Note: Descriptions are shown in the official language in which they were submitted.
CROSS-R~F~RENCES TO RELATED PAT~MTS
This application is related to the follo.r~ng
U.S. Paten's:
U.S. Patent No. 3,972,225 issued Augus~ 3, 1976 to
Emil M. Fort, Thomas D. Kaczmarek, and David Colin Phillips.
U.S. Patent No. 3,973,439 issued August 10, 1976
to J. D. B. Smith and D. C. Phillips.
U.S. Patent No. 4,100,121 issued July 11, 1978
to J. D. B. Smith and D. C. Phillips.
U.S. Patent No. 3,955,417 issued May 11, 1976
to J. D. B. Smith and Do C. Phillips.
UOSo Patent No. 3,979,353 issued September 7~ 1976
to J. D~ B. Smith, Do C. Phillips and K. ~;1. Grossett~
U.SO Patent No. 4,016,745 issued April 12, 1977
to J. D. B. Smith, J. F. Meier, and D. C. Phillips.
-1-
~r
,..
1079165
BACKGR~UND OF 1~ INVENTION
Electrical apparatus, such as motors and tur-
blne generators, occasionally overheat due to shorts or
other malfunctions. The longer the overheating continues
the more damage i8 done to the apparatus. A malfunc-
tion detected immediately may mean only a quick repair
but if the overheating contlnues, 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 rlrst to be affected by the over-
heating 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 appara-
tus when too many particles are detected.
Descriptions of such monitors and h~ they
function may be found in U.S. Patent ~,427,880 titled
"Overheating Detector For Gas Cooled Electrical Machine"
and in U.S. Patent 3,573,460 titled "Ion Chamber For
45,718
107gl65
Submicron Partlcles." Another monitor, "The Condensa-
tion Nuclel Detector, ~! iS described by F. W. VanLuik, Jr.
and R. E. Rippere, in an article titled "Condensation
Nuclei, A New Technique For Gas Analysis," in Analytical
Chemistry 34, 1617 (1962) and by G. F. Skala, in an
article titled "A New Instrument For The Continuous
Detection Of Condensation Nuclei," in Analytical Chemis-
try 35, 702 (1963) .
As U.S. Patents 3,427,880 and 3,807,218, and
- 10 the hereinbefore-cited related U.S. Patents dis-
close, special coatings may be applied to the apparatus
which decompose to form detectable particles (i.e., thermo-
particulate) at a lower temperature than the usual organic
compounds found in the apparatus. However, merely knowing
that an area in the generator is being overheated may not
be enough information on which to base a decision to shut
down the generator. Since shuttlng down a generator means
the loss of the electricity which would have been generated
plus the cost of inspecting, disassembling, and reassembling
the generator, such decisions are not made lightly.
SUMMARY OF THE INVENTION
We have discovered that the rate at which the
temperature rises in a particular area of a generator can
be determined by applying to a surface in the gas stream of
the generator a coating which contains at least two compounds
which thermoparticulate at different temperatures between
60 and 200C. If the rate or temperature increase is rapid,
a runaway situation is probably occurring and the generator
must be shut down. On the other hand, if the temperature
rise is slow, the load on the generator can be reduced while
--3--
:10791 65
the generator is checked and analyzed. Also, because
various combinations of thermoparticulating compounds
can be used in the coating, the location of the over-
heating in the generator can be determined by analyzing the
products of thermoparticulation. The location of over-
heating can also be determined visually because the thermo-
particulating compounds described herein (except for the
grease) blister and darken when they decompose.
DESCRIPTI ON OF THE INVENTION
A composition is prepared of at least two
thermoparticulating compounds (hereinafter "TPC's") in
a solution of a resinous carrier. The TPC's may be dis-
persed if they are insoluble in the solvent (e.g., tolu-
ene) or they may be in solution if they are soluble in
the solvent (e.g., ethyl alcohol ar diethyl ether).
Dispersions are preferred as they produce much more
particulation than do solutions. A particle size of
the dispersed IPC's of about 25 to about 1000 microns is
suitable.
A suitable composition is a resinous carrier,
about 20 to about 250 phr (parts by weight per hundred
parts of resinous carried not including solvent) total
of the TPC's and about 25 to about 75% (by weight based
on the resinous carrier) of a solvent for the resinous
carrier. If the total amount of the TPC is less than
about 20 phr, the quantity of particles given off during
decomposition may be too low to be detected by presently
existing detectors. However, the construction or more
sensitive detectors would permit a lower amount of TPC.
If the amount of TPC exceeds about 250 phr, the composition
1079165
is thick, difficult to apply, and does not bond well.
