MEDIDAS Y ACCIONES DE PROTECCIÓN AMBIENTAL

Lubricating oil and hydraulic fluid analysis should proceed from simple, subjective techniques onto more sophisticated techniques. The more sophisticated techniques should be used when conditions require additional information and the equipment cost or criticality justifies it.

Visual and Odor 6.6.2.1

The equipment operator may perform weekly inspections to see and smell the lubricating oil. A visual inspection looks for changes in color, haziness or cloudiness, and particles. This test is subjective, but the test can indicate recent water or dirt contamination and advancing oxidation. A small sample of fresh lubricating oil in a sealed, clear bottle can be stored for visual comparison. A burned smell may indicate oxidation of the oil; other odors may indicate contamination. The operator must not introduce dirt into the system when taking a sample.

Viscosity 6.6.2.2

Viscosity indicates oil flow rate at a specified temperature. An increase or decrease in viscosity over time measures changes in the lubricant condition or lubricant contamination. Viscosity can be tested using portable equipment or more accurately in a laboratory using

ASTM D445, Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids. Viscosity is measured in Centistokes (cSt) and minimum and maximum values are

identified by International Organization for Standardization (ISO) grade. Testing is usually included in a commercial laboratory standard test package.

Water 6.6.2.3

Water in lubricating oil and hydraulic fluid contributes to corrosion and formation of acids. Small amounts of water (less than 0.1 percent) can be dissolved in oil and detected using the crackle test or infrared spectroscopy (minimum detectable is .05 percent or approximately 500 parts per million (PPM) for both methods); the ASTM D95 distillation method (minimum detectable is .01%/100 PPM); or the ASTM D1744 Karl Fischer method (minimum detectable is .001%/10 PPM). Greater than 0.1 percent water, if suspended or emulsified in the oil, will appear cloudy or hazy. Free water in oil collects in the bottom of reservoirs and drains from the bottom.

Percent Solids/Water 6.6.2.4

This simple, inexpensive test provides a gross estimate of solids and water in the oil. A sample is centrifuged in a calibrated tube and the resulting volume is measured. The test is effective for amounts in the range of 0.1 percent to 20 percent of volume and is generally included in a commercial laboratory standard test package.

Total Acid Number (TAN) 6.6.2.5

Total acid is an indicator of the lubricating oil condition and is monitored relative to the total acid number (TAN) of new oil. In some systems the TAN may also indicate acid contamination. TAN is measured in milligrams of potassium hydroxide (KOH) per gram of oil (mgKOH/g). KOH is used in a titration process where the end point is indicated by color change (ASTM D974,

Standard Test Method for Acid and Base Number by Color-Indicator Titration) or electrical

conductivity change (ASTM D664, Standard Test Method for Acid Number of Petroleum

Products by Potentiometric Perchloric Acid Titration).

Total Base Number (TBN) 6.6.2.6

Similar to TAN, the total base number (TBN) test measures alkalinity (ability to neutralize acid) of the oil sample. The test is used on oil with high detergent additives such as diesel and gasoline engines. KOH is used in a titration process and the end point is indicated by electrical conductivity change (ASTM D664 , Standard Test Method for Acid Number of

Petroleum Products by Potentiometric Perchloric Acid Titration or ASTM D2896, Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration). When comparing test results, ensure that the same test method is used, as results

can vary between test methods. Spectrometric Metals 6.6.2.7

Also known as emission spectroscopy, this technique examines the light (spectrum) emitted from the oil sample during testing and identifies up to 21 metals. Metals are categorized as wear, contaminate, or additive metals. The procedure identifies both soluble metal and metal particles up to 5 to 10 microns (5-10 mm). The test is moderate in cost and is usually

part of a commercial laboratory standard test package. Other techniques, such as absorption spectroscopy and X-ray spectroscopy, are also used by some laboratories to identify metals.

Infrared Spectroscopy 6.6.2.8

Infrared spectroscopy is also known as infrared analysis, infrared absorption spectroscopy or spectrophotometry, and Fourier Transform Infrared (FTIR) spectroscopy. The technique examines the infrared wavelength that is absorbed by the oil sample. The test is used to identify non-metallic contamination (see 6.6.2.3 Water) and lubricant conditions such as oxidation and anti-oxidant and other additive depletion.

Ongoing work couples computer expert system analysis with known oil spectrums to produce highly accurate diagnosis of small changes in the oil condition. Costs vary depending on the level of sophistication required. Infrared spectroscopy is usually part of a commercial laboratory standard test package.

Particle Counting 6.6.2.9

Particle counting is used to identify metal and non-metal particles between 5 microns and 50 microns. There are two methods (visual and electronic) which both result in particle counts (parts per milliliter) by size category. For example, the ISO size categories are greater than 5, 10, 15, 25 and 50 microns.

The visual method of particle counting is time-consuming and relies on the skill of the analyst. Its benefit is the identification of types of particles such as dirt, seal material, and metal. The electronic counting method is much faster and is independent of the skill of the analyst. It does not identify the particle make up. A commercial laboratory will quote

electronic particle count; visual particle counting is more expensive and done by request only and is fiscally more demanding.

Direct-Reading Ferrography 6.6.2.10

Ferrography, the analysis of ferrous material, uses a magnetic technique to separate wear particles from the oil sample. In the direct reading (DR) process the wear particles are further separated into small (5 to 15 microns) and large (greater than 15 microns) categories. This results in a ratio of large to small particles and a total particle concentration. Both values can be tracked and trended to indicate increases in wear and type of wear. This test supplements the spectrometric metals test and identifies large wear particles not identified by

spectrometric metals test. The cost of this test is moderate. Analytical Ferrography

6.6.2.11

Analytical ferrography is typically initiated based on changes in DR, spectrometric metal increases, or increased particle count. The analysis may be performed regularly for high-cost or critical machines. The process is labor intensive, involving the preparation of sample and examination under magnification. The procedure may provide details regarding wear material such as wear type (rubbing, sliding, cutting), color, particle types (oxide, corrosive,

crystalline), and other non-ferrous particles. This detailed information can lead to the root cause of wear problems. Costs are moderately high; the test is performed on a fixed price basis (per sample) from a commercial laboratory.