U.S.C.G. Merchant Marine Exam Chief Engineer, Limited · PDF fileQ606 Gas Turbine Plants...

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U.S.C.G. Merchant Marine Exam

Chief Engineer, Limited

Q606 Gas Turbine Plants

(Sample Examination)

of 26 Q606 Gas Turbine Plants

8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10

Choose the best answer to the following Multiple Choice Questions.

1. What is the primary purpose of the diffuser and distributor on the GE LM2500 gas turbine engine?

o (A) To provide even temperature distribution at the compressor • (B) To provide uniform air flow to the combustor o (C) To provide uniform air flow to the compressor o (D) To provide uniform air flow to the turbine

If choice B is selected set score to 1.

2. Which of the following is the main advantage of a split-axial compressor case?

• (A) Easier to repair and inspect. o (B) Stronger construction. o (C) Cheaper to manufacture. o (D) Simpler to disassemble.

If choice A is selected set score to 1.

3. 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 more fuel and the particulate and nitrogen oxide (NOx) levels in the exhaust would be higher than that of a recuperated gas turbine configuration

o (B) 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 (C) 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.

• (D) 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.

If choice D is selected set score to 1.

4. 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



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 5. In a gas turbine engine, the majority of the energy is added to the working fluid in which of the

following components?

o (A) Compressor. • (B) Combustor. o (C) Power turbine. o (D) High-pressure turbine.


6. While underway on a ship with gas turbine engines, the most likely indication of an engine stall is which of the following?

o (A) Combustor temperature increases. o (B) A loud bang is heard. o (C) Engine fails to accelerate. • (D) All of the above.


7. Each stage of an axial compressor of a gas turbine can compress the atmospheric air a total of how many times?

• (A) 1.2 times o (B) 2.2 times o (C) 3.2 times o (D) 4.2 times


8. In the marine gas turbine engine shown in the illustration, the 9th stage bleed air is used for which of the following? Illustration GT-0017

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


9. The primary function of a flame safeguard system, as used on an automatically fired auxiliary boiler, is to prevent __________.

o (A) accidental dry firing and overpressure o (B) uncontrolled fires in the furnace • (C) explosions in the boiler furnace o (D) overheating of the pressure parts

If choice C is selected set score to 1.


8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 10. The dimples of a combustor dome band that has a low operating time will usually have what kind of

damage?

o (A) Burn away. o (B) Bowing. • (C) Cracks. o (D) Burn through.


11. Which of the following types of feedwater regulators is commonly used with a water-tube, natural circulation, auxiliary boiler?

• (A) Thermo mechanical o (B) Bimetallic element o (C) Ring thermostat o (D) Modulating pressuretrol


12. In cases where both the pinion and gear teeth of the main reduction gear have been slightly indented by foreign material, what action should you take?

• (A) Both the pinion and gear should be relieved of all raised metal around the indentation. o (B) Closely monitor the damage to see if it spreads. o (C) Remove the foreign material that caused the indentation and return the unit to service. o (D) Replace both the pinion and gear.


13. Burner ignition failure in an automatically fired auxiliary boiler would be caused by __________.

• (A) a burned out solenoid in the oil supply valve o (B) high temperature excess air o (C) incorrectly setting the hotwell dump valve o (D) an incorrectly positioned burner snubber relay


14. Turbine stages are generally sealed to prevent gas leakage by which of the following methods?

o (A) The flow of the working fluid across the blades. o (B) Compressed air injected between stages at the nozzles. • (C) Rotating labyrinths and stationary sealing segments. o (D) Rotating sealing segments and stationary labyrinths.



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 15. What type of main reduction gear arrangement prevents independent axial and rotational movement

of the pinions?

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


16. What does the term "lock-out" of a synchro-self-shifting (SSS) clutch system mean? Illustration GT-0018

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


17. 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


18. A centrifugal compressor assembly consists of which of the following?

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


19. If a fire is detected in a main propulsion gas turbine enclosure, which of the following would occur prior to automatic release of the fire extinguishing agent?

o (A) Cooling water to the enclosure would be secured. • (B) If open, bleed air valves would be closed. o (C) Water wash valves to the engine would be opened. o (D) Reduction gear oil systems would be secured.



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 20. During unsafe firing conditions in a large automatic auxiliary boiler, various control actuators are

interlocked with the burner circuit to prevent start-up, in addition to safety shutdown. These controls are referred to as __________.

• (A) limit controls o (B) flame safeguard controls o (C) combustion controls o (D) programming controls


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

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


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

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


23. 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


24. Your first step in response to a gas turbine engine high lube oil sump temperature alarm would be which of the following?

o (A) Check the oil filter differential pressure. o (B) De-couple the engine from the main reduction gear. o (C) Check the oil pressure to the sump. • (D) Reduce engine speed.



