The Oil Analysis Handbook A Comprehensive Guide to Using and Understanding Oil Analysis
Michael Holloway NCH Corporation
[email protected] 972-438-0030 (office) 214-450-7864 (cell)
Oil Analysis - Table of Contents Introduction
1
Understanding Oil Analysis Results
2
I) Elemental Analysis The Metal Source Wear Metal Limits Other Sources of Metals & Elements Test Results
3 7 9 10
II) Contamination Analysis Internal & External Sources & Damage Contaminants, Oxidation, Water & Particles Contaminant Test Results Particle Count Analysis Reporting Particle Analysis Size Range Code Particle Test Results
11 13 14 15 16 17
III) Oil Condition Analysis Viscosity & Acid Neutralization (TBN/TAN) Test Results
18 19
IV) Taking Oil Analysis Samples Crankcase or Reservoir Samples Using a Vacuum Pump Sump or Reservoir Samples Using a Sampling Valve
20 21
V) Sampling Frequency
22
VI) Summery
23
Index and Common Terms
24
Comparative Viscosity Table
28
Oil Analysis - Table of Contents Introduction
1
Understanding Oil Analysis Results
2
I) Elemental Analysis The Metal Source Wear Metal Limits Other Sources of Metals & Elements Test Results
3 7 9 10
II) Contamination Analysis Internal & External Sources & Damage Contaminants, Oxidation, Water & Particles Contaminant Test Results Particle Count Analysis Reporting Particle Analysis Size Range Code Particle Test Results
11 13 14 15 16 17
III) Oil Condition Analysis Viscosity & Acid Neutralization (TBN/TAN) Test Results
18 19
IV) Taking Oil Analysis Samples Crankcase or Reservoir Samples Using a Vacuum Pump Sump or Reservoir Samples Using a Sampling Valve
20 21
V) Sampling Frequency
22
VI) Summery
23
Index and Common Terms
24
Comparative Viscosity Table
28
Oil Analysis - Introduction Oil analysis is similar similar to visiting visiting your doctor for an annual blood blood test. The doctor can determine your overall health and well-being from a very small sample of your your blood. The same can be done with oil lubricated equipment such as engines, gearboxes, hydraulics, air compressors, and turbines. It has been estimated that many maintenance technicians change oil 40% Change 40% Change too early or too late. Changing oil too Early too Late too early wastes money on oil, filters and labor. Changing oil too late can lead to deposit build-up and costly equipment repairs. The best way to determine when to accurately change 20% Change on Time oil is through oil analysis. Oil analysis analysis can help extend oil life. When considering oil analysis, analysis, consider consider these facts: The storage, handling, handling, dispensing and and disposal of of lubricants will will typically cost 4 times the cost of a gallon of the same lubricant. The budget to maintain equipment is at least 14 times the cost the lubricant. Industrial plants regularly document that comprehensive oil analysis has decreased their overall maintenance cost up to 28%. Fleet vehicles on the average can expect to see a minimum 30% increase in engine life. An Oil Analysis Provides the Following: I) Elemental Elemental Analysis Analysis - detect detectss the amount amount and type type of element elementss in the the oil from component wear, contamination and various ingredients found in oil. II) Contaminat Contamination ion Analysis Analysis - detect detectss the physical physical presence of unwanted unwanted fluids fluids (water, fuel, antifreeze) or particles (dirt, metal, etc…) in the oil and identifies oil by-products such as soot, nitration and sulfur. III) Oil Condition Analysis - tests viscosity viscosity and an oils ability to neutralize neutralize acids (TBN for engines or TAN for non-engines). 1
Understanding the Oil Analysis Results The oil analysis test results will be broken down into wear metal concentration, oil condition and contaminants. Each analysis normally has past results included. The most important information the oil analysis lab will provide would be the overall comments made by the oil analysis technician. The technician will take past results and the existing results and formulate a course of action. The most important information that the customer will provide is a thorough representation of the equipment being tested and the oil being used. Effort should be made to ensure that consistent and accurate information is provided. Customer and Equipment Information
Latest Analysis Recommendations
History and Trend Analysis
History and Trend Analysis: Test results from previous analysis are important for comparison purposes. The past results help the oil analysis technician and the customer establish any trends that may be emerging and take the appropriate action.
2
I) Elemental Analysis - The Metal Source Elemental analysis tests for various elements found in the oil that may be from wear debris, contamination or the additives found in the oil. When an oil lubricated component begins to wear, small amounts of metal become suspended in the oil. These trace amounts of metal are the first indicators of component wear. If left unattended, the wear will increase and potential part failure will occur. In extreme cases, metal shavings from worn gear teeth can be found in the oil. If the wear is severe, metal shavings can be seen during the oil change. The shavings will contribute to more wear. This situation can occur in gearboxes, hydraulics, engines, and air compressors. Many components and parts are made-up of several different metals. An oil analysis technician can determine which component is beginning to show signs of wear just by the type of metal and the concentration found in the test sample. The following tables are a guide to the sources of specific wear metals for a given piece of equipment. Iron (Fe) The most common of the wear metals. It is present in some form in virtually all equipment. Its widespread presence means that there are many sources of the wear particles. Metallurgy of the component allows the analyst to distinguish the source of the wear debris, e.g. cast iron bolts vs. stainless steel lube oil piping. Equipment Engines
Bearings Gears Transmissions Hydraulic Systems Compressors Turbines
Wear Metal Source Most common of the wear metals. Engines: Cylinder Liners, Piston Rings, Valve train, Crankshaft, rocker arms, spring ge ars, lock washers, nuts, pins, connecting rods, Engine Blocks, Oil pump, Rolling element Bearings: rollers (tungsten alloyed steel), raceways and cages, Journal Bearings: Journal shaft, bearing Shoe backing. Locking keys Bull gears, pinions, case hardened teeth, locking pins Gears, bearings, Brake bands, clutch, shift spools, pumps, power take off (PTO) Pump, motor, vanes, pump housing, cylinder bores and rods, servo valves, pistons Rotary Screw, lobes, vanes, connecting rods, rocker arm, bearings, cylinders, housing, shafts, roller bearings (se e above) oil pump, piston rings Reduction gear, shaft, bearings, piping, case
