Question 1

What is the typical flash point of a polyalkylene glycol (PAG) lubricant?

Accepted Answer

Depending on the ISO VG viscosity grade and molecular weight, the flash point of synthetic PAG fluids typically ranges from 220°C up to over 280°C. This high threshold offers excellent thermal safety for demanding industrial operations.

Question 2

How does the flash point of PAG compare to mineral oil?

Accepted Answer

Synthetic PAG lubricants generally have higher flash points and significantly better thermal resistance than mineral oils of equivalent viscosity. When PAGs degrade at high temperatures, they oxidise into soluble vapours rather than forming flammable carbon deposits or sludge.

Question 3

What standard testing method is used to measure lubricant flash points?

Accepted Answer

The most widely accepted standard is the ASTM D92 Cleveland Open Cup method. Another common standard is ASTM D93 Pensky-Martens Closed Cup method, typically used for lower-volatility fluids or fuels.

Question 4

What is the difference between a lubricant's flash point and fire point?

Accepted Answer

The flash point is the lowest temperature at which the fluid generates enough volatile vapour to briefly ignite when exposed to a flame. The fire point is slightly higher, representing the temperature at which the vapour continues to burn for at least five seconds after ignition.

PAG and Lubricant Flash Point Reference Table