Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
INSULATING OIL
This invention relates to a novel insulating oil
and more particularly pertains to paraffinic insulating
oils for use in electrical transformers, switch gears
and the like, and to a process for their manufacture.
Insulating oils for transformers, switch gears
and the like are commonly acid- or hydrogen finished
naphthenic oils which provide cooling and the proper
dielectric properties under various conditions of use.
Naphthenic oils are now in short supply and somewhat
expensivet and it has become important to find substitutes
for these types of insulating oils which have all of the
requisite properties. Highly refined viscous petroleum
oils possess unusually good oxidation sta~ility. These
oils possess oxidation stability which surpasses the require-
ments for transformer oil. However, many of these oils
tend to absorb oxygen when heated, particularly in the
,~
presence of metals such as copper, causing undesirable
~; formation of acids in the oil. Such oils, therefore,
;~; 20 are unsuitable for use as transformer oils.
~' Naphthenic oils which traditionally have been
used as transf~rmer oils in the past have been obtained
from erude oils from wells located in the Gulf Coast
region of the United States. Many of these wells are
old wells and no longer of economic importance. The long
~; term outlook for naphthenic oils is thus for a decreased
supply and rising cost.
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Heretofore, paraffinic-based oils per se have
been excluded as candidates for insulating oils because
of their poor low-temperature performance and their
marginal resistance to oxidation under use conditions.
Previous practice in transformer oils has been
to formulate paraffinic oils with naphthenic base oils
(see U.S. Patent No. 3,095,366, for instance) because
the paraffinic oils did not have the necessary dielectric,
low temperature, and oxidation resistance required for
this application.
- I have now discovered an insulating oil
formulation based on a paraffinic oil which is in good
supply from petroleum refineries which paraffinic oil is
derived from the decanted oil stream resulting from the
catalytic cracking operation in a petroleum oil refinery.
This decanted oil stream is purified for the purpose
; of this invention by subjecting it to extraction, e.e.
with furfural, to remove aromatic hydrocarbons and yield
a raffinate. This raffinate is then fractionated and
dewaxed to yield a low viscosity base oil of about
. ~ :
60 saybolt viscosity at 100F. and pour point 0F. This
; base oil is then subjected to clay contacting at 225F.
for about 15 minutes using attapulgite at a treating level
of about 10 pounds of clay per barrel of oil. It is also
preferred that a small amount of a filter aid such as
; diatomaceous earth (1-2 pounds per barrel of oil~ be added
in the clay contacting to improve the moisture removal
from the oil and to improve the filterability through
the filter cake.
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This clay treatment is believed to improve the dielectric strength and
interfacial tension and it reduces the moisture level of the oil. Transformer
oils, for instance, are required to have good low-temperature service life. Thus,
the oil of this invention is usually compounded with a pour depressant. We have
found that Exxon PDX 149 (which i8 a complex condensation produc~ of paraffin wax
and naphthalene which is prepared by chlorinating paraffin wax and condensing the
chlorinated product with naphthalene by the Friedel-Crafts reaction) in the range
of from 0.25 to 0.5% by weight will depress the pour point of our oil to -35 F.
without adver6ely affecting the other required performance parameter~. In
addition, $t is preferred to add to our insulating oil a metal suppressant to
control the catalytic affect of source copper which is normally found in electri- -
cal systems. Typical levels of pour depressant in the oil is about 0.25~ by weight
and for the metal suppressant is about 0.10~ by weight.
Thus, in accordance with the present teaching~, an insulating oil formulation
i8 provided which has excellent oxidation stability and consists essentially of a
solvent refined and dewaxed catalytic cracker decanted oil boiling within the range
of about 590 P. to 700 F. and which ha6 a viscosity at 100 F. of about 35 ssu, a
fla~h point of 325F. and a pour point of -5F. and from 0.25 to 0.5% based on the
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weight sf oil of complex condensation product of paraffin wax and naphthalene
which i8 prepared by chlorinating paraffin wax and conden~ing the chlorinated
:, . ..
