Question 1

How does the RPVOT test measure oxidation stability in PAG lubricants?

Accepted Answer

The Rotary Pressure Vessel Oxidation Test (RPVOT), conducted under ASTM D2272, measures the time it takes for a lubricant to react with oxygen under high pressure (90 psi) and elevated temperature (150°C) in the presence of a copper catalyst and water. The test monitors the drop in oxygen pressure, indicating active oxygen absorption once antioxidants are depleted.

Question 2

What does a high RPVOT value mean for lubricant service life?

Accepted Answer

A higher RPVOT value indicates superior oxidation resistance. A formulation with an estimated RPVOT of 1000+ minutes will have a significantly longer active service life in a compressor or turbine than one with only 200 minutes.

Question 3

How does temperature affect the oxidation rate of PAG lubricants?

Accepted Answer

The oxidation rate increases exponentially with temperature, roughly doubling for every 10°C rise above 70°C, in accordance with the Arrhenius rate equation. This rapid acceleration significantly reduces fluid service life if the antioxidant package is not optimized.

Question 4

Can you predict lubricant oxidation life based on antioxidant treat rates?

Accepted Answer

While exact service life depends on field conditions, you can reliably estimate relative oxidation life and RPVOT ranges by analyzing the base oil and antioxidant concentration. Our estimator uses empirical kinetic models to show how treat rate changes impact the relative life multiplier.

PAG and Lubricant Oxidation Life Estimator