4-55. Which of the following actions is a part  of  the  procedure  for  cleaning a  hydraulic  system? 1. Allow the system to remain idle for  15  minutes  after  operating it with a light load for 4 minutes 2. Operate the system for 1 hour while it is filled with cleaning  fluid 3. Operate the system at high pressure  while  it  is  filled with  cleaning  fluid 4. Dilute  the  old  hydraulic  oil with  cleaning  fluid  and  operate the  system  for  15  minutes,  then allow the system to remain idle for about 5 minutes 4-56. You are replenishing the hydraulic system with oil. What strainer should you use with the oil? 1. A  cheese  cloth 2. An aluminum filter 3. A  200-mesh  wire  screen 4. A  400-mesh  wire  screen 4-57. If you are filling a hydraulic system and notice water in the oil, which  of  the  following  actions should you take? 1. Centrifuge  the  oil  or  reject  it 2. Run  the  oil  through  a  180-mesh wire  screen 3. Heat the oil to permit the water  to  evaporate 4. Allow the oil to stand until the water settles to the bottom 4-58. What material is used to form the shaft  seal  of  most  modern  hydraulic pumps? 1. Rubber 2. Neoprene 3. Asbestos 4. Flax 4-59. Which  of  the  following  conditions can cause the packing of a shaft stuffing box to wear out quickly? 1. Hard  packing 2. Rough shaft 3. Shaft  deflection 4. Excessive  packing 4-60. What is the main purpose of packing a  shaft  packing  gland  uniformly  and lightly? 1. To allow for cooling and lubrication 2. To prevent scoring of the shaft 3. To  prevent  leakage  of  seawater 4. To prevent binding of the shaft 4-61. A routine inspection revealed a leak in the line of a hydraulic system at a flanged joint. If the leak persists after you have tightened  the  bolts  evenly,  what corrective  action  should  you  take next? 1. Replace  the  flange 2. Install  new  packing 3. Inspect  the  fluids  for contaminants 4. Install  square-braided  asbestos packing 4-62. The relief valve in a hydraulic system leaks. What should you do to the valve seat? 1. Reface  it 2. Replace it 3. Regrind it 4. Fit the valve with a seat insert 4-63. The  selector  switch  on  the  conveyor is improperly set. Which of the following  troubles  is  most  likely to occur? 1. Conveyor  will  not  start 2. Conveyor  will  not  hoist 3. Conveyor  will  run  continuously 4. Conveyor  will  not  lower 32