US2399510A - Steam turbine oils - Google Patents

Description

sea water.

Patented Apr. 30, 1946 2,399,510 STEAM TURBINE OILS Albert G. Rocchini, Aspinwall, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing.

4 Claims.

This invention relates to steam turbine oils and it is particularly concerned with the production of steam turbine oils adapted to prevent corrosion of metal turbine parts in the presence of salt water.

In the lubrication of steam turbines, highly refined parafilnlc petroleum oils to which have been added small percentages of antioxidants resistant to solution in water and to hydrolysis, have been found to be particularly satisfactory. Steam turbine oils compounded in this manner develop acidity quite slowly and are resistant to Application January 17, 1944, Serial No. 518,589

vented even in the presence of substantial amounts of salt water, such as sea water. and a steam turbine lubricating oil is obtained which increase in steam emulsion number and to the development of sludge. Highly refined parafiinic petroleum oils containing alkyl phenol oxidation inhibitors are particularly suitable'for this use. Also when there is incorporated in such compounded steam turbine oils a small amount of a higher fatty acid, such as stearic'acid, palmitic acid. maleic acid and the like, as described in my U. S. Patent No. 2,261,888, the steam turbine oils produced are adapted to prevent corrosion of metal parts of the turbine under ordinary conditions.

However, it has been found that when such highly refined lubricating oils containing phenolic antioxidants and fatty acids are used under conditions such that salt water, such as sea water, comes in contact with the metal parts of the tur-- bine substantial corrosion of such parts may take place. In marine storage and use, steam turbine oils are often contaminated by small amounts of When oils thus contaminated. are subsequently used in the lubrication of a steam turbine substantial corrosion may be encountered. It is desirable, therefore, to produce a steam turbine oil adapted to prevent the corrosion of the metal parts of the steam turbine in the presence of salt water, such as sea water.

It is an object achieved by this invention to provide a steam turbine oil adapted to preventthe corrosion of the metal parts of a steam turbine in the presence of salt water, such as sea water. It is a further object of this invention to provide a method for the lubrication of steam turbines in the presence of salt water such as sea water without substantial corrosion of the metal parts of the turbine.

I have found that by incorporating a minute amount of cyclohexylamine oleate in a steam turbine oil consisting essentiallyof a highly refined paraflinic oil containing a small amount of an antioxidant, particularly a. phenolic antioxidant, corrosion of metal parts of steam turbines in which such oil is used as a lubricant can be preis substantially resistant to increase in acidity as measured by the neutralization number, increase in steam emulsion number and sludge formation and which is adapted to prevent corrosion of metal parts of steam turbines in the presence of salt water, such as sea Water.

By the term "highly refined paramnic oil as used herein and in the appended claims, is meant a petroleum lubricating oil which has been refined by one of the more drastic refining methods known in the art, for example, by a full aluminum chloride refining or by a solvent extraction adapted to remove all or substantially all of the unsaturated and naphthenic constituents of the oil. Aluminum chloride refined or solvent extracted paramnic base oil, such as a Pennsylvania oil provides the best ty e of highly refined oil for the purposes of my invention. However, drastically refined Mid-Continent and Gulf Coastal oil may also be used.

The oxidation inhibitors which may be added to these highly refined lubricating oils for use in steam turbines, according to my invention, are characterized by insolubility in water and resistance to hydrolysis under the conditions of use.

They should also be such that upon hydrolysis.

they do not form compounds which are acidic or corrosive in themselves. The water-insoluble phenolic antioxidants such as beta-naphthol, para-benzylamino phenol, and the alkyl phenols, for example, 2,6-di-tertiary-butyll-methyl phenol, 2,4,6-tri-tertiary-butyl-phenol and the like are particularly suitable. Of these, the water-insoluble alkyl phenols have proved most advantageous and are customarily used in amounts corof the oil. When other phenolic oxidation in: hibitors are used somewhat larger amounts are required, generally about 1.0 per cent.

The cyclohexylamine oleate used according to my invention is added to the highly refined lubrlcating oil containing the antioxidant in minute amounts. With an amount of cyclohexylamine oleate as small as 0.005 per cent by weight of the oil noticeable corrosion preventive properties are imparted to the lubricant. However, it is generally desirable to use somewhat larger amounts in order to obtain substantial protection against salt water corrosion and I usually find it advantageous to use amounts between 0.03 and 0.08 per cent by weight of the oil.

