TM   5-4930-227-14 Section  Il.  TANK  AND  FRAME 6-9.   Tank   and   Frame The  tank  shells  are  of  durable  aluminum  con- struction;  the  frame  is  of  welded  sheet  metal. The tank and f rames will require a minimum of maintenance. Make certain every precaution is taken prior to attempting any repair on a tank. 6-10.   Welding   Repairs a. Tanks.  No repair  will  be  initiated  until  the tank  has  been  thoroughly  vented  and  cleaned.  Ob- serve necessary precautions and weld the dam- aged  area  in  accordance  with  standard  tech- niques,  Refer  to  paragraph  6-10d  for  welding precautions. b.  Frame.  Make  certain  the  frame  is  free  of dirt,  oil,  grease,  or  other  foreign  matter,  and bare metal is exposed for welding. Remove neces- sary  components  before  welding. c.  Tank  Cleaning.  The  tank  must  be  free  of explosive vapors and thoroughly cleaned before any repairs are attempted; drain the tank of all contents and open filler plug, allow filler to re- main  open  for  several  minues.  If  compressed  air is  available,  blow  out  the  tank.  Clean  the  tank  in- terior  with  an approved solvent   and   dry thoroughly.  Precautions  and  procedures  outlined in  TM  10-1114  will  be  adapted  to  the  tank. Areas of the tank to be subjected to severe heat must be cleaned to the bare metal; use a stiff stainless steel wire brush or other suitable tool for  this  purpose.  Pay  particular  attention  to  the seams; heat from a welding torch tends to vola- tilize   tetraethylened   deposits,   causing   toxic fumes. The tank exterior must be cleaned of all dirt,  sand,  oil,  or  other  foreign  matter  with  a solution  of  trisodium  phosphate  and  water;  rinse with plain water and dry. Remove paint from any area  to  be  welded. d.   Welding   Precautions. (1) Completely  drain  all  fuel  from  tank  to be purged; be sure the drained fuel is removed from  the  area  where  work  will  be  performed. (a)  Remove  all  fuel  from  floor;  remove all fuel-soaked rags and waste from area. (b) If electrical welding is to be perform- ed, be sure you have adequate shielding to pro- tect other workers from injury. (c)  This  process  is  to  be  undertaken  by field and depot maintenance units. Supporting agencies  will  furnish  additional  skills  and  equip- ment when required. 6-10 (2) Essentials: (a) Efficient  purging  of  fuel  tanks,  pipe lines, pump housings, hoses,   and   distribution manifolds  may  be  accomplished  by  adherence  to procedures  outlined  herein. (b)  Materials  required: 1.  Adequate  source  of  water  with  a large  diameter  hose  long  enough  to  reach  the vehicle or fuel tank. 2. Compressed air source and air hose of sufficient length to reach depth of fuel tank. 3. Sufficient quantity of gas tank purg- er obtainable through local procurement. Only known source available to date: Product-Sol, Inc., 2010 Cole, Birmingham, Mich. (3) Safety precaution: Warning:  Prior  to  and  during  all  operations outlined  in  this  bulletin,  coordinate  with  safety, medical,  and  fire  departments  to  comply  with safeguards   contained   herein   and   other   applica- ble  directives. (a) The  tank  being  purged  must  have  a static   ground   during   all   operations;   caution should  be  taken  with  all  tools  and  metal  objects around  tank  to  insure  no  contact  of  sufficient force is made to create a spark. (b) Conduct a combustible vapor test read- ing  prior  to  purging  the  tank,  using  an  accep- table  explosive  meter,  such  as  MSA  explosive meter  6665-664-4650  or  Davis  Vapotester  6665- 562-8103. (c) Only competent personnel, thorough- ly  instructed  in  the  proper  handling  and  reading of  the  vapor-indicating  instruments  (explosion meter), will perform vapor tests. (d)  Conduct   a   combustible   vapor   test reading immediately after purging. Under no cir- cumstances will repair of fuel tank begin until declared  safe  by  safety  personnel. (e) Discontinue all operations if an elec- trical  storm  is  threatening  or  in  progress. (f) Eliminate  all  possible  causes  of  ex- plosion. (g) Personnel engaged in purging opera- tions  will: 1. NOT  wear  wool,  nylon,  silk,  rayon or  other  similar  static  electricity-generating  cloth- ing. 2. Wear  clean  cotton  clothing  with  no metal  buttons  or from  pockets. fittings.  Remove  all  contents