Diamond Class®Heat Transfer Fluids

Premium Heat Transfer Fluids

Phillips 66®Diamond Class Heat Transfer Fluids are premium quality fluids specifically developed for use in liquid-phase heat transfer systems. They are available in two different formulations, designated “O/S” for use in open systems and “C/S” for use in closed systems.

Features & Benefits

• Outstanding performance in closed or open systems

• Outstanding thermal stability to minimize deposits

• Long service life

• Less waste oil disposal

• Reduced operating costs


Diamond Class Heat Transfer Fluid O/S is optimized for use in pressure-relieved, liquid-phase heat transfer systems with expansion tanks, where there is the possibility of contact between the heat transfer fluid and air in the expansion tank. It is fortified with oxidation and corrosion inhibitors to prevent fluid degradation and deposit buildup in the system. The O/S fluid is recommended for use in systems operating with continuous maximum bulk oil temperatures up to 550°F (290°C), intermittent maximum temperatures as high as 650°F (343°C), and a maximum skin film temperature of 600oF (316oC).

Diamond Class Heat Transfer Fluid C/S is optimized for use in pressure-relieved, expansion tank-equipped liquid-phase heat transfer systems that are closed to the atmosphere and potential air contamination. The system must be equipped with a cold-oil seal pot on the expansion tank vent, or operated with low-pressure nitrogen blanketing of the oil so there is no possibility of air contacting the oil during operation. The C/S fluid is fortified with special additives to prevent thermal degradation. It is recommended for use in systems operating with continuous maximum bulk oil temperatures up to 620°F (327°C) and maximum skin film temperatures up to 650°F (343°C).

Some common applications include:

• Liquid-phase heat transfer systems

• Heat transfer medium for industrial manufacturing processes

• Heat transfer equipment used in the manufacture of resins and coatings

• Asphalt heating

• Die casting

• Plastic injection molding and extrusion

• Wax coating equipment

Technical Details

Licenses & Approvals
Additional Details
GradeO/S 32
ISO Grade32
Specific Gravity @ 60°F0.865
Density, lbs/gal @ 60°F7.2
Color, ASTM D15000.5
Flash Point (COC), °C (°F)225 (437)
Autoignition Temperature, ASTM E659, °C (°F)357 (675)
Pour Point, °C (°F)-42 (-44)
cSt @ 40°C (104°F)32
cSt @ 100°C (212°F)5.4
cSt @ 204°C (400°F)1.35
cSt @ 260°C (500°F)0.91
cSt @ 316°C (600°F)0.69
Viscosity Index102
Acid Number, ASTM D974, mg KOH/g0
Carbon Residue, ASTM D524, wt %<0.1
Copper Corrosion, ASTM D1301a
Oxidation Stability, RPVOT, ASTM D2272, minutes875