3
I) Elemental Analysis (continued) - The Metal Source Copper (Cu) Widely used as an alloying element, copper is prized because of its materials properties such as ductility, excellent thermal and electrical conductivity. It is heavily used in bearing systems, as well as heat exchangers. Equipment Engines Bearings Gears Transmissions Hydraulic Systems He at Exchange rs Compressors Turbines
Wear Metal Source Valve train bushing, Wrist pin bushing, Cam bushings, Oil Cooler core, Thrust washers, governor, connecting rods bearings, valve gear train thrust buttons, Rolling element Bearings: alloyed element in cages, Journal Bearings: journal bearing pads, slinger rings, Locking ke ys Bushings, thrust washers Clutches, steering discs, bearings Pump thrust plates, bushings, cylinder gland guides, pump pistons, oil coolers Coole r tube s, baffle s, plate s. Bearings, cylinder guides, wear plates, thrust washers, bearings (see above) oil pump, oil coolers, thermostats, separator filters Bearings (see above) piping, coolers
Tin (Sn) Used as an alloying element with copper and lead for sacrificial bearing liners. Equipment Engines B earings Gears Transmissions Hydraulic Systems Compressors Turbines
Wear Metal Source Valve train bushing, Wrist pin bushing, Cam bushings, Oil Cooler core, Thrust washers, governor, connecting rods bearings, valve gear train thrust buttons, Rolling element Bearings: alloyed element in cages, Journal Bearings: journal bearing pads (babbited Bushings Clutches, steering discs, bearings Pump thrust plates, bushings, Can be a residue from catalyst in some oils (Quintolubric series) Bearings, separator filters Bearings (see above) piping, coolers
Aluminum (Al) Has high strength to weight ratio, and excellent corrosion resistance. Alloyed with other elements improves its wear and temperature resistance. Equipment
Wear Metal Source
Engines
Engine blocks, pistons, blowers, Oil pump bushings, bearings (some) Cam bushings (some), Oil coolers (some)
Be arings
Rolling e le me nt Be arings : alloye d e le ment in cage s, Locking ke ys
Gears
Bushings, thrust washers, grease contamination
Transmissions
Bushings, clutches
Hydraulic Systems
Cylinder gland (some) pump, motor pistons, oil coolers. Aluminum complex grease
He at Exchange rs
contaminant Coole r tube s, baffle s, plate s
Compressors
Housing, bearings, cylinder guides, wear plates, thrust washers, bearings (see above), oil pump, oil coolers
Turbines
Bearings (see above) piping, coolers EHC Systems: Residue from synthetic media (alumina) filters
4
I) Elemental Analysis (continued) - The Metal Source Chrome (Cr) Used as an engineering material for its great hardness and corrosion resistance. It is found in many systems operating under harsh conditions. Equipment Engine s Be arings Gears Transmissions Hydraulic Systems He at Exchange rs Compressors Turbines
Wear Metal Source Rings , Line rs , e xhaus t valve s, zinc chromate from cooling s ys te m inhibitor Rolling e le me nt Be arings: alloye d /coate d e le me nt in rolle rs, tape rs Bearings (some), shaft coatings, some special gears are chrome plated Bearings, water treatment Cylinder liners, rods, spools Coole r tube s, baffle s, plate s Housing, bearings, cylinder guides, wear plates, thrust washers, bearings (see above), oil pump, oil coolers Shaft coating (some) bearings,
Lead (Pb) A soft metal used for sacrificial wear surfaces such as journal bearings. Lead based babbitt bearings are widely used. Equipment Engines B earings Gears Hydraulic Systems Compressors Turbines
Wear Metal Source Main B earings, connecting rod bearings. Lead can be present as a contaminant from Gasoline (Leaded gas) (Octane improver, anti-knock compound) Rolling element Bearings: alloyed element in cages, Journal B earings: Major alloying ele ment in Babbitt bearings, alloying elements Bearings, can also be red lead paint flakes from gear case walls Bearings Bearings Bearings
Silicon (Si) The most common contaminant found in lube oil analysis. Abundant in all areas, sand is a very hard crystalline material, and very abrasive to metal components. Equipment Engines Be arings Gears Transmissions Hydraulic Systems He at Exchange rs Compressors Turbines
Wear Metal Source Engine blocks (alloying element with aluminum parts), ingested dirt from breathers, external sources. Can also be from defoamant additive in lubricant Rolling e le me nt Be arings: alloye d e le ment with aluminum in cage s Bushings, thrust washer, silicone sealant, defoamant additive Brake shoe s, clutch plate s, inge ste d dirt Elastomeric seals (some) pump, motor pistons, oil coolers Coole r tube s, baffles , plate s Ingested dirt, silicone sealant, bearings, cooler (alloyed with aluminum) Ingested dirt, silicone sealant, defoamant additive
5
I) Elemental Analysis (continued) - The Metal Source -
Silver (Ag) Has exceptional thermal conductivity, and is an excellent bearing plate material, providing minimum friction. It is susceptible to corrosive attack by zinc-based additives. Some bearing, turbine and compressor manufacturers specify that only zinc free oils are used. Silver is used more outside of the US in general industrial equipment. Equipment Engine s Bearings Gears Hydraulic Systems Compressors Turbines
Wear Metal Source Valve s, Valve guide s, Cylinde r line rs, Be arings. Can also be from he avy Rolling element Bearings: alloye d element in rollers, race s Alloying element for tool steel gears Bearings, servo valve plating pumps, pistons Bearings Bearings, shaft, reduction gears
Other Metals Other metals can be found in oil samples due to wear or contamination. Element Titanium Vanadium Magnesium Molybdenum Zinc
Possible Sources Wear metal for aircraft engines, bearings, Can also be contaminant from paint (titanium dioxide is used as a pigment) Fue l Contaminant, can also be alloying e le ment for ste el Alloying element in steels Solid/liquid antiwear additive, alloy in bearing and piston rings Antiwe ar, Corros ion inhibitors , Anti-oxidants , alloying e le me nt for be arings , thrus t washers, galvanized cases
6
