US1460718A - Process of purifying and dehydrating switch oil - Google Patents

Description

July 3, 1.923.

C. H. HAPGOOD PROCESS OF PURIFYING AND DEHYDRATING SWITCH OIL Filed May 5 1921 \\\\x\\\\\\\\\\\\ I- 6 Q r42 gram fi ward/r cyvyaao Patented July 3, 1923.

UNITED STATES I 1,460,718 PATENT OFFICE.

C YBUS HOWARD HAPGOOD, OF NUTLEY, NEW JERSEY, ASSIGNOR TO THE DE LAVAL SEPARATOR COMPANY. OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

PROCESS OF PUBIFYING AND DEHYDRATING SWITCH OIL.

Application filed May 3, 1921.

To all whom it may concern:

Be it known that I, CYRUs ,HOWARD HAP- coon, a citizen of the United States, residing at Nutley, county of Essex, and State of New Jersey, have invented a new and useful Improvement in Processes of Purifying and merse electric switches in oil in order to avoid the formation or persistence of destructive arcs. This is especially true where the amperage is so high that the blowring out of the arc could not be effected by a magnet or other known means and when, therefore, there would be a destructive burning of the switch contact points.

After each use of the oil there is more or less breaking down of the oil into carbon, a large part of which is colloidal carbon. After repeated operations of the switch, the accumulation of carbon becomes so great that the oil is unfit for further use. There is, also, more or less contamination of the oil by dirt and water. While the percentage of water that is absorbed by the oil is very small, the presence of an amount of water so small as to be negli ible for most uses for which oil is ava1la%le is objectionable in switch oil, as it seriously reduces its dielectric strength. a

Water cannot be wholly separated from oil by gravity. Where 011 contains a substantial percentage of water, prolonged settlement will yield an oil that contains approximately only one-quarter of one per cent of water. For many purposes this degree of purification suffices. Where a still further purification is desired, it may be effected by centrifugation. Centrifugation may be effected in any machine of the cream separator type, wherein the water will escape from one outlet and the oil from the other. However, the percenta e of water that will resist elimination y gravity treatment is far greater than suffices, in switch oil, to so lower its dielectric strength so as to render it unfit for use, while the specified centrifugal treatment, when con ducted in the most effective type of centrifuge specified, yields an oil of scarcely greater dielectric strength than switch 011 Serial No. 466,496.

that has been contaminated to a permissible degree by prolonged use. In other words, used switch oil requiring purification and dehydration contains far less moisture than oil after it has been dehydrated to the greatest extent possible by gravity, while the specified centrifugal treatment is ineffective to reduce the proportion of water to the almost absolute degree required to meet the requirements for fresh switch oil.

To urify switch oil, resort is usually had to a lter press comprising approximately 1000 sheets of blotting paper, through which the oil is forced. The blotting paper takes up practically all the water as well as the carbon, and any particles of dirt. The process is fairly expeditious, as it purifies about thirty gallons per hour.

However, the process is open to serious objections. Minute shreds of blotting paper are found suspended in the otherwise purified oil and these particles tend to accumulate on the switch surfaces. Moreover, after each operation, a certain percentage of the paper units are found to be so torn and broken as to require replacement. My own observation shows that often as many as one-third of the sheets of paper are so impaired or destroyed. Their constant renewal is an item of some expense, as is also the labor required to eifecttheir replacement.

The object of my invention is to provide a more expeditious method of purification, whereby the results secured, with respect both to removal of carbon and dirt, and elimination of water, will be at least as satisfactory as those secured by the blotter filter, and whereby the expense of labor and material required for upkeep will be practically eliminated.

In the first step of my process I utilize a process the same as, or similar to, that set forth in my Patent No. 1,363,784, dated December 28, 1920, That is, to one hundred gallons of oil I add about three pounds of a readily saponifiable oil, such as any of the glyceride, or more preferably oleic acid (red oil), which is miscible in all proportions with the mineral oil usually used. While maintaining the solution heated I add an alkaline solution (say about one and onehalf pounds of soda ash) of a sufiicient concentration to completely saponify the oleic acid and form a counter colloid, which takes up the colloided carbon suspended in the oil.

I may also add a suitable salt (say about one and one-half pounds of sodium chlorid or sodium sulfate) to facilitate separation and prevent the formation of an emulsion. The soda ash, or soda ash and salt (if the latter be used) should be dissolved in about nine gallons of water.

I then apply centrifugal force to remove from the lighter oil the heavier saponified matter or soap solution and the previously suspended carbon and dirt that have been transferred from the oil to the soap solution.

