National Maritime Center

Transcription

1 National Maritime Center Providing Credentials to Mariners U.S.C.G. Merchant Marine Exam (Sample Examination) Page 1 of 27

2 Choose the best answer to the following Multiple Choice Questions. 1. Traditionally, which of the listed refrigerants has been more suitable than the others for use in a centrifugal refrigeration compressor? (A) R-11 o (B) R-12 o (C) Ammonia o (D) Carbon dioxide 2. Which of the following substances is normally classified as a low-pressure refrigerant? o (A) R-12 o (B) R-22 (C) R-123 o (D) R-134A 3. What is the color-coding for a storage container of R-134a refrigerant? o (A) grey o (B) green o (C) purple (D) light blue 4. Properties of a good refrigeration compressor lubricating oil include which of the following? (A) low wax content o (B) high pour point o (C) high viscosity o (D) all of the above 5. The "tare weight" of a refrigerant storage cylinder refers to what weight? (A) the weight of an empty cylinder o (B) the total weight of a fully charged cylinder o (C) the weight of a cylinder AND its current contents o (D) the maximum weight of the refrigerant allowed Page 2 of 27

3 6. What is the pressure and condition of the refrigerant entering the receiver of a refrigeration system? o (A) superheated low-pressure vapor o (B) superheated high-pressure vapor o (C) subcooled low-pressure liquid (D) subcooled high-pressure liquid 7. Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions? (A) Low-pressure vapor o (B) Low-pressure liquid o (C) High-pressure liquid o (D) High-pressure vapor 8. Which pair of the illustrated service gauge manifold sets would require switching hoses when transitioning from a dehydration evacuation to refrigerant charging? Illustration GS-RA-30 o (A) A and B (B) B and D o (C) C and D o (D) D and A 9. With a service gauge manifold set connected to a refrigerant compressor as shown in the illustration, which arrangement of the gauge manifold set valves and compressor service valves would allow for simultaneous reading of the compressor suction and discharge pressures? Illustration GS-RA-03 o (A) Valves "2" and "5" both open, along with valves "1" and "6" both frontseated. o (B) Valves "2" and "5" both open, along with valves "1" and "6" both open in the mid-position. (C) Valves "2" and "5" both closed, along with valves "1" and "6" both cracked open off their backseats. o (D) Valves "2" and "5" both closed, along with valves "1" and "6" both backseated. 10. Which of the following statements is true concerning the gauge labeled "A" of the illustrated gauge manifold set? Illustration GS-RA-01 (A) The gauge labeled "A" is a compound gauge and is usually color-coded blue. o (B) The gauge labeled "A" is a compound gauge and is usually color-coded red. o (C) The gauge labeled "A" is a standard pressure gauge and is usually color-coded blue. o (D) The gauge labeled "A" is a standard pressure gauge and is usually color-coded red. Page 3 of 27

4 11. The amount of HCFC-123 in a storage cylinder is measured by what means? (A) weight o (B) saturation temperature o (C) volume o (D) saturation pressure 12. In a refrigeration system, from what location would air and non-condensable gases be removed? o (A) expansion valve equalizer connection o (B) the bottom of the receiver drain connection o (C) compressor oil fill connection (D) the top of the condenser purge connection 13. In reclaiming recovered refrigerant, which type of contamination will the reclamation process be unable to separate? o (A) acid (B) mixed refrigerants o (C) air o (D) moisture 14. The process of removing refrigerant from a system and storing it without testing or processing it in any way is known as what under the EPA Clean Air Act rule definitions? o (A) reclaiming o (B) recycling o (C) recouping (D) recovering 15. Moisture is removed from recovered refrigerant using a recycling machine by what means? (A) circulating the refrigerant through a dehydrator o (B) condensing the moisture in the condenser o (C) opening a drain petcock on the oil separator o (D) purging non-condensables off the top of the recovery cylinder Page 4 of 27

5 16. Concerning frost appearing on one set of evaporator coils of a multi-box, direct expansion type refrigeration system, what is true? o (A) the frost can be quickly removed by simply shutting off fluid flow to the coils o (B) the frost will increase the value of superheat to the fluid leaving the coils o (C) the frost will assist in increasing the refrigeration effect (D) the frost can be removed by passing hot vapors through the coils 17. If the combination moisture indicator and sight glass indicates an accumulation of moisture within the system, which of the listed procedures would be the most practical to follow? o (A) Secure the system, disassemble and de-ice the thermostatic expansion valve. (B) Close the king valve, pump down the system, isolate the drier, remove the desiccant core and replace with new drier cartridge. o (C) Purge the entire system to the atmosphere, replace the drier cartridge, and recharge the system with refrigerant. o (D) Using a vacuum pump, draw the entire system down to 1,270 microns for a period of three hours. 18. What is the maximum volume to which refillable refrigeration cylinders should be filled? o (A) 60% full o (B) 70% full (C) 80% full o (D) 90% full 19. The primary purpose of the liquid line strainer used in a refrigeration system is to prevent dirt and scale from entering what system component(s)? o (A) condenser and receiver o (B) compressor and oil separator o (C) evaporator coil piping (D) thermal expansion valves Page 5 of 27

