US2019339A - Snuffer composition - Google Patents

Description

Patented 29, 1935 UNITED STATES PATENT OFFICE General Electri New York c Company, a corporation oi No Drawing. Application September 29, 1934, Serial No. 748,274

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The present invention relates to compositions suitable for use in electrical devices, such as transformers, circuit breakers, cables, and the like, for insulating and cooling purpoms, and also for non-electrical purposes, for example, as lubricants.

It is the object of my invention to provide means for guarding against combustion or explosion of gaseous admixtures containing air and gases given oil by such compositions. My invention is of general application to materials of widely varying properties, including both hydrocarbon compounds which inherently are noncombustible in the usual sense of the word, as well as ordinary combustible materials, such as mineral oil.

Various aromatic hydrocarbon compositions have been employed or proposed for industrial uses which contain combined halogen in sumciently large proportion to secure non-inflammability of the liquid mass and substantial noninflammabllity and non-explosiveness of vapor derived from such compositions. However, under special conditions even such non-inflammable vapors may be decomposed and yield enough finely divided carbon to result in a nonexplosive, weak co-mbustibility. For example, when such compositions are heated to a temperature depending on the volatility of the composition itself and usually in the range of 110 to 200 C. and the resulting vapors come in contact with electric arcs, or sparks, then a momentary glow may occur, providing, course, that sufiicient oxygen (air) has become mixed with such .vapors. Such conditions may be referred to as flash-producing conditions. At higher temperatures the concentration of the halogenated vapors derived from such compositions becomes suillciently great to diminish the air ratio to a degree sufllcient to prevent flash-producing conditions from arising.

While the combustion of carbon liberated in this way is not dangerous and cannot lead to a destructive fire, it is desirable in the operation of electrical and other apparatus, that even the possibility of such weak combustion should be eliminated.

In accordance with my present invention the possibility of even this sort of weak pseudo-combustibility is avoided by associating such halogenated compositions with a relatively minor proportion of a halogenated snufler compound containing preferably at least a chemical equivalency of chlorine and hydrogen in its molecule, and having a suitably chosen degree of volatility.

(Cl. tSl-l) In carrying out my invention, the volatile snuiler compound ordinarily need be present only in relatively minor amounts, not exceeding of the entire composition in order to reduce the quantity of oxygen in a body of collected s vapor below combustion limits. An amount 01. snufler should be used which will give from about two to four per cent of vapor derived therefrom in the gas space above the level of the liquid containing the snuil'er.

In the usual construction of electrical apparatus, such as transformers, the volume of air space does not exceed ten per cent of the volume of liquid. In such cases even a quarter per cent (0.25%) by weight of the volatile snuiler compound is capable of preventing the described glow phenomenon. The amount of snufier will depend upon circumstances in particular cases.

Halogenated olefin compounds, such as the chlorinated derivatives of the ethylenes (dichlor ethylene, boiling point 3'7.55 C.; trichlor ethylene, boiling point 87 C.; tetrachlor ethylene, boiling point 119 C.) of the propylenes (trichlor propylene, boiling point 142 C.; tetrachlor propylene, boiling point 165 C.) and the butylenes (tetrachlor butylene, boiling point 200 C.; pentachlor butylene, boiling point 185 C. under plus 60 m. m.) are illustrative of the materials which have been found to possess good snufler action in combination with dielectric materials subject to even a pseudo-combustibility.

As already indicated the essential requirement of a snuil'er is that it shall possess chemical stability, that it shall be present in sufllcient amount and be 01' such volatility that in the temperature range where pseudo-combustion of the volatilized chlorinated aromatic liquid would normally be expected, the snufier vapor will be of such concentration as to prevent flash-producing conditions.

The following experiment illustrates the described phenomenon: An iron tube six inches in diameter and 26 inches long is heated to a temperature within the range of to C.

It a small amount (60 c. c.) of a liquid mixture 45 containing equal parts of trichlor benzene and pentachlor diphenyl is admitted and an electric arc is drawn in the vapor space, then a glow or pseudo-combustion eflect may be observed. If the temperature 01' the iron tube then is in- 50 creased to higher than to C., the vapor zation of an admitted chlorinated mixture is sumciently great to reduce the air ratio below that necessary to produce the pseudocombustion. It now with the iron tube temperature at 110 to 115' C., the liquid mixture which is added contains sutlcient trichlor ethylene so that at least 2% concentration of its vapors will occur in the gas space. then the pseudo-combustion phenomenon is eliminated.

with pure pentachior diphenyl, the pseudocombustion will occur at higher temperatures. The eilect c! an admixed snuiier compound. however. is similar.

