Fluid-Assets Submicron Particle Oil Analysis
Nanoparticle Oil Particle Tracking Analysis; 20nm to 2,000nm
A new off shoot of a new technique just developed over the past years has been devised to measure and quantify nano-particles of many different sizes. It is known as Nano-particle Tracking Analysis (NTA).
NTA was originally developed for use in biological applications in water based systems. “The initial application of NTA is to evaluate viruses which typically range in size from one to ten nanometers.”
NTA measures the size and shape of submicron particles through the use of video microscopy by tracking the Brownian Motion of particles in all types of liquids. The imaging is done by focusing a fine laser beam of light with a wavelength of 638 nanometers through a sample containing the nano-particles. These particles are seen by an optical microscope and then analyzed.
Water has proven to be a fairly easy medium to use in NTA analysis. Water is very transparent and a high contrast can be seen between clean and relatively contaminated water. The viscosity of water is also low which helps with the analysis. In service oil is a totally different story.
In contrast, using Nano Tracking Analysis to do particle analysis in oils is much more challenging…..viscosity and refractive index vary depending upon the oil. Temperature is also a critical factor to ensure that the results are accurate.” The reason is that these parameters all affect the Brownian Motion of the nano-particle and fluid density.
After years of work, Fluid-Assets has the ability to evaluate the condition of in-service lubricant oils by using specific dilution and sample preparation procedures to evaluate the sample within a narrow viscosity and refractive index ranges. Through many years of trial and tribulation, Fluid-Assets has with in-house improvements, sample preparation, and procedures specifically targeted for inservice lubricants, been able to use the core Nano Tracking Analysis technology to evaluate turbine and hydraulic oils based on mineral oils, polyalphaolefins, and now phosphate esters.
Nano Tracking Analysis can be used to measure particles ranging in size at the low end from 10 to 20 nanometers in diameter. Successful measurement of the submicron particle size, count, distribution, volume and surface areas is predicated on the ability to have sufficient contrast between the oil and the nano-particle. Historically, it can be very difficult to detect nano-particles in dark oils. Sample opacity is a major limiting factor for the Nano Tracking Analysis. Particles cannot be tracked on a nano-scale if they cannot be seen in situ.
Fluid-Assets has been able to harness the core Nano Tracking Analysis capabilities to detect and evaluate particles size, count, distribution, volume and surface area up to 2 microns. The accuracy of the Nano Tracking Analysis in turbine oil test is typically +/- 2% from 20nm to 800nm. The accuracy of the nano Tracking Analysis in turbine oils for the full 20nm to 2 micron range is typically +/- 5%. From a precisions standpoint, additional testing is needed for phosphate ester fluids.
The accuracy of the NTA test is better than +/- 1% according to Munson. From a precisions standpoint, additional testing is needed to evaluate a larger sample size.