Foaming
Air (dissolved or dispersed) is a general problem with oils.
This problem is combated with various additives. Some additives inhibit the foaming characteristics (less foam or instable bubble formation) and others improve the outflow of air (improved air separation characteristics). Silicon oil, for instance, inhibits the foaming properties, but reduces the air separation characteristics.
| Dissolved Air in Lubricants (Bartz, Page 115) | |
| Liquid | Air percentage in 1013 mbar and 20°C [%] |
| Mineral oil | 7–9 |
| Silicon oil | 15–25 |
| Dicarbon acid ester | approx. 9 |
| Phosphate ester | approx. 9 |
| PCB | approx. 4 |
| Water | 1.87 |
Tests at Intertek with Defoamers and Breathers
We examined the effect of various defoamers and breathers (separately and in combination) in a laboratory experiment.
Tests with Defoamers and Breathers
Sample: Shell Tellus 46, approx. 12 years in use (turbines/gears with transmission failure)
| Analysis | 180437
Shell Tellus 46 |
Experiment 1 | Experiment 2 | Experiment 3 | Experiment 4 | Experiment 5 |
| Appearance | brown-yellow, clear | |||||
| Breather | … | … | … | EEK (0.05%) | EEK (0.05%) | |
| Defoamer | MKO 812 (20ppm) | MYW (0.025%) | CHB (0.2%) | … | MYW (0.025%) | |
| Odour | rancid | |||||
| Viscosity at 40°C | 44.8 | |||||
| Neutralisation number | 0.5 | |||||
| Fl | >= 100 | |||||
| Fll | >= 100 | |||||
| Water content (coulometry.) | 40 | |||||
| Air separation characteristic | 7.2 | 4.3 | 7.5 | 7.6 | ||
| Sequence I (24°C) | 500 | 270 | 10 | 10 | 10 | 0 |
| Sequence ll (93.5°C) | 50 | 30 | 20 | 10 | 20 | 10 |
| Sequence III (24°C according to Seq. II) | 500 | 200 | 10 | 30 | 0 | 0 |
Dissolved Air in Lubricants (Bartz, Page 115)
| Liquid | Air percentage in 1013 mbar and 20°C [%] |
| Mineral oil | 7–9 |
| Silicon oil | 15–25 |
| Dicarbon acid ester | approx. 9 |
| Phosphate ester | approx. 9 |
| PCB | approx. 4 |
| Water | 1.87 |