6 20. A thermostatic expansion valve is properly controlling evaporator superheat. Adjusting this valve to lower the evaporator superheat setting will result in which of the following? o (A) the expansion valve will further close (B) the evaporator feed will increase o (C) the expansion valve diaphragm will rupture o (D) the evaporator pressure will decrease 21. Which of the conditions listed may be an indication of an excessive amount of refrigerant circulating through the system? o (A) Frosting of the evaporator (B) Sweating of the compressor crankcase o (C) Colder than normal solenoid valve o (D) Weeping of the purge valve 22. If the refrigeration compressor crankcase is sweating or frosting and is operating with an unusual noise, what is most likely the cause? o (A) a shortage of refrigerant (B) liquid refrigerant returning to the compressor o (C) the compressor running continuously o (D) the compressor short-cycling on the high-pressure cut-out 23. If you find a refrigerant leak while using a halide torch, what will happen to the flame as the exploring tube approaches the leak? (A) it will change from blue to green o (B) it will stay blue o (C) it will change from green to blue o (D) it will change from blue to orange 24. Which of the following statements is correct concerning the testing of an R-22 refrigeration system for leaks in an enclosed compartment with a halide torch? o (A) The flame of a halide torch will turn blue in the presence of R-22. o (B) To gain sensitivity, the largest possible flame should be used with the halide torch. o (C) Halide torches are not suitable for detecting R-22 leaks. (D) Halide torches are useful in locating very small R-22 leaks. Page 6 of 27

7 25. Excessive moisture being collected in the purge unit of a low-pressure refrigeration system could indicate which probable condition? o (A) dryer core needs replacement o (B) low efficiency purge unit (C) leaking condenser or chiller tubes o (D) improper charging of refrigerant 26. When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, what should be done to compensate for or to correct this situation? o (A) increase the amount of cooling water to the condenser (B) remove some refrigerant from the system o (C) raise the high-pressure cut-out opening pressure o (D) decrease the amount of cooling water to the condenser 27. A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve all the way in, and then turning the compressor over by hand. If the discharge valves are leaking, the compound gage will show pressures which react in which way? (A) rising and falling with each stroke o (B) decreasing with each stroke o (C) increasing with each stroke o (D) decreasing to a vacuum 28. If a refrigeration compressor had developed a slightly high suction pressure accompanied with an abnormally low suction temperature, the problem could be a result of which of the following? o (A) a clogged subcooler (B) liquid refrigerant flooding back from the cooling coil o (C) a leaking king valve o (D) a minor accumulation of air or non-condensable gases in the system Page 7 of 27

8 29. Which of the following conditions will occur if the power element of the thermostatic expansion valve shown in the illustration loses its charge? Illustration GS-RA-07 o (A) The valve will fail open and the cooling capacity will be increased. o (B) The valve will fail open as designed to provide continuous cooling. o (C) The valve will begin to close, but the external equalizing line will assist in keeping the valve unseated. (D) The valve will fail closed, providing no cooling capacity. 30. If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result? (A) the suction line of the compressor will be abnormally warm o (B) the heat removal capacity of the evaporator will increase o (C) the evaporator will be overfed with liquid refrigerant o (D) the suction line of the compressor will be abnormally cold 31. A refrigeration compressor used in a multi-box refrigeration system, is designed with six of its eight cylinders able to be controlled for variable load conditions. If all of the reefer boxes are currently feeding, what percentage of the total number of compressor cylinders will be loaded after start up? (A) 100% o (B) 50% o (C) 25% o (D) 0% 32. To prevent motor overload during start-up of a hermetically sealed centrifugal refrigeration system, what is true concerning the compressor suction gas variable inlet guide vanes? o (A) closed until the motor is connected across the line at full voltage and current drawn is up to full load current o (B) opened until the motor is connected across the line at full voltage and current drawn is below full load current o (C) opened until the motor is connected across the line at full voltage and current drawn is up to full load current (D) closed until the motor is connected across the line at full voltage and current drawn is below full load current Page 8 of 27

