Claims:We Claim:

1. A turbine oil composition comprising:
a. severely hydrotreated oils of required viscosity;
b. a silicon based defoament;
c. an aryl amine type Antioxidant;
d. triaryl phosphate ester.

2. The composition as claimed in claim 1, wherein the oils of lubricating viscosity are severely hydrotreated oils of API group II.

3. The composition as claimed in claim 1, wherein the oil is in the range of 40 to 99 wt%.

4. The composition as claimed in claim 1, optionally comprises of synthetic base oil in the range of 0 to 50 wt %.

5. The composition as claimed in claim 1, wherein the triaryl Phosphate Ester is 1.5 % of the total composition; and aryl amine is 0.8 % of the total composition.

6. The composition as claimed in claim 1, wherein the aryl amine is selected from dioctyl diphenylamine, or phenyl-alpha-naphthylamine or combination thereof.

7. The composition as claimed in claim 1, wherein the composition results in a sludge less than 80 mg/kg after at least 1,000 hours test duration in a Dry TOST test at 120° C.

8. The composition as claimed in claim 1, wherein the composition have an extreme load bearing capacity with fail load stage 10.

9. The composition as claimed in claim 1, comprising:
a. oils of lubricating viscosity in a range of 40 to 99 wt%;
b. a silicon based defoamant at 0.2wt%;
c. an aryl amine at 0.8 wt%;
d. triaryl phosphate ester at 1.5 wt%.

10. The composition as claimed in claim 1, wherein the silicon based defoamant is Siloxane dimethyl; aryl amine is N-[(1,1,3,3-Tetra methyl butyl) phenyl] naphthalen-1-amine and triaryl phosphate ester is Phenol isopropylated phosphate.
, Description:FIELD OF THE INVENTION

The present invention relates to a lubricating oil composition that can be used for steam, gas turbine oils and circulating oils.

BACKGROUND OF THE INVENTION

Lubricating oil compositions are generally composed of a majority of base oil plus a variety of additives to impart desirable properties. Lubricants are typically used to separate moving parts in systems. Gas and steam turbines use a flow of hot combustion gas or steam to generate energy in the form of thrust and / or shaft power, in any combination.

A turbine comprises of rotary engine and extracts energy from flowing of gases that have undergone combustion. It has compressor coupled with downstream turbine with combustion chamber in between. The lubricant lubricates bearings and function as heat removal medium to prevent degradation of the lubricant. Depending upon the bearing temperature the severity faced by turbine lubricant varies. Hence varnish formation tendency is found in the turbine bearings with change in operating conditions and it varies with change in hardware of OEM.

Gas, steam, and combined cycle power generation units are often operated in extreme environments and exposed to changes in atmospheric pressure, changes in ambient temperature, water, sea water, dust, and a host of other liquid and solid contaminants. Sludge and other deposits are particularly undesirable in power generation units used in a peak-load or cyclic manner. In such circumstances, the turbine will be activated and put into service for relatively short periods of time to meet peak loads on the electrical grid. Once the demand softens, the units are shut down and the oil stops circulating. Sludge and other deposits are more likely to settle out of the oil composition as the oil cools down to ambient temperature. The problem is aggravated by repetition of this heating-cooling process and probably the stagnation of the oil.

The present invention relates to the development of turbine oil which has low deposit formation tendency in comparison to turbine oils which may have higher oxidation life but low varnish resistance.

CN109097172A describes a low oil sludge turbine oil composition and its application, which has the advantages of excellent high temp. oxidation. resistance, rust resistance, and foam resistance. The turbine oil composition includes the following components in parts by wt.: antioxidant 0.3-0.9-part, metal passivator 0.05-0.2-part, antirust agent 0.05-0.1-part, dispersant 0.03-0.05 part, demulsifier 0.01-0.05-part, antifoaming agent 0.003-0.005-part, base oil remaining. The turbine oil composition is used for lubrication of gas turbines and large gas-steam combined cycle units.

