US1055327A - Means for preventing corrosion of underground metallic structures. - Google Patents

Description

G. HERINf.

MEANS POB. PRBVBNUNG GoRRosloN of UNDERGROUND METALLIC STRUGQURES.

APPLIGATXON HLED HGV. 27, 19084 Patented Mar, 11, i913.

, ers, lakes, and oceans.

CARL HERING, OF PHILADELPHIA, PENNSYLVANIA.

MEANS FOR PREVENTING CORROSION OF UNDERGROUND METALLIC STRUCTURES.

Specification of Letters Patent.

Patented Mar. 11, 1913.

Application filed November 27, 1908. Serial No. 464,673.

T o all lwhom, t may concern.'

Be it known that I, CARL HERING, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Means for Preventing Corrosion of Underground Metallic Structures, of which the following is a specification.

The object of my invention is to prevent or mitigate the corrosion of underground metallic structures by stray electric currents from light, trolley and other power circuits, when they pass through or leak out of such structures. It applies not only to underground pipes, lead covered cables, etc., but also to the metallic parts of foundations of buildings, bridges, anchorages of suspension bridge cables, etc.

The basic principles of my invention are to use the ground water as the return circuit for such stray earth currents; to connect the metallic parts, which are to be protected, to the ground water by means of a lower resistance than through the earth, or by means of direct electromotive forces sometimes called boosters; to make these connections replaceable, as the corrosion will be concentrated on them; to cause this ground water to be negative to the earth above it; to break the electrical continuity of long lines of pipes in order to make their resistance greater than that of the ground or the ground water; and to electrically interconnect the ground waters of different basins across intervening water sheds or divides, when necessary.

Ground water exists everywhere, except in solid rock. The plane of its surface is always higher than that of the creeks, riv- Its depth below the surface varies and is shown by the depth of water wells. While its electrical resistivity is generally higher than that of the buried metallic structures, it is lower than that of the moist or dry earth above it, and its depth and width and hence its cross section normal to the fiow of current, are in most districts so very great that its ohiuic resistance becomes low notwithstanding its high resistivity. It therefore forms a suitable available return conductor for stray earth currents.

In the accompanying drawing, Figure l is a diagrammatic illustration of one mode of arrangement. as applied to the metal frame work of a building; Fig. 2 is a similar view of the connections as adapted to a sys-v tem of underground pipes; F ig. 3 illustrates a modified arrangement; Fig. 4 illustrates methods of interconnecting the ground waters of different basins; and Fig. 5 illustrates a modified arrangement.

When a portion of an electric circuit, like y the tracks of an electric railway, lie uninsulated in the earth, a part of the current will fiow through the earth, forming the socalled stray currents. Other metallic conductors like a line of pipes, buried in-this earth, or a suspension bridge anchored at both ends in the earth, are a far better conductor than the earth, and hence collect and transmit these stray currents. lVhere such currents finally leave such struct-ures to pass back into the earth, that is, where such conductors are positive to the earth, electrolytic corrosion takes place. Or when steel structures, like the large modern buildings, come into contact with electric circuits which may be permanently grounded, as when the socalled grounded neutral is used, or temporarily grounded, as by some false or accidental connection, stray currents are apt to pass into the ground through the metallic parts of the foundations, like the anchor bolts, whereby these parts may be subjected to abnormally rapid corrosion. In my inl vention such underground metallic conductors are connected inetallically to ground water at suitable places by means of conductors of lower resistance than the earth which separates them from the ground water. The electric generator from which these stray currents originate, is also preferably connected with the ground water.

