Oxidation Test Results

Oxidation is a continuing concern for some of PULSAIR’s potential customers. They believe that heating their product and mixing with PULSAIR would promote oxidation. Perhaps it seems obvious to them that introducing air into liquids would invite oxidation. The facts, however, are quite different.

In 1997, PULSAIR Systems and Lilyblad Petroleum (Tacoma, Washington) conducted comparison testing to determine whether PULSAIR mixing would cause any change in the color or oxidation stability of lube oils. The test was run in a 7,400-gallon tank that was fitted with both a PULSAIR FT-1 system and a Lightnin' mechanical mixer.

The first phase involved loading the tank with Chevron 500 Neutral base oil and taking a sample at ambient temperature. The oil was then heated to 148 degrees F. and the Lightnin' mixer was run for 30 minutes (double axial-flow impeller at 56 RPM). Then a second sample was taken and the oil was pumped into a storage tank.

For the second phase an identical load of base oil was loaded and sampled at ambient temperature, then heated to 148 degrees F. and mixed with a PULSAIR FT-1 system for thirty minutes (11 pulses per minute, 80 psi injection pressure) and sampled again.

The only difference noticeable during the testing was that the temperature of the oil dropped to 140 during the mechanical mixing, but dropped only to 146 during PULSAIR mixing. In both cases the end-point temperature was reached fairly quickly and then remained steady.

The samples were sent to Southwest Research Institute, one of the leading independent testing labs in the U.S., where they were tested for oxidation stability and color. Results: All samples were identical. Meaning: Neither the mechanical mixing nor the PULSAIR mixing had any measurable effect on color or oxidation stability.

Some details of the testing:

A. Each sample was tested twice for oxidation (initial test and duplicate test) in order to make sure that the tests were valid. The results show no statistically significant difference between the initial tests and the duplicate tests, i.e. for practical purposes they were identical.

B. There is no statistically significant difference among any of the oxidation testing results. This means that neither the mechanical mixing nor the PULSAIR mixing had any measurable effect on the oil's oxidation stability.

C. The results of the oxidation tests are what would be expected from a base oil with no additives. The time to reach "breakdown" (27-31 minutes) is very short compared to what it would be for a finished product containing an anti-oxidant, which might be several hours.

D. There is no difference in color among any of the samples, meaning that neither the mechanical mixing nor the PULSAIR mixing had any measurable effect on color.

There are several explanations for the results of these tests:

Ambient air consists of only 21% oxygen (air is 78% nitrogen and 21% oxygen, with the remaining 1% composed of neon, carbon dioxide, argon, hydrogen, helium and other gases), therefore the compressed air used by PULSAIR is only 21% oxygen.

The PULSAIR bubble remains more or less a single large bubble as contrasted by a sparge system that puts millions of small bubbles into the product. PULSAIR does not put any more air into a product than the surface effect created by a mechanical mixer.

Another factor is temperature. Some of our first installations were in Seattle at the Texaco lube blending plant. Using PULSAIR, Texaco was able to lower their final mixing temperatures from the low 160s to about 120º Fahrenheit. Not only was this an energy savings, but the lower temperature substantially reduced the chances of oxidation. For many lubricants the temperature must be in the 160º Fahrenheit range or greater for any substantial oxidation to occur. This is why most modern lubricants contain an anti-oxidation additive in their formula.