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TABLE 19-continued 71 TABLE 19-Continued Review Exercises The following exercises are study aids. Write your answerin pencilin thespaceprovidedaftereachexercise. Use the blank pages to record other notes on the chapter content. Immediatelycheckyour answerswiththekey at theend of the text. 1. The refrigerant charge is approximately ___________ pounds. (Sec. 9, Par. 1) 72 2. Which component reduces the horsepower requirement per ton of refrigeration? (Sec. 9, Par. 2) 3. (Agree)(Disagree) The refrigerant flows through the tubes in the cooler. (Sec. 9, Par. 3) 4. The liquid refrigerant, from the condenser, enters the _______________. (Sec. 9, Par. 5) 11. The oil pump is driven from the _____________________. (Sec. 10, Par. 7) 12. Which component does the pump lubricate first? (Sec. 10, Par. 8) 13. How is oil returned from the oil pump drive gear? (Sec. 10, Par. 9) 14. How is the shaft seal actuated? (Sec. 1, Par. 10) 5. How much pressure is there within the economizer chamber? (Sec. 9, Par. 5) 15. What purpose do the two holes in the inner floating seal ring serve? (Sec. 10, Par. 11) 6. The suction gas is taken in by the compressor in _____________ the shaft. (Sec. 10, Par. 1) 7. How are the wheels (impellers) protected from corrosion? (Sec. 1, Par. 2) 16. The automatic stop valve is set to approximately ________________ (Sec. 10, Par. 12) open at pounds. 8. Each bearing has ______________ large oil rings. (Sec. 10, Par. 3) 17. Which oil pressure gauges are mounted on the control panel? (Sec. 10, Par. 13) 18. How is the oil heater energized during shutdown? (Sec. 10; Par. 14) 9. What prevents interstage leakage of gas? (Sec. 10, Par. 4) 19. (Agree)(Disagree) During operation the two polished surfaces of the shaft seal are held together with a spring. (Sec. 10, Par. 16) 10. Which end of the compressor will axial thrust affect? (Sec. 10, Par. 5) 20. What type oil is used in centrifugal compressors? (Sec. 10, Par. 17) 73 21. The compressor gear drive (increases, decreases) the motor to compressor speed. (Sec. 11, Par. 1) 22. The grade of oil to use on a gear depends on __________, ___________, and ______________.(Sec. 11, Par. 3) 23. When would you turn on the gear drive cooling water? (Sec. 11, Par. 5) 24. Worn bearings in the gear drive will cause ___________________. (Sec. 11, Par. 9) 30. The motor furnished with the centrifugal machine is __________ phase, _________________ cycle, and has an ________________ rotor. (Sec. 13, Par. 1) 31. The secondary drum control is used to adjust the amount of resistance in the ___________________ of the motor which regulates motor ____________________ (Sec. 13, Par. 3) 32. Which switch is bypassed when the start button is held closed? (Sec. 13, Par. 4) 25. Which coupling uses a spool piece? (Sec. 12, Par. 1) 33. What is the secondary function of the condenser? (Sec. 14, Par. 1) 26. How is the hub expanded when it is to be installed on the shaft? (Sec. 12, Par. 2) 27. The angular alignment of a coupling is checked with a _________________. (Sec. 12, Par. 3) 34. What prevents the discharge gas from directly hitting the condenser tubes? (Sec. 14, Par. 2) 35. What precaution would you observe while removing the water box cover? (Sec. 14, Par. 3) 28. Which instrument is used to check the offset alignment of a coupling? (Sec. 12, Par. 4) 36. A burst rupture disc is caused by __________________ (Sec. 14, Par. 6) 29. Which type of coupling can be lubricated while the compressor is running? (Sec. 12, Par. 8) 37. How can you determine the refrigerant charge of the system? (Sec. 14, Par. 11) 38. What is indicated when the temperature differential of the refrigerant and chilled water increases? (Sec. 14, Par. 13) 74 39. ________________ is prevented by the hot gas bypass. (Sec. 15, Par. 1) 40. Why is the liquid injector used in the hot gas bypass? (Sec. 15, Par. 2) 41. What controls the amount of liquid refrigerant flowing to the hot gas bypass? (Sec. 15, Par. 3) 42. (Agree) (Disagree) The high-pressure control on the purge unit must be reset manually. (Sec. 16, Par. 3) 43. Where is the weir and trap located on the purge unit? (Sec. 16, Par. 3) 48. When are large quantities of air normally purged from the centrifugal refrigeration system? (Sec. 16, Par. 10) 49. When is water drained from the separator unit? (Sec. 16, Par. 12) 50. The four safety controls that will stop the centrifugal are _______________, ________, ___________, and _______________. (Sec. 17, Par. 1) 51. Which safety control does not require manual resetting? (Sec. 17, Par. 2) 52. What is the differential for the high condenser pressure control? (Sec. 17, Par. 3) 44. High head pressure ___________________. indicates that (Sec. 16, Par. 5) 53. How can you change (switch over) controllers? (Sec. 17, Par. 6) 45. How is the air pressure in the condenser released to the atmosphere? (Sec. 16, Par. 6) 46. What amount of water collected by the purge unit is an indication of leaky tubes? (Sec. 16, Par. 8) 47. When will a pressure drop exist across the pressure-regulating valve? (Sec. 16, Par. 9) 54. The most efficient method of controlling the capacity of the centrifugal is to ____________________. (Sec. 18, Pars. 1 and 2) 55. What will occur if you add more resistance to the rotor circuit of the drive motor? (Sec. 18, Par. 3) 56. When is suction damper control more effective than speed control? (Sec. 18, Par. 4) ... - tailieumienphi.vn
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