.

• (B) The gas turbine power would drop due to reduced mass air flow. o (C) The exhaust temperature would drop significantly. o (D) The mass air flow through the gas turbine would increase.


31. On a GE LM2500 gas turbine powered vessel you are conducting a borescope inspection of the compressor. What is used on each compressor stage as a reference for indexing the blades?

o (A) Scribe marks located on the stator and rotor diaphragm. o (B) The IGV actuator. • (C) The locking lug blades. o (D) Witness marks center punched on the #1 nozzle and blade.


32. The term used to describe a gas turbine in which air drawn from the atmosphere passes through the engine only once is which of the following?

• (A) Open cycle. o (B) Uni-cycle. o (C) Semi-closed cycle. o (D) Closed cycle.


33. In general, diesel engine waste heat boiler construction is usually of the _________.

o (A) cyclone furnace boiler type • (B) water-tube type o (C) dry back boiler type o (D) critical circulation boiler type



8/30/2017

U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 34. In the marine gas turbine engine shown in the illustration, the HP turbine 1st stage nozzle vanes are

cooled by which of the following? Illustration GT-0020

o (A) 8th stage compressor air o (B) 9th stage compressor air o (C) 13th stage compressor air • (D) 16th stage compressor air


35. Once a compressor is broken in, which of the following factors will most likely cause blade tips to rub?

• (A) Failure of a rotor bearing o (B) Sprayed material in the stator case o (C) Profiles on the blade tips o (D) Elongation of the blade tips


36. Provisions for avoiding the buildup of ice on the intake air surfaces of a gas turbine plant can be found where?

o (A) In the stack intake ducting. o (B) In the inlet duct frame at the inlet to the engine. o (C) In the exhaust and intake ducting. • (D) Both A & B.


37. What is a compressor midspan shroud?

o (A) A method of securing stator blades. • (B)

A brace built into the middle of a rotor blade for damping. o (C) A support for the tips of the stator blades. o (D) The center of a two-piece rotor blade.


38. The buildup of contamination in a gas turbine will cause all of the following conditions EXCEPT which of the following?

• (A) Reduced fuel consumption o (B) Increased combustion gas temperatures o (C) Restricted air flow o (D) Turbine blade corrosion



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 39. What type of air seal is used in the combustor and turbine midframe of a gas turbine?

o (A) Lip-type • (B) Fishmouth o (C) Labyrinth-Honeycomb o (D) Pneumatic carbon ring


40. The turbine nozzle blades convert the combustion gases heat and pressure energy into what form of energy?

o (A) Thermal • (B) Velocity o (C) Chemical o (D) Electrical


41. On a gas turbine powered vessel, what is the last step after an off-line water wash?

o (A) Secure the starting system. o (B) Release the gas generator brake. • (C) Start the engine to dry it out. o (D) Open the variable stator vanes.


42. HP turbine blades are generally cooled by which of the following methods?

o (A) Compressed air entering the tip and exiting the root. o (B) Cooling water entering the root and exiting the tip. o (C) Cooling water entering the tip and exiting the root. • (D) Compressed air entering the root and exiting the tip.


43. On a gas turbine engine, a high outside air temperature can cause high turbine inlet temperature, low mass/weight of air flow through the turbine, and which of the following conditions?

• (A) A requirement for more energy to achieve adequate compression o (B) Cooler exhaust gas temperature o (C) A requirement for less energy to achieve adequate compression o (D) None of the above



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44. The gage glass on a coil-type auxiliary boiler is connected to the __________.

o (A) surge chamber o (B) water softener o (C) heating coil inlet and outlet • (D) accumulator


45. A photoelectric cell installed in an automatically fired auxiliary boiler burner management system __________.

• (A) opens the burner circuit upon sensing a flame failure o (B) detects a flame failure by monitoring radiant heat from glowing refractory o (C) requires mechanical linkage to secure the burner fuel supply o (D) must be bypassed at low firing rates


46. What type of gas turbine cycle configuration is shown in the illustration? Illustration GT-0026

o (A) Intercooled type. o (B) Simple type. o (C) Recuperative type. • (D) Intercooled-recuperated type.


47. You are preparing for a borescope inspection of a gas turbine engine. Prior to the inspection it is recommended that you do which of the following?

o (A) Water wash both the compressor and the power turbine. • (B) Water wash the compressor. o (C) Water wash the power turbine. o (D) Not water wash the engine prior to the inspection.


48. The turbine nozzles convert heat and pressure energy to velocity energy by means of which of the following?

o (A) Divergent process. o (B) Deflection process. • (C) Convergent process. o (D) Convergent-Divergent process.



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 49. For the same amount of available power, how does a low-speed two-stroke diesel engine compare

to a recuperated gas turbine configuration?

o (A) The two-stroke diesel engine would burn less fuel and the nitrogen oxide (NOx) levels in the exhaust would be much lower than that of a recuperated gas turbine configuration.

o (B) The two-stroke diesel engine would burn more fuel than a recuperated gas turbine; however, the particulate and nitrogen oxide (NOx) levels in the exhaust would be lower.