9 33. How does a refrigeration solenoid valve differ from a modulating valve? (A) A liquid line solenoid valve is either completely opened or closed, whereas a modulation valve is infinitely positioned according to the strength of the applied electrical signal. o (B) Both valves operate in exactly the same manner, only the manufacturer's terminology is the differentiating factor. o (C) A solenoid valve can only be installed in liquid lines. o (D) Solenoid valves are only used in low voltage refrigeration control systems, while modulation valves are used in high voltage applications. 34. The sensing line for the low-pressure cut-out switch for a refrigeration system is typically connected at what location? o (A) at the outlet side of the receiver o (B) at the inlet side of the receiver (C) at the suction side of the compressor o (D) at the discharge side of the compressor 35. In refrigeration systems with multiple evaporators, the metering of refrigerant to each refrigerated space evaporator is accomplished by what device? o (A) the king valve (B) the individual thermal expansion valves o (C) the individual back pressure regulating valves o (D) the individual box solenoid valves 36. A thermal expansion valve installed in a refrigeration system is controlled by the action of what device? o (A) the receiver level controller o (B) the compressor unloader mechanism (C) the TEV sensing bulb mounted on the evaporator tail coil o (D) the box solenoid valve operating coil Page 9 of 27

10 37. The carbon seal ring of a refrigeration compressor crankshaft mechanical seal is held in position against the stationary ring face by using what device? o (A) woodruff key (B) spring o (C) snap ring o (D) thrust washer 38. When opening or closing compressor service and line isolation valves on a typical refrigeration system that is fitted with packed valves, what must you do? (A) you must first remove the stem seal cap o (B) you should turn valves slowly to avoid thermal stresses due to low temperatures o (C) you should replace the gasket each time the valve position is changed o (D) you should never loosen or tighten the packing gland 39. In a refrigeration system, what component is installed directly downstream of the thermal expansion valve? o (A) box solenoid valve o (B) receiver (C) evaporator coil o (D) compressor 40. Zinc plates commonly found in refrigeration systems and used as sacrificial anodes are located where? o (A) evaporator coils o (B) cooling water suction strainer (C) salt water side of the condenser o (D) refrigerant side of the condenser 41. Personnel servicing refrigeration systems and subject to the exposure to commonly used refrigerants should wear what type of personal protective equipment? o (A) an all-purpose gas mask o (B) rubber soled shoes (C) goggles and gloves o (D) a respirator Page 10 of 27

11 42. In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decompose and form what chemical substance? o (A) petroleum crystals (B) phosgene gas o (C) carbon monoxide o (D) water vapor 43. Overfilling a refrigerant container is extremely dangerous because of the high pressures generated. The generation of pressure is the result of what? o (A) vapor pressure of the refrigerant at saturation temperature (B) hydrostatic pressure of the expanding liquid o (C) discharge pressure of the recovery compressor o (D) discharge pressure from the recovery cylinder 44. Inhalation of high concentrations of chlorofluorocarbon refrigerants (CFCs) may have which of the following effects? o (A) loss of concentration o (B) drowsiness o (C) cardiac arrhythmias (D) all of the above 45. If there is a "large" release of R-134a refrigerant gas in a confined area, which of the following statements would be true? o (A) safety goggles and lined butyl gloves would be required before entering the space (B) a self-contained breathing apparatus (SCBA) would be required before entering the space o (C) an explosive atmosphere would be created o (D) dust or particle masks would be required before entering the space 46. Which of the following is true concerning the class "D" air conditioning system shown in the following illustration? Illustration GS-RA-42 o (A) System cooling is the direct result of the Freon circuit of a direct type air conditioning unit. o (B) The heat load will increase by increasing the amount of recirculated air. o (C) The room thermostat controls the wet bulb temperature of the air conditioned space. (D) The duct thermostat determines the amount of water flow circulating through the cooling coil. Page 11 of 27

12 47. In an air conditioning system, moisture is removed from the air by what means? o (A) filters o (B) separators (C) cooling coils o (D) ducted traps 48. What is the wet bulb temperature of air if the dry bulb temperature of the air is 90 degrees and the relative humidity is 65%? Illustration GS-RA-22 o (A) 62 degrees F o (B) 63 degrees F o (C) 77 degrees F (D) 80 degrees F 49. The compressor used in a water-cooled air conditioning system is short-cycling. A service check determines that the suction pressure remains above the normal cut-in point during cycling and that the discharge pressure rapidly builds up to the cut-out point while running and gradually falls to the cut-in point during the off cycle. What is likely the cause? (A) reduction in condenser water flow (scaled condenser) o (B) backseated discharge service valve o (C) loosely fitted compressor drive belt o (D) frontseated liquid line service valve 50. To add small amounts of refrigerant to the low side of an air conditioning system, the refrigerant should be introduced through a particular valve and in a particular state. What valve and state combination is correct? o (A) discharge service valve as a liquid o (B) suction service valve as a liquid (C) suction service valve as a vapor o (D) discharge service valve as a vapor 51. The surging that occurs in a centrifugal air conditioning compressor is a result of what conditions? o (A) low-pressure in the condenser at low load o (B) low-pressure in the condenser at high load (C) low-pressure in the evaporator at low load o (D) low-pressure in the evaporator at high load Page 12 of 27