Referring to Fig. l, F is the metallic foundation of a building, bridge, etc., down which stray currents may tend to iiow. G,

is the ground water plane and C is the metallic connection with the earth plate E, which connection should have a lower resistance than that of the alternative path from F to G through the ground to the ground water. A recording, integrating or indicating instrument A may be inserted in this circuit. This circuit preferably includes a source of direct elect rmnotive force either by making the earth plate of Zinc, aluminum, or other metal which in earth water is positive to the conductor E. which latter is usually iron or steel. Or it may contain a d vnamo l) with its negative pole connected'to Fand its positive to the ground plate.

more certain, but i of suii'ciently hig elecvtromotive vforce they 'will even cause a cur. rentto circulate from the ground to thel 'structure F 'which tends to clean that conductor of oxidation, and if the'current. is

sutliciently strong,

moist, it willtendto dry out the llayer of moisture around F, thereby effectively insulating' the conductor F from the earth. vSuch a current develops or tends to develop hydrogen at F and oxygen the former is'tlierefore chemically reduced and t-he latter is consumed sionally be replaced. Such an arrangement of circuits may 'be said to transfer the corrosion'from the valuable structure F to thecheap replaceable plates E. Preferably vthe original source of these stray currents S should have its negative pole connected to .an earth late E', also located below the ground .wa as L, is used, it is preferable to insert a resistance R- or its equivalent in this circuit between the negative terminal lof the source S and the grounded line, as this will tend to increase the tendency of the current to flow back to the source'- S through the ground water, rather than. through the ound or the grounded line L, that is, it wlll tend to l make the ground water electronegat-ive to nected between the the ground, thereb causin the ground wa` ter to become a co lector o these stray currents. I inay use a source of direct electromotive force, B, such as a booster, conne ative pole-` of the source and the earth plate E. This will make the ground water still more negative and will tend to make the drop of potential more nearly equal in the ound'wire and ground water, land thereirre `also 4inthe ground, at equal. distances from the source,4

and when these potentials are equal, no currents will tend, to flow from one to the other. When the ground .water is thus made strongly ne ative, it willtend to cause the currents in t borhood Aof an underground conductor, to be drawn into those conductors and'ow into the groundwater 'through Athe ground water plates, as that path should have a lower resistance than the path through the earth. Such negative currents tendto clean iron Astructures of rust formed by ordinary corrosion, .and hence will tend to -preservesuch JQstructures even better than if there were no currents. v

The devices shown in Fig. v1, when the source of electromotive force' D and plate E is used, willevidently operate also when the stray currents are alternating. The posit-ive current'l which would tend to corrod'erthe l structure F, will .tend -to flow Suchv sourcesv of electrolnotive force not only make the rotection of the lart F and the ground onlyat the plate E;

and must occa- Y er plane. When a grounded line, track, P is an under e earth in the immediate neighthrough D to the earth plate, because there is a direct electromotive force in that path; while the reversed current, which tends to clean the oxids on F, will prefer the direct ath through the earth to F. When-the un-v erground conductor to be protected is very long, it may gather Yup from the earth rather i large currents which may require inconveniently large earth Cplates and which currents l at side of this joints, G the groun earth plates, the pipe to the eafrth'plates. The currents will How as shown by arrows. If desired, these ground connections nearto the surface, as at -I-I, for conveniently connecting an instrument for measuring the current, or for a recordinginstrument. I desirable a booster Bf may be introduced in Water plane, E, E, the

.by occasional inlate connectlons the protection from corand C, C, the connections from" The round pipe, I insulated '..1

maybe brought I one or mo-re of the ground connections, when the ound Water resistance is not low. The trac T, Fig. 2 may also be connected to ground water as shownl at K, when the "ground water resistance is very low. Or the track may be connectedl with the ground water, and the pipe bonded to the track, as shown in Fig. v3, Aand the current may be reversed A Fig. 4 shows how' the ground waters on two different sides of a long divide of a water shed, over which an electric railway goes, may beelectrically connected. N represents poorly conducting dry rock. Either the pipe line -P ,must -be well bonded at its joints b, b, between the last earth plate con-v nection on one side of the divide andthe vrst onthe other; or else a suitable con;

ductor t is provided for connectin aground waterearth plate on one side with one on .the other. Similar connections may be made i l across a stream flowing over a solid rock bottom, where the ground water may be ln the form of only a'thin layer, and therei .fore poorly conflufctingxvV Instead of'using .two generators 1n seriesjcasshown -1n the 125 left-hand side of Fig. l, I 'can also use two virtually in parallel, as shown im Fig. 5, one Vof them S being connected with itsnegative pole to the :track or'grounded line, and the lother S having its negative .pole connected with the ground-water plate, lE', the latter i'so i alllSI5

generator having a slightly higher voltage than the other; their positive poles are both connected to the out-going insulated circuit.

