Foam Formation in Lubricating Oils
During use lubricating oils can form an undesired foam, which can greatly affect their performance.
The causes of this foam formation can vary – from contamination of the oil with water or solids, mechanical issues with the machine, grease contamination of the oil or an incorrect amount of defoamant.
Foaming can present serious problems for system operation – lubrication is reduced, resulting in increased risk of friction and heat buildup, oxidation and cavitation can occur, and the oil may even leak out of the machine.
Overall these issues cause reduced efficiency or performance, and can even present a risk of unsafe operation.
Assessing Foaming Characteristics of Lubricating Oils
To test the foaming characteristics of a lubricating oil, a sample is blown with a set volume of air at a set temperature then the amount of foam created is measured.
In order to obtain repeatable, comparable results ASTM and IP methods stipulate set conditions for all aspects of the tests, from sample volume to temperature.
In the ASTM D892 specification the standardised temperatures reflect different test “sequences”;
- Sequence I tests at 24°C
- Sequence II tests at 93.5°C
- Sequence III tests are performed on a sample previously tested by Sequence II then cooled to 24°C for a second test.
A second method, ASTM D6082, performs tests at 150°C to assess the lubricating oil’s suitability for high temperature applications. This final temperature is also referred to as sequence IV.
A Complete Analysis
In order to have a thorough understanding of the lubricating oil’s characteristics, all four test sequences can be performed. This ensures a complete and in depth analysis.
The K43095 apparatus by Koehler Instruments is a unique offering which allows all 4 test sequences to be performed on one unit.
Combining all 4 sequences into one unit presents not only a saving on laboratory bench space, but also a significant cost advantage – the cost of the combined unit is around 30% less than purchasing separate units for Sequence I-III and Sequence IV tests.
The instrument offers digital temperature control, built in overtemperature protection and full compliance with all common test methods ASTM D892, D6082, IP 146, DIN 51566 and others).
For more information on the combined sequence I to IV foaming characteristics apparatus, follow the links above or contact us with any queries or questions;