GB1604717A - Mixed grease thermoparticulating composition - Google Patents

Description

(54) MIXED GREASE THERMOPARTICULATING COMPOSITION (71) We, WESTINGHOUSE ELEC TRIC CORPORATION, a corporation organised and existing under the laws of the state of Pennsylvania, United States of America, residing at Westinghouse Building, Gateway Center, Pittsburgh, Pennsylvania 15222, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to thermoparticulating compositions as well as to a method of protecting electrical apparatus from damage due to overheating and for thereafter determining the location of the overheating.

It is to be understood that a compound thermoparticulates if it forms particles which can enter a gas stream passing over the compound and which can be detected in the gas stream.

Electrical apparatus, such as motors and turbine generators, occasionally overheat due to shorts or other malfunctions. The longer the overheating continues the more damage is done to the apparatus. A malfunction detected immediately may mean only a quick repair but if the overheating continues, the entire machine may be damaged.

Large rotating electrical apparatus is usually cooled with a hydrogen gas stream. The organic compounds in the apparatus are first to be affected by the overheating and they decompose to form particles which enter the gas stream. Monitors then detect particles in the gas stream and sound a warning or shut down the apparatus when too many particles are detected. Special coatings, however, may be applied to the apparatus which contains compounds which decompose and form detectable particles at a lower temperature than the usual organic compounds found in the apparatus.

Until now most thermoparticulating compositions consisted of a thermoparticulating compound in a solution of an air-dryable resin.

The composition was applied to an area inside a generator and when the solvent had evaporated a solid coating was formed.

However, there are certain locations in a generator, such as where flaking may block passages (e.g., the inside of parallel rings), where resinous coatings cannot be used. Also, the residual solvent emanating from a resinous coating may occasionally give a false signal in the monitor.

For these reasons the greases described in U.S. Patent 3,955,417 may be more suitable, because the greases do not flake and do not contain a solvent. The principal disadvantage of using those greases, however, is that they do not thermoparticulate at very low temperatures. Thus, a warning signal may not be given until considerable damage has already occurred.

According to the present invention a solventless composition free of non-grease resin comprises at least one compound stable at 600C which thermoparticulates between 800C and 2000 C; and at least one grease unreactive with said compound and stable at the thermoparticulation temperature of said compound.

The invention also includes a method of protecting electrical apparatus from damage due to overheating and for thereafter determining the location of said overheating, said electrical apparatus including a gas stream and a monitor for detecting particles in said gas stream and for emitting a signal when said particles are detected, said method comprising preparing a composition as recited in the last preceding paragraph; applying said composition to said electrical apparatus at positions exposed to said gas stream; and monitoring said gas stream for the presence of particles therein.

It has thus been found that compounds which thermoparticulate can be incorporated directly into greases, without the use of a solvent or a resin in the final composition.

The compounds thermoparticulate from the grease as easily and at the same temperature as they did from the resin. In addition, if a thermoparticulating grease is used, it will also thermoparticulate, giving an additional signal.

The mixed grease of this invention can be easily applied to inside portions of the generator. It does not flake or give off solvent vapors.

A suitable composition is from 10 to 300 parts by weight thermoparticulating compound per 100 parts by weight of grease, and a pre ferred composition is from 150 to 250 parts by weight thermoparticulating compound per 100 parts by weight grease. A ratio which has been used experimentally and has been found to work well is 2 parts by weight thermo particulating compound per part by weight of grease.

Compounds which thermoparticulate bfr tween 80 and 200"C are now well known in the art. An extensive list of such compounds can be found in U.S. Patent 3,957,014 and in Canadian Patent No. 1,079,165. Families of such compounds include diazonium salts, malonic acid and its derivatives, metal acetyl acetonates, blocked isocyanates, sulfonic acids (U.S. Patent 4,179,926) and metal dithiocar bamates (U.S. Patent 4,056,006). A par ticularly useful thermoparticulating compound is zinc acetylacetonate because it therm particulates at a low temperature with a strong signal. Mixtures of thermoparticulating corn pounds can also be used to provide a series of signals as the temperature rises.

Although greases which do not thermo particulate can be used, preferably the grease is a thermoparticulating grease which prefer ably thermoparticulates at a temperature at least 20 higher than the thermoparticulating compound, so that two distinct signals are received, thereby providing additional con formation that overheating is occurring. Des criptions of thermoparticulating greases can be found in U.S. Patent 3,955,417. Mixtures of greases are also contemplated.