It will be understood that the system employing a grounded booster in circuit with the main generator, the lattergrounded to the conductor to be protected through a resistance or its equivalent, as illustrated in Fig. l, is designed to be used with any conductor, for example either with a con,-

tinuous partly-buried conductor, as in Fig.

venting the 'flow of stray positive currentsv from the surface of such underground conductor to the earth, comprising an earthplate located' below the ground-water plane, a metallic connection between the conductor and said earth-plate, and a generator in circuit to deliver current from said conductor to said earth-plate.

3. A system comprising an underground` conductor, an earth-plate and means for reducing or preventing the flow of stray positive currents from the surface of such underground .conductor to the earth, consisting of a metallic connection between the conductor and an easily-replaceable earth late located below the ground-water lane, 1n combination with a source of E. F. electrically connected to the ground water at a distant place for maintaining the ground water negative to the said underground conductor.

4; A system comprising'an underground' conductor and means for reducing or pre'fventing the flow of stray positive currents. from the surface of such underground con-11,; ductor to the earth, consisting of an earth-1 plate located below the ground-water plane, a 'metallic connection .between the conductor and said earth-plate, and a generator for establishing an electromotive force tending to cause currents to flow from such earthi l plate into-the ground water.

5. A system comprising a g/u'nded workcircuit, an underground conductor, and means for reducing or preventin the flow of stray positive currents from t e surfacev of such underground conductor to the earth, consisting of an earth-plate located below the ground-water plane, a metallic connection between the conductor and said earthwire, a conductor .connecting said second earth-plate and the negative ter- 3,0-

minal of said source.

6. In a grounded electrical distributionI system, a current generator, a line wire, a'

conductor or conductors connecting said line wire with the ground, an earth plate located below the ground water plane and electrically connected with that terminal' of the source of the current which is connected to the grounded line, in combination with oneV or more'earth-plates in groundwater connected metallically to those conductors which are electrically connected with the ground.

7. In' a grounded electrical distribution system, a vmain current generator, a line said line wire with the ground, an earth plate located below' the ground-water plane and electrically connected with that terminal of the source of the current which is connected to the grounded line, and a source of direct electromotive force connected between the main generator and earth plate.

8. In a grounded electrical distribution system, a' current generator, a line wire, aV

' grounded line.

9. In a grounded electrical distribution system, a current generator, a line wire, a conductor connecting said line wire with the ground, an earth plate located below the ground-Water plane, and electrically connected with that terminal of the source ot the current which is .connected to the grounded conductor, and a similar earthV 'i plate or' earth plates located below the ground-water plane and electrically connected with the grounded conductor.

10. In combination with a conductor ern'- v, bedded in or surrounded bythe earth and receiving earth currents, an earth late electrically connected with such embe ded conductor, and located below the ground water plane, thesaid earth plate connection containing a source of direct electromotive force.

ll. In combination with a groundable cir` cuit including a source of current and an underground conductor, an earth late or earth` plates located below the groun -water plane and electrically connected to said conductor, I'

and another earth plate located below the ground-water planev near the original source of the current and connected with that ter-v minal of this source the outgoing line from which is groundable.

l2. In a grounded electrical distribution System, a grounded "conductor, earth-plates bclowgthe ground-waterplane, said earthplzttes electrically1 connected to said conductor, said connectlon and conductor constitut-v ing a circuit between ground Water at one point and ground Water at another point.

.13. A system comprising conductors buried inthe ground, an earth-plate or earth-plates located in the ground water, metallic connections between the conductors und plates, and e source of electromotive force so connected as to cause currents from the earth to flow into said underground conductors and thence int-o the earth through said plate or plates, thereby reducing oxide which have formed on such conductors.

In testimony whereof, I alix my signa- 20 lVitnesses:

ETHEL B. PAUL, CARL P. NACHOD.

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