• (C) The two-stroke diesel engine would burn less fuel than a recuperated gas turbine; however, the levels of particulate and nitrogen oxide (NOx) levels in the exhaust would be higher.

o (D) The two-stroke diesel engine would burn more fuel and the particulate and nitrogen oxide (NOx) levels in the exhaust would be higher than that of a recuperated gas turbine configuration


50. How many fuel igniters would be installed on the marine gas turbine engine shown in the illustration? Illustration GT-0017

o (A) 1 • (B) 2 o (C) 3 o (D) 4


51. What is the term used to describe the stationary vanes preceding the first stage of an axial compressor?

o (A) Variable inlet vanes. • (B) Inlet guide vanes. o (C) First stage stator vanes. o (D) Variable stator vanes.


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



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53. 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 heat energy of the hot gases into potential 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 potential energy of the hot gases into heat energy and direct the flow of gases to the turbine rotor blades.


54. In the marine gas turbine engine shown in the illustration, the 13th stage bleed air is used for __________. Illustration GT-0017

• (A) high-pressure turbine 2nd stage nozzle cooling o (B) sump pressurization and cooling o (C) power turbine balance piston cavity pressurization o (D) power turbine cooling


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

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


56. To prevent overheating of the illustrated turbine blade, which of the following fluids is circulated through it via the shaped internal passages? Illustration GT-0029

o (A) External compressed air. o (B) Cooling oil. o (C) Cooling water. • (D) Bleed air.



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57. What type of main lube oil supply and scavenging pump is installed on the marine gas turbine engine shown in the illustration? Illustration GT-0017

• (A) Vane. o (B) Flexible diaphragm. o (C) Reciprocating piston. o (D) Centrifugal.


58. The main thrust bearing directly positions which part(s) of the main reduction gear?

• (A) Bull gear. o (B) Low-speed pinion. o (C) High-speed pinion. o (D) High-speed gear.


59. What is the disadvantage of a dual-entry centrifugal compressor compared to a single-entry centrifugal compressor?

o (A) The dual-entry compressor has a greater efficiency. o (B) The dual-entry compressor is larger in diameter. o (C) The dual-entry compressor rotates at slower speeds. • (D) The dual-entry compressor utilizes a more complicated inlet ducting.


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

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


61. A white-gray powdery deposit can usually be found on which of the following metals?

• (A) Aluminum. o (B) Magnesium. o (C) Magnetite. o (D) Steel.



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 62. The gas generator section of the GE LM2500 gas turbine engine is composed of all of the following

components EXCEPT for which of the following?

o (A) FOD screen o (B) Bellmouth o (C) Two-stage HP turbine • (D) Six-stage LP turbine


63. An axial compressor basically consists of which of the following?

o (A) A rotating impeller and a stationary diffuser. o (B) Rotating pistons and stationary liners. • (C) Stationary vanes and rotating blades. o (D) A stationary impeller and a rotating diffuser.


64. Which of the following components prevent(s) objects smaller than 1/4 inch from entering the engine?

o (A) Inlet louvers o (B) Demister pads • (C) FOD screens o (D) Centerbody


65. What are the two prime sources of deposits that build up on compressor blades?

o (A) Carbon residue and lube oil mist • (B) Lube oil mist and salt spray o (C) Lube oil mist and fuel oil spray o (D) Salt spray and carbon residue


66. If after reducing power to a GTE in response to a high lube oil supply temperature alarm, the temperature continues to rise; your next step should be to __________.

o (A) continue to reduce power o (B) waterwash the engine • (C) shutdown the engine o (D) check oil consumption



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U.S.C.G. Merchant Marine Exam First Assistant Engineer, Unlimited Q515 Gas Turbine Plants Illustrations: 9 67. What type of main reduction gear arrangement prevents independent axial and rotational movement

of the pinions?

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


68. A reddish-colored oxide usually forms on which of the following metals?

o (A) Magnesium. o (B) Chromium. o (C) Aluminum. • (D) Steel.


69. When tip clang takes place on a gas turbine engine, the major damage occurs to what area of the blade?

o (A) Chord o (B) Tip o (C) Midspan • (D) Root


70. 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) Inlet guide vane (IGV) o (B) Static guide vane (SGV) o (C) Variable guide vane (VGV) • (D) Variable stator vane (VSV)



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6/15/2015

GT-0014

Adapted for testing purposes only from Gas Turbine Systems Supervisor

NAVEDTRA 14111

Further reproduction prohibited without permission.

A

B



6/25/2015

GT-0016

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. of 25 Q515 Gas Turbine Plants


6/26/2015

GT-0017



NAVEDTRA 14114


EE DD

FF

CC

BB AA



6/29/2015

GT-0018



NAVEDTRA 14113



7/1/2015

GT-0020



NAVEDTRA 14114



7/7/2015

GT-0021



NAVEDTRA 14114


A

B 1 2

3

5

4 6



7/14/2015

GT-0024



NAVEDTRA 14114


national maritime center - dco.uscg.mil · which of the following conditions will not be the result...

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