tanks 42 56 removed and exchanged for the other the tanks 42 56 may be secured on the skid 12 by any suitable means such as bolts evaporated water from evaporation tanks 42 56 may be provided through condenser 78 the condenser 78 may comprise a peaked steam hood placed above the evaporation tank 42 56 whichever is used at locations 86 88 respectively leaving an air space to avoid pressurization the hood of the condenser 78 has a handle 80 and is hinged on one side with hinges 81 that allow the hood to be fully opened if steam recovery is not desired a condensation tube 82 runs from the condenser 78 to clean water recovery tank 20 and is provided with an electric fan 84 that may be automatically controlled to be powered when the hood is lowered and the boil off tank burner float low water level has been reached according to the position of the float of float operated switch 40 the operation of the burner float operated switch 40 signals the fan 84 in the condenser 78 as the case may be to be powered the condensing tube 82 is preferably connected to and runs the length of the exterior.