Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2002-09-09
2004-09-07
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
Reexamination Certificate
active
06787509
ABSTRACT:
This invention concerns a gas engine lubricating oil composition.
Gas engines, which are also called gas-fuelled or gas-fired engines, are used to drive pumping stations of natural-gas pipelines, blowers and generators in, for example, purification plants and on gas tankers. Gas engines may be two- or four-stroke, spark-ignited or compression-ignited. Gas Otto engines ignite a mixture of gas and air using spark plugs. Gas diesel engines use a continuous injection of a small amount, such as, for example, 5-10%, of diesel fuel.
Gas engines operate at high temperatures such as greater than 200° C. in a piston environment. These high temperatures cause oxidation of the gas engine lubricating oil composition, which produces undesirable acids. These acids cause corrosion of the gas engine, in particular, corrosion of bearings in crankshaft journals and crankpins. Acids are also produced if the gas engine uses a fuel that is rich in sulfur.
It is important that a gas engine lubricating oil composition does not produce piston deposits or in the case of two-stroke engines cause plugging of exhaust slots. The gas engine lubricating oil composition should therefore preferably have either a low ash content such as, for example, below 0.6 wt % ash, or a medium ash content such as, for example, between 0.6 and 1.5 wt % ash, as determined by ASTM D874. If a lubricating oil composition has an ash level that is too low, it will shorten the working life of valves and cylinder heads. If, on the other hand, a lubricating oil composition has an ash level that is too high, excessive deposits will be produced in upper combustion chambers and upper piston areas.
Gas engine lubricating oil compositions usually include a major amount of base oil of lubricating viscosity and the following additives: up to 10 wt % of detergents, 0.5 to 8 wt % of dispersants, 0.05 to 2.0 wt % of antioxidants, 0.01 to 0.2 wt % of metal deactivators, 0.05 to 1.5 wt % of anti-wear additives, 0.05 to 0.6 wt % of pour point depressants, 0.001 to 0.2 wt % of anti-foam agents and 0.1 to 3.0 wt % of viscosity index improvers.
The present invention is concerned with the problem of providing an improved gas engine lubricating oil composition. In particular, the present invention is concerned with the problem of providing a gas engine lubricating oil composition that exhibits reduced corrosion of the gas engine. The present invention is also concerned with the problem of providing a gas engine lubricating oil composition that exhibits reduced deposits at high temperatures.
In accordance with the present invention there is provided a gas engine lubricating oil composition having a TBN in the range of 3.5 to 20, the gas engine lubricating oil composition comprising:
an oil of lubricating viscosity; and
at least one metal detergent;
characterised in that the gas engine lubricating oil composition is substantially free from dispersant.
In accordance with the present invention there is also provided a method of lubricating a gas engine, the method comprising the step of operating the gas engine while lubricating it with a gas engine lubricating oil composition that is substantially free from dispersant, the gas engine lubricating oil composition comprising at least one metal detergent.
In accordance with the present invention there is also provided a gas engine lubricating oil concentrate that is substantially free from dispersant, the concentrate comprising at least one metal detergent.
By ‘substantially free’ we include the gas engine lubricating oil composition being totally free from dispersant and the gas engine lubricating oil composition comprising only negligible amounts of dispersant which are insufficient to provide a dispersant effect, such amounts being, for example, less than 0.5 wt % dispersant, preferably less than 0.1 wt % dispersant, or, in terms of nitrogen content, less than 0.01 wt % nitrogen, preferably less than 0.001 wt % nitrogen and most preferably around 0.000 wt % nitrogen.
The gas engine lubricating oil composition preferably includes less than 0.5 wt % dispersant, even more preferably less than 0.1 wt % dispersant. Most preferably, the gas engine lubricating oil composition is completely free from dispersant.
The inventors have surprisingly found that removing dispersant from gas engine lubricating oil compositions reduces corrosion of the gas engine (as shown, for example, using the Ball Rust test). The inventors have also found that removing dispersant from gas engine lubricating oil compositions reduces the build-up of deposits (as shown, for example, using the Panel Coker Test).
Lubricating Oil Composition
The lubricating oil composition preferably has a TBN in the range of from 4 to 20, more preferably from 6 to 20, even more preferably 6 to 15.
Oil of Lubricating Viscosity
The oil of lubricating viscosity (also referred to as lubricating oil) may be any oil suitable for the lubrication of a gas engine. The lubricating oil may suitably be an animal, a vegetable or a mineral oil. Suitably the lubricating oil is a petroleum-derived lubricating oil, such as a naphthenic base, paraffinic base or mixed base oil. Alternatively, the lubricating oil may be a synthetic lubricating oil. Suitable synthetic lubricating oils include synthetic ester lubricating oils, which oils include diesters such as di-octyl adipate, di-octyl sebacate and tridecyl adipate, or polymeric hydrocarbon lubricating oils such as, for example, liquid polyisobutene and poly-alpha olefins. Commonly, a mineral oil is employed. The lubricating oil generally comprises greater than 60, typically greater than 70, wt % of the lubricant. The lubricating oil typically has a kinematic viscosity at 100° C. of from 2 to 40, for example from 3 to 15, mm
2
s
−1
and a viscosity index of from 80 to 100, for example, from 90 to 95. Another class of lubricating oils is hydrocracked oils, where the refining process further breaks down the middle and heavy distillate fractions in the presence of hydrogen at high temperatures and moderate pressures. Hydrocracked oils typically have a kinematic viscosity at 100° C. of from 2 to 40, for example from 3 to 15, mm
2
s
−1
and a viscosity index typically in the range of from 100 to 110, for example from 105 to 108.
The oil may include ‘brightstock’ which refers to base oils that are solvent-extracted, de-asphalted products from vacuum residuum generally having a kinematic viscosity at 100° C. of from 28 to 36 mm
2
s
−1
and are typically used in a proportion of less than 30, preferably less than 20, more preferably less than 15, most preferably less than 10, such as less than 5, wt %, based on the weight of the composition.
Metal Detergent
A detergent is an additive that reduces formation of piston deposits, for example high-temperature varnish and lacquer deposits, in engines; it has acid-neutralising properties and is capable of keeping finely divided solids in suspension. It is based on metal “soaps”, that is metal salts of acidic organic compounds, sometimes referred to as surfactants.
The detergent comprises a polar head with a long hydrophobic tail. The polar head comprises a metal salt of a surfactant. Large amounts of a metal base are included by reacting an excess of a metal compound, such as an oxide or hydroxide, with an acidic gas such as carbon dioxide to give an overbased detergent which comprises neutralised detergent as the outer layer of a metal base (e.g. carbonate) micelle.
The metal may be an alkali or alkaline earth metal such as, for example, sodium, potassium, lithium, calcium, barium and magnesium. Calcium is preferred.
The surfactant may be a salicylate, a sulfonate, a carboxylate, a phenate, a thiophosphate or a naphthenate. Metal salicylate is the preferred metal salt.
The detergent may be a complex/hybrid detergent prepared from a mixture of more than one metal surfactant, such as a calcium alkyl phenate and a calcium alkyl salicylate. Such a complex detergent is a hybrid material in which the surfactant groups, for example phenate and salicylate, are incorporated durin
Chambard Laurent
Owen Yolanda
Infineum International Ltd.
McAvoy Ellen M.
LandOfFree
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