Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic phosphorus compound – wherein the phosphorus is...
Reexamination Certificate
2000-08-25
2003-07-22
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic phosphorus compound, wherein the phosphorus is...
C508S436000, C508S460000, C508S572000
Reexamination Certificate
active
06596673
ABSTRACT:
This invention relates to the lubrication of the cylinder or cylinders of a cross-head marine diesel (compression-ignited) engine for raising the temperature of the onset of scuffing-type mechanical wear of the cylinder walls of the engine during its operation.
One type of marine diesel propulsion engine is characterised as a slow speed, two-stroke engine which is frequently referred to as a cross-head engine because of its construction. The firing cylinder and crankcase are lubricated separately by cylinder and system oils respectively. The cylinder oil, sometimes referred to as a marine diesel cylinder lubricant (MDCL), is fed to the internal walls of the cylinder by injection and, unlike the system or crankcase oil, is consumed.
“The Motor Ship”, May 1999 pages 27-33, reports the emergence of a new generation of large bore cross-head marine diesel engines, the cylinders of which are subjected to higher gas pressures and temperatures then hitherto in order to improve engine efficiency. The article states that this has given rise to ‘disastrous’ instance of scuffing, that is to say adhesive wear of the internal walls of the cylinder, for example defined by cylinder liners, due to thinning of the lubricant film between the piston and the wall under the above-mentioned conditions.
The phenomenon of “scuffing” is approached when the lubricant becomes so thin that its thickness is similar to the height of the microscopic roughness (or asperities) on the opposing surfaces to be lubricated. Further thinning of the lubricant gives rise to actual solid/solid contact between opposing surfaces. When solid/solid interactions occur between asperities, they tend to adhere and give rise to so-called “adhesive friction”. The stresses on the asperities are sufficient to remove material, which material loss is called “adhesive wear” or “scuffing”.
The present invention ameliorates the above problem, as evidenced by test results described in this specification, by lubricating the cylinder with an MDCL that includes a specific auxiliary additive.
Thus, in a first aspect, the invention is a combination of a cylinder of a two-stroke cross-head marine diesel engine with a cylinder lubricant comprising, or made by admixing:
(A) a base stock of lubricating viscosity, in a major amount;
(B) at least one overbased metal detergent, in a minor amount; and
(B) at least one auxiliary, preferably ashless or non-metal-containing, additive component, in a minor amount, and that is different from (B), comprising:
(C1) an oil-soluble sulfur-containing compound, and/or
(C2) an oil-soluble phosphorus-containing compound,
wherein the cylinder is characterised by a power output of 4000 or greater, such as 4200 or greater, preferably 4500 or greater, more preferably in the range of 4500 to 6000, kW. The bore of the cylinder may, for example, be 850 or greater, such as 900 or greater, preferably in the range of 900 to 1000, cm.
A second aspect of the invention is a method of lubricating a cylinder of a two-stroke cross-head marine diesel engine which comprises supplying to the walls of the cylinder, a cylinder lubricant as defined in the first aspect of the invention, wherein the cylinder is defined as in the first aspect of the invention.
A third aspect of the invention is a method of raising the temperature of the onset of scuffing-type mechanical wear of the walls of a cylinder of a two-stroke cross-head marine diesel engine by lubricating the walls with a cylinder lubricant as defined in the first aspect of the invention, wherein the cylinder is as defined in the first aspect of the invention.
In this specification, the following words and expressions shall have the meanings ascribed below:
“major amount”—in excess of 50 mass % of the lubricant;
“minor amount”—less that 50 mass % of the lubricant, both in respect of the stated additive and in respect of the total mass % of all the additives present in the lubricant, reckoned as active ingredient of the additive or additives;
“active ingredient (a.i.)” refers to additive material that is not diluent,
“comprises or comprising, or cognate words”—specifies the presence of stated features, steps, integers or components, but does not preclude the presence or addition of one or more other features, steps, integers, components, or groups thereof;
“TBN”—Total Base Numbers as measured by ASTM D2896;
“oil-soluble or oil-dispersible”—do not necessarily indicate solubility, dissolvability, miscibility or capability of suppression in oil in all proportions. They do mean, however, solubility or stable dispersibility sufficient to exert the intended effect in the environment in which the oil is employed. Moreover, additional incorporation of other additives may permit incorporation of higher levels of a particular additive, if desired;
it will be understood that the various components of the lubricant, essential as well as optimal and customary, may react under the conditions of formulation, storage or use and that the invention also provides the product obtainable or obtained as a result of any such reaction.
The features of the invention will now be discussed in more detail as follows:
Two Stroke Cross-Head Marine Diesel Engine
Certain characteristics of the engines of this invention and their cylinders have been indicated above. Further, the engines may, for example, have from 6 to 12 cylinders and their engine speed may, for example, be in the range of from 40 to 200, preferably 60 to 120, rpm. Their total output may, for example, be in the range of 18,000 to 70,000 kW.
Cylinder Lubricant
The lubricant may, for example have a TBN of 15 or greater, preferably, 40 or greater, for example in the range of from 60 to 100. Preferably, the viscosity index of the lubricant is at least 80, such as at least 90, for example at least 100.
The lubricant may, for example, have a kinematic viscosity at 100° C. (as measured by ASTM D445) of at least 14, preferably at least 15, more preferably in the range from 17 to 30, for example from 17 to 25, mm
2
s
−1
.
(A) Base Stock of Lubricating Viscosity
The base stock is an oil of lubricating viscosity (sometimes referred to as base oil) and may be any oil suitable for the lubrication of a cross-head engine. The lubricating oil may suitably be an animal, 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 tri-decyl adipate, or polymeric hydrocarbon lubricating oils, for example liquid polyisobutene and poly-alpha olefins. Commonly, a mineral oil is employed. The lubricating oil may generally comprise greater that 60, typically greater than 70%, by mass of the lubricant and 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 from 80 to 100, for example from 90 to 95.
Another class of lubricating oil 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 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 term ‘brightstock’ as used herein refers to base oils which are solvent-extracted, de-asphalted products from vacuum residuum generally having a kinematic viscosity at 100° C. from 28 to 36 mm
2
s
−1
and are typically used in a proportion of less that 30, preferably less than 20, more preferably less than 15, most preferably less than 10, such as less than 5, mass %, based on the mass of the lubricant.
(B) Overbased Metal Detergent
Overbased metal compounds suitable for use in the lubricant of the present invention include alkali metal
Bovington Charles H.
Garner Terence
Infineum International Ltd.
Johnson Jerry D.
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