3/5/2015. Oil Analysis Tests. Lubricating Oils. Six Functions of Lubricating Oil

Transcription

1 Oil Analysis Tests Oil analysis is a series of laboratory tests used to evaluate the condition of used lubricants and equipment components. By studying the results of the used oil analysis tests, a determination of equipment/component condition can be made. Primarily, this is possible because of the cause and effect relationship of the condition lubricant to the condition of the component sampled. When the oil speaks, you should listen! Lubricating Oils Six Functions of Lubricating Oil Reduce Frictional Resistance Protect Against Wear and Corrosion Assist Sealing Contribute to Cooling Removal of Contaminants Transmission of Power 1

2 What do laboratories look for? Detecting Dirt Water Glycol/Coolant Soot Fuel Sulfation and Nitration Particles Dirt Entrainment (Si) ICP Spectrometric Analysis poorly maintained air intake systems faulty air cleaners. Example In Figure ICP-1 the severe silica (Si) level indicates dirt ingress. The resulting severe iron (Fe) and Aluminum (Al) levels are as a direct result of abrasive wear from the dirt particles to the cylinder assembly. damaged gasket and seals component wear damage potential failure Check air filters Check air intake Check gaskets and seals 2

3 Water KF-Karl Fischer Low operating temperature Defective seals New oil contamination Coolant leak Improper storage Cracked head Weather/moisture Product of combustion Oil cooler leak Engine failure High viscosity Poor lubrication Corrosion Increased engine heat Acid formation Weld spots Reduced additive effectiveness Tighten head bolts Check head gaskets Inspect for cracked head Inspect heat exchanger and oil coolers Avoid intermittent use Check for external water/moisture sources Change oil filters Glycol/Coolant ICP Spectrometric Analysis Cracked head Leaking gaskets Cracked liner Coolant leak Oil cooler leak Engine failure High viscosity Poor lubrication Corrosion Increased engine heat Acid formation Weld spots Reduced additive effectiveness One of the worst enemies of lubricating oils is glycol. Found in most anti-freeze solutions, glycol can enter oil supplies in many of the same ways water does. When mixed with oil at operating temperatures, the glycol/oil mixture changes chemically to form highly corrosive sludge deposits. When sodium and potassium levels surpass 300 ppm and 200 ppm respectively, a coolant system inspection is advised. Tighten head bolts Check head gaskets Inspect for cracked head Inspect heat exchanger and oil coolers Avoid intermittent use Check for external water/moisture sources Change oil filters Soot Fourier-Transform Infra-Red Soot is a product of diesel fuel combustion resulting from blow-by, low temperature and overload operation, richmixture excessive idling and/or poor ignition. Engine "sootiness" levels reveal the engine's overall combustion efficiency. The presence of soot causes overall degradation by increasing oil viscosity, promoting sludge and deposit formation when moisture is present. Additionally the function of many oil additives can be seriously impaired. While some soot contamination is normal and expected, excessive amounts rapidly increase wear and shorten component lifetime. Improper air/fuel ratio Improper injector adjustment Poor quality fuel Incomplete combustion Clogged air induction Defective injectors Improper equipment operation Low compression Worn engine parts/rings Poor engine performance Poor fuel economy Increased operating cost Harmful deposits or sludge Increased wear Shortened oil life; Poor lubrication Lacquer information Carbon deposits Clogged filters Ensure injectors are working properly Check air induction/filters Change oil Evaluate oil drain intervals Check compression Avoid excessive idling Analyze driving/operating conditions Check fuel quality Evaluate operator experience/training 3

