US2525665A - Packaged galvanic anodes for cathodic protection - Google Patents

Description

Oct. 10, 1950 J. G. GLESNER ET AL PACKAGED GALYANI C ANODES FOR CATHODIC PROTECTIUN Filed Jan. 7, 194a INVENTORS. Josep/z 6. G/esner BY Me/v/n 0. Robinson ATTORNEYS Patented Oct. 10, 1950 UNITED; STATES PATENT 2,525,665

PACKAGED GALvANIo ANODES FOR A 1 GATHODIC PROTECTION jaseph G; ciesherana Melvin 0. Robinson, Mia- I 'land, Mich., assignors to The Dow Chemical I Company, Midland, Mich.,' a

Delaware corporation of Application January 7, 1948, Serial No. 838

3 Claims. (Cl. 204-197) This invention relates to packaged anodes for fusejinthecathodic protection of underground metals. It also concerns the containers for making such packaged'j anodes.

In galvanic systems for the cathodic protection of pipelines and other undergroundstructuies', sacrificial anodes of a metal "electronegative to the structure, usually magnesium, zinc, or aluminum, are buried'in the earth near the structure andjconnected to it by electrical conductors. The resulting flow of current maintains the structure cathodic with respect to the soil and greatly minimizes its corrosion. In

such service, it is often desirable, when using magnesium metal as a sacrificialanode, to bury it in a prepared bed or backfill designed to con trol the chemical nature of the anode environment. a

In making cathodic protection installations, conventional practice has been to transport the sacrificial anodesand "the backfill ingredients separately to the site. Each anode is then sunk in a hole dug for "the purposefafter which the backfill,ingredients are mixed and the mixture is tamped or otherwise placed around the anodes.

This procedure, while effective, is cumbersome and occasionally results in the installation of a Efforts have therefore been made to develop a packaged anodeyji. 'e. a

preformed package containing an anode with the proper quantity of appropriate backfill already in place around it. Such a packaged anode could, of course, be'installed very readily simply by burying it in the earth. Two principal types of packaged anodes have been proposed heretofore; neither has been fully satisfactory. In one, the anode is embedded in a mass of backfill cemented together by a bondin'g agent. quite brittle, sometimes breaking off in chunks during handling. In the other .type,;the anode .iscentered in a water-permeable carton or sack to the disadvantages mentioned. A related ob- Such cemented b'ackfills have been ject is to provide a simple clothcontainer or sack for making packaged anodes which positively retains the' anode centered in the backfill.

The improved container according to the invention consists essentially oi an inner. waterpermeable sack closed near the bottom by a transverse seam at a spaced distance above the bottom and an outer .water permeable sack enclosing the inner sack andsecuredalong its bot-- tom to the bottom ofthe inner sack. The galvanic anode is placed'within the inner sack above the seam and is surrounded by comminuted backfill which fills thespace between the inner and outer sacks. In this'construction, the anode is positively retained centered in the backfill under all conditions to which the packaged anode is subjected.

The invention, in a preferred form, will be further explained with reference to the accompanying drawing, in which;

Fig. 1 is an elevation of a finished packaged anode with the top tie in place;

Fig. 2 is a sectional elevation taken at right angles to the view of "Fig. 1 and along the line Z2 of Fig. 3, before the top is tied;

Fig. 3 is .a horizontalsection through the packaged anode of Figs. 1 and2, along the line 3--3 of Fig. 2;

Fig. 4 is a cutaway viewof the double-sack container of Figs. 1 to "3 before the anode and.

backfill are inserted; and

Fig. 5 is an elevation of another form of finished packaged anode.

