US 1994259 A
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March 12, 1935. 1,994,259
METHOD OF AND APPARATUS FOR PROTECTING ELECTRICAL INSULATORS c. B. THQRNE Filed March 3, 1932 (f/A2155 BPOOAE THO/PM (I ttornegs Patented Mar. 12, 1935 v UNITED STATES.
PATENT OFFICE METHOD OF AND APPARATUS FOR PRO- TECTING ELECTRICAL INSULATORS Claims.
This invention relates to electrical insulators and particularly to a method of and apparatus.
for protecting high tension insulators used in electrical precipitators and the like and preventing 5 the collection of dust or other harmful deposits thereon.
In electrical precipitators, and particularly in.
the type illustrated in my co-pending United States application, Serial No. 596,943, filed March 5, 1932, it is customary to use an electric current of high voltage. The conductors carrying this current must pass through the outer shell of the apparatus and must be suitably insulated therefrom. In practically all forms of insulators used for this purpose one end extends into the body of the precipitator and, unless protected therefrom, is exposed to the dust and foreign matter carried by the gas which is being treated in the precipitator. As is well known, the collection of dust and dirt on the outside of an insulator of this type generally reduces its insulating properties and may result'in harmful leakage or short circuiting.
In the present types of electrical precipitators with which I am familiar the insulators used to support the discharge electrodes are usually mounted in separate compartments at the side of or above the treating chamber of the precipitator. These compartments are open to the treating chamber and a certain amount of the gases under treatment may circulate into this insulator compartment and deposit dust or sludge upon the surfaces of the insulator. This deposit in time causes short circuits or necessitates shutting down of the unit for cleaning the insulators.
Various methods have been proposed to reduce the trouble from this source. Among these is the provision of an auxiliary supply of pure, dry gas which is passed through the insulator compartment to prevent the deposit of dust, etc. Another suggestion has been to create a corona curtain to prevent dust particles from entering the insulator pocket or compartment, and others have proposed to insert heating elements within the insulator compartment to keep the air or gas therein in dry condition and thus reduce the tendency for a conducting film to form on the surfacev of the insulator.
In the present invention I have overcome certain of the difficulties which have been experienced with the types of insulator protecting devices above referred to and it is among the objects of my invention to provide an insulator for high potential electric currents which may be operated in a dust-laden atmosphere without matically, an electrical precipitator of the type danger of flash-over or failure due to the formation of a film of dust or sludge on the insulater surfaces. Other objects of my invention are: the provision of a protective mounting for insulators used in electric precipitators which will positively and 5 effectively keep the surfaces of the insulator clean; the provision of apparatus for protecting the insulators of electrical precipitators, which-is susceptible to economical construction and operation, and the provision of means for continuously 10 washing the insulator surfaces and at the same time maintaining a dust free atmosphere around the insulator.
The above and other objects of my invention will appear from the following description of a preferred form thereof, reference being had to the accompanying drawing, in which:
Fig. 1 is a side elevation, partly in section,of an electrical precipitator unit including an insulator for supporting the discharge electrode and showing my improved apparatus for preventing the formation of a conducting film upon the surfaces of the insulator.
Fig. 2 is an enlarged vertical cross section of the insulator shown in Fig. 1, together with its supporting means and protecting apparatus.
Fig. 3 is a horizontal section of the apparatus taken on line 33 of Fig. 2.
In Fig. 1 I have illustrated, rather diagram- 30 described and claimed in my co-pending United States patent application, Serial No. 596,943, filed March 5, 1932. This precipitator includes an outer shell 1, a drum shaped discharge electrode 2 and a supporting member 3 for the discharge electrode 2. This supporting member 3, in this instance, also acts as a conductor to conduct the high potential electrical current to the electrode 2. The electrode 2 is supported within the shell 1 without contact therewith and the supporting conductor 3 is insulated from the shell 1 by the insulator 4 which may be made of any suitable insulating material, such as porcelain or the like. The upper part 4a of the insulator 4 extends above and is disposed outside of the top of the shell 1 while its lower part 4b extends down within the upper part of the shell 1. To support the insulator 4 in position a suitable clamping ring 5 may be provided. 'I'hisring is adapted to grip the insulator at approximately its center and is secured to the top of the precipitator housing 1 in any suitable manner.
An open bottomed drum shaped tubular shell or housing 6 is secured at its upper end to the top of the housing 1 and extends downwardl around the lower portion 4b of the insulator 4. The lower edge '7 of the cylindrical housing 6 is preferably disposed below the lower end of the insulator 4 and the shell forms a pocket or compartment in which the lower part 417 of the insulator is disposed. A corona discharge ring 8 may be supported by a disc 9 of conducting material such as copper or the like, which is supported by and electrically connected to the conductor 3. The corona ring 8 may be provided with a number of radial discharge fins 10 and is so spaced from the grounded drum 6 that the high voltage of the conductor 3 will cause a corona discharge between the fins 10 and the inner wall of the shell 6. A pipe 11 enters the interior of the cylindrical drum or shell 6, and as best seen in Fig. 3, has a circumferentially extending nozzle portion 12 lying along the wall of the shell 6.