CN105733762A relates to the field of turbine lubrication technology, the low oil sludge turbine lubricating oil composition and the wt. ratio of content: alkyl diphenylamine antioxidant 0.03-1.5%, from carboxylic acid derivatives and imidazoline derivatives. rust inhibitor compd. 0.03-0.2%, anti-foam agents 0.001-0.1%, polyether 1-20%, base oil as balance. The invention has the advantage of excellent high-temp. oxidation. resistance, in 120°C Dry-TOST test, the remaining rotating bomb rate 25% oxidation life is at least 500-hours, rotating bomb is greater than 900 min, TOST oxidation life is greater than 10000 hours. The invention has minimal sludge formation tendency, in 120 °C Dry-TOST test, when the remaining rotating bomb rate is 25%, the sludge generation is less than 60 mg/kg, 1000 h after TOST test, the sludge generation is less than 200 mg, the composition may well meet the lubrication needs of steam turbine, gas turbine with low sludge requirements.

There is a need for lubricant compositions having enhanced load-carrying, excellent oxidative stability and minimal deposit and sludge formation, and attainment of these benefits without deleteriously affecting the other salient features of the turbine oil.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: illustrates amount of sludge at Dry TOST (different temperatures)

SUMMARY OF THE PRESENT INVENTION

The present invention relates to a turbine oil composition comprising:
a. severely hydrotreated oil of required viscosity;
b. a silicon based defoamant;
c. an aryl amine type antioxidant; and
d. triaryl phosphate ester.

In another embodiment the oils of lubricating viscosity are severely hydrotreated oils of API group II, and oil is in the range of 40 to 99 wt%.

In another embodiment, the turbine oil composition may optionally comprise of synthetic base oil in the range of 0 to 50 wt %.

In one of the embodiments, the triaryl phosphate ester is 1.5 % of the total composition; and aryl amine is 0.8 % of the total composition.

In a preferred embodiment aryl amine is selected from dioctyl diphenylamine, or phenyl-alpha-naphthylamine or combination thereof.

In another embodiment the turbine oil composition having sludge less than 80 mg/kg after at least 1,000 hours test duration in a Dry TOST test at 120° C.

In another embodiment the turbine oil composition having extreme load bearing capacity with fail load stage 10.

In a preferred embodiment the turbine oil composition comprises of:
a. oils of lubricating viscosity in a range of 40 to 99 wt%;
b. a silicon based defoamant at 0.2wt%;
c. an aryl amine at 0.8 wt%; and
d. triaryl phosphate ester at 1.5 wt%.

In a preferred embodiment, the aryl amine is N-[(1,1,3,3-Tetramethylbutyl) phenyl] naphthalen-1-amine and triaryl phosphate ester is Phenol, isopropylated, phosphate.

OBJECTIVES OF THE PRESENT INVENTION
It is a primary objective of the invention to provides a lubricant oil composition for steam, gas turbine oils and circulating oils.

It is the further objective of the present invention to provide a lubricant oil composition having excellent oxidation stability with low sludge formation tendency.

It is the further objective of the present invention to provide a lubricant oil composition with good load bearing capacity for the application having higher bearing temperature.

DESCRIPTION OF THE INVENTION

The lubricant oil composition for steam, gas turbine oils and circulating oils, for bearing temperature greater than 200°C with reduced deposit formation tendency or low varnish formation tendency. The lubricating oil has better oxidation stability in the Dry TOST, Rotating Pressure Vessel Oxidation Test (RPVOT) and the IP-280 tests which are industry benchmark.

The main embodiment of the present invention provides a lubricant composition comprising a blended mixture of atleast two oils of lubricating viscosity, silicon based defoamant, aryl amine, triaryl phosphate ester, such compositions being capable of a residual RPVOT of 25% after 1000 hours.

Wherein two oils of lubricating viscosity are turbine oil of VG32 and VG46 are selected from known base oil derived from severely hydrotreatment in API Groups II. The Viscosity is as per ISO 3448. The range of VG 32 lies from 28.8 to 35.2 c.St and VG 46 lies from 41.4 to 50.6 c.St. The present invention has viscosities falling in the range in accordance with ISO 3448. The base oil is derived from the API Group II classification. The base stocks in Group II have at least 90% saturates, no more than 0.03% sulfur, and a viscosity index of 80 - 120. The base stock can also comprise of specialty synthetic oil offering outstanding solubility plus excellent thermo-oxidative stability. The oil of lubricating viscosity can be a combination of base stocks. The combinations can include at least two different types of a group of base stocks, such as at least two Group II base stocks.

In another embodiment the composition comprises alkylated phenyl-a-naphthylamine and at least oil soluble triazole or triazole derivative in an oil of lubricating viscosity.

In another embodiment the composition comprises of aryl amine and aryl phosphate.