I prefer to use a centrifugal separator of,

the type shown in the'Snyder Patent No. 1,283,343 of October 29, 1918, such as a machine being especially available where it is desired to separate from a light liquid heavier impurities comprising one or more heavier liquids and one or more solids.

Less desirably, the oleic acid and alkali ma be dissolved in water to form a soap an the soap. thus formed added to the switch oil and the oil then centrifuged. Or prepared soaps, such as Gold-Dust, may be used. The preferred procedure, however, wherein the soa is formed in the body of the switch oil, is more efiicient, in that it insures a very intimate preliminary admixture of the saponifiable oil with the mineral oil, thereby insuring, after the addition of the alkali, that the counter colloid formed by the resultant soap will take up every particle of suspended colloidal carbon.

The process above described gives an oil which is free from carbon and dirt, and con. tains so little water that it would normally be considered substantially dehydrated, being adapted to most purposes for which oil is used; but it is not comparable with the product of the described filter press in that it still contains too much water to adapt it for use as switch oil. Indeed, owing to the addition of water involved in the treatment with a water solution of an alkali and a saponifiable oil, the partially purified oil may contain slightly more water than before treatment.

To further dehydrate the partially purified oil, I then subject the oil .to centrifugal force under conditions which will insure the elimination of a large part of the remaining water. Preferably centrifugal force is applied while continuously introducing fresh quantities of the oil and providing for the continuous outflow of the dehydrated oil and confining from escape the water which is carried to the periphery, so that it builds up an envelope of gradually increasing thickness as the operation proceeds. This step of the process is preferably carried out in a separator of the Snyder type specified, but modified by sealing the discharge for the heavy liquid, as set forth in another application filed by me Mayo, 1921, Serial No. 466,962.

The second step of the process may also be carried out in an ordinary cream separator having a liner of the known multiple disc t pe, provided a water seal for the heavy liqui discharge outlet is initially established; but with such a separator the maximum degree of dehydration is not obtainable, because the oil is not initially distributed throughout the peripheral portion of the bowl so as to insure the subjection of all the oil to the maximum centrifugal force.

Both steps of the processmay also be carried out in a single chamber open bowl clarifier, which is intended primarily for the separation of solid ingredients from a liquid. If such a bowl is used for carrying out my process, the water will tend to be forced out toward the periphery and remain there, but a very small proportion of the water will flow out with the oil. While, in

' the second step of the process, the maximum dehydration will exceed that obtainable with a cream separator of the multiple disc type, it will not meet the exacting requirements of high voltage limits.

modified as described, provision is made, 1n the dehydrating step of the process, for initially distributing the oil throughout the peripheral part of the bowl, and the multiple disc liner divides the bowl into a multiplicity of separating compartments, wherein the oil is subjected to be repeated centrifugations, showing the elimination of the maximum percentage of water before the oil is free to escape. Moreover, these discs With a separator of the Snyder type,

afford'a large area for catching and holding an impurities, such, for instance, as partic es of dirt, or fine shreds of blotting paper that have been carried off by oil that has previously been dehydrated by filtration through a filter of the blotter press type. 'VVhile, at the end of the process, all the water in the total quantity of oil treated remains in the separator bowl, so little water is left in the oil after the first centrifugal treatment that the thickness of the surrounding wall of water at the end of the second centrifugal treatment is not sufficiently great to materially reduce the bowl volume available for separation.

It is found more economical to use the same separator for both centrifugating steps and leave open the discharge for the heavier liquids and solids in the first step and seal the discharge in the iast step. Thus the necessity for buying two separatlng machines is avoided.

By my process I can purify one hundred gallons of switch oil per hour, or over three times the amount purifiable by means of the filter press. The approach to absolute dehydration, where the second step of the process is carried out in preferred manner described, is even more nearly cbmplete,

tests showing the oil to have a dielectric strength of 53,000 volts as compared with 47,000 volts when filtered. The carbon and dirt are at least as completely removed and there is, of course, no carrying off of minute shreds of blotting paper. There are no elements in the separator requiring replacement after use, the expense of upkeep being negligible.

I have heretofore stated that my process is not dependent for its execution on any particular types of centrifuge. I have mentioned that the first centrlfugal step of the present process may be carried out in a bowl the second step may be carried out in a .similar bowl with the discharge for the heavy liquid sealed, as disclosed in my Patent No. 1,422,856, issued July 18, 1922. In the drawings I have shown a most eflicient and convenient bowl of the Snyder type, with means to seal the discharge for the heavy liquid, and which can be adapted to carry out both steps of my process, the same being specificallIyIdisclosed in a patent granted to Selden H. 852.

Fig. 1 is a vertical section through the bowl when adapted to function as a separator or purifier. Fig. 2 is a vertical section through the bowl when adapted to function as a clarifier.