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 25. Control of the fuel oil metering valve in an automatically fired auxiliary boiler is accomplished by a

__________.

o (A) pressure magnifying device in the steam coil outlet • (B) steam pressure sensing device with linkage to the damper air vanes o (C) metering device in the air supply line o (D) signal from the feedwater electrode


26. 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 once from inlet to outlet. o (C) Changes only at the compressor discharge. o (D) Changes only at the compressor inlet.


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


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

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


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

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



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 30. 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.


31. When conducting a borescope inspection of the compressor, why can airfoil and tip cracks be difficult to detect?

o (A) Rotating the rotor too fast. o (B) Borescope optics have deteriorated. o (C) The cracks are generally tight and shallow in depth. • (D) All of the above.


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

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


33. 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) o (C) Inlet guide vane (IGV) • (D) Variable stator vane (VSV)


34. What type of air seal is used in the combustor and turbine midframe of a gas turbine?

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



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 35. Why are the high-pressure turbine blades generally of the impulse/reaction type?

o (A) To evenly distribute the stress over the entire blade. o (B) To keep the tip pressure higher than the root pressure thereby preventing air flow over the tip. o (C) To keep the tip pressure lower than the root pressure thereby preventing air flow over the tip. • (D) Both A and B.


36. The fuel oil service system supply pressure to the marine gas turbine engine shown in the illustration, is designed to be regulated at approximately ______. Illustration GT-0021

o (A) 30 psig • (B) 45 psig o (C) 60 psig o (D) 75 psig


37. The term used to describe a gas turbine in which the turbine exhaust passes through a cooler and back to the compressor inlet is which of the following?

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


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


39. The boiler shown in the illustration would be classed as __________. Illustration MO-0064

• (A) single-pass, fire-tube, scotch marine o (B) forced circulation, coil-type o (C) two-pass, scotch marine o (D) two-pass, water-tube



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 40. Fuel oil manifolds are shrouded on marine gas turbine installations for which of the following

reasons?

o (A) Simplify maintenance. • (B) Collect leaking fuel. o (C) Provide heat protection. o (D) All of the above.


41. As shown in the illustration, the component labeled "H" would be identified as a ________. Illustration MO-0128

o (A) waste heat boiler circulating pump o (B) fuel oil service pump • (C) main condensate pump o (D) boiler water feed pump


42. Assuming you maintain the same power output, how will a decrease in the compressor inlet air temperature effect a gas turbine engine's efficiency and fuel consumption?

• (A) Efficiency will increase and fuel consumption will decrease. o (B) Efficiency will decrease and fuel consumption will increase. o (C) Efficiency and fuel consumption will not be effected by a change in inlet air temperature. o (D) Efficiency and fuel consumption will both increase.


43. A turbine stage is represented by which of the following components and in which order?

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


44. As shown in the illustration, what component would normally be installed at location "D"? Illustration MO-0128

o (A) Boiler soot blower unit • (B) Oil fired mechanical burner o (C) Boiler water level indicator o (D) Flue gas smoke indicator



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 45. When dissimilar metals come in contact with a conductor, which of the following types of metal

deterioration takes place?

o (A) Rust erosion. o (B) Chemical corrosion. • (C) Electrochemical corrosion. o (D) Etching erosion.


46. What is the function of the stator in an axial gas turbine compressor?

• (A) To convert velocity to pressure. o (B) To convert pressure to velocity. o (C) To increase volume. o (D) To provide velocity energy.


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

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


48. Compressor rotor blade tip curl is usually caused by which of the following?

o (A) Misalignment. o (B) Object damage. o (C) Vane rub. • (D) Blade rub.


49. Auxiliary boilers are divided into several classifications, one of which is __________.

o (A) water-tube supercritical circulation o (B) fire-tube express circulation • (C) water-tube forced circulation o (D) fire-tube controlled circulation



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 50. Which of the following is the most likely cause for the main propulsion gas turbine engine tripping

during start up?

o (A) Inlet air ice detection. o (B) High oil filter differential pressure. o (C) Low sump oil level. • (D) Failure to achieve the minimum rpm in a certain period of time.


51. What action should you take if full power vibration limits are exceeded on a gas turbine engine?

• (A) Reduce power to stay within limits. o (B) Borescope the engine. o (C) No action is needed. o (D) Water wash the engine.


52. The two main types of "compressor" stalls are known as _________.

• (A) steady state and transient o (B) overspeed and overload stall o (C) flame out and inlet temperature stall o (D) rapid rise and temperature inversion


53. On marine gas turbines equipped with fuel oil nozzles as shown in the illustration, the minimum fuel oil manifold pressure for proper operation should be _________. Illustration GT-0005

o (A) 40-80 psi • (B) 80-200 psi o (C) 200-300 psi o (D) 300-500 psi


54. 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 turbine rotor blades.