A snufler compound chosen in accordance with the principles of my invention may be mixed with various halogenated compositions, for example, such compositions as are described in my prior United States Patent 1,931,973, issued on October 17, 1933. Other similar compositions which may exhibit in the absence oi a snuiler a momentary glow phenomenon besides trichlorbenzene and chlorinated diphenyl mixed or unmixed with one another or with other chlorinated aromatic compounds, are chlorinated diphenyl methane, chlorinated diphenyl ketone, chlorinated diphenyl oxide and chlorinated naphthalene. Such compositions all are chemically inert with respect to copper and other metals present in electrical devices. The addition of a halogen oleiin snufler does not depreciate this highly desirable property of chemical inertness. The halogenated oleflns possess a viscosity by themselves which easily adapts these materials for dielectric purposes in admixture with liquids especially in apparatus such as transformers, where low viscosity of a liquid cooling and dielectric agent is demanded for thermal reasons. Trichloror tetrachlor-ethylene are examples of halogenated oleflns suitable for dielectric use. These materials have a viscosity of about 30 seconds Saybolt Universal and show little change in viscosity over a range of temperatures. The electrical characteristics oi these materials are good. Their dielectric strength, tested in a .1 inch disc electrode gap. gives a value higher than 30 kilovolts. Their dielectric constant is approximately 3.3 and the power factor is less than 1% at 1000 cycles, 25' 0., coupled with a characteristic resistivity of about 1 x 10" ohms per centimeter cube at 500 volts direct current. These characteristics make these materials particularly well adapted for admixture with other dielectric materials in transformers, circuit breakers, capacitors, cables, and the like. While particular reference has been made to snufl'ers containing chlorine. it should be understood that snuiler compounds containing other halogens may be similarly employed.

- While my invention has been described with particular reference to the prevention of a speciai form of secondary combustibility oi decomposed vapor derived i'rom otherwise non-combustible halogenated cyclic hydrocarbons, the benefits oi halogenated oleilns as snuflers also may be obtained to a considerable degree with materials which are combustible in the ordinary sense. such for example, as mineral hydrocarbon oil. In the case 01 such materials flash-producing conditions" assume the aggravated form of explosion conditions. The presence about 5 per 6 cent or a properly chosen halogenated olefin compound (for example, trichlorethylene) in the mineral oil which commonly is used in transformers, cables, and other electric devices, will eflectively reduce the explosion hazard attendant in upon the use or such oil.

What I claim as new and desire to secure by Letters Patent oi the United States is:

l. A composition of matter comprising a hydrocarbon compound the vapor 01 which is combustibie under flash-producing conditions and trichlorethylene within the limits of 0.25 to 10 per cent by weight associated with said hydrocarbon.

2. A composition of matter comprising a major proportion of halogenated hydrocarbon compound and sufficient trichiorethylene to result in the presence of about two to four per cent of the vapor thereof in a confined space above said composition.

3. A composition of matter consisting preponderantly or pentachlor diphenyl and trichlorbenzene and containing also less than ten per cent of a chlorinated ethylene, which has sufliciently high volatility to eflectively prevent silent glow combustion over said composition in a confined space.

4. A composition or matter comprising a carhon-containing compound the vapor of which is combustible under flash-producing conditions and less than ten per cent by weight but a substantial amount of halogenated olefin compound associated therewith, the amount and volatility 0! said compound being chosen to eflectively prevent silent glow combustion oi vapor emanating from said composition.

5. A composition comprising a substantially non-combustible liquid hydrocarbon, the vapor of which when decomposed is cable 01' silent glow combustion and a minor but substantial proportion of halogenated ethylene associated with said hydrocarbon, the amount and volatility of said ethylene compound being suflicient to e1 fectively prevent silent glow combustion.

6. A composition of matter comprising a major proportion of chlorinated diphenyl and a minor but substantial proportion of chlorinated olefin, which has suillciently high volatility to prevent silent glow combustion in a space deriving vapor from said composition.

7. A composition of matter comprising chlorinated diphenyl and trichlor benzene and at least about a quarter per cent (0.25%) by weight 01' chlorinated ethylene.

FRANK M. CLARK. so.

CERTIFICATE or CORRECTION.

Patent No. 2,019,339. October 29 1935:

FRANK M. CLARK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 27, claim 3, for "or" read of; and line 44, claim 5. for "cable" read capable; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 10th day of December, A. D. 193 5.

(Seal) Acting Cormki c i on fi Patents.