I) Elemental Analysis (continued) - Wear Metal Limits Wear metal analysis is performed by emission spectroscopy. This test provides the concentration of metals for wear, additive concentration and contamination found in lube oils and is measured in parts per million (1000 p.p.m. = 0.1%). Emission spectroscopy measures metallic particles that are less than 10 microns in size. Many components have different levels of acceptable concentrations of wear metals. A transmission or gearbox can Technician testing oil for wear metals withstand higher levels of wear metals using emission spectroscopy compared to a hydraulic pump or engine. A trained oil analysis technician can determine critical levels and provide the appropriate recommendations. Keep in mind, all systems are different. Some systems by their design will produce high levels of wear metals. It is essential that periodic test results are compared in order to establish if any trends are emerging. The following table is a “rule-of-thumb” for metal concentration limits in parts per million (ppm) for different components. It is important to examine past test results in order to identify potential trends or emerging problems. Hydraulic Gearbox Diesel Engine Gasoline Engine Transmission Differential Iron Chromium Lead Copper Tin Aluminum Nickel Silver Silicon
75 5 20 75 10 25 5 5 75
300 n/a n/a 250 250 250 n/a n/a 250
80 25 50 50 25 30 10 5 25
300 40 n/a 75 40 40 15 5 50
300 10 50 400 20 50 20 5 50
1000 n/a n/a 250 250 250 n/a n/a 250
7
I) Elemental Analysis (continued) - Other Sources of Metals & Elements Oil analysis is helpful in understanding how fast a system is wearing. It is also helpful in understanding contaminants and even the performance ingredient levels in oils. Contaminants: the source of these contaminants can be internal or external. The only way to insure that the elements can be considered a contaminant is to compare the results against a reference sample of the oil being used. Contaminant Silicon
•
•
Sodium & Potassium
•
•
Boron
•
Source and Potential Problem Silicon Dioxide (sand & dirt) is a common contaminant – may indicate a faulty air filter or seal. May have also entered when top-filling. Polysiloxane (silicone rubber) is commonly used in gaskets and seals – may indicate that a gasket is wearing out and abrading. Found as additives in anti-freeze – potential cracked block or cross-contaminated from the oil container that may have been used for coolant. Sodium Chloride or Potassium Chloride (salt) – road salt or sea salt entered thorough breather filter or through broken seal. Found as additives in anti-freeze – potential cracked block or cross contaminated from an oil container that may have been used for coolant.
Additive Elements Found in Oil: Many oils use various chemicals (additives) to obtain certain levels of performance. It should be noted that certain elements found in these additives (calcium for instance) may not decrease as the oil begins to wear out. These elements continue to exist but may loose functionality. Keep in mind, the performance additives change into different compounds as they are used up and are not as effective as their original design. In other cases, elements found in certain additives may actually decrease in concentration (zinc and phosphorous) because they are adhering to the surface of the metal and are no longer in the oil. The only way to truly know when the oil additives are being used up is the sharp rise in wear metal concentrations. Element Barium Boron Calcium Copper Magnesium Molybdenum Phosphorus Silicon Sodium Zinc
Function Detergent or dispersant additive Anti-wear additive Detergent or dispersant additive Anti-wear additive Detergent or dispersant additive Lubricity modifier Corrosion inhibitor, anti-wear additive Anti-foaming additive Detergent or dispersant additive Anti-wear or anti-oxidant additive
9
I) Elemental Analysis (continued) - Test Results -
Elements Accounting for Wear Metals, Contaminants and Oil Additives
10
II) Contamination Analysis - Internal & External Sources & Damage Many gearboxes, hydraulic systems, air compressors and engines can quickly become contaminated with water, particulate and various deposits such as varnish and sludge that are the products of oil oxidation. These contaminants contribute to the degradation of the lubricant, increased operating temperature, energy demand, component wear and oil usage. Deposits on a Hydraulic Pump Contaminant Water
Particles
Oxidation
Soot (in engine oil)
Source Naturally formed from condensation or during combustion in engines. Enters sumps and reservoirs through leaking seals, top-filling or inadequate breathers. The chemical breakdown of oil from heat, water, and / or dissimilar metal contact. Typically from partially burned fuel.
Fuel (in engine oil)
Typically from piston wash – fuel washes past compression rings and enters oil sump. Antifreeze (in engine Enters oil sump through oil) cracked engine block or from contaminated oil can. Nitration (in engine Occurs during combustion oil) stage in engines Sulfur
Found in off-road diesel fuel and some mineral oil based products
Problem Leads to heat build-up, foaming, additive depletion, rust and oil oxidation. Leads to premature component wear and facilitates deposit build-up. Results in thickened oil, deposits, acid formation, increased operating temperature and plugged filters. Leads to poor combustion can lead to excessive wear and increased fuel costs. Leads to oil viscosity loss, heat build-up, additive depletion and oxidation. Leads to oil contamination, sludge and varnish build-up and potential engine failure Can form acids, which lead to sludge, varnish, additive depletion and oil breakdown. Can form acids, which lead to sludge, varnish, additive depletion and oil breakdown.
11
II) Contamination Analysis (cont.....) - Deposit Sources & Damage When lubricants oxidize, they form reactive materials that can re-constitute into different deposits. Oil analysis can help to identify the degree of oxidation that has occurred. More sophisticated analysis may have to be preformed in order to identify the exact contaminant. The following are several of the typical deposits that are formed and the problems that can occur when lubricating oil breaks down.
Deposit Formation
Potential Problem
Varnish: Found on bearings, cylinders, pistons, gears, vanes, pumps, and turbines. Oil or fuel oxidizes, forming a gummy substance that develops into a coating with highly crosslinked molecules that are insoluble in oil.
Varnish coating can lead to uneven gear wear due to unbalancing, increased drag/energy demand and increased temperatures due to lack of lubrication on metal surface, oil viscosity increase.