When using amounts correspending to 0.05 per cent by weight of the oil, I a

crease in steam emulsion number of the oil as a result of addition of cyclohexylamine oleate can be substantially overcome by adding along with the cyclohexylamine oleate a small percentage of a demulsification or anti-foam agent. In general I have found that it is not necessary to use antifoam or demulsification agent with turbine oils having viscosities below about 200 S. U. V. at 130 F. Most turbine oils for conventional uses have viscosities below this limit but for specialized uses somewhat heavier turbine oils are sometimes used. In the latter case the use of demulsiflcatlon agents is generally recommended. Various types of commercially available agents may be used, such as Foamex, which is a butyl phosphate containing a minor amount of a calcium soap of a fatty vegetable acid, or Visco 7-70, which is a readily hydrolyzable ammonium sulfonate, or Aerosols which are surface active sulfonic acids of complex organic molecules. These materials may be used in amounts corresponding to about 0.02 to 1.0 per cent by weight of the 011 along with the cyclohexylam-ine oleate without deleteriously aflecting the anti-corrosion properties of the resulting composition.

The advantages to be obtained by the use of cyclohexylamine oleate according to my invention are illustrated in the following specific examples:

In these tests, a highly refined Pennsylvania parafiin base oil, such as is used commercially for the lubrication of steam turbines and having a viscosity at 130 F. of 192 and API gravity of 30.8, was used. The efieot of a sample of this oil containing 0.2 per cent by weight of 2,6-di-tertiarybutyl-4-methyl phenol. on polished cold rolled steel strips in the presence of sea water was compared with the efiect of another sample containing 0.2 per cent by weight of 2,6-di-tertiary-butyl- 4-methyl phenol and 0.05 per cent by weight of cyclohexylamine oleate.

In carrying out these tests, the cold rolled steel strips were immersed in the respective 011 samples in separate glass containers. About 10 per cent by volume of synthetic sea water was added to each oil sample. The oil samples were agitated and maintained at a temperature of 140 F. for 48 hours. The steel strips were then removed and examined for corrosion. The strip which had been immersed in the highly refined oil containing the alkylated phenol antioxidant, but no cyclohexylamine oleate, showed rust formation on both surfaces. The strip which had been immersed in the highly refined oil containing both the alk lated phenol antioxidant and the cyclohexylamine oleate showed no rust and was clean and bright. A comparison of these test samples showed clearly the protective efi'ect produced by the cyclohexylamine oleate.

Tests similar to the above-outlined test, except that they were carried out at room temperature for 500 hours, produced the following results:

Steel strips immersed in the oil containing 0.2 per cent of 2,6-di-tertiary-butyli-methyl phenol and 0.05 per cent of cyclohexaylamine oleate showed no rusting. However. the steel strips which were immersed in the 011 containing no cyclohexylamine oleate were severely rusted. These tests indicate that even on long-time exposure the cyclohexylamine oleate effects protection oi! the metal parts from corrosion.

While my invention has been described herein with particular reference to certain specific embodiments thereof by way of illustration, it is to be understood that the invention is not limited to such embodiments except as hereinafter defined in the appended claims.

What I claim is:

1. A method of preventing the corrosion of metal parts of steam turbines lubricated by a highly refined parafilnie oil containing a waterinsoluble alkyl phenolic antioxidant in the presence of salt watercomprising incorporating in said lubricating oil 0.005 to 0.5 per cent by weight of cyclohexylamine oleate.

2. A method of preventing the corrosion of metal parts of steam turbines lubricated by a highly refined parafiinic oil containing a waterinsoluble alkyl phenolic antioxidant in the presence of salt water comprising incorporating in said lubricating oil 0.03 to 0.08 per cent by weight of cyclohexylamine oleate.

3. A method of preventing the corrosion of metal parts of steam turbines lubricated by a highly refined parafilnic 011 containing a waterinsoluble alkyl phenolic antioxidant in the presence of salt water comprising incorporating in said lubricating oil 0.05 per cent by weight of cyclohexylamine oleate.

4. A method of preventing the corrosion of metal parts of steam turbines lubricated by a of cyclohexylamine oleate and 0.02 to 1.0 per cent of a demulsification agent.

ALBERT G. ROCCI-IINI.