PerkinElmer OilExpress System, Руководство пользователя

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Background to Used Oil Analysis . 73
A high nitration value, also known as NO
X
or nitro-oxidation, indicates incorrect fuel/air ratio,
incorrect spark timing, excessive loads, low operating temperature or piston ring blow-by.
Sulfate
Sulfur oxides are produced by the combustion of sulfur compounds present in the fuel. These
oxides react with water, also produced by the combustion process, to form sulfuric acid. The
sulfuric acid is neutralized by the oil’s basic additives, forming inorganic sulfates. A rapid
increase in the sulfate value may indicate the use of a high sulfur content fuel, poor
combustion, over-cooling or the rapid depletion of anti-wear additive.
Ester breakdown
Synthetic lubrication oils usually contain a high proportion of synthetic polyol esters. These
esters are susceptible to breakdown in the presence of water and acids (hydrolysis). Ester
breakdown contributes to the acidity of the oil and can result in the formation of crystals of
the base polyol, leading to clogging of filters. Ester breakdown may indicate the presence of
water from condensation caused by low operation temperatures or from a coolant leak.
Common Contaminants
Soot
Soot particles result from the incomplete combustion of fuel and, since they are too small to
be removed by the filter, remain suspended in the oil. Soot builds up continuously until it
reaches an unacceptable level, that level depends on the type of engine and lubricant. Diesel
oils tolerate higher soot levels than gasoline oils. The rate of soot build up depends on
engine design, type of fuel and operating conditions. A high soot value may indicate poor
combustion due to incorrect fuel/air ratio, a clogged air filter or an over-extended oil change
period.
Water and glycol
The presence of water and glycol indicate a leak from the cooling system. It is essential to
detect such a problem early to avoid a serious failure. The presence of water alone does not
necessarily indicate a coolant problem, but may result from condensation due to a low
operating temperature.
Unburned fuel
The fuel measurement depends not only on the level of contamination, but also on the
aromatic hydrocarbon content of the fuel. The amount of aromatic content in fuels vary in
location and season, therefore a calibration must be done on the fuel being used. The
presence of fuel indicates poor combustion due to incorrect fuel/air ratio, clogged air filter or
an ignition problem. It may also indicate an over-extended oil change period.
Analysis Methods
The OilExpress System ships with a set of default analysis methods that will appear in the
drop-down menu. The methods vary in the analytes they determine, the peaks used and the
warning limits on the results. For further information about the default analysis methods see
the on-screen Help.