MRO Magazine

Oil Analysis

“Basic Wear” Programs Provide Inadequate Condition Monitoring.

Many equipment reliability managers and engineers who maintain industrial equipment in mining, pulp and paper, oil and gas, and other heavy industries do not use oil analysis programs effectively. The primary reason is because the “basic wear” oil analysis programs marketed by oil analysis laboratories provide insufficient information.

There is a perception among these users that the “basic wear” packages provide sufficient condition monitoring detail, because the programs cover component wear rates, additive levels, viscosity levels, and basic physical oil condition. Unfortunately, these fundamental programs do not provide the detail necessary to indicate oil degradation conditions such as oxidation and nitration or types of contamination, depending on the equipment type.

The analyses that should be included are acid number analyses for natural gas engines, turbines, and recirculating systems and base number analyses for diesel engines. In addition, ISO standard 4406, or membrane filtration (patch tests) should be included for all recirculating systems in order to monitor contamination levels that spectroscopic wear analyses are incapable of “seeing.” The inclusion of these analyses would provide “root cause failure detection,” making oil analyses truly proactive.

1. How do you monitor potential lubricant end-of-life conditions such as oxidation, compression heating, or thermal degradation, or a combination of these chemical reaction mechanisms?

Logic: The cause of high nitration and/or oxidation is often combined with high levels of carboxylic acids and/or higher-than-normal viscosity levels. In order to monitor these lubricant conditions and determine the remaining life of the lubricant, it is recommended to include acid number analysis to natural gas engine and recirculating systems (hydraulic, gear drive, pump, and compressor) oil analyses packages.

The addition of base number analyses should be applied to diesel engine oil analyses packages to determine correct oil drain intervals. Without these additional tests, the generation of varnishing, sludge, carbon, and other causes of potential equipment failure may never be known until it’s too late.

2. How do you monitor recirculating lubrication system contamination levels?

Logic: Over 70 per cent of lubrication-related failures are caused by contaminated oil. This is particularly true in gear drives and pumps whose shafts are supported by rolling element bearings with critical clearances, screw-type compressors, and high-pressure hydraulic systems using piston pumps and motors. This contamination is dirt, dust, water, and other large particle contamination that cannot be “seen” with just the application of spectroscopic wear rate analyses. As a result, it is recommended that the addition of ISO 4406 fluid cleanliness analyses using optical particle counters is included in these oil analysis packages.

(The use of optical particle counters is recommended over pore blockage instruments because optical instruments will determine all contaminants, including varnish.)

Karl Fischer water analysis is essential wherever water is a potential concern, such as in screw compressors.