The conductor 3 may be secured to the insulater 4 by any suitable means such as the flange 13 at the bottom of the insulator 4 and the spring 14 and nut 15 at the top of the insulator. The spring 14 provides a resilient support for the discharge electrode 2.
In the operation of the precipitator shown in Fig. 1, the dust-laden gas or air enters through the inlet pipe 16 and passes out through the circumferentially spaced outlets (Fig. 3). A certain amount of the dust-laden air or gas may escape into the upper part of the housing 1 and unless the insulator 4 is protected therefrom dust may settle on the insulator and eventually form a conducting film thereon which might seriously interfere with the operation of the apparatus. To prevent this I connect the pipe 11 to a source of supply of steam or other condensible vapor, (not shown in the drawing). During the operation of the precipitator steam is directed into the shell or housing 6 through the nozzle 12. As this nozzle 12 is directed circumferentially of the housing 6 the steam is given a whirling motion and passes around the lower portion 4b of the insulator 4 in a spiral path in the direction indicated by the small arrows in Fig. 3. As the steam continuously enters the insulator pocket or compartment formed by the shell 6, this pocket becomes completely filled with a swirling, rotating body of steam. Some of this steam will condense into water upon the surface of the lower portion 41) of the insulator and will serve to continuously flush and keep this surface clean. The downward flow of steam through the insulator pocket will also tend to prevent the entry of any dust-laden air or gas. The corona discharge from the discharge ring 8 and its fins 10 to the wall of the shell 6 will also form a barrier which will assist in preventing the entry of dust-laden gas to the space within the insulator pocket. This corona also serves to break up and scatter water which condenses on the insulator and runs down over the disc 9 and thus prevents streams of water from being discharged upon the apparatus below.
It will be understood that in designing apparatus for use with my insulator protecting means the insulator will be designed to have a wet flashover voltage suflicient to handle the potential used and thus the condensing of the steam upon the insulator surfaces will not interfere with the operation of the apparatus. A part of the steam which enters the insulator pocket through the pipe 11 and the nozzle 12 continually condenses upon the insulator surfaces and the condensed :1 moisture drips oiI, thus keeping the surfaces washed clean at all times. Another part of the steam condenses upon the interior wall of the shell 6 and thus keeps its surfaces clean, while the remainder passes out into the main treating chamber, thus keeping up a continuous downward flow of steam and vapor which effectively prevents the entry of dirty gas into the insulator pocket. An additional advantageous result is that the insulator is kept warm by the steam so that tendency for dust and moisture to settle on the surface of the upper part 4a of the insulator which extends outside of the housing 1 is very much reduced.
It will be understood by those skilled in the art that the corona ring 8 assists in preventing the entry of dirty gas into the insulator pocket, but that in some cases it may not be necessary or desirable to utilize such a ring as the downward flow of steam together with the washing action of the condensed water vapor may be sufficient to keep the insulator free from harmful deposits. If desired the upper exposed portion 4a of the insulator 4 may also be protected in like manner by a surrounding shell into which steam may be injected and caused to flow continuously therethrough thus washing the insulator surfaces and protecting them from the accumulation of dust.
The field of usefulness of my invention is not limited to the protection of insulators used in electrical precipitators as it may be adapted to protect insulators of any type which are exposed to an atmosphere which might cause a harmful deposit to form on the insulator surfaces.
Although I have described the illustrated form of my invention in some detail, it will be understood by those skilled in the art that variations and modifications therein may be made without departing from the spirit of my invention. I do not, therefore, limit myself to the exact form shown and described but claim as my invention all embodiments thereof coming within the scope of the appended claims.
1. In apparatus of the class described the combination of an insulator, a housing disposed around said insulator and forming an insulator compartment, said housing being open at one end and closed at its opposite end, a conduit' entering said housing adjacent its closed end and a nozzle on said conduit within said compartment, said nozzle having an outlet directed to impart a whirling movement to fluid passing therethrough.
2. In combination with an electrical insulator, a cylindrical housing surrounding said insulator, said housing being closed at one end and open at its opposite end and means for injecting fluid into said housing at a point adjacent its closed end, said means including a nozzle having an outlet directed circumferentially of said housing whereby the fluid from the nozzle will pass through said housing in a spiral path.
3. The method of protecting electrical insulators from the formation of harmful surface deposits which consists in enclosing the insulator in a chamber and causing steam to flow through said chamber to prevent the entry of harmful substances thereto and condensing a suflicient-portion of said steam upon the surface of the insulator to effect a continuous washing thereof and formation of a moving film of pure water thereon.
4. The method of protecting electrical insulators from the formation of surface deposits thereon which includes the steps of surrounding the insulator surfaces to be protected with a moving body of steam and condensing a sun!- cient portion of said steam into water 'on said surface of the insulator to form a moving film of pure water thereon.
5. In apparatus for protecting electrical insulators, a housing adapted to form a compartment about the portion of the insulator to be protected, said housing having an opening at one end only,
means for injecting steam into said housing at a point removed from said opening and means for creating a corona discharge across said opening, said corona creating means including a corona ring having a plurality of radially projecting discharge fins spaced about its periphery and having their outer edges spaced from said housing.
CHARLES BROOKS 'I'HORNE.