In the drawings, the galvanic anode is an elongated cylindrical body of magnesium metal 6 having a central core I of galvanized iron pipe .cast integrally with it. An insulated copper lead wire 8 is soldered to the inside of the pipe core 1 at its upper end, the joint being protected by an insulating caulking such. as pitch 9. The

anode is surrounded by ,a, suitable comminuted backfill In, such as a powdered mixture of 75 percent by weight gypsum, 20 percent bentonite,

and 5 percent sodium sulfate. I

The anode and backfill are placed in a special of the top of the anode. inner and outer sacks are then gathered together stitched seam [4 at a spaced distance above its bottom edge. The outer sack I2 is made of water-permeable cloth of sufficient fineness to retain the comminuted backfill without loss, muslin or canvas being ordinarily used. This sack is likewise sewed longitudinally along a full-length seam I5.

In the finished container, as shown particularly in Fig. 4, the inner sack II is centered inside the outer sack l2 with the bottom edges of the two sacks registering. These edges are then turned over and stitched together forming a common hem 16 which holds the two sacks firmly together and prevents the lower end of the inner sack from moving either longitudinally or laterally relative to the outer sack.

In making the finished packaged anode, the magnesium anode 6 is slipped into the inner sack H until it rests on the lower seam l4. Powdered backfill I6 is then poured into the space between the inner sack II and the outer sack [2 until it completely surrounds the anode. It may be necessary to shake the assembly somewhat to insure that the backfill flows under the anode, i. e. into the spaces between the bottom hem 16 of the outer sack and the lower seam Id of the inner sack. Filling is continued u'ntil the level of the backfill is somewhat above that The upper ends of the and secured with a cord or wire tie H, which serves not only to close the sacks but also to .hold the upper end of the inner sack from mov- 'ing relative to the outer sack. The lead wire 8 of the anode is brought out through the tie.

In anoptional construction shown in Fig. 5, the common bottom corners'o'f the inner and outer sacks are folded over and hemmed dogeared,;as at 18. the corners somewhat and also makes the packaged anode easier to install.

In a typical packaged anode according to the invention, the anode is a cylindrical body of magnesium 4 inches in diameter and 20 inches,

long. The inner sack is 6-mesh net, 5 inches in diameter and 28 inches long, with the lower seam 2 inches above the bottom edge. The outer sack is muslin 7 inches in diameter and 3 inches .longer than the inner sack.

on the newly installed packaged anode to hasten the beginning of galvanic action. The number and'spacing of the packaged anodes required for a given installation are determined by procedures well known to corrosion engineers.

It will be appreciated that the present inven- This construction strengthens tion is concerned with improved packaging for galvanic anodes, and is applicable with all galvanically active metal anodes, regardless of the metal of which they may be formed. Likewise, the chemical nature of the backfill does not form a part of the invention, several such backfills being well known in the art. The specific gypsum, bentonite, and sodium sulfate backfill mentioned above is claimed in a co-pending application Serial No. 982 filed January 7, 1948, now Patent No. 2,480,087.

What is claimed is:

1. A container for making packaged galvanic anodes comprising elongated inner and outer water-permeable tubular sacks, each closed at its lower end by a transverse seam, the inner sack being spaced an appreciable distance above the bottom of the outer sack by a strip of sack material which holds the inner and outer sacks .together only along their parallel bottom seams.

2. A packaged anode for use in 'cath'odic'protection systems comprising inner and outer water-permeable sacks, each closed at its lower end by a transverse scam, the bottom of the inner sack being spaced an appreciable distance above the bottom of the outer sack by a strip of sack material which holds the inner andouter sacks together only along their'parallel bottom seams, a galvanically active metal "anode having a" wire conductor secured to one end thereof contained within the inner'sack, and a comminuted anode backfill composition filling the space between the inner and outer sacks so as to surround the anode. 3. A packaged anode according to claim 2 wherein a tie closes the inner and outer sacks centrally at the top withthe wire conductor extending therethrough.

JOSEPH G. GLESNER. 'MELVIN O'. ROBINSON.

REFERENCES CITED The following references are of record in the .file ofthisjpatent:

UNITED STATES'PATENTS Number OTHER REFERENCES Corrosion, vol. 2, No. 4, Oct. 1946. Article by Robinson, Magnesium Anodes for Cathodic Protection of Underground Structures.

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