'r~ ~ ~ product with naphthalene by the ~riedel-Crafts reaction.
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In the following exsmple, which will further illustrate the pre~ent
!~ invention, the am:ounts of ingredient~ are expressed in parts by weight unless
otherwi~e lndicated.
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' EXA~PLE
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The oils useful in my invention as transformer oil6 are prepared fr~m
the ~o-called ~decanted oils" which are obtained from the catalytic crac~ing
operation~. In the catalytic operations, the total cracked
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products are removed from a cracking zone and are conducted
1o a product fractionator. This fractionating is done
to separate the cracked products into materials of
different boiling ranges. The bottom product obtained
from the fractionator will always contain a small
percentage of catalyst particles which are carried over
from the cracking zone. It is usually desirable to
remove these catalyst particles before the oil can be
subjected to further treatment, and the removal of the
catalyst particles can be conveniently accomplished in
a decanting zone wherein the catalyst particles are
permitted to separate from the oil by means of gravity,
hence the term decanted oil. Decanted oil usually
comprises that fraction of the cracked products boiling
in the range of about 500-1100~.
In order to render the decanted oil suitable
for use as a transformer oil, it is necessary to subject
the oil to conventional refining techniques including
solvent extraction and dewaxing. In the instant case,
furfural extraction followed by MDU dewaxing to about
0F. pour point of decanted oil yields an oil (HVI 70)
having a viscosity of 70 saybolt seconds at 100F. This
oil is then fractionally distilled to yield an overhead
fraction (HVI 55) having a viscosity of 55 saybolt seconds
at 100F. This H~I 55 oil which is embodied in my invention
has the following boiling characteristics:
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93 3
IBP 595F
50% 679F
end point 754F
The HVI 55 oil described above was then clay
contacted with an activated attapulgite clay using a
dosage of 10 pounds of clay per barrel of HVI 55. In
the clay-contacting treatment, the oil was heated to 225F.,
the clay was added and the mixture was agitated for
15 minutes. The clay was then removed by filtration
using a small amount of diatomaceous earth as filter aid.
The resulting oil was then treated with 0.25% by
weight of Paraflow PDX ~ 149 for proper pour-point depres-
sion.
Although the foregoing blend of HVI 55 and
Paraflow is ordinarily sufficient for a final transformer
oil formulation, if the formulation should not fully
meet the ASTM 1275 corrosion specification, it is
.
preferred to add to the formulation about 0.10% by weight
of DuPont DMS~ (an alkyl acid salt of a complex organic
~ amine) and about 0.07% by weight of dibutyl paracresol
fo~ improved storage stability.
The folIowing is a typical non-naphthenic
transformer oil (HVI 55) formulation in accordance
with the present lnvention:
HVI 55 Balance
PDX 149 0.25 - 0.50% by weight
alkyl acid salt
; o~ a complex
~ organic amine 0 - 0.15% by weight
; ~ 30 dibutyl paracresol 0 - 0.08% by weight
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The non-naphthenic oil HVI 55 has the following typi-
cal inspections:
gravity, API 34.5
specific gravity 0.8628
pounds per gallon 7.184
pour, F -5
flash, F 325
color
viscosity @210F., cst 2~45
viscosity @210F., sus 34.4
viscosity @100F., cst 9.33
viscosity @100F., sus 34.4
viscosity index 92.5
gravity constant 0.833
refractive index @20C. - 68F. 1.4558
refractive index @70C. - 158F. 1.4549
carbon residue, ramsbottom,
` ~ by weight 0.057
~i :
ASH, % by weight 0.00
copper corrosion ASTM D130
3 hrs. @.100F. lA
24 hrs. @ 100F. lA
: 3 hrs. @ 210F. lA
24 hrs. @ 210F. lB
Molecular Weight 282
: Distil~lation Range
%:Recovered ASTM
IBP 595F.
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2~ 617
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:~L~3~L3 . ~4942)
% Reco~ered A~3TM
638
651
65Ç
659
673
679
684
6~38
- 80 699
71~
724
EP 754
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