Lacquer: Found on bearings, cylinders, pistons, gears, vanes, pumps, and turbines. When varnish is exposed to excessive temperatures and pressure, it becomes baked on and ironed out, forming lacquer Sludge: Found in oil pans, sumps, housings, reservoirs, and bearings. Formation begins when contaminants begin to settle out of the oil. Sludge develops with excessive accumulation of contaminants, leading to additive depletion and oxidation. Gum:
Lacquer, like varnish, can lead to uneven gear wear, increased drag/energy demand and increased temperatures due to lack of lubrication on metal surface. Lacquer is exceptionally difficult to remove. Sludge is composed of water, carbon residue, oxidized oil, and acidic compounds, which can lead to further oil decomposition. Sludge can restrict oil flow, leading to increased system pressure, temperature, wear, and oil viscosity Gum canincrease. form on valves,
Typically found in the crankcase or combustion area of an engine. Gum develops when oil or fuel hydrocarbons break down due to high temperature and combustion by-products. Gum acts as a binder for contaminants to adhere to pistons, rings and valves.
pistons, rings, ring grooves and on the cylinder walls, causing contaminants and residue to adhere and restrict lubrication. Lack of lubrication increases friction and wear and restricts the heat transfer function of lubricating oil.
Carbon Deposits: Found in all lubricated systems such as engines, bearings, pumps, gears, and journals. Most common form is soot; can also be a tar-like residue. Soot is considered to be an advanced deposit formation.
Carbon deposits form, additional contaminants adhere, facilitating continued oil oxidation. The deposits can form a slurry or gelled mass. The deposits restrict lubrication flow and additive functionality.
Example
12
II) Contamination Analysis (cont...) - Contaminants, Oxidation, Water & Particles Oxidation, sulfur, soot, fuel, antifreeze, and nitration are measured by an instrument called a Fourier Transform Infrared Spectroscopy (FTIR). The lab must know the type of oil in service to produce accurate results. Engine oils are tested for oxidation, nitration and sulfur content. A base-line reference samples is required in order to compare the test sample against a base-line. The FTIR will scan the sample and look for a build-up. Water contamination is typically screened using a hot plate technique. The oil sample is dripped onto a hot plate. If the sample crackles, water is present. This method is used to quickly screen samples for further analysis. Positive results are confirmed and quantified using the Karl Fischer Titration Method. Results may be reported in parts per million or by percent by weight. Water can be found in hydraulic and compressor oil samples due to large temperature swings and a large air cavity in the sumps. Particle Count Analysis: In the early 1950’s when particle counting was first employed, the particles were counted manually. This involved someone actually counting the particles under an optical microscope and then classifying them into size ranges. Optical microscopy techniques for particle measurement consist of the maximum particle diameter technique. This technique measure the maximum straight line diameter of an irregular shaped particle. This technique is very effective, and is still used today but is very time consuming. Modern particle counters do not measure particle diameter. The instruments use a device called a light blocking sensor diode. The particle produces a shadow. The detector senses the shadow and determines the size, which is based on the surface area of the particle. The particles are counted by a computer and put into a size range standard. If a sample is too dark due to contamination, an accurate reading cannot be taken.
13
II) Contamination Analysis (cont.....) - Test Results -
Fuel, Water, Soot/Solids, and Antifreeze (glycol) are Measured in % by Weight
Oil Oxidation, Nitration and Sulfur Content are measured using the FTIR. Values are compared to a baseline reference of the oil. If the values exceed 20, the technician alerts the customer.
14
II) Contamination Analysis (cont....) - Particle Count Analysis Reporting The first size range standard used only accounted for two values; particles greater than 5 microns and those greater than 15 microns. This standard is known as ISO 4406. This is reported in the form X/Y. This standard is still being used. A new reporting standard referred to as ISO 4406:1999 or ISO 4406 (MTD) is being used by many oil analysis labs. The new standard uses a three "digit" code in the form X/Y/Z. The new standard counts particles greater than 4, 6, and 14 microns. An example of a typical particle test value would be 16/15/12. The first number, "16", is the range code number that corresponds to a range of the number of particles present in an oil that are greater than 4 microns (µm or micrometers). That count is typically based on the number of particles per milliliter (ml). The second number, "15", is the range code number corresponding to the number of particles/ml that are greater than 6 microns and the third number, in this case 12, corresponds to the range code number of particles/ml greater than 14 microns in size. It should be noted that the first range code “X” includes the particles from both the second “Y” and third “Z” range codes. Likewise, the second range code includes the particles counted in the third range code. The actual numbers of particles counted per milliliter in each size category (4, 6, and 14 microns) are converted to the appropriate ISO Code. The number code range can be found on the following table. It is difficult to determined the level of cleanliness for any given component. Examining past results will help determine if particles have increased, provided that the sampling techniques are consistent. It is good practice to keep a system free of particulate as much as possible. It is also very difficult to obtain an oil sample and not contribute particles during sampling. Strict attention must be made to ensure that the test sample has not been compromised due to improper sampling methodology. Educating the technician who is taking the oil sample is as important as oil analysis itself. Particle counts can be reduced by installing air breathers on large sumps. Moisture and particulate accumulation are major factors of oil contamination. Use a filter element that can filter down to 3 micron absolute, a 200-beta minimum, and 8oz/237ml water absorption minimum, allowing at least 20cfm of airflow.
15
II) Contamination Analysis (cont....) - Particle Analysis Size Range Code ISO 4406 (MTD) ISO Range Code
Minimum particles per m l of oil
Maxim um particles per m l of oil
1
0
0.02
2
0.02
0.04
3
0.04
0.08
4
0.08
0.15
5
0.15
0.3
6
0.3
0.6
7
0.6
1.3
8
1.3
2.5
9
2.5
5
10
5
10
11
10
20
12
20
40
13
40
80
14
80
160
15
160
320
16
320
640
17
640
1,300
18
1,300
2,500
19
2,500
5,000
20
5,000
10,000
21
10,000
20,000
22
20,000
40,000
23
40,000
80,000
24
80,000
160,000
25
160,000
320,000
26
320,000
640,000
27
640,000
1,300,000
28
1,300,000
2,500,000
29
2,500,000
5,000,000
30
5,000,000
10,000,000
16
II) Contamination Analysis (cont.....) - Test Results -
Particle Count Using the ISO 4406 (MTD Number Range Code
17
III) Oil Condition Analysis - Viscosity and Acid Neutralization (TBN/TAN) Viscosity is considered the single most important characteristic of a lubricating oil. Viscosity is a fluid’s resistance to flow with respect to temperature. Oil will thicken in cold temperatures and thin out at high temperatures. Viscosity is measured using a bubble viscometer and kept at 40°C or 100°C, depending on equipment application. Single weight or ISO grade oils such as some gear and hydraulic oils are tested at 40°C (105°F). Multi-grade oils such as SAE transmission and engine oils are tested at 100°C (212°F). Results are reported in centistokes, cSt. Other viscosity tests include Saybolt (SUS) and Brookfield (cPs). Viscosity may increase or thicken due to oil oxidation or excessive particulate. Viscosity may also decrease or thin down due to fuel or contamination from solvents, another lighter oil or thermal breakdown.