4 Fuel Dilution Gas Chromatography Cold starts, over-rich mixtures, dribbling injectors, leaking fuel fittings and seals, ruptured pump diaphragms, inadequate operating temperatures, use of improper fuel, excessive idling, over-choking and faulty carburetion all contribute to oil "fuel dilution" problems, by not allowing the fuel to completely vaporize. Lubricating oil thins out (lower viscosity) when fuel contamination is present. This results in inadequate lubrication and scuffing of engine parts. Bearing failures, increased fuel and oil consumption, oxidation, sulfanation, oil detergent loss, lowered operating temperatures and power loss can all be associated with "fuel dilution" problems. Fuel additives, combustion by-products, lead and sulfur compounds all contribute to the development of corrosive acid deposits, providing increased probability of accelerated engine wear and shortened component life. Incorrect air to fuel ratio Extended idling Stop and go driving Defective injectors Leaking fuel pump/lines Incomplete timing Metal to metal contact Poor lubrication; Oil thinning Increased overall wear Cylinder ring wear Decreased additive effectiveness Risk of fire or explosion Reduced MPG Decreased oil pressure Reduced engine performance High operating cost Shortened engine life Check fuel lines, worn rings, leaking injectors/seals, pumps Analyze driving/operating conditions Check timing Avoid prolonged idling Change oil and filters Check fuel quality Repair/replace worn parts Sulfation & Nitration Fourier-Transform Infra-Red Sulfation - The sulfate index measures the extent to which sulfur-based acids have entered the oil. A rapid increase in the sulfate index could be due to depletion of oil additives, poor combustion or over-cooling. Nitration - The nitrate index measures the build-up of nitrogen compounds in the oil.. These compounds cause oil thickening and deposits that interfere with lubrication. Nitration is influenced by incorrect fuel/air ratios, improper spark timing, high loads, low operating temperatures and piston-ring blow-by. Improper scavenge Low operating temperature Defective seals Improper air/fuel ration Abnormal blow-by Accelerated oxidation Nitrous oxides introduced into environment Acidic by-products formed Increased cylinder and valve area wear Oil Thickening Combustion area deposits Increased TAN Increased operating temperature Check crankcase venting hoses and valves Ensure proper air/fuel mixture Perform compression check or cylinder leak-down test PC - Particle Count ISO 4402/4406 (OF HIGH READING) Water contamination Machining burrs Filling techniques Oil oxidation Contaminated new oil Worn wiper seals System generated debris Built in contamination Defective breather Performance degradation Intermittent failure Wear Plugging Leakage Particle count measures the cleanliness of an oil. Pressure overshoot Particles are quantified at 5 size ranges and reported per Momentary hesitation System failure 1 ml of fluid. All particles are counted including wear particles, process and environmental contaminants. This test is of particular importance to clean oil systems, e.g., Filter new oil hydraulics, transmissions, turbines, compressors and Change hydraulic fluid other fluid power systems. It has been shown that 70-85% Inspect/replace filters of hydraulic component failures is due to particulate Check particle sizes contamination with up to 90% of these failures due to System flushing at high pressure abrasive wear. Check air breather Evaluate equipment vs. design Evaluate for proper service techniques 4

5 Mobile Oil Contamination Reaction Chart Detecting Viscosity Oil Oxidation Acid Number Base Number 100 C /40 C ASTM D445 Viscosity refers to the oil's flow characteristic. Under normal operating conditions, oil viscosity (thickness) increases gradually because lighter base oil fractions evaporate while the contaminant and degradation product levels build-up. Viscosity measurement will determine the extent to which the oil has become contaminated and/or degraded. Example In the example below we see that the increase in fuel dilution from 0.0% to 12.0% has resulted in a corresponding drop in the viscosity at 100 C from 14.0 cst (the typical value for this oil) to 7.96 cst. (this sample is from a Caterpillar 3176 diesel engine. The engine was showing a substantial increase in the iron level by the time the oil showed 12.0% fuel dilution.) Check air to fuel ratio Check for incorrect oil grade Inspect internal seals Check operating temperature Check with lube supplier for advice High viscosity Contamination soot/solids Incomplete combustion A/F ratio Oxidation degradation Leaking head gaskets Extended oil drain High operating temperature Improper oil gradeviscosity Additive shear Fuel dilution Improper oil grade High viscosity Increased operating costs Engine overheating Restricted oil flow Accelerated wear Oil filter by-passed Harmful deposits/sludge Low viscosity Engine overheating Poor lubrication Metal to metal contact Increased operating costs Check for leaking injectors Use trained operators Change oil and filters Check for loose fuel crossover lines 5

