I use a thermal oil which has a rated max service temperature of 340 C. The oil temperature during service is normally 280 C. What is the normal service life of mineral based Thermal Oils (in terms of operating hours)? How do we decide when an oil changeout is required? For thermal oils what physical and chemical characteristics are trended in an oil analysis? Would appreciate if anyone could share their experience on this issue.

Thanks.
ramendran@acidchem.com.my

Flashpoint and viscosity decrease indicates the oil has been cracked from heat. Flashpoint should be more than 150C (closed-cup) for safety reason.

TAN increase indicates the severity of oxidation.