The aryl amine is present in the amount of 0.1 to 1.0 % and the oil soluble phosphate in the range of 0.2 to 2.0 %. The present composition includes base oils which is severely hydrotreated and synthetic base oil in varied range of 90 to 99 % and 5 to 50%.

In one of the preferred embodiment, the composition comprises of silicon based defoamant at 0.2wt%, aryl amine at 0.8 wt%, and triaryl phosphate ester at 1.5 wt%.

The lubricating composition having low sludge formation in Dry TOST (D7873) with load bearing capacity with fail load stage 10.

Lubricating oil having outstanding oxidation stability with low sludge formation tendency and better extreme load bearing capacity for the application having higher bearing temperature.

In an embodiment, the amount of oil of lubricating viscosity is in the range of 90 to 99 wt % of the composition. The synthetic base oils (selected from the group of polyol ester, diseter, alkylated naphthalene, polyalkylene glycol) is in the range of 0 to 50% in combination with severely hydrotreated base oil.

In embodiment, aryl amine, alkylated amine, diphenylamine is mixture of aminic antioxidants or single aminic antioxidants but not limited to diphenylamine and in the range of 0.1 to 1.0 %. It is selected from the group of dioctyl diphenylamine, or phenyl-alpha-naphthylamine or both in different combination to achieve the desired oxidation characteristics.

In an embodiment the composition may optionally comprises of antiwear and extreme pressure additive selected from Tris(4-tert-butylphenyl) phosphate, Phenol, 4-(1,1-dimethylethyl)-, phosphate, Phenol, 4-(1,1-dimethylethyl)-, 1,1',1''-phosphate, Phenol, isopropylated, phosphate in the range of 0.2 to 2.0 % wt.

In another embodiment the composition optionally comprises of tolutriazole derivative with N content ranging from 10-30% as an oil soluble metal passivator cum corrosion inhibitor

In another embodiment, the finished lubricant composition further comprises at least one additive selected from rust inhibitor, pour point depressant, demulsifier, diluent oil, defoamer, antifoam agents, dispersants, detergents, diluent oil, succinated polyolefins, viscosity modifiers, antistatic agents, antirust agents, extreme pressure/antiwear agents, and seal swell agents, and combinations thereof.

Rust inhibitors are a single compound or a mixture of compounds for inhibiting corrosion of ferrous metal surfaces, in the range of 0.001 wt % to 0.04 wt % based on the total weight of the composition.

In another embodiment, the lubricating composition comprising:
a. severely hydrotreated oil of required viscosity as per API base Oil Classification.
b. a silicon based defoamant;
c. an aryl amine; and
d. triaryl phosphate ester
e. tolutriazole
In an embodiment, the lubricating composition comprises:
a. an oil of lubricating viscosity which is severely hydrotreated in nature and low viscosity of VG46 and or combination of different base oils;
b. an aryl amine; alkylated amine, diphenylamine
c. tolutriazole derived oil soluble metal passivator cum corrosion inhibitor
d. phenyl phosphate as ashless antiwear and extreme pressure additive e.g., Tris[4-(2-methyl-2-propanyl) phenyl] phosphate.
In another embodiment, the lubricating composition optionally comprises of synthetic base oil in the range of 0 to 50 wt %.
Standard Test Method for determination of Oxidation Stability and Insoluble Formation of Inhibited Turbine Oils at 120 °C Without the Inclusion of Water (Dry TOST Method):
• Six tubes containing 360 mL of sample each are heated at 120 °C with oxygen (with a flow capacity of at least 3 L of oxygen/hour, and an accuracy of 60.1 L /h.) in the presence of an iron-copper catalyst. Each tube is taken out over time and aged sample is analyzed by Test Method D2272
• The insolubles are measured until the RPVOT residual ratio reaches below 25 % . The insoluble mass (mg/kg oil) is plotted against RPVOT residual ratio.
• The mass of insoluble material of aged oil sample is determined gravimetrically by filtration of a 100 g oil sample through a membrane filter with pore size 1 µm. The insoluble mass in milligrams per kilogram oil at 25 % RPVOT residual ratio is reported.
• RPVOT residual ratio is defined as the percentage (%) obtained when by dividing the aged RPVOT by the fresh RPVOT value.

Example
The experiments were carried out by mixing the different candidates (compositions) in different % by weight. The candidates were heated and stirred at 60°C till the final blend was cleared.

