Chapter  7—AUXILIARY  MACHINERY feed to the first effect will raise the liquid level in the first effect. More heat will be required to raise the feed to the boiling point, so that less heat will be available for evaporation in the first-effect shell and a smaller amount of heat will flow to the second-effect tube nest. These changes would work  out  to  a  new  balanced  condition,  but  other adjustments  would  be  required  to  make  the  new balance  satisfactory.  Under  such  circumstances, overcontrolling can cause many readjustments. The operator will always find it is better to make adjustments singly and in small increments, allow- ing enough time between each adjustment for the conditions to become steady. gland  properly  vented,  gland  properly  packed  and sealed, no air leaks in piping). f.  Tube  nests  properly  drained. (1)   Proper   operation   of   all   drain regulators. (2) Proper operation of the tube nest drain pump. 3.  Highest  possible  vacuum  in  the  last-effect shell. a.  No  air  leaks. Causes of Low Plant Output b.  Proper  air  ejector  operation. Failure to obtain full rated capacity is one of the  most  frequent  troubles  encountered  during operation of a distilling plant. The trouble may be very difficult to remedy since it may result from a combination of things. Following are the various factors which promote full output of the distill- ing plant. Any variations of these may cause a decrease in the plant’s efficiency. (1) Clean nozzle and strainer. (2) Steam at the required quality and quantity. c. Ample flow of circulating water. 1. Proper steam pressure above the orifice. 2. Highest possible vacuum in the first-effect tube nest. (1)  Clean  strainer,  pipeline,  and  tubes. (2) Proper valve settings. (3)  Proper  operation  of  the  circulating pump. a. b. shells. c. vented. d. No air leaks Proper water levels in the evaporator Evaporator   tube   nests   continuously Evaporator  tube  nests  reasonably  clean. (1) Continuous feed treatment. (2) Tubes mechanically cleaned when necessary. e.  Density  of  brine  overboard  not  over 1.5/32. (1) Overboard piping reasonably clean. (2) Proper valve settings. (3)  Proper  operation  of  brine  pump (clean  piping  and  strainers,  proper  speed  and direction  of  rotation,  pump  properly  vented, d.   Effective   surface   in   the   distilling condenser. tubes. (1) No undue deposits inside the tubes. (2)  Proper  venting  of  the  condenser (3)  Proper  operation  of  the  condensate pump. Steam Pressure A distilling plant cannot maintain its full out- put unless it is supplied with dry steam at the designed   pressure.   The   orifices   supplied   are designed to pass the proper amount of steam to ensure designed plant output with a pressure of about 5 psig above the orifice. Orifices should be inspected annually. An orifice should be measured and the reading compared with the figure stamped 7-23