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Oxidation / Nitration
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Oxidation is a chemical reaction of oil with oxygen. Oil oxidation can be fought by adding inhibitors, however, it
will always develop when oil is mixed with air and it will accelerate under the effect of the combustion gas
temperature, contaminants and oxidizing agents. As oxidation grows, the oil loses its lubricating properties and
thickens, organic acids build up, forming deposits and gum.
Nitration occurs in all engines, but reaches high levels in natural gas engines. Nitrogen compounds, formed
during the combustion, make oil thicken and lose its lubricating properties.
Water Content
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The presence of water in oil means there is contamination either through the cooling circuit or due to combustion
steam condensation. Any small amount of water - in particular from the cooling system - which has been treated
with chemical inhibitors will have a harmful effect on oil. It will bring about a reduction of the oil lubricating
capacities and the build up of sludge; also it may induce corrosion.
If Na or B is found in a metals analysis, this means water an/or anti-freeze is present. This will be the case, if
water has leaked out of the cooling system. Both sodium silicate and potassium metaborate are typical inhibitors
and responsible for introducing Si, K or N and B into oil. Another way of detecting the presence of coolant
consists in determining the glycol level in oil.
Insoluble Substances
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A check for insoluble substances will indicate if there are carbonaceous matter, powders, wear-induced particles
and oxidation products present in oil.
The presence of solids in oil affects the oil detergency and dispersancy, giving rise to a fast-growing tendency of
deposit formation in several engine components. Generally, the quantity of insoluble substances is greater when
wear intensifies.
A high content of solids leads to an increase in oil viscosity, wear of bearings and moving parts, and clogging of
filters.
Content of Metallic Particles
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The test includes a measurement of oil-borne metal particles, like:
- Fe: Iron
- Cr: Chromium
- Al: Aluminium
- Cu: Copper
Other elements may be added to the above list. It is essential to compare the test results with previous ones
before drawing final conclusions on their meaning.
Metal concentrations in oil are initially low and increase with the operating time of the engine. A sudden rise would
mean abnormal wear and operating conditions. Consequently, it is important to take into account not only the
metals content but also the engine operating conditions and the mechanical interventions carried out on the
engine.
PRODUCT INFORMATION
IO-G-M-25-001e
GAS-FUELED ENGINE OIL SERVICING INSTRUCTIONS
- Pb: Lead
- Na: Sodium
- Sn: Tin
- Si: Silicon
5.2.3
INDEX
DATE
G
January 2015
O&M_2.002211.810_A_10_2016
Dep.2
3/4
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