Stray currents in water pipes: how to fix the problem

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Accord­ing to stud­ies, the accel­er­at­ed destruc­tion of under­ground com­mu­ni­ca­tions from met­al occurs due to the occur­rence of elec­tro­chem­i­cal cor­ro­sion. Its cause is the pur­pose­ful move­ment of charged par­ti­cles, which are stray cur­rents. This sit­u­a­tion indi­cates that in order to ensure the safe­ty of met­al struc­tures, it is nec­es­sary to fig­ure out how to elim­i­nate stray cur­rents under­ground in pipes for water sup­ply.

Concept definition

stray cur­rents

Stray cur­rents are charged elec­tric par­ti­cles with a cer­tain tra­jec­to­ry of move­ment that occur in the ground, which is a con­duc­tor. The term wan­der­ing arose due to the fact that it is impos­si­ble to pre­dict the local­iza­tion of par­ti­cles and the onset of the process. The influ­ence of stray elec­tri­cal par­ti­cles has an extreme­ly neg­a­tive effect on met­al prod­ucts locat­ed above and below the ground.

Sim­i­lar process­es arise due to the grow­ing num­ber of elec­tri­fied facil­i­ties that are the back­bone of mod­ern coun­tries. And since the soil is a con­duc­tor for elec­tric­i­ty, there is an inter­ac­tion between the ele­ments.

Wan­der­ing par­ti­cles arise like elec­tric ones, for the inter­ac­tion of which a com­par­i­son of the poten­tial dif­fer­ence at 2 arbi­trary points is required, only for the wan­der­ing vari­ant the con­duc­tor is the earth. As a result, the metal­lic mate­r­i­al in the vicin­i­ty of the process is destroyed faster due to cor­ro­sion.

Formation process

How they are formed

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The rea­son for the occur­rence of stray cur­rents is a large num­ber of equip­ment oper­at­ing on elec­tric charge, as a result, the fol­low­ing ele­ments are poten­tial sources:

  • the pres­ence of a charg­er in such facil­i­ties as sub­sta­tions, over­head lines with a neu­tral con­duc­tor, dis­trib­u­tors;
  • the occur­rence of activ­i­ty as a result of the destruc­tion of the insu­lat­ing lay­er of wires car­ry­ing cur­rent in cables and over­head lines, where the neu­tral is iso­lat­ed;
  • the pres­ence of a con­nect­ing tech­no­log­i­cal link between the con­duc­tor and the soil in struc­tures with a ground­ed neu­tral and rail vehi­cles dri­ven by cur­rent.

The mech­a­nism of the occur­rence of spon­ta­neous dis­charges can be con­sid­ered on the exam­ple of one of the above points.

One end of the neu­tral wire is con­nect­ed to the pow­er plan­t’s charg­er, and the oth­er end is con­nect­ed to the pow­er-con­sum­ing PEN bus, which has a con­nec­tion to the charg­er. It fol­lows that the poten­tial dif­fer­ence of the elec­tri­cal val­ue between the ter­mi­nals forms stray cur­rents, since the ener­gy will be trans­ferred to the mem­o­ry, which in turn will form a cir­cuit.

In this case, the vol­ume of loss­es does not have a large per­cent­age, since it will pass along the path of the least resis­tance, how­ev­er, a cer­tain part will fall into the ground.

Sim­i­lar­ly, ener­gy leak­age occurs in the case of dam­age to the insu­la­tion of the wiring.

At the same time, a con­stant unin­ter­rupt­ed leak does not take place, since the sys­tem sig­nals about its occur­rence and the site is auto­mat­i­cal­ly local­ized, and also, accord­ing to the reg­u­la­tions, there is a cer­tain peri­od of time allot­ted for trou­bleshoot­ing.

Impor­tant! Accord­ing to sta­tis­tics, the main places for the for­ma­tion of elec­tric­i­ty leak­age and the for­ma­tion of stray cur­rents fall on urban and sub­ur­ban areas where there is ground trans­port that depends on the pow­er grid.

Cur­rents on rails

When using urban elec­tri­fied trans­port, volt­age is sup­plied from the sub­sta­tion to the trac­tion sys­tem, which pass­es to the rails and makes a reverse cycle. If the rails as an iron base are not suf­fi­cient­ly sta­ble rel­a­tive to the con­duc­tor, this leads to the for­ma­tion of stray cur­rent loca­tions in the soil, then any met­al struc­ture that appears in their path, for exam­ple, plumb­ing prod­ucts, act as a con­duc­tor.

Impor­tant! This inter­ac­tion occurs due to the fact that the cur­rent, mov­ing, choos­es the path of least resis­tance, which is low­er for the met­al than for the ground.

All this will lead to accel­er­at­ed destruc­tion of met­al prod­ucts.

