Rotating Pressure Vessel Oxidation Test (RPVOT)

Lubricating oil will inevitably come into contact with metal during use, and will be oxidized under the action of light and heat.

The anti-oxidation stability of lubricating oil is an important characteristic that reflects the tendency of lubricating oil to oxidize and deteriorate or age during actual use, storage and transportation.

As a result of oxidation, the color of the lubricating oil becomes darker, the viscosity increases, the acidic substances increase, and precipitation occurs. These will undoubtedly bring a series of adverse effects to the use of lubricating oil, such as corroding metals, clogging oil passages and so on. Usually, a certain amount of antioxidant is added to the oil to increase its anti-oxidation ability and prolong its service life.

How to evaluate the antioxidant capacity of lube oil?

Rotating Pressure Vessel Oxidation Test (RPVOT), or the Rotating Bomb Oxidation Test (RBOT) is the method to test the anti-oxidation ability of lubricating oil. Generally, The longer the time of the RPVOT test, the better the oxidation ability of the oil.

The approximate test method is as follows:

Put 50g oil (the target to be tested) 5 ml of water, and a catalyst (copper wire) into a cylindrical test tube (Rotating Pressure Vessel), and at a temperature of 25 degrees C, fill in oxygen to increase the pressure inside the tube to 620KPa.
Put the tube in an oil bath at 150°C, rotate to 150rpm,
The pressure inside the pressure vessel will rise and then fall back as the oil is oxidized.
When the pressure drops to 175Kpa from the highest point, record the time required from the start of the oil bath to this moment.
This time is the index of the oil's antioxidant capacity.
The longer the time, the higher the quality of the oil.
Very high quality oils can go up to 1000 minutes.

The Rotating Bomb refers to the Oxidation Pressure Vessel, which can be subjected to pressure, and is the main tool of this test method.

Chinese Standard
SH/T 0193-2008 Lubricating oils - Determination of oxidation stability - Rotating pressure vessel method

ASTM Standard

ASTM-D2272-02 Standard Test Method for Oxidation Stability of Steam Turbine Oils by Rotating Pressure Vessel