EVALUATION AND INTERPRETATION
With the emergence of long life synthetic lubricants, oil
analysis is becoming an increasingly popular tool for monitoring the
serviceability of the lubricant as well as foreshadowing developing
problems. With synthetic lubricants being recommended for eight to ten
times the life of petroleum lubricants, a good oil analysis program is a
must for assuring that there is no contamination or degradation of the
lubricant and that it can continue to function for the extended drain
The Petron Plus Global, Inc. Oil Analysis Program is
designed to give a complete overall view of the physical and chemical
characteristics of the lubricant to determine any significant lubricant
deterioration as well as detect any machinery problems before they become
serious and expensive to repair. These benefits can only be realized
through proper evaluation and interpretation of analysis results. All the
test results must be considered, along with the user's knowledge of his
compressor's performance history, to correctly diagnose the condition of a
given oil sample. Although there are given interpretations and
recommendations on each lab report returned, it is very helpful for the end
user to have a working knowledge of the tests involved and their
VISCOSITY: The viscosity of a lubricant is monitored for
significant increases or decreases from the original specification. A
substantial decrease in viscosity could indicate a contamination of the
lubricant causing a diluting effect. An increase in viscosity could also
indicate a contamination or a degradation of the oil due to oxidation. A
change of viscosity of more than 10 cSt at 100°F from the original
specification usually indicates that the oil should be replaced.
TAN (TOTAL ACID NUMBER): The TAN of a lubricant measures
the amount of acid and acid-acting constituents in the lubricant. This does
not necessarily denote metal corroding materials as many chemicals and
additives used in lubricants have an acid number.
Increase in TAN from the original specification usually
indicates oil oxidation or corrosive acid contamination. A sudden increase
in TAN can also indicate mechanical problems. An increase in TAN to greater
than two (2) is significant in a petroleum oil; however, a gradual increase
in TAN of a diester synthetic should be of no real concern until it becomes
greater than ten (10).
WEAR METALS: In monitoring wear metals, it should be
observed that the significant factor is not so much the amount of metal
present as the rate of deposit with respect to time. A sudden increase in
wear metals usually indicates an incipient wear problem and machine
inspection is highly recommended. A slow, constant increase in wear metals,
however, can be considered normal for most equipment and no cause for alarm
or required action. These metals will usually show in the form of iron,
lead, copper, aluminum, nickel, silver or tin.
ADDITIVE METALS: Additive metals tend to remain fairly
stable over the life of the lubricant but can fluctuate +20 percent under
normal circumstances. The emergence of an element which was not present in
the original sample could indicate the addition of make-up oil whose
additives differ from the original product. These metals are usually
phosphorous, zinc, calcium, barium, molybdenum or antimony. Silicon is also
used as an oil additive but can indicate the presence of dirt as well.
WATER CONTENT: The presence of water in a lubricant can
decrease its lubricating effectiveness; therefor, a lubricant should be
monitored for percent water volume. The limit for water is virtually none
and can be measured to 0.05 percent (500 ppm).
POSSIBLE SOURCES OF ELEMENTS IN OIL
- ALUMINUM (Al) - Pistons,
bearings, bushings, pump vanes, blower/turbos, washers, dirt, shims.
- ANTIMONY (Sb) - Babbitt
- BARIUM (Ba) - New oils
(dispersant/detergent), grease, water.
- BORON (B) - New oils,
coolant, seals, dust, fuel dilution.
- CADMIUM (Cd) - Bearings,
- CALCIUM (Ca) - New oils,
(Dispersant/detergent), water, grease.
- CHROMIUM (Cr) - Plated
parts (primarily piston rings), coolant, anti-friction bearings,
shafts, gears, seals, bearing cages, fuel leaks gas turbines.
- COBALT (Co) - Bearings,
- COPPER (Cu) - Bearings,
bearing cushions, bushings thrust washers, valves, guides, injectors
shields, oil cooler tubes, wet clutches, coolant (copper radiator)
- IRON (Fe) - Rings,
crankshaft, cylinder walls, calve train, pistons, anti-friction
bearings, gear train, shafts, clutch plates, washers, rust, water.
- LEAD (Pb) - Babbitt or
copper-lead bearings, plating, leaded gear lubes, leaded gasoline,
grease, paint, seals, solder.
- MAGNESIUM (Mg) - New oils,
(dispersant/detergent), bearings, superchargers, water.
- MANGANESE (Mn) - Steels,
valves, valves, corrosion, blowers (exhaust & intake systems).
- MOLYBDENUM (Mo) -
Additives, piston rings, electric motors.
- NICKEL (Ni) - Shafts,
valves, anti-friction bearings, gears, rings, turbine components.
- PHOSPHOROUS (P) - New oils
(zinc dithiophosphate) chlorinated phosphorous anti-wear additives,
gears, coolant leaks.
- SILICON (Si) - Sand, dirt,
dust, anti-foam, anti-freeze, gasket sealing compounds.
- SILVER (Ag) - Anti-friction
bearings, silver solder, wrist pin bushings, gear teeth, shafts.
- SODIUM (Na) - Some new
oils, coolant, salt water, grease.
- TIN (Sn) - Babbitt
bearings, platings, solder, coolers, wrist pins, pistons, rings.
- TITANIUM (Ti) - Wear
turbine engines, springs, valves, bearing hud, compressor disc,
- VANADIUM (V) - By products
heavy fuel oil, occasionally wear metal, turbine blades, valves.
- ZINC (Zn) - Anti-oxidant,
anti-corrosive, anti-wear agent, bearings, platings, gears, seals,
coolant leaks, grease.