Viscosity is measured by using a bubble viscometer. The device is filled with oil and kept at a constant temperature. When the viscometer is tipped, an air bubble in the sample is timed to see how long it takes to go from one etched line to the other. The value is converted into a unit of measure called centistokes (cSt).
As a oil begins to breakdown, various types of acids form which can lead to further oil degradation, metal wear and additive depletion. It is important to establish a starting point in order to compare the oil that is being used. A baseline sample from the oil drum is essential. The TAN or Total Acid Number is used to check the acid neutralization of hydraulic, gear and air compressor oils. The TAN normally increases over time. The TAN of a reference sample should be tested in order to establish an oils initial TAN. If the used oil increases 3 points above the TAN number from the reference sample, the oil should be changed. The TBN or Total Base Number measures the amount of basic (alkaline) materials in engine oil that will neutralize acids. The TBN decreases as it approaches the end of it’s useful life. TBN is used to test the acid neutralization ability of engine oils. The lower the value, the less effective the oil will be at neutralizing acids. As acids increase, so do deposits. Deposit build-up will shorten engine life. The TBN is also known as BN or Base Number.
18
I) Elemental Analysis (continued) - Test Results -
Viscosity for Single Weight Oils are Tested at 40°C (100 °F) Viscosity for Multi-grade Oil are Tested at 100 °C (212 °F)
TAN for Gear, Hydraulic, & Air Compressor Oil TBN for Engine Oil
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IV) Taking Oil Analysis Samples Crankcase or Reservoir Samples Using a Vacuum Pump When taking an oil sample, the system should have been running for at least 30 minutes. This will heat the oil and also allow for an equal distribution of wear metals and contaminants. The system should be turned off before a sample is drawn. The oil sample should feel warm. The 7 Steps for Proper Oil Sampling: 1) Cut a length of 1/4 inch poly tubing approximately 6 inches longer than the oil dipstick or long enough to reach the near bottom of the sump. (always cut the tubing at an angle). 2) Loosen the knurled knob on the sample pump and insert the tubing through hole in the knob until the tubing extends about 1 inch into the bottle. Tighten the knob so that the “O” ring seats tightly around the tubing. 3) Remove the cap from the sample bottle and screw the bottle into the pump, making sure the bottle is seated properly. 4) Insert the tubing into the dipstick tube, making sure it extends into the crankcase or reservoir. 5) Pull out plunger on pump one time only, wait for the bottle to fill. If everything is tight, the bottle should fill within seconds. You may have to pump it several times in order to create a vacuum. 6) When the bottle is full, release the vacuum that has been created by unscrewing the sample bottle or opening the rubber cover in front of the sample pump. The rubber cover seals the sampling valve. Pull the tubing from the dip stick or reservoir, remove the bottle from the pump and cap the bottle, put it in the shipping container. 7) Carefully and completely fill out the sample identification form and send it to the lab and discard the tubing, never re-use it.
20
IV) Taking Oil Analysis Samples (cont.) Sump or Reservoir Samples Using a Sampling Valve Another method would be to obtain a sample using a permanently installed sampling valve. This valve is mounted in the oil flow circuit prior to the filter. The steps for sampling are outlined below. Sample the hot oil after it has left the mechanical system(s) but before it has passed through the filter. 1) Unscrew the dust cap from the valve. Allow a few ounces of oil to drain from the valve. 2) Take the sample bottle and place it under the valve discharge opening. 3) Depress the button on the valve, fill the sample bottle and then cap it tightly. The hand pump is also equipped with a built-in sampling valve which has a rubber cover. 4) Screw the dust cap back on to the sampling valve.
Always sample oil from a machine that has been running for a minimum of 30 minutes. This will provide a uniform sample.
5) Carefully and completely fill out the sample information form, place in shipping container and mail the sample to the lab.
Alternative Sampling Technique - The Drain Pan Method In certain instances the only way to obtain an oil sample is by taking it while the oil is being drained from the sump or the oil pan. Sample by: 1) Assure that the sample is warm from a system that has been running for at least 30 minutes. 2) Wipe the surrounding area clean to reduce cross-contamination. 3) Drain at least a quart of oil before passing the sample bottle into the stream of oil. The oil will be hot, wear the appropriate protection or use a pair of pliers or channel-locks to hold the sample bottle under the oil stream. 4) Carefully and completely Fill out the sample information form, place in shipping container and mail the sample to the lab.
21
V) Sampling Frequency An oil sample should be taken just before the regularly scheduled oil change. If the oil analysis results indicate that the oil is in good shape, extend out the change interval by 30%. It is recommended to test the oil again prior to the extended change-out.
New Oil Regular Change Out
Change Time or Miles Sample New Change
Adjusted Change Out 30% Additional Time or Miles
Sample
New Oil
In certain cases, it may be difficult or impractical to sample every system. If this is the case, it is recommended that sampling be done on: • Critical Systems - systems or equipment that are responsible for production. If a component on a critical system fails, production is halted. The critical systems are the ones that have been identified as being essential for continuous operation. These systems may require quarterly or semi-annual sampling. • Sample Population of Representative Systems - The sampling of less critical systems may not be necessary but would still improve plant reliability. If, for example a plant had 48 gearboxes that run machines that are essential but not critical. The 48 gearboxes are essentially all the same make, model and year and have the same operating conditions. Oil samples can be taken on 10% of the total and still provide information that could be transferred. Taking samples on 5 of the 48 would provide information that could be transferred to the other systems. Note that every system has unique operating conditions. Sweeping generalizations should be avoided.
