5-21. What person is responsible for ensuring  operator  maintenance  is performed  on  quarry  equipment? 1. Operations chief 2. Maintenance  supervisor 3. Maintenance field crew 4.  Quarry  supervisor 5-22. What NAVFAC publication provides guidelines  for  wearfacing  equip- ment  parts? 1. P-404 2. P-433 3. P-405 4. P-300 5-23. Putting off maintenance to satisfy immediate  production  demands  sets a  good  precedence  and  increases the life of the equipment. 1. True 2. False 5-24. What is the NEC of a qualified blaster? 1. 5710 2. 5709 3. 5708 4. 5707 Learning  Objective:  Recognize the  principles  and  methods  of crusher  operations. 5-25. What command directs the tasking of  crusher  operations  for  an  NMCB? 1. NAVFACENGCOM 2. NAVCHAPGRU 3. COMSECOND/COMTHIRDNCB 4. COMNCFNCB 5-26. The classification of a crusher plant is based on what factor? 5-27. What is the function of the heavy-duty  apron  type  of  feeder? 1. Feeds material to the secondary  unit 2. Sorts  material  before feeding  the  secondary  unit 3. Feeds material to the primary unit 4. Sorts material before feeding the primary unit 5-28. What component of the primary unit prescreens material that is already  down  to  the  desired  size? 1. Vibrating screens 2. Apron feeder 3. Under crusher delivery conveyer 4. Vibrating grizzly 5-29. In a rock crusher, what problem occurs when two rocks interlock and bridge the jaws open? 1. Blocking 2. Bridging 3. Choking 4. Packing 5-30. What factor determines the production  setting  for  a  dual roll  crusher? 1. The shell combination 2. The speed setting 3. The spacing between the rolls 4. The  hydroset  control  pressure 5-31. The fineness of the product being produced  by  a  hydrocone  crusher  is adjusted  by  what  action? 1. By raising or lowering the mantle 2. By adjusting the feed spout 3. By controlling the hydroset pressure 4. By adjusting the concave ring 1. Capacity output 2. Weight of crusher unit 3. Size  jaws 4. Area displacement 35