Mack MRU - Page 10

6SafetyInformation
MethaneLeaks
Duringthedailywalkaround,inspecttheoutsideoftheLNGfueltankforfrost.
FrostedLNGtank(s),otherthanattheshroudarea*,indicatesthattheinnertank
isleakingintotheoutertank.Theappearanceofavaporcloudaccompaniedbya
hissingnoisemayalsoindicateamethaneleak.Aleakrequiresserviceonthetank(s)
beforethevehiclecanbeoperated.
*Rearfueltankdoorandplumbingxtures.
WARNING
Donotoperateavehiclewhichhasa
methaneleak.
RapidPressureRise
TherearethreemaincausesofrapidpressureriseonLNGsystems;overlling,fuel
systemleaksormalfunctionsandlossofvacuum.Aproperlyfunctioning,properly
lledLNGfuelsystemshouldbuildlessthan15psig/day.Anysystembuildingmore
than40psig/dayneedstroubleshootingtondthecause.
VacuumLoss
TotalvacuumlossisanunusualeventforanLNGtank(resultinginfrostingtheentire
shell),howeverthevacuumwillslowlydecaywithtimeasgassesdiffuseoutof
thetankmaterials.Thiswillshowupovertimeasamorerapidpressurerisetime,
eventuallyexceeding40psig/day.Oncethevacuumhasdecayedtothispoint,the
tankwillneedtobere-evacuatedbyacompetentmaintenancefacility.