The preferred amour,t of TPC, which generally gives
the best results, is about 40 to about 60 phr. If the
amount of solvent is less than about 25%, the composition
is generally too viscous to apply easily and if the amount
of solvent is greater than 75%, the composition is unne-
cessarily dilute and the coating may be too thin to pro-
duce ar. adequate number of particles during decomposition,
at least while the malfunction is highly localized. Best
resul~s are usually obtained with about 45 to about 55%
solvent.
The resinous carrier performs the function of
bonding the TPC to the apparatus since a coating of a
TPC by itself does not adhere well. The resinous carrier
should be compatible with the other resins used in the
apparatus ar,d therefore it is usually advantageous to use
the same resin used elsewhere. The resinous carrier is
curable at 60 C, and is preferable air-dryable since it
cannot be easily cured in place with heat. Also, it should
be stable after curir,g for several years at 60C. l`he resin
must be unreactive with the TPC for otherwise suitable
thermoparticulation will not occur. The TPC and the resin
from a mixture and the TPC does not catalyze the cure of the
resin. Epoxy resins are preferred as they are usually used
elsewhere in the apparatus, but polyester, silicone rubber,
styrene, etc. could also be used.
The solvent for the resinous carrier depends
on the particular resinous carrier used. Toluene, xylene,
benzene, methyl ethyl ketone, ethyl alcohol, diethyl
ether, acetone ? cellosolve, etc. are common solvents that
45,718
~,o79~65
may be used. Toluene is preferred as it is inexpensive
and dissolves most resins.
The composition also preferably contains about
0~1 to about 3 phr of a drier when the resinous carrier
is an epoxy resin or similar resin, to promote its room
temperature cure. Lead naphthenate or cobalt naphthenate
is preferred although stannous octoate, zinc stearate,
etc. could also be used. Resins such as polyesters may
also require the presence of an organic peroxide as is
known in the art. Mixtures of various resins, solvents,
or driers are also contemplated.
The composition may be prepared by simply mix-
ing the ingredients, but it is preferable to mix the
drier, resinous carrier, and solvent first and then add
the TPC to prevent the occlusion of the drier in the TPC
and thereby to obtain a more homogeneous dispersion of the
TPCc Certain TPCIs, such as the greases described herein,
can be applied directly and need not be mixed into a com-
position wlth a solvent and reslnous carrier.
The TPC's of this invention are compounds which
are stable solids or greases at 50C, but which decompose at
60 to 200~C to produce detectable particles. With pre-
sently-existing monitors particles must be larger than about
25A in order to be detected, but future monitors may be
capable of detecting smaller particlesO The previously
cross-referenced patents, de~cribe many
suitable TPC's. Br~efly~ these com-
pounds include diazonium salts, malonic acid and its deri-
vatives, metal acetyl acetonates, blocked isocyanates, and
certain greases. The following tables are lists of useful
l~5,71~
1~)7916S
therrnoparticulating compounds from those previously cross
referenced applications.
Thermoparticulating
Metal Days Aged Temperature Range
Acetylacetonate At 60C (c)
Zn(C5H7020) o 2H2 110 95-100
Al(CsH702) 3 44 159-161
Fe( C5H702) 3 6 171-174
Mg(C5H702)2O2H2o 6 192-195
Mn(C5H702)3 1 132-133
Mn(C5H702) 2 1 182-185
Co ( C 5H7 2) 2 1 128- 131
Co ( C5H702) 3 1 150-152
Co ( C5H702) 2 ~ H20 1 165-168
Cr(C5H702) 3 1 179-183
Ni (C5H702)2~ 2H2 1 169-173
Agin~ Time at 120C (days)
Grease 3 59 _ ~ 4
A mixture of about 20%
telomer of polytetrafluoro- 194-198C 191-198C 200-207c
ethylene and about 80% per-
fluoroalkyl polyether, sold
by DuPont under the trademark
"Krytox 24 0-AD"
The above table gives the thermoparticulation
temperature after various periods of aging~
45, 718
1079165
Llterature Concentra- Additlonal Thermopartlcula-
Temperature Support tlon in b lleat tlon Temperature
Diazonlum Salt C) Materlal ~poxy (phr) Treatment (C)
3-chloro - 4-diethyl Dacron ~?elt 26.2a None None
an~nobenzene diazc~ 113
lum chlorozlncate Copper 20.0 20 days
~ at 80C 190
p-diethylamlno- Dacron relt 4o.5a None None
0 benzene-dlazonium 117
chlorozlncate Copper 20 0 20 dayS 190
~ at 0 C
p-diethylamino- Dacron felt 3o.8a None 120
benzene dlazonium lOB Copper 20.0 1 day at ~OvC 125
rluoroborate Copper 20.0 20 days at ~O"C 190
2, 5-dietho~- 3 d2ys at 80C
4-morphollnobenzene 120 Copper 20.0 (sample
diazonium chlorozincate _ deca~osed)
4-diethylamlno-2-- 3 days at 80C
n~thylbenzene- diazon- 120 Copper 20.0 (sample
Ium chlorozincate à~composed)
4-dlethylarnino -2-
ethoxybenzene - dia- 140 Copper 20.0 24 days at 80C 180
zoni~n chlorozlncate
4-ethylamlno -3- 2 days at 80C
methylben ene - dia~ 125 Copper 20.0 (sample
zonlwn chlorozlncate decomposed)
~amino-N-benzyl-
N~ethylbenzene - dia- 160 Copper 20.0 24 daya at 80C 159
31) zonlum chlorostannate
p-dlmethylamino- 2 days at BOC
benzene- diazonium 145 Copper 20.0 (sample
chloroz1 ncate 7~77 decomposed)
p-chlorobenzene- Dacron felt 63.5 None 110
diazonium penta- 150
fluorophosphate Copper 20.0 3 days at Booc
_ decomposed)
~i probably due to decomposltlcn Or epoxy resin.