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VI) Summary An effective oil analysis program increases the reliability and availability of equipment while reducing the costs associated with labor, repairs and downtime. The oil analysis process consists of: 1) Properly taking the oil sample. 2) Sending it into the laboratory for analysis with accurate information. 3) Receiving the results in a timely manner and in an a concise format. Without the proper controls in place prior to analysis, testing may be performed on non-representative, mislabeled or out-dated samples, which in turn will lead to the wrong corrective actions and to added costs on the oil analysis program. If these issues of control are not considered prior to the sample arriving at the laboratory, any test results obtained will be of small value. There are also control issues to consider once the analysis has been performed and the results have been obtained. Things to consider when setting up an oil analysis program:
• Establish base-line test of new lubricants. • Use proper sample labeling procedures. • Select applicable test methods (pump or valve). • Timely sampling, analysis and corrective action if needed. • Establish preventive maintenance schedule. An oil analysis program can provide critical information for any piece of equipment requiring lubricants-both gasoline and diesel engines, transmissions, gears, bearings, air compressors, turbines, generators and hydraulic systems. It's useful for owners of passenger cars, over-the-road fleets, off-highway equipment, boats, or high performance vehicles. Oil analysis has been able to identify problem areas before they become catastrophes and dramatically extend out oil change intervals.
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Index & Common Terms Term Absolute Viscosity -- a term used interchangeably with viscosity to distinguish it from either kinematic viscosity or commercial viscosity. Absolute viscosity is the ratio of shear stress to shear rate. It is a fluid's internal resistance to flow. The common unit of absolute viscosity is the poise. Absolute viscosity divided by fluid density equals kinematic viscosity. It is occasionally referred to as dynamic viscosity. Absolute viscosity and kinematic viscosity are expressed in fundamental units. Commercial viscosity such as Saybolt viscosity is expressed in arbitrary units of time, usually seconds. Acid -- in a restricted sense, any substance containing hydrogen in combination with a nonmetal or nonmetallic radical and capable of producing hydrogen ions in solution. Acidity -- in lubricants, acidity denotes the presence of acid-type constituents whose concentration is usually defined in terms of total acid number. The constituents vary in nature and may or may not markedly influence the behavior of the lubricant. Additive -- a compound that enhances some property of, or imparts some new property to, th e base fluid. In some hydraulic fluid formulations, the additive volume may constitute as much as 20 percent of the final composition. The more important types of additives include anti-oxidants, antiwear additives, corrosion inhibitors, viscosity index improvers, and foam suppressants. Additive stability -- the ability of additives in the fluid to resist changes in their performance during storage or use. Air Breather -- a device permitting air movement between atmosphere and the component in/on which it is installed. Alkali -- any substance having basic (as opposed to acidic) properties. In a restricted sense it is applied to the hydroxides of ammonium, lithium, potassium and sodium. Alkaline materials in lubricating oils neutralize acids to prevent acidic and corrosive wear in internal combustion engines. Anti-foam agent -- one of two types of additives used t o reduce foaming in petroleum products: silicone oil to break up large surface bubbles, and various kinds of polymers that decrease the amount of small bubbles entrained in the oils. Anti-oxidants -- prolong the induction period of a base oil in the presence of oxidizing conditions and catalyst metals at elevated temp eratures. The additive is consumed and d egradation products increase not only with increasing and sustained temperature, but also with increases in mechanical agitation or turbulence and contamination -- air, water, metallic particles, and dust. Antiwear additives -- improve the service life of tribological elements operating in the boundary lubrication regime. Antiwear compounds (for example, ZDDP and TCP) start decomposing at 90° to 100°C and even at a lower temperature if water (25 to 50 ppm) is present. API engine service categories -- gasoline and diesel engine oil quality levels established jointly by API, SAE, and ASTM, and som etimes called SAE or API/SAE categories; formerly called API Engine Service Classifications. A.S.T.M. = American Society for Testing Materials" -- a society for developing standards for materials and test methods. Atomic absorption spectroscopy -- measures the radiation absorbed by chemically unbound atoms by analyzing the transmitted energy relative to the incident energy at each frequency. The procedure consists of diluting the fluid sample with methyl isobutyl ketone (MIBK) and directly aspirating the solution. The actual process of atomization involves reducing the solution to a fine spray, dissolving it, and finally vaporizing it with a flame. The vaporization of the metal particles depends upon their time in the flame, the flame temperature, and the composition of the flame gas. The spectrum occurs because atoms in the vapor state can absorb radiation at certain well-defined characteristic wave lengths. The wave length bands absorbed are very narrow and differ for each element. In addition, the absorption of radiant energy by electronic transitions from ground to excited state is essentially and absolute measure of the number of atoms in t he flame and is, therefore, the concentration of the element in a sample.
