A  few  figures  for  the  amount  of  water  required  or  in  circulation
per  B.  H.  P.  hour  are  given  below.
In  a  producer  plant  an  additional  amount  of  water  is  required
for  the  producers  and  scrubbers.  The  water  vaporized  for  the
producers  of  course  is  not  again  available.  That  used  for  the
washing  plant  is  in  general  subject  to  the  same  considerations  as
that  used  for  cooling  the  engines.  But  where  a  cooling  system  is
used  for  both,  they  should  never  be  combined,  because  the  re-
quirements for  clean  cooling  water  for  the  engines  are  much  more
strict.  The  scrubber  water  usually  carries  considerable  quantities
of  sediment  and  is  contaminated  with  ammonia  and  sulfur  com-
pounds, so  strongly  in  some  cases  as  to  give  it  a  very  noxious
odor.  In  such  cases,  settling  tanks  and  ponds,  together  with  a
considerable  addition  of  clean  water,  seem  to  be  the  only  remedies
to  recover  at  least  a  part  of  the  water.
The  approximate  quantity  of  cooling  water  required  may  be
figured  from  the  following  considerations:

One  horse-power,  assuming  an  engine  efficiency  of  say  25  per

cent  at  the  cylinder,  requires  the  expenditure  of  — —  =  10,200

.25

B.  T.  U.  per  I.  H.  P.  hour.     The  jacket  loss  approximates  about

40  per  cent  of  the  heat  expended,  that  is,  in  this  case  the  jacket

water  must  carry  off  .40  X  10,200  =  4080   B.  T.  U.  per  hour.
COST  OF  installation'  AND  OP  OPERATION      563

Assuming  the  inlet  temperature  at  70  degrees,  the  outlet  at  150
degrees,  we    find    the    number  of  pounds    of  water  required  =

approx.  =51  pounds  =say  6^  gallons  per  I.  H.  P.  hour

at  full  load.