a This flE;ure is the wel~t % on the Dacron felt -
no resin was used.
b "phr" includea solvent.
1075165
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45, 718
1(~79165
m ~ ~
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--10--
45,718
1l)79165
ChemicalAging Thermoparticulating
Compound FormulaCondition Temperature Range (C)
Malonic Acid CH2(COOH)2 140 days at 60C 132 - 142
Methylmalonic
Acid CH3CH(COOH)2 140 days at 60C 132 - 138
Dimethylmalonic
Acid (CH3)2C(COOH)2180 days at 80C 152 - 158
Ethylmalonic
Acid C2H5CH(COOH)2140 days at 60C 119 - 127
10 Diethylmalonic
Acid (C2Hs)2(COOH)23 days at 80C 168 - 180
Di-n-Propylmalonic
Acid (C3H7)2C(COOH)2 120 days at 80 C 155 - 160
Benzy~E~onic
Acld C6H5CH2CH(COOH)2 50 days at 60C 143 - 151
Phenylmalonic
Acid C~HsCH(C05H)2 1 day at 60c 150 - 157
The thermoparticulating temperatures given in
the abo~Je tables are approximate and may vary depending
on the resin used, aging time, and other factors
In preparing the composition at least two TPC's
are included which thermoparticulate at different tem-
peraturesO More than four TPC's may be included, but lr
this is done, resolution of the separate signals may be
dif~icult~ Preferably, the temperatures at which the
TPC's thermoparticulate should be separated by at least
25C to provide a clear resolution of the signals~
If two TPC's are included in the composition,
the first preferably thermoparticulates at about 125
co about 175C (first stage) and the second at about
175C to about 200C (second stage)~ Preferably, how-
ever, the composition contains three TPC's, the first
preferably thermoparticulating at about 80 to about
125C (~irst stage), the second at about 125 to about
45,718
1079165
175C (second stage), and the third at about 175C to
about 200C (third stage). If two stages are used, the
first stage can serve as a warning that something may
be wrong, and after the second signal is detected, the
machine can be shut down or the load reducedO If three
stages are used, the first can function as a warning,
the second to reduce load or shut down, and the third
for an automatic shutdown.
Whether to shut down or reduce load depends
on a number of factorsO If the second signal is received
within a few hours of the first, a runaway condition
may be occurring which would make a shutdown advisableO
On the other hand, if the power is badly needed, a deci-
sion may be made to accept the risk of damage to the
machine while operating at a reduced loadO Also, after
checki.ng it may be determined that the malfunction is
correcta~le -- for example, it may be due to a reduced
cool:ing gas pressure~ Analysis of the products of thermo-
particulation may also aid in deçiding whether a shut-
down or a reduced load is advisable since different areasof the machine can be coated with compositions contaln-
ing different TPC's and the products of thermoparticula-
ting may indicate whether the area being overheated is
criticalO
Consecutive signals may, of course, be due tc
two separate first stages from different parts of the
machineO While analysis of the thermoparticulation pro-
ducts would determine if this is occurring, a coinciden-
tal occurrence of two first stages is not likely because
overheating in these machines is fairly infrequentO
4~, 718
107916~
An alternative to mixing two or more TPCIs into a
single composition is to apply two or more separate coatings
to the machine one atop the other, each containing a TPCo
In this case, the resin is preferably the same in each
coating to avoid problems of adherence and compatabilityD A
thickness of about 1 to about 3 mils per layer is preferred~
Three layers having stages as described for the mixture
would be preferred and more than four layers may make it
difflcult to resolve the separate signalsO A layer con-
taining a compound which thermoparticulates at a lowertemperature than a compound in an adjacent layer is pre-
ferably on top of the ad~acent layer so that when the layer
thermoparticulates, it does not cause the adjacent layer to
flake off before the compound therein has thermoparticu--
latedO Layers may contain more than one TPC. A mixture of
TPC's is preferred to a layered structure because it is less
expensive to apply it to the machineO The layered structure
does offer an advantage over a mixture, however, in that a
physical examination or chemical analys~s of the layers
after thermoparticulation may indicate the maximum tempera-
ture to which the area was exposed since the lower layers
may not be as severely damaged This information is useful
in determining the extent of damage to the inslllation in
the generator.
