TM   1-4220-250-12&P 4.7.2  LRU-18/U  Leakage  Teat  (Continued). Measuring  device  ON/OFF  valve  must  be closed  when  air  feed  valve  is  open. NOTE Refer to Table 4-3 for quick reference of life raft  test  pressures.  Both  cells  may  be  tested simultaneously. If  a  suitable  air  source  is  not  available, water-pumped  nitrogen  (D13)  may  be substituted. b. Unlock oral inflation valve of CO₂ cell and insert  into  1/2-inch  diameter  rubber  hose. Close  measuring  device  ON/OFF  valve  and open valve to air supply and inflate life raft. Alternately   position   valves   at   measuring device  and  air  supply  until  proper  pressure  of 2.0  psi  is  attained.  Repeat  procedure  for  oral cell,  but  inflate  to  1.0  psi. c. The air supply shall be securely shut off. After a  minimum  of  15  minutes,  the  pressure  shall be  readjusted  in  both  cells  to  the  original pressures  called  out  in  Table  4-3. d. Disconnect  air  supply  and  check  test  Future for  leaks.  Ensure  that  all  valves  are  closed. e. Six  hours  after  the  readjustment  period,  the pressure  shall  be  measured  and  corrections  for changes  in  temperature  made.  For  each  lo  F rise  or  drop  in  temperature,  0.031  (31/1000) psig  shall  be  subtracted  from  or  added  to  the final  pressure  reading  to  obtain  the  corrected pressure.  For  0-10°F  change  see  Table  4-4. Table   4-3.    LRU-18/U   Test   Pressures. Leakage  Test Minimum Pressure   (PSIG) Pressure   (PSIG) CO₂  cell 2.0 1.6 Oral Cell 1.0 0.6 NOTE If  the  life  raft  has  been  stacked  during  the 6-hour  inspection  period,  remove  from stacking  and  place  in  a  horizontal  position  on the  floor  or  table  in  the  inspection  area  and take  test  pressure  reading.  In  no  event  shall the  pressure  in  the  raft  be  determined  with another  raft  stacked  upon  it. f. If  corrected  pressure  in  CO₂  cell  is  below  1.6 psi  or  corrected  pressure  in  oral  cell  is  below 0.6 psi, inflate to leakage test pressure and coat with a soap solution to locate leaks. Mark leak areas. Rinse life raft with fresh water, air dry, and  repair  IAW  paragraph  4.8.1. NOTE Steps  g  through  i  shall  be  performed  only  after leakage test readings have been recorded. g. Deflate  raft  in  accordance  with  paragraph  4.7.1. h. Ensure  that  inflation  valve  lever  is  cocked. i. Install new CO₂ cylinder in accordance with paragraph  4.6.2. Table  4-4.  Temperature  Conversion  Chart. Temperature     Difference correction (Degree  F) (psi) 1 0.031 2 0.062 3 0.093 4 0.124 5 0.155 6 0.186 7 0.217 8 0.248 9 0.279 10 0.310 Rise  in  temperature:  subtract  from  gauge  reading. Fall  in  temperature:  add  to  gauge  reading. END  OF  TASK 4-13