13 52. The air temperature associated with a direct reciprocating air conditioning plant is found to be too warm, and the compressor is not operating. A service check determines the compressor suction pressure to be above the normal cut-in point, with a normal head pressure, and high evaporator superheat. Which of the following could be the cause of this problem? o (A) A liquid line solenoid valve is stuck open. o (B) Cooling water flow to the condenser is excessive. (C) The low-pressure control contacts are stuck open. o (D) A liquid line solenoid valve has failed closed. 53. Which of the following statements is true regarding oxygen indicators? (A) Prolonged exposure to gases such as CO2 may affect the accuracy of the indicator. o (B) The instrument is capable of providing an immediate accurate reading of any space with no delay. o (C) A cotton filter placed in the end of the sampling tube prevents damaging the instrument when exposed to strongly acidic gases. o (D) All of the above. 54. High concentrations of hydrogen sulfide gas are most dangerous to personnel because they can. o (A) cause involuntary skeletal muscle contractions o (B) cause eye inflammation o (C) cause dizziness (D) paralyze your breathing system 55. Expansion tanks when used in a ships hot water heating system may be of the open or closed type. In a closed type system, what would be the normal temperature range of the water? o (A) 180 F to 212 F (B) 220 F to 240 F o (C) 260 F to 280 F o (D) 320 F to 360 F Page 13 of 27

14 56. Which of the following procedures would be correct when first lighting off an oxyacetylene torch? o (A) Open the acetylene valve very slightly and the oxygen valve the same amount to light off. o (B) Open the oxygen valve wide open and the acetylene valve slightly to light off. o (C) Open the oxygen valve very slightly to light off and then open and adjust the acetylene valve. (D) Open the acetylene valve very slightly to light off and then open and adjust the oxygen valve. 57. Acetylene should never be used at pressures in excess of 15 psig because the. o (A) relief valve will lift o (B) acetylene cylinders have a maximum allowable pressure of 15 psig (C) slightest shock could cause an explosion o (D) fusible plug will blow out 58. Which of the following maintenance procedures would require a tag-out/lock-out to be performed? o (A) Draining compressed air system moisture separators of condensation. o (B) Shifting and cleaning a duplex strainer. o (C) Adding makeup oil to a main engine while underway. (D) Changing the oil of an air compressor. 59. Under what circumstances could equipment be operated when tagged with DANGER tags? o (A) Whenever permission is granted by your supervisor. o (B) Whenever there is a break in the actual maintenance activity. (C) Under NO circumstances should the equipment be operated when tagged. o (D) Whenever you feel that it is safe to do so. 60. Which of the following statements is true concerning the valve shown in the illustration? Illustration GS-0047 (A) The valve is a non-rising stem design. o (B) The valve is normally used to throttle the flow of liquid. o (C) The valve seats cannot be replaced or repaired. o (D) The valve only requires one turn of the handwheel to fully open. Page 14 of 27

15 61. What type of valve is shown in the illustration? Illustration GS-0047 o (A) Butterfly valve o (B) Globe valve o (C) Check valve (D) Gate valve 62. The primary purpose of the liquid line strainer used in a refrigeration system is to prevent dirt and scale from entering what system component(s)? o (A) evaporator coil piping o (B) condenser and receiver (C) thermal expansion valves o (D) compressor and oil separator 63. For most multi-box refrigeration systems, the refrigerant sight glass would be located where in the system? o (A) after the compressor in the discharge line (B) after the receiver in the liquid line o (C) before the compressor in the suction line o (D) after the condenser in the drain line to the receiver 64. In a refrigeration system, the valve shown in the illustration is used for what purpose? Illustration GS-RA-14 (A) head pressure regulating valve o (B) suction pressure regulating valve o (C) evaporator pressure regulating valve o (D) thermostatic expansion valve 65. An arrow stamped on the valve body of a water regulating valve indicates which of the following? (A) direction of the flow o (B) open position o (C) direction of the plunger slide o (D) closed position Page 15 of 27