The compositlon is applied to portions of the
electrical apparatus which are exposed to the gas stream
The coating formed does not function as insulation and is
usually applied on top of insulation, but can also be
applied to conductorsO The greases are usualiy applied to
conductors. The application may be made by painting,
45,/18
1079~65
spray~nK, dipping, grease gun, or other techniquesO A
suitable coating thickness (after drying) is about 1/16
inch The particles of TPC should not be covered with
excessive resinous carrier as that may prevent the decom-
position particles from escaping into the gas stream.
After evaporation of the solvent and room temperature
cure of the resinous carrier, if necessary, the apparatus
ls ready to be operated.
The following examples further illustrate
this invention.
~; EXAMPLE I - A MIXTURE
~ The following composition was prepared~
Parts by Weight
Zinc acetyl acetonate 2
(Zn(C5H702)~2H2o)
~tmethyl malonic acid
( (C2H5)2(COOH)2)
"Krytox 240-AD" grease 2
Epoxy resin (50% solids in toluene)
20 made from 200 pbw (parts by weight)
linseed fatty acids, 200 pbw styrene
and 300 pbw diglycidyl ether of
Bisphenol A, sold by Westinghouse
Electric Corporation as "B-276"
Varnish (See Example I of U.S~
Patent 2,909,497 for detailed
description) 10
6% sollltion ln low-boiling hydrocarbons
of cobalt naphthenate 0O15
30 24% solution in low-boiling hydro-
carbons of lead naphthenate 0O38
r14~htf) e n ~ t~
The cobalt and lead ~a~he~at-e solutions were
,dded to the epoxy resin prior to the addition of t;he
TPC's.
A sample was prepared by brush~ng the above
composition onto a 3 inch by 1 inch aluminum sheet to a
1079165
thickness of about 1/8 to about 1/4 inch. The sample
was placed in an oven at 60 for 3 days to determine
if it was stable and would functior. after aging.
The sample was placed in a stainless steel
boat within a 1 inch stainless steel tube. Hydrogen
was passed over the sample at a flow rate of 7 l/min.
A phase-controlled temperature regulator and programmer
controlled the temperature in the boat. The temperature
in the bot 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 5 C/min. heating rate was maintained in each experi-
ment after the insertion of the sample in the boat.
The threshold temperature at which considerable particu-
lation occurred ~as taken from the chart produced by
the recorder. Ihe "alarm" temperature at which consi-
derable particulation occurred corresponded to a 50%
decrease in the initial ion current of the detector
(usually from 0.8 to 0.4 mA). The occurrence of particula-
tion was detected using a Ger,erator Condition Monitor,
sold by Environment One Corporation.
Three distinct signals were obtained, one at
92C (due to the zinc acetyl acetonate), one at 145 C
(due to the dimethyl malonic acid), and one at 200 C
(due to the fluorinated hydrocarbon grease).
EXAMPL ~ AAYERED STRUCTURE
The following composition was prepared using
the procedure of Example 1:
45,718
1079165
Parts by Weight
Dimethyl malonic acid 4
B-276 resin 5
6% solutlon ln low-bolling
hydrocarbons of cobalt naphthenate 0.08
24% solutlon ln low-boillng
hydrocarbons of lead naphthenate 0.019
An alumlnum foil was smeared wlth a layer
about 2 mlls thlck of "Krytox 240-AD" grease and the
above compositlon was applled to the grease to form a
layer about 1/16 to about 1/8 lnches thick. The layer
was dried for one hour at 60C to form a tack-free
coating.
The followlng composition was prepared uslng
the procedure of Example 1:
Parts by Welght
Zinc acetyl acetonate
B-276 resin 5
6% solution in low-boiling
hy~rocarbons o~ cobalt naphthenate OoO8
20 24% solution in low-boillng
hydrocarbons of lead naphthenate 0.019
The above composition was applied over the
dimethyl malonic acid layer on the alumlnum foil to
a thickness of about 1/16 to about 1/8 lnch~
The foil was aged for three days at 60C and
tested as in Example lo Three distinct slgnals were
detected, one at 83C from the zinc acetyl acetonate,
one at 140C from the dimethyl malonic acid, and one
at 185C from the grease.
The thermopartlculation temperatures ln this
example were slightly lower than in Example 1 and the
-16-
45,718
1~)7gl6S
signals appeared to be slightly stronger, but the reason
for these dlfferences has not as yet been ascertainedO
In both examples the coatings were dark brown and hea-
v.lly pitted, and appeared to be more distinctly marked
than coatings containing only one TPCo
