Hazards of Electromagnetic Radiationto Fuels (HERF)

Many  studies  have  been  done  about  fuel  vaporsbeing   accidentally   ignited   by   electromagneticradiation. Tests aboard ships and in laboratories haveshown   that   the   chances   of   this   happening   are   lowbecause of other conditions that must exist at the sametime   to   support   combustion   of   the   fuel.   Althoughaccidental ignition of fuel by RFR is unlikely, you stillneed  to  be  aware  of  the  potential  hazards.  The  mostlikely time this might occur is during a ship’s refuelingevolutions,   commonly   called   UNREPs   (UnderwayReplenishment).  Many  ships  also  carry  at  least  onehelicopter or have the ability to refuel a helicopter and,therefore, carry fuel to support helo operations. All ofthese   operations   are   inherently   dangerous   bythemselves   and   require   the   utmost   attention   andalertness. As a junior Fire Controlman you most likelywill   be   personally   involved   in   these   refuelingoperations.   You   need   to   be   aware   of   the   potentialhazards  associated  with  Fire-Control  radar  and  fuel.As  a  senior  Fire  Controlman,  you  need  to  know  thehazards  of  electromagnetic  radiation  to  fuel,  so  youcan ensure that your division personnel are working ina safe environment.

RADAR   RESTRICTIONS.—ElectromagneticRadiation  Hazards  (U)  (Hazards  to  Personnel,  Fueland  Other  Flammable  Material)  (U),   NAVSEA  OP3565/NAVAIR16-1-529/NAVELEX   0967-LP-624-6010/Volume   I   specifies   the   safe   distances   fromradiating sources at which fueling operations may beconducted. Figure 3-1 indicates safe distances betweenfueling  operations  and  a  conical  monopole  antenna,based on transmitter power. Each type of antenna hasits own chart. Refer to your ship’s Emissions Control(EMCON)   bill   for   specific   guidance   concerningfueling operations.

FUEL  RESTRICTIONS.—As  the  RFR  energyradiated   from   high-powered   communications   andradar equipment installed on ships increased in recentyears,  the  Navy  shifted  to  less  volatile  fuels.  Undernormal   operating   conditions,   volatile   mixtures   arepresent only near aircraft fuel vents, open fuel inletsduring over-the-wing fueling, and near fuel spills.Before   fuel   vapors   can   ignite,   three   conditionsmust exist simultaneously:

1. For  a  given  ambient  temperature,  the  mixture must contain a specific ratio of fuel vapor to air.
2. There must be enough energy in the arc or spark to produce the appropriate temperature for ignition.
3. The   length of the arc must be sufficient to sustain the heat in the arc for the time required to initiate a flame.

Each of these conditions is likely to vary for every situation, and two of the conditions may exist at anygiven time. Although all three conditions will probablynot   occur   simultaneously,   the   consequences   of   anaccidental   explosion   make   it   very   important   to   becareful.