The thermoparticulating grease composition of this invention can usually be made by simply blending the thermoparticulating com pound and the grease together until a homo geneous blend is produced. However, some thermoparticulating compounds, such as, for example, zinc acetylacetonate, do not blend well. As to these compounds it may be necessary to dissolve the compound, and pre ferably also the grease, in a solvent, e.g. Freon 113 (CC12FCCIF2) (Freon is a Registered Trade Mark). The solvent is then evaporated so that the final composition contains no sol vent, nor does it contain any organic resin.

The absence of solvents in the composition eliminates the problems of residual solvent vapors in the generator. The absence of resins eliminates problems with resin flakes clogging ducts and signals resulting from the decomposition of the resin. The composition may contain a small amount (up to 20;, and preferably 3 to 5%, of a thixotrope, e.g. finelydivided silica (e.g., "Cab-O-Sil") if the composition is too liquid to stay in place. ("Cab O-Sil" is a Registered Trade Mark). The composition is applied by wiping or other means to areas inside the generator which are exposed to the cooling hydrogen gas stream.

The composition is particularly applicable to those areas of the generator where only greases can be used, such as the inside surfaces of parallel rings, or where flaking from decomposing resins could clog passage ducts, or where solvents are not easily evaporated.

The invention will now be illustrated with reference to the following Example: EXAMPLE.

Compositions of various thermoparticulating greases and various thermoparticulating compounds were prepared using a ratio of 2 parts by weight thermoparticulating compound to 1 part by weight grease. The compositions were prepared by blending until homogenous, except for the composition containing zinc acetylacetonate, which was prepared by form ing an 80% solids solution of the grease and zinc acetylacetonate in Freon 113 and evaporating the Freon 113. The compositions were coated on 10 mil thick, 4 inches X 1 inch aluminium straps to a depth of about 1 to 3 mils and aged for 16 hours at 60"C except for the compositions which contained benzene sulfonic acid and benzene disulfonic acid which were not aged as they tended to flow at 60"C.

The samples were placed one at a time in a stainless steel boat within a 1-inch stainless steel tube. Hydrogen was passed over the samples at a flow rate of 7 1/mien. A phasecontrolled temperature regulator and pro gramme controlled the temperature in the boat and the temperature in the boat was measured by mounting a hot junction chromel-alumel thermocouple within a small hole in the boat.

The output of the thermocouple and the detector were monitored on a two-pen potentiostatic recorder. A 6"C/min. heating rate was maintained in each experiment after the in sertion of the sample in the boat. The threshold temperature at which considerable particulation occurred was taken from the chart produced by the recorder. The occurrence of particulation was detected using a Generator Condition Monitor or a Condensation Nuclei Monitor. Both instruments are sold by Environment One Corporation.

The following table gives the results: Thermoparticulating Organoparticulation Grease Compound Temperature Range ( C) A mixture of about 20% (by weight) telomer of polytetrafluoroethylene and about 80% perfluoro- None 194-198 alkyl polyether, sold by DuPont under the trade-mark "Krytox 24eAD" A polyurea-thickened hydrocarbon oil sold by Chevron Oil Co.None 181-184 under the trademark "Chevron BRB2" A grease made of colloidal copper, molybdenum,-sulfide, and a hydrocarbon oil solid None 174-178 by Fel-Pro Company under the trademark "Fel-Pro C-100" "Krytox 240-AD" Zinc acetylacetonate 132-142 "Krytox 240-AD" Malonic acid 133-140 "Krytox 24WAD" pchlorobenzene- diazonium penta fluorophosphate, sold 125-129 by Ozark-Mahoning Co.

under the trademark "Phosfluorgen 'A' " "Krytox 240-AD" Benzene-sulfonic acid 125-128 "Krytox 24eAD" Benzene disulfonic acid 147-153 The first number in the organoparticulation range is the temperature of the sample when the alarm sounded on the ion chamber monitor. The second number in the organoparticulation range is the temperature of the sample when the current in the ion chamber had dropped to about half its normal value (i.e., from about 0.8mA to about 014mA).

