Monitoring of heat transfer oil parameters
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How should the specifications of heat transfer oil used for heat exchange be evaluated? This includes new oil standards as well as quality monitoring of oil in use. What data should be used as a basis to determine the oil change interval?
Thermal oil generally causes few problems; we conduct analyses every three months here, and it has been in use for three years without any issues. 1. Viscosity: Changes in viscosity generally indicate contamination of the heat transfer fluid within the system, as well as the degree of thermal cracking and oxidative degradation. When the rate of change is greater than 15%, it should be taken seriously. 2. Flash point: Changes in the flash point indicate the formation of low-boiling substances within the system; when the rate of change exceeds 20%, it warrants attention. 3. Acid value: Changes in the acid value indicate that the heat transfer fluid in the system is contaminated or oxidized; attention should be paid when the acid value reaches 0.5 mgKOH/g. 4. Residual carbon: An increase in residual carbon generally indicates that it is caused by dirt, corrosion, severe oxidation, or intense thermal decomposition; when it reaches 1.5%, it should be taken seriously. Once the test results are available, if all indicators remain within the acceptable range, it indicates that the heat transfer fluid is functioning properly ； If one or more parameters are out of range, measures should be considered to partially or fully replace the heat transfer fluid in order to restore it to good condition.
The answer above was very professional; viscosity, flash point, acid value, residual carbon – a carbon value of over 1.5 is the criterion for discarding the material.