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



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 55. Once a compressor is broken in, which of the following factors will most likely cause blade tips to

rub?

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


56. The fuel oil back pressure regulator on the fuel system shown in the illustration, returns fuel to which of the following? Illustration GT-0021

o (A) Booster pump suction. o (B) Purge valve discharge. o (C) Fuel oil day tank. • (D) Booster pump discharge.


57. When the main reduction gear lube oil system is secured, which of the following components maintains the air within the casing at less than 35 percent relative humidity?

o (A) Rehumidifier o (B) Precipitator • (C) Dehumidifier o (D) Reciprocator


58. Why is safety-wiring, or lock wiring of gas turbine parts required?

• (A) Prevent disengagement of parts. o (B) Prevent corrosion. o (C) Maintain lubrication. o (D) Maintain fastener torque.


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



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 60. When conducting a borescope inspection, you must be aware of all of the following factors EXCEPT

which?

o (A) The inspection areas and ports. • (B) The engineer’s experience. o (C) The internal reference points. o (D) The limitations of your equipment.


61. The primary function of an axial compressor rotor blade is which of the following?

o (A) To act as a diffuser to the air flow causing an increase in pressure with a resultant decrease in velocity.

• (B) To impart acceleration to the air mass, resulting in an increase in velocity. o (C) To change the direction of the air flow. o (D) To use centrifugal force to increase the pressure of the air stream.


62. Why are loose-fitting blades used on the first several stages of large axial compressors?

o (A) To compensate for the abrasive action of the blade tips. o (B) To compensate for a malfunctioning compressor support bearing. • (C) To minimize vibration while the engine is passing through critical speed ranges. o (D) To maintain close tolerances in the compressor.


63. 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) Abrasive wear in the compressor 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) Corrosion in the combustor section of the turbine.


64. On the gas turbine shown in the illustration, which of the following best describes the main principle of operation of the component contained within the area labeled "C"? Illustration GT-0001

o (A) Bernoulli's Law of Divergency o (B) Newton's Law of Motion • (C) Combustion at a constant pressure o (D) Otto Cycle



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 65. When the steam pressure drops below a set value on an automatically fired auxiliary boiler, fitted

with rotary cup atomizers, the combustion control system will __________.

• (A) increase the fuel oil control valve opening o (B) increase the rotary cup speed o (C) decrease the back pressure regulating valve opening o (D) decrease the supply steam control valve opening


66. In the event of a flame failure in an auxiliary water-tube boiler, you must __________.

o (A) relight the boiler immediately to prevent loss of steam pressure o (B) relight the fire off the brickwork as long as the bricks are cherry red • (C) purge the furnace of any combustible gases before attempting to relight the fire o (D) speed up the feed pump to prevent dry firing when the burner flame is re-established


67. 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.


68. The turbine nozzles function to direct the gases in what direction?

o (A) Radial to the turbine axis o (B) Parallel to the turbine axis o (C) In the direction opposite of turbine rotation • (D) In the direction of turbine rotation


69. A safety valve on an auxiliary boiler simmers constantly and cannot be stopped by several quick blow-offs using the hand relieving gear. The problem may be __________.

o (A) loose dirt on the seat o (B) exposed valve springs o (C) a clogged drain line • (D) a damaged seat



8/30/2017

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited Q606 Gas Turbine Plants Illustrations: 10 70. The divergent area of the exhaust duct aids in what process?

o (A) Increasing the velocity of the exhaust gases. • (B) Increasing the volume of the exhaust gases. o (C) Decreasing the volume of the exhaust gases. o (D) Increasing the pressure of the exhaust gases.



8/30/2017


5/22/2015

GT-0001

Adapted for testing purposes only from WOODYARD, Pounder’s Marine Diesel Engines

and Gas Turbines, Ninth Edition. Copyright © 2009 Elsevier Ltd.

Further reproduction prohibited without permission.

A B C D E F G

H J



5/29/2015

GT-0005

Adapted for testing purposes only from Gas Turbine Systems Technician

(Electrical) 3/ Gas Turbine Systems Technician (Mechanical) 3, Volume 2

NAVEDTRA 14114


A

C

E

F

B

D



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


EE DD

FF

CC

BB AA



6/29/2015

GT-0018



NAVEDTRA 14113

Further reproduction prohibited without permission. of 26 Q606 Gas Turbine Plants


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



8/4/2015

MO-0064

Adapted for testing purposes only from SHIELDS, Boilers, Types, Characteristics, and

Functions

Copyright © 1961 by McGraw-Hill, Inc.




10/20/2016

MO-0128

Adapted for testing purposes only

Further reproduction prohibited without permission of 26 Q606 Gas Turbine Plants

U.S.C.G. Merchant Marine Exam Chief Engineer, Limited · PDF fileQ606 Gas Turbine Plants...

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