Question 4-18 is to be judged True or False. 4-18. The two   basic  types   of heat   exchangers used  on  engines  are  radiator  and  tubular. 4-19. In  the  Harrison-type  heat  exchanger,  how do the liquid coolants pass through the unit? 4-20. 1. Freshwater  passes  through  the  tubes, and  seawater  passes  around  the  tubes 2. Freshwater  passes  through  the  tubes, and  freshwater  passes  through  the tubes 3. Seawater  passes  through  the  tubes, and  freshwater  passes  around  the tubes 4. Seawater  passes  through  the  tubes, and  the  seawater  passes  around  tubes How  is  excessive  scale  on  the  cooler  of  a heat  exchanger  usually  indicated? 1. By  a  slow  increase  in  freshwater temperature 2. By  a  similiarity  between  inlet  and outlet  pressures 3. By  the  decrease  in  freshwater temperature 4. By  a  rise  in  the  freshwater  tank level 4-21. The  temperature  in  the  saltwater  cooling system  of  an  engine  should  never  be allowed  to  exceed  what  maximum temperature? 1. 130°F 2. 140°F 3. 170°F 4. 180°F 4-22. Which  of  the  following  conditions  can cause  a  cooler  element  to  become  clogged with  foreign  matter? 1. Leak in oil cooler 2. Dirty  freshwater 3. Faulty  seawater  strainers 4. All of the above Questions  4-23  is  to  be  judged  True  or False. 4-24. Erosion  holes  in  the  cooler  element  of  a heat  exchanger  are  usually  caused  by which  of  the  following  conditions? 1. A  clogged  cooler  element 2. A low-pressure water flow 3. Air  entrapped  in  the  cooler  casing 4. Fast  movement  of  grit  particles 4-25. By  which  of  the  following  actions  will you  cause  internal  leaks  of  a  heat exchanger  element  installed  in  the engine  cooling  system? 1. By  increasing  the  oil  temperature  of the  cooler 2. By  reducing  the  water  pressure  to  the cooler 3. By  allowing  continued  cooler operation  at  excessive  pressure 4. By  allowing  continued  cooler operation  at  reduced  pressure 4-26. The  heat  exchanger  outlet  side  is  used  to admit the proper amount of steam required to  blow  through  a  clogged  cooler  element containing  which  of  the  following deposits? 1. Oil 2. Sand 3. Grease 4. Roth 2 and 3 above 4-27. YOU are performing an air test on a heat exchanger  to  check  for  leaks. What should  you  do  after  attaching  a  pressure gage  to  the  inlet  line  of  the  element? 1. Immerse the element in a tank of water 2. Block  off  the  discharge  side  of  the element 3. Admit  low-pressure  air  to  the  inlet side  of  the  element 4. Remove  the  element  from  the  casing 4-28. Which  of  the  following  methods  should  you use to make an emergency repair to a strut-type  heat  exchanger? 1. Plug the tube 2. Replace  the  element 3. Soft  solder  the  element 4. Silver  solder  the  element 4-23. Overlubrication  of  the  circulating  water pump  bearings  will  NOT  affect  the  cooling capacity  to  the  heat  exchanger  element. 24