6 Viscosity Equivalents Oil Oxidation Fourier-Transform Infra-Red Overheating Extended oil drain Improper oil type/inhibitor additives Combustion by-products/blow-up Shortened equipment life Lacquer deposits Oil filter plugging Increased oil viscosity Corrosion of metal parts Increased operating expense Increased overall wear Decreased engine performance All engines, transmissions and drive-axle component oils oxidize. A chemical reaction between oil molecules and oxygen takes place at high operating temperatures. This reaction increases viscosity, causes formation of insoluble engine deposits and corrosive acids which further increases component wear. Higher operating temperatures, fuel consumption, rapid additive depletion and substantial loss of power can also be expected when oil oxidation takes place. When severe, oxidation makes the oil very hard to pump causing lubrication starvation to moving parts, with inevitable results. Oils that are oxidized have a very pungent, sour odor. Use oil with oxidation inhibitor additives Shorten oil drain intervals Check operating temperatures Check fuel quality AN - Acid Number ( formerly TAN ) ASTM D664/ D974 (OF HIGH READING) High sulfur fuel Overheating Excessive blow-by Extended oil drain Improper oil type Corrosion of metallic components Promotes oxidation Oil degradation Oil thickening Additive depletion Acid Number (AN) measures the level of acid and acidproducts present in the oil. The corrosive acid level tolerable before damage occurs to a component varies with both the oil and application. A high AN in oils correlates with increased wear and could signal high oxidation or overheated oil. Drain oil Reduce oil drain interval Verify correct oil type in service Check for overheating Check fuel quality 6

7 BN - Base Number ( formerly TBN ) ASTM D2896/D4739 (OF LOW READING) High sulfur fuel Overheating Extended oil drain Improper oil type Increased TAN Oil degradation Increased wear Corrosion of metal parts Acid build-up in oil Base Number (BN) is an expression of the amount of alkaline additives in the lubricant which are capable of neutralizing the acidic products of combustion. A new oil starts with the highest BN it will possess. During the time the lubricant is in service, the BN decreases as the alkaline additives neutralize acids. BN is an essential element in the establishment of oil drain intervals since it indicates whether the additives are still capable of providing sufficient engine protection. Use low sulfur fuel Follow manufacturer s recommendations for oil drain interval (ODI) and decrease if engine is operated under severe conditions Verify BN of new product/use correct oil type Change oil/top off with fresh oil Test fuel quality Mobile Oil Condition Reaction Chart Wear Detection ICP Spectrometric Analysis Spectrometric Analysis for wear is the oldest use for oil analysis. In the 1940s the railways used Atomic Absorption units to detect iron, chromium, copper and lead in railway engines. Today modern ICP units can analyze for over 20 elements in under 1 minute. Wear metal analysis by ICP can detect potential problems sometimes months before they actually show up in vibration analysis. Example Trending of the wear metals quickly identifies abnormal wear as in this gearbox sample illustrated in the graph (top right). In the example at the bottom right the iron (Fe), chromium (Cr), aluminum (Al) and tin (Sn) levels are abnormal to severe indicating cylinder assembly wear in this Detroit 6V71 diesel engine. 7

8 Mobile Oil Wear Reaction Chart Basic Steps for a Quality Used Oil Analysis Program 1. Select the a Laboratory for your location. 2. Determine the correct test package for your equipment. 3. Take samples regularly 4. Ensure you are consistent in your sampling process. 5. Provide the laboratory with good, factual information about the equipment and the lubricant. 6. Do not hold samples send them to the lab ASAP. 7. Review, analyze and use the reports sent to you by the laboratory. 8. Call the laboratory if you have problems or questions. 9. Be an informed user of oil analysis. Use the manuals and materials provided by the laboratory. 10. Remember! This is your program and it will work for you if you use the information provided. Thank You! Questions? 8