Heat Transfer Thermal Oil System

Dave2,

All mineral oils in the VG 32 classification will have a Flash point between 180 to 200 deg C. The flash point goes up as VG number increase to say VG 680 to about 220 to 250 deg C.

In heating /thermal systems there is no direct contact with the Heat Transfer fluid is use. Allowing for a 15 deg C temperature tolerance many Boiler mnfrs, heating/thermal systems manufacturers recommend an ISO VG 32 oil.

For increased oil life and safety considerations some users have switched to synthetics.

Hussam Adeni

Hussam has rightly pointed that Flash Point(FP) increases with higher ISO VG but MSDS normally say FP of Above 200 for all Mineral Based Lube Products and so you are right, it might be 250 C, but thats only the FP (The temperature at which the naked flame would ignite the vapors momentarily). The oil will not catch fire at that temperature so you should look at the Fire Point though FP is necessary.

The other thing is that you dont need a high FP oil if the system is closed. Dow Corning, Marlotherm, Fuchs and SASOL etc. have synthetic products that i came across that you can look at.

A perusal of detailed brochure/MSDS will reveal three values related to flash point.

1. Flash Point (reported in COC- Open cup and also Closed cup by different companies)

2. Auto ignition temperature

3. Fire Point

Most commercial or marketing brochures do not report the Auto ignition temperature or the Fire point. May be, because the info is too scary. Such info is normally tucked away in the MSDS sheets.

To reassure new users, I have never seen a lubricant catching fire in my 18 years with Castrol in India.

Hussam Adeni