In both views, a is the supporting rotary spindle, b the bowl body, a the bowl top, 0? the ring by which the bowl top is secured to the bowl body, e the central feed tube, f radial channels leading from the central feed tube to the separating space of the bowl, 9 the liner composed, as usual, of a all, July 18, 1922, No. 1,422,-

T number of superposed discs, and vanes or wings h for compelling the liquid near the periphery to rotate with the bowl. In each bowl there is a top disc above the liner.

In the'separator or purifier (Fig. 1) the top disc m is provided with a neck n having an internal discharge weir 0, while a weir p, having a diameter slightly eater than. the outside diameter of the neo is secured, by means of a" flanged ring 1', to the upper end of the bowltop. The lower end of the top disc extends substantially outside the liner g, overhanging the free space between the liner and the bowl periphery, and terminates a relatively short distance from such periphery, leaving a space .9 outside and above its edge, around which the heavier liquid escapes into the conduit between the top disc and the bowl to To convert the centrifuge into a clarifier, the top disc m and weir p are removed and there are substituted atop disc u and weir o, as shown in Fig. 2. The weir o is of a diameter not greater than, and preferably the same as t e diameter of the weir 0. The top discs at is unprovided with a neck and its central opening is of somewhat greater diameter than that of weir 'v. The lower end of the top disc u is provided with a ring or enlargement t, which rests against, or closely approximates, the cover of the bowl, thereby blocking or substantially obstructing the outflow of liquid from the peripheral part of the bowl into the space above the top disc;

In the first centrifugal step of my process, when carried out in. the purifier of Fig. I, a mixture of soap solution and carbon flows out around the lower edge of the top disc m, fills the conduit above the top disc and discharges over the neck of the bowl. The lighter liquid, containing a very small percentage of heavier-liquid, mostly water, is displaced inward, flows upward inside the neck a of the top disc m and is discharged over the neck. The process may be repeated if the percentage of heavier liquid is greater than is practicable to permit the successful execution of the final step.

In the final step of my process, when carried out in the clarifier of Fig 2, there is fed into the bowl the contaminated oil that has been separated out in the preceding step of the process. I state that the oil is contaminated, although for man purposes it would be regarded as pure. ut for switch oil, its condition has merely been changed by the first centrifugal process, from one state of impurity to another state of impurity. That is, ori inally the impurity consists of water an carbon. Prior to the last step the impurity consists of soapy water with the carbon practically eliminated, although what slight proportion may remain has been taken up by the soap. The small proportion of soa y water present is thrown to the perip cry of the clarifier, where it accumulates and forms an envelope of gradually increasing thickness. The lighter liquid is continuously discharged over the weir. This lighter liquid is the practically absolutely pure oil which it is the object of my process to secure.

Having now fully described my invention, what I claim and desire to protect by Letters Patent is l. The process of purifying and dehydrating oil containing carbon and water, such as switch oil, which comprises forming a. mixture of the oil with soap, subjecting the mixture to centrifugal force to eliminate the carbon, dirt, soap and a large part of the water, and subjecting the thus partially purified but imperfectly dehydrated oil to centrifugal dehydration.

2. The process of purifying and dehydrating oil containing carbon and water, such as switch oil, which comprises forming a mixture of the oil with soap, subjecting the mixture to centrifugal force to eliminate the carbon, dirt, soap and a large part of the water present in the mixture, subjecting the thus partially purified but imperfectly dehydrated oil to centrifugal force and during the centrifugal operation admitting fresh quantities of oil and allowing the outflow of oil from which the water has been eliminated while confining the water from escape so as to build up a surrounding water envelope of gradually increasing thickness.

3. The process of purifying a liquid containing solid and relatively heavy liquid impurities in relatively small proportion, which comprises adding a liquid heavier than the liquid to be purified, eliminating the solid impurity andmost of the heavier liquid by centrifugal force, and eliminating practically all the remaining heavy liquid from the partially purified light liquid by subjecting the same to centrifugal force and during the centrifugal operation admitting bon taken up. by the soap are discharged simultaneously with and separately fro-m the lighter oil, while in the last centrifugal operation, which is applied to the thus separated but imperfectly dehydrated oil, the lighter liquid, namely: the oil, is allowed to discharge, while the small proportion of heavier liquid is restrained from discharge and allowed to build up a surrounding film or envelope of slowly increasing thickness as the operation proceeds.

In testimony of which invention, I have hereunto set my hand, at New York, on this 28th day of April, 1921.

CYRUS HOWARD HAPGOOD.

Witnesses: 7

JOHN G. PAUL, HERBERT R. WILLIAMS.

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