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Index & Common Terms (cont.) Babbitt -- a soft, white, non-ferrous alloy bearing material composed principally of copper, antimony, tin and lead. Beta Rating -- the method of comparing filter performance based on efficiency. This is done using the Multi-Pass Test which counts the number of particles of a given size before and after fluid passes through a filter. Beta-Ratio (ß-Ratio) -- the ratio of the number of particles greater than a given size in the influent fluid to the number of particles greater than the same size in the effluent fluid, under specified test conditions (see "Multi-Pass Test"). Blow-by -- passage of unburned fuel and combustion gases past the piston rings of internal combustion engines, resulting in fuel dilution and contamination of the crankcase oil. Capillarity -- a property of a solid-liquid system manifested by the tendency of the liquid in contact with the solid to rise above or fall below the level of the surrounding liquid; this phenomenon is seen in a smallbore (capillary) tube. Carbon -- a non-metallic element - No. 6 in the periodic table. Diamonds and graphite are pure forms of carbon. Carbon is a constituent of all organic compounds. It also occurs in combined form in many inorganic substances; i.e., carbon dioxide, limestone, etc. Carbon residue -- coked material remaining after an oil has been exposed to high temperatures under controlled conditions. Centipoise (cp) -- a unit of absolute viscosity. 1 centipoise = 0.01 poise. Centistoke (cst) -- a unit of kinematic viscosity. 1 centistoke = 0.01 stoke. Compound -- (1) chemically speaking, a distinct substance formed by the combination of two or more elements in definite proportions by weight and possessing physical and chemical properties different from those of the combining elements. (2) in petroleum processing, generally connotes fatty oils and similar materials foreign to petroleum added to lubricants to impart special properties. Contaminant -- any foreign or unwanted substance that can have a negative effect on system operation, life or reliability. Corrosion -- the decay and loss of a metal due to a chemical reaction between the metal and its environment. It is a transformation process in which the metal passes from its elemental form to a combined (or compound) form. Corrosion inhibitor -- additive for protecting lubricated metal surfaces against chemical attack by water or other contaminants. There are several types of corrosion inhibitors. Polar compounds wet the metal surface preferentially, protecting it with a film of oil. Other compounds may absorb water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Another type of corrosion inhibitor combines chemically with the metal to present a non-reactive surface. Deposits -- oil-insoluble materials that result from oxidation and decomposition of lube oil and contamination from external sources and engine blow-by. These can settle out on machine or engine parts. Examples are sludge, varnish, lacquer and carbon. Detergent -- in lubrication, either an additive or a compounded lubricant having the property of keeping insoluble matter in suspension thus preventing its deposition where it would be harmful. A detergent may also redisperse deposits already formed. Dispersant -- in lubrication, a term usually used interchangeably with detergent. An additive, usually nonmetallic ("ashless"), which keeps fine particles of insoluble materials in a homogeneous solution. Hence, particles are not permitted to settle out and accumulate. Emission spectrometer -- works on the basis that atoms of metallic and other particular elements emit light at characteristic wavelengths when they are excited in a flame, arc, or spark. Excited light is directed through an entrance slit in the spectrometer. This light penetrates the slit, falls on a grate, and is dispersed and reflected. The spectrometer is calibrated by a series of standard samples containing known amounts of the elements of interest. By exciting these standard samples, an analytical curve can be established which gives the relationship between the light intensity and its concentration in the fluid. Engine deposits -- hard or persistent accumulation of sludge, varnish and carbonaceous residues due to blow-by of unburned and partially burned fuel, or the partial breakdown of the crankcase lubricant. Water from the condensation of combustion products, carbon, residues from fuel or lubricating oil additives, dust and metal particles also contribute.
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Index & Common Terms (cont.) EP (Extreme Pressure) lubricants -- lubricants that impart to rubbing surfaces the ability to carry appreciably greater loads than would be possible with ordinary lubricants without excessive wear or damage. Extreme pressure (EP) additive -- lubricant additive that prevents sliding metal surfaces from seizing under conditions of extreme pressure. At the high local temperatures associated with metalto-metal contact, an EP additive combines chemically with the metal to form a surface film that prevents the welding of opposing asperities, and the consequent scoring that is destructive to sliding surfaces under high loads. Reactive compounds of sulfur, chlorine, or phosphorus are used to form these inorganic films. FTIR = Fourier Transform Infrared Spectroscopy -- a test where infrared light absorption is used for assessing levels of soot, sulfates, oxidation, nitro-oxidation, glycol, fuel, and water contaminants. Infrared spectroscopy -- an analytical method using infrared absorption for assessing the properties of used oil and certain contaminants suspended therein. See FTIR. Infrared spectra -- a graph of infrared energy absorbed at various frequencies in the additive region of the infrared spectrum. The current sample, the reference oil and the previous samples are usually compared. ISO Solid Contaminant Code (ISO 4406) -- a code assigned on the basis of the number of particles per unit volume greater than 5 and 15 micrometers in size. Range numbers identify each increment in the particle population throughout the spectrum of levels. ISO viscosity grade -- a number indicating the nominal viscosity of an industrial fluid lubricant at 40°C (104°F) as defined by ASTM Standard Viscosity System for Industrial Fluid Lubricants D 2422. Essentially identical to ISO Standard 3448. Karl Fischer Reagent Method (ASTM D-1744-64) -- the standard laboratory test to measure the water content of mineral base fluids. In this method, water reacts quantitatively with the Karl Fischer reagent. This reagent is a mixture of iodine, sulfur dioxide, pyridine, and methanol. When excess iodine exists, electric current can pass between two platinum electrodes or plates. The water in the sample reacts with the iodine. When the water is no longer free to react with iodine, an excess of iodine depolarizes the electrodes, signaling the end of the test. Kinematic viscosity -- the time required for a fixed amount of an oil to flow through a capillary tube under the force of gravity. The unit of kinematic viscosity is the stoke or centistoke (1/100 of a stoke). Kinematic viscosity may be defined as the quotient of the absolute viscosity in centipoises divided by the specific gravity of a fluid, both at the same temperature-- Centipoises / Specific Gravity = Centistokes Lacquer -- a deposit resulting from the oxidation and polymerization of fuels and lubricants when exposed to high temperatures. Similar to, but harder, than varnish. Metal oxides -- oxidized ferrous particles which are very old or have been recently produced by conditions of inadequate lubrication. Trend is important. Micrometre (µm) -- See Micron. Micron -- a unit of length. One Micron = 39 millionths of an inch (.000039"). Contaminant size is usually described in microns. Relatively speaking, a grain of salt is about 60 microns and the eye can see particles to about 40 microns. Many hydraulic filters a re required to be efficient in capturing a substantial percentage of contaminant particles as small as 5 microns. A micron is also known as a micrometre, and exhibited as µm Microscope method -- a method of particle counting which measures or sizes particles using an optical microscope. Multigrade oil -- an oil meeting the requirements of more than one SAE viscosity grade classification, and may therefore be suitable for use over a wider temperature range than a singlegrade oil. Neutralization number -- a measure of the total acidity or basicity of an oil; this includes organic or inorganic acids or bases or a combination thereof (ASTM Designation D974-58T) Nitration -- nitration products are formed during the fuel combustion process in internal combustion engines. Most nitration products are formed when an excess of oxygen is present. These products are highly acidic, form deposits in combustion areas and rapidly accelerate oxidation.