The different candidates (compositions) subjected to several tests including Rotary Pressure Vessel Oxidation Test (RPVOT) in accordance with ASTM D2272 and the Dry-TOST Test in accordance with ASTM D7873.
Table 1.
Chemical Name Components Candidate 1 Candidate 2a Candidate 2b Candidate 2 Candidate 2c Candidate 2d Candidate 3 Candidate 4 Candidate 5 Candidate 6
Severely Hydro-treated Base Oil Base oil 1 62 62 62 62 61.97 62 62 62 62 62
Severely Hydro-treated Base Oil Base oil 2 37.38 36.95 36.94 36.91 36.91 36.88 37.36 37.45
37.43
36.56
Synthetic base oil Base oil 3 - - - - - - - - -
-
Silicon based Defoamant Additive 1 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02
Hindered Phenol Additive 2 0.6 - - - - - 0.6 - - 0.9
dialkyldithiophosphate. Additive 3 - 0.02 0.02 0.02 0.02 0.02 0.02 - 0.02 0.02
Methylnapthalene Additive 4 - - - - - - - 0.53 0.53 -
Aryl Amine Additive 5 - - - - - - - - - -
Triaryl Phosphate Ester Additive 6 - - - - - - - - - -
Alkyl substituted phenyl naphthylamine Additive 7 - - - - - - - - - -
Mixture of Aminic Antioxidants Additive 8 - 1.0 1.0 1.0 1.0 1.0 - - - -
tolutriazole derivative Additive 9 - 0.01 0.02 0.05 0.08 0.1 - - -
Dialkyl thiocarbamate Additive 10 - - - - - - - - - 0.5
Amine phosphate Additive 11 - - - - - - - - - -
Total 100 100 100 100 100 100 100 100
Effect of N (nitrogen) content (ppm) on the properties “-“ 15 30 73 117 146 “-“ “-“ “-“ “-“
RPVOT (minutes)-ASTM D 2272 @150° C 1195 2880 2900 3310 3185 3059 1298 1828 1404 1925
Sludge (mg/Kg), after ASTM D7873@120° C for 1000 hours, (Dry TOST Method) 250 “-“ “-“ 190 “-“ “-“ 286 210 280 300
Copper Rating, ASTM
D 130@ 100?°C,3 hours 1a 2a 2a 1a 1a 1a 1b 1a 1b 1a
FZG (A/8.3/90), Failure Load Stage 9 8 8 9 10 10

Table 2
Chemical Name
(Broad) Exact Chemical Name Components Candidate 7 Candidate 8 Candidate 9 Candidate 10 Candidate 11a Candidate 11 Candidate 11b Candidate 11c Candidate 11d Candidate 11e
Severely Hydro-treated Base Oil Base oil 1 52 62 62 60.5 52 42 32 22 12 02
Severely Hydro-treated Base Oil Base oil 2 37.43 37.11 37.18 37.13 40.68 40.68 40.68 40.68 40.68 40.68
Synthetic base oil Base oil 3 10 - - - 5 10 20 30 40 50
Silicon based Defoamant Siloxane, dimethyl Additive 1 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02
Hindered Phenol Additive 2 - - - - - - - - - -
Dialkyldithiophosphate. Additive 3 0.02 0.02 - - - - - - - -
Methylnapthalene Additive 4 0.53 - - - - - - - - -
Aryl Amine N-[(1,1,3,3-Tetramethylbutyl)phenyl]naphthalen-1-amine Additive 5 - 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8
Triaryl phosphate ester Phenol, isopropylated, phosphate Additive 6 - - - 1.5 1.5 1.5 1.5 1.5 1.5 1.5
Alkyl substituted phenyl naphthylamine Additive 7 - - - - - - - - - -
Mixture of Aminic Antioxidants Additive 8 - - - - - - - - - -
tolutriazole derivative 1H-Benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl- Additive 9 - - - 0.05 - - - - - -
Dialkyl thiocarbamate Additive 10 - - - - - - - - - -
Amine phosphate Additive 11 - 0.05 - - - - - - - -
Total 100 100 100 100 100 100 100 100 100 100
Effect of N (nitrogen) content (ppm) on the properties 73
RPVOT (minutes)-ASTM D 2272 1407 1239 1600 1343 1200 1187 1008 970 812 690
Sludge (mg/Kg), after ASTM D7873 after 1000 hours, (Dry TOST Method) 270 329 50 79 79 72 70 71 79 78
FZG (A/8.3/90), Failure Load Stage 10 12 7 10 9