16 66. Which of the lettered components shown in the illustration indicates the high-pressure cut-out? Illustration GS-RA-12 o (A) W (B) X o (C) Y o (D) Z 67. In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component? (A) motor shaft and compressor main bearings o (B) the prime mover drive pulley o (C) the shaft of the prime mover o (D) the compressor drive pulley 68. Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition? o (A) premature wear of the pulley end motor shaft bearing, but normal wear of the pulley end compressor crankshaft main bearing o (B) normal wear of the pulley end motor shaft bearing, but premature wear of the pulley end compressor crankshaft main bearing (C) premature wear of both the pulley end motor shaft bearing and the pulley end compressor crankshaft main bearing due to overloading o (D) premature wear of both motor shaft bearings and both compressor crankshaft main bearings due to belt slippage 69. If the compressor is heard to knock while pumping down the low side for repairs, but otherwise the compressor sounds normal, this is a possible indication of what condition? o (A) air being introduced to the system o (B) worn piston rings (C) foaming of the crankcase oil o (D) faulty bearings Page 16 of 27

17 70. An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature setpoint of -15 F, but it is currently operating with a stable return air temperature of 0 F. The fresh air makeup vent is closed, the unit is operating at 460 VAC/60 Hz, and the unit is in full capacity cool (modulating valve 100% open). Using the illustrated troubleshooting guide, what would be the normal range of expected discharge pressures if the ambient air temperature is 90 F? Illustration GS-RA-52 (A) psig o (B) psig o (C) psig o (D) psig Page 17 of 27

18 National Maritime Center Providing Credentials to Mariners GS /7/2016 Adapted for testing purposes only from Machinist Mate 3 & 2 NAVEDTRA Further reproduction prohibited without permission Page 18 of 27

19 National Maritime Center Providing Credentials to Mariners GS-RA-01 2/17/2017 Adapted for testing purposes only from ALTHOUSE, Modern Refrigeration and Air Conditioning Copyright 1992 by The Goodheart-Willcox Company, Inc. Further reproduction prohibited without permission Page 19 of 27

20 National Maritime Center Providing Credentials to Mariners GS-RA-03 2/22/2017 Adapted for testing purposes only from ALTHOUSE, Modern Refrigeration and Air Conditioning Copyright 1992 by The Goodheart-Willcox Company, Inc. Further reproduction prohibited without permission Page 20 of 27

21 National Maritime Center Providing Credentials to Mariners GS-RA-07 3/9/2017 Adapted for testing purposes only from ALTHOUSE, Modern Refrigeration and Air Conditioning Copyright 1992 by The Goodheart-Willcox Company, Inc. Further reproduction prohibited without permission Page 21 of 27

22 National Maritime Center Providing Credentials to Mariners GS-RA-12 10/10/2017 Adapted for testing purposes only from HARBACH, Marine Refrigeration and Air-Conditioning Copyright 2005 by Cornell Maritime Press Further reproduction prohibited without permission Page 22 of 27

23 National Maritime Center Providing Credentials to Mariners GS-RA-14 3/20/2017 Adapted for testing purposes only from ALTHOUSE, Modern Refrigeration and Air Conditioning Copyright 1992 by The Goodheart-Willcox Company, Inc. Further reproduction prohibited without permission Page 23 of 27

24 National Maritime Center Providing Credentials to Mariners GS-RA-22 3/27/2017 Adapted for testing purposes only from ALTHOUSE, Modern Refrigeration and Air Conditioning Copyright 1982 by The Goodheart-Willcox Company, Inc. Further reproduction prohibited without permission Page 24 of 27

25 National Maritime Center Providing Credentials to Mariners GS-RA-30 4/12/2017 Adapted for testing purposes only Further reproduction prohibited without permission Page 25 of 27

26 National Maritime Center Providing Credentials to Mariners GS-RA-42 5/5/2017 Adapted for testing purposes only from HARRINGTON, Marine Engineering Copyright 1992 by The Society of Naval Architects and Marine Engineers Further reproduction prohibited without permission Page 26 of 27

27 National Maritime Center Providing Credentials to Mariners GS-RA-52 Note: Curves to be used as a troubleshooting guide only for model series 69NT40 with fresh air makeup vent closed with unit powered on 460 VAC/60Hz and the suction modulating valve 100% open. 5/11/2017 Adapted for testing purposes only from CARRIER, Operation and Service for 69NT TO 399 Container Refrigeration Units Copyright 2007 by Carrier Corporation Page 27 of 27 Further reproduction prohibited without permission