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Index & Common Terms (cont.) Oil ring -- a loose ring, the inner surface of which rides a shaft or journal and dips into a reservoir of lubricant from which it carries the lubricant to the top of a bearing by its rotation with the shaft. Open bubble point (boil point) -- the differential gas pressure at which gas bubbles are profusely emitted from the entire surface of a wetted filter element under specified test conditions. Oxidation -- occurs when oxygen attacks petroleum fluids. The process is accelerated by heat, light, metal catalysts and the presence of water, acids, or solid contaminants. It leads to increased viscosity and deposit formation. Oxidation inhibitor -- substance added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or s torage life; also called anti-oxidant. An oxidation inhibitor may work in one of these ways: (1) by combining with and modifying peroxides (initial oxidation products) to render them harmless, (2) by decomposing the peroxides, or (3) by rendering an oxidation catalyst inert. Oxidation stability -- ability of a lubricant to resist natural degradation upon contact with oxygen. Particle count -- the number of particles present greater than a particular micron size per unit volume of fluid often stated as particles > 10 microns per milliliter. Poise (absolute viscosity) -- a measure of viscosity numerically equal to the force required to move a plane surface of one square centimeter per second when the surfaces are separated by a layer of fluid one centimeter in thickness. It is the ratio of the shearing stress to the shear rate of a fluid and is expressed in dyne seconds per square centimeter (DYNE SEC/CM2); 1 centipoise equals .01 poise. Polymerization -- the chemical combination of similar-type molecules to form larger molecules. Reservoir -- a container for storage of liquid in a fluid power system. Reservoir (sump) filter - a filter installed in a reservoir in series with a suction or return line. Return line -- a location in a line conducting fluid from working device to reservoir. Return Line Filtration -- filters located upstream of the reservoir but after fluid has passed through the system's output components (cylinders, motors, etc.). Rings -- circular metallic elements that ride in the grooves of a piston and provide compression sealing during combustion. Also used to spread oil for lubrication. Ring sticking -- freezing of a piston ring in its groove in a piston engine or reciprocating compressor due to heavy deposits in the piston ring zone. Saybolt Universal Viscosity (SUV) or Saybolt Universal Seconds, (SUS) -- the time in seconds required for 60 cubic centimeters of a fluid to flow through the orifice of the Standard Saybolt Universal Viscometer at a given temperature under specified conditions. (ASTM Designation D 88.) Sludge -- insoluble material formed as a result either of deterioration reactions in an oil or of contamination of an oil, or both. Stoke (St) -- kinematic measurement of a fluid's resistance to flow defined by the ratio of the fluid's dynamic viscosity to its density. Surfactant -- surface-active agent that reduces interfacial tension of a liquid. A surfactant used in a petroleum oil may increase the oil's affinity for metals and other materials. Total Acid Number (TAN) -- the quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize all acidic constituents present in 1 gram of sample. (ASTM Designation D 974.) Total Base Number (TBN) -- the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 gram of sample. (ASTM Designation D 974.) Varnish -- when applied to lubrication, a thin, insoluble, nonwipeable film deposit occurring on interior parts, resulting from the oxidation and polymerization of fuels and lubricants. Can cause sticking and malfunction of close-clearance moving parts. Similar to, but softer, than lacquer. Viscometer or Viscosimeter -- an apparatus for determining the viscosity of a fluid. Viscosity -- measurement of a fluid's resistance to flow. The common metric unit of absolute viscosity is the poise, In addition to kinematic viscosity, there are other methods for determining viscosity, including Saybolt Universal Viscosity (SUV), Saybolt Furol viscosity, Engier viscosity, and Redwood viscosity. Viscosity varies in inversely with temperature.
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Index & Common Terms (cont.) Viscosity, absolute -- the ration of the shearing stress to the shear rate of a fluid. It is usually expressed in centipoise. Viscosity, kinematic -- the absolute viscosity divided by the density of the fluid. It is usually expressed in centistokes. Viscosity, SUS -- Saybolt Universal Seconds (SUS), which is the time in seconds for 60 milliliters of oil to flow through a standard orifice at a given temperature. (ASTM Designation D88-56.) Viscosity grade -- any of a number of systems which characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils. Viscosity index improvers -- additives that increase the v iscosity of the fluid throughout its useful temperature range. Such additives are polymers that possess thickening power as a result of their high molecular weight and are necessary for formulation of multi-grade engine oils. Viscosity modifier -- lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil's viscosity to change with temperature. ZDDP -- an antiwear additive found in many types of hydraulic and lubricating fluids. Zinc dialkyldithiophosphate.
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Comparative Viscosity Classifications
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CTC Oil Analysis - On-Line Results Enrollment Set-Up CTC offers oil analysis results on-line. The on-line services provides quick access to the results. The first step in accessing the results page is to enroll. In order to enroll, you must access the CTC’s website by typing in www.ctclink.com.
Enrollment Steps (1) Access site - www.ctclink.com (2) Click on “Our Services”. (3) Select the “Online Service Online Registration” option. Click on “I Agree ” in the Terms and Conditions page
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(3) Any Problems - Call CTC at 800-332-8055
Enrollment Steps (4) Fill in all the appropriate information, note that the customer number for NCH Corp is 89000. (5) Select the Kansas City KS lab. (6) Click on the “Submit” button located at the bottom of the page. (7) You will receive an e-mail within 24 hours from CTC concerning your registration. From that point on you are enrolled.
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Any Problems - Call CTC at 800-332-8055
Accessing Test Results As soon as you receive your confirmation e-mail, you can begin accessing your oil analysis results. Go to the WWW.ctclink.com, and follow these steps: Test Access Steps (1) Type in your User ID and Password (2) Click on “Sample Results Search”
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Any Problems - Call CTC at 800-332-8055
Test Access Steps (4) Select the specific information pertaining to the results you are looking for. You can select all tests performed or according to a specific customer or date range or when sampled or tested. (5) You can also select how many results you want to see. (6) You can also select the components that were tested. (7) Click on “Go” to obtain the results
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(6) Any Problems - Call CTC at 800-332-8055
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Test Access Steps (8) Once you click on go, the results will come up. You can view the specifics by clicking on the “View History” option. (9) You can also view the equipment specifics by clicking on the component
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Any Problems - Call CTC at 800-332-8055
