Optimus Thermic are recommended for use in thermic systems where fuel oil, gas, or electricity is used to heat a fluid, which then transfers the heat to the point of application. In closed, forced circulation systems equipped with expansion tanks, Optimus Thermic Oil Grade 22 can be used with bulk oil temperatures up to 316°C (600°F) and skin temperatures up to 343°C(650°F) where good thermal stability and pumpability are required. Optimus Thermic Oil Grade 22 is also ideal where high thermic rates combine with high flow rates, and for systems where repeated heating and cooling cycles are required. In closed or open systems with forced circulation, Optimus Thermic Oil Grade 46 can be used where bulk oil temperatures do not exceed 288°C (550°F) and skin temperatures may be as high as 316°C (600°F). The oil surface in contact with air in open systems should not exceed 107°C(225°F). Copper and copper alloys should not be used in heat transfer systems with a hydrocarbon fluid unless air (oxygen) is excluded from contact with the fluid by hermetic sealing and/or an inert gas blanket.