WHAT WE CLAIM IS:- 1. A solventless composition free of nongrease resin which comprises at least one compound stable at 600C which thermo particulates, as herein defined, between sOOC and 200"C; and at least one grease unreactive with said compound and stable at the thermoparticulation temperature of said compound.

2. A composition according to claim 1, wherein the grease thermoparticulates between 80"C and 200"C, at a temperature higher than the thermoparticulation temperature of the compound.

3. A solventless, resinless composition according to Claim 2, wherein the grease thermoparticulates at least 20"C higher than the thermoparticulating temperature of the compound.

4. A composition according to claim 1, 2 or 3, wherein the amount of the compound is from 10 to 300 parts by weight per every 100 parts by weight of the grease.

5. A composition according to claim 4, wherein the amount of the compound is from 150 to 250 parts by weight per every. 100 parts by weight of the grease.

6. A composition according to claim 1, wherein the weight ratio of the compound to the grease is about 2:1.

7. A composition according to any of claims 1 to 6, wherein the compound is zinc acetylacetonate.

8. A composition according to claim 7, wherein the compound is prepared by dissolving said zinc acetylacetonate and the grease in a solvent and evaporating said solvent.

9. A method of protecting electrical apparatus from damage due to overheating and for thereafter determining the location of said overheating, said electrical apparatus including a gas stream and a monitor for detecting par

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. Thermoparticulating Organoparticulation Grease Compound Temperature Range ( C) A mixture of about 20% (by weight) telomer of polytetrafluoroethylene and about 80% perfluoro- None 194-198 alkyl polyether, sold by DuPont under the trade-mark "Krytox 24eAD" A polyurea-thickened hydrocarbon oil sold by Chevron Oil Co.None 181-184 under the trademark "Chevron BRB2" A grease made of colloidal copper, molybdenum,-sulfide, and a hydrocarbon oil solid None 174-178 by Fel-Pro Company under the trademark "Fel-Pro C-100" "Krytox 240-AD" Zinc acetylacetonate 132-142 "Krytox 240-AD" Malonic acid 133-140 "Krytox 24WAD" pchlorobenzene- diazonium penta fluorophosphate, sold 125-129 by Ozark-Mahoning Co. under the trademark "Phosfluorgen 'A' " "Krytox 240-AD" Benzene-sulfonic acid 125-128 "Krytox 24eAD" Benzene disulfonic acid 147-153 The first number in the organoparticulation range is the temperature of the sample when the alarm sounded on the ion chamber monitor. The second number in the organoparticulation range is the temperature of the sample when the current in the ion chamber had dropped to about half its normal value (i.e., from about 0.8mA to about 014mA). WHAT WE CLAIM IS:-

1. A solventless composition free of nongrease resin which comprises at least one compound stable at 600C which thermo particulates, as herein defined, between sOOC and 200"C; and at least one grease unreactive with said compound and stable at the thermoparticulation temperature of said compound.

2. A composition according to claim 1, wherein the grease thermoparticulates between 80"C and 200"C, at a temperature higher than the thermoparticulation temperature of the compound.

3. A solventless, resinless composition according to Claim 2, wherein the grease thermoparticulates at least 20"C higher than the thermoparticulating temperature of the compound.

4. A composition according to claim 1, 2 or 3, wherein the amount of the compound is from 10 to 300 parts by weight per every 100 parts by weight of the grease.

5. A composition according to claim 4, wherein the amount of the compound is from 150 to 250 parts by weight per every. 100 parts by weight of the grease.

6. A composition according to claim 1, wherein the weight ratio of the compound to the grease is about 2:1.

7. A composition according to any of claims 1 to 6, wherein the compound is zinc acetylacetonate.

8. A composition according to claim 7, wherein the compound is prepared by dissolving said zinc acetylacetonate and the grease in a solvent and evaporating said solvent.

9. A method of protecting electrical apparatus from damage due to overheating and for thereafter determining the location of said overheating, said electrical apparatus including a gas stream and a monitor for detecting par

ticles in said gas stream and for emitting a signal when said particles are detected, said method comprising preparing a composition according to any of claims 1 to 8; applying said composition to said electrical apparatus at positions exposed to said gas stream; and monitoring said gas stream for the presence of particles therein.

10. Solventless compositions free of nongrease resin according to claim 1 and substantially as described herein with particular reference to the foregoing - Example.