Fluid Metrics, LLC
4514 Chamblee Dunwoody Rd. #252
Dunwoody , GA 30338
Phone: (770) 393-8636
Fax: (770) 393-8631
Fluid Metrics is not affiliated with any compressor manufacture. Any reference made to a trademarked name is done so for the convenience of our customers. Logos and names are the trademarks of their respective owners.
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Oil-injected Rotary Screw Air Compressors are one of the harshest lubricant applications found in industry. The compressor’s forced-contamination design, elevated operating temperatures, and extreme oxidative environment create excessively harsh conditions that accelerate oil degradation and reduce the fluid’s ability to perform several key functions:
Compressor fluid performance has the single greatest impact on compressor maintenance cost and reliability; and thus routine Fluid Analysis should be an integral part of every compressors’ maintenance plan. Performing routine oil analysis is cheap insurance that provides compressor users with critical information that will warn of potentially catastrophic problems with the fluid, and compressor, before they occur. Oil Analysis is the backbone of Condition Based compressor maintenance and it allows compressor users to know in advance:
Fluid Analysis is an important first step in any Reliability Centered Maintenance program, and knowing which tests are best suited for air compressor fluids is critical. Many compressor OEMs and high volume laboratories offer a one-size-fits-all oil analysis package that often includes information that is meaningless for compressor fluids. The following tests are especially useful for rotary screw air compressors and provide valuable information to help users monitor the health of their compressors’ fluid and internals, and warn of impending failures.
TAN - Total Acid Number (ASTM D664): TAN is a measure of the total concentration of acids, both weak and strong, present in the oil. TAN is a leading indicator of the fluid’s oxidative state and its remaining useful life. High TAN values (> 1.0), when all other properties are normal, are the normal result of the weak acids produced from oxidation accumulating in the oil. TAN does not distinguish between weak and strong acids, thus TAN values can also increase when strong acid or oxidizing contaminants are ingested from the atmosphere, or when residual acid contaminants from a previous fill, including varnish and sludge, are left behind after an oil change.
pH: pH measures the relative strength of the acids present in the oil. Normal fluid oxidation produces only weak acids, and thus low fluid pH (< 4.50), when TAN and other properties are normal, confirms the presence of strong acid contaminants ingested from the atmosphere. Whenever fluid pH gets low, the oil has not degraded, it has been contaminated by an external source.
Viscosity: Viscosity is a measure of a fluid’s resistance to flow. While in service, compressor fluids normally experience a small increase in viscosity (< 20%) as the fluid oxidizes, volatile components evaporate, and ultra-fine solids accumulate in the fluid. Large increases in fluid viscosity (> 30%) are rare and normally associated with harmful, varnish-producing, polymerization reactions experienced by PAO synthetics and mineral based oils. Abnormal viscosity increases and decreases can also be caused when the wrong fluid is added.
Spectrochemical Analysis: Spectrochemical analysis identifies up to 21 metallic elements that are commonly associated with wear metals, additives, and contaminants. Comparing the baseline spectrochemical of a new fluid with that of an in-service fluid, enables users to identify contaminants and detect the depletion of important additives.
ISO Particle Count (pore blockage method): ISO Particle Counts provides compressor users information about the relative cleanliness of a fluid by counting the number of particles across an array of increasing micron sizes. Studies show that fluid cleanliness has a major impact on bearing life, and therefore monitoring fluid cleanliness provides critical information about the bearings’ operating environment, and the effectiveness of the compressor’s filtration. Optical, or Laser Particle counting, is not recommended for many types of compressor fluids because they are very dark in color and can contain large amounts of water that can obscure instrument optics and produce erroneous readings.
Time-based oil changes, as promoted by the compressor OEMs’, is a wasteful practice solely designed to increase oil consumption and sales.
Did You Know?
Changing compressor fluids based on time, instead of its condition, only guarantees it will be changed at the WRONG TIME - too early (wasteful) or too late (risky).
Oil analysis is the only way compressor users can determine the actual physical and chemical properties of their fluid, and whether it needs to be changed.
Fluid Analysis provides critical information about the actual health of your compressors’ fluid and internals, and can warn of potential problems.
Fluid Analysis more than pays for itself with extended oil drain intervals and reduced compressor maintenance and downtime.
ISO 17025 Accreditation
ASTM Analytical Testing