Relationship between currents and corrosion processes

Stray cur­rent cor­ro­sion

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Any water sup­ply sys­tem locat­ed in the soil is dam­aged by cor­ro­sion due to expo­sure to mois­ture and salts, how­ev­er, if the activ­i­ty of cur­rents is also con­nect­ed here, then an elec­trolyt­ic process occurs. In this case, the rate of the elec­tro­chem­i­cal reac­tion is affect­ed by the charge flow­ing between the anode and cath­ode. It fol­lows that the activ­i­ty of dam­age to met­al prod­ucts will be affect­ed by the resis­tance of the soil to the move­ment of charges, as well as the com­plex­i­ty of the cur­rents in the anode and cath­ode zones.

In such an envi­ron­ment, the water sup­ply sys­tem is sub­ject to nor­mal cor­ro­sion due to leak­age cur­rents. The impact forms a gal­van­ic cou­ple, which accel­er­ates the devel­op­ment of cor­ro­sion. There are many moments in his­to­ry when the laid pipeline was sup­posed to serve 20 years, but in fact the destruc­tion occurred after 2 years.

Options for possible protection

To pro­tect met­al prod­ucts from harm­ful effects, var­i­ous meth­ods are used, which are divid­ed by the nature of their appli­ca­tion into pas­sive and active.

Passive option

Pas­sive iso­la­tion

This option is the use of a dif­fer­ent insu­lat­ing mate­r­i­al that forms a pro­tec­tion between the con­duc­tor and the met­al. Used as insu­la­tion:

  • epoxy resin mix­tures;
  • incor­po­ra­tion into poly­mers;
  • bitu­men coat­ing.

But if we lim­it our­selves only to this option, then full-fledged pro­tec­tion will not work, since the insu­lat­ing mate­r­i­al is not a 100% bar­ri­er due to the pres­ence of dif­fu­sion per­me­abil­i­ty. There­fore iso­la­tion occurs in a par­tial way. In addi­tion, in the process of mov­ing pipes, such a lay­er can be dam­aged, result­ing in sig­nif­i­cant scratch­es, cuts, through holes and oth­er flaws.

Impor­tant! There­fore, a pas­sive method of pro­tec­tion can only be used as an addi­tion.

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Active protection

Indi­cates the use of an active method of local­iz­ing the source of expo­sure through the use of cathod­ic polar­iza­tion, where the neg­a­tive charge dis­places the nat­ur­al one.

To imple­ment such pro­tec­tion, it is nec­es­sary to use one of two tools:

  • Gal­van­ic method — the effect of a gal­van­ic pair, the destruc­tion of the sac­ri­fi­cial anode is per­formed, there­by ensur­ing the pro­tec­tion of the met­al struc­ture. The method is active when the soil resis­tance is up to 50 Ohm per meter, if the resis­tance is low­er than the method is not effec­tive.
  • Direct cur­rent source — pro­vides avoid­ance of depen­dence on the resis­tance of the soil. Cathod­ic pro­tec­tion is used, the source of which is enclosed in a formed con­vert­er con­nect­ed to an alter­nat­ing cur­rent elec­tri­cal cir­cuit. Since the source is spe­cial­ly formed by means of its reg­u­la­tion, it is pos­si­ble to set the required lev­el of cur­rent pro­tec­tion, depend­ing on the cir­cum­stances.
Active iso­la­tion

A sim­i­lar method can also pro­vide a neg­a­tive impact:

  • over­pro­tec­tion — excess of the required poten­tial, as a result, the destruc­tion of a met­al prod­uct occurs;
  • incor­rect cal­cu­la­tion of pro­tec­tion — lead­ing to accel­er­at­ed cor­ro­sion destruc­tion near locat­ed met­al objects.

The above exam­ples can be con­sid­ered on the pro­tec­tion of such a prod­uct as a heat­ed tow­el rail.

Cor­ro­sion process­es on such prod­ucts or oth­er end plumb­ing prod­ucts have nev­er occurred, but it was real before the use of met­al-plas­tic pipes, where there is con­tact with alu­minum inside the wall. As a result, the for­ma­tion of wan­der­ing ele­ments occurs not only due to the use of plas­tic pipes in the imme­di­ate room, but also in oth­ers, since in an apart­ment build­ing they can be used by a neigh­bor from anoth­er floor.

Impor­tant! To avoid the neg­a­tive impact of the gen­er­at­ed cur­rents on your own design, it is nec­es­sary to equal­ize the poten­tials by pro­vid­ing a heat­ed tow­el rail, bat­ter­ies and water pipes with a ground­ing ele­ment.

At the same time, the use of the much-need­ed ground­ing occurs in rela­tion to any com­mu­ni­ca­tion that is made of met­al pipes, for exam­ple, a gas pipeline in the ground.

Measurement rules

Tak­ing a mea­sure­ment

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To assess the extent of the cur­rent sit­u­a­tion with the leak­age of elec­tric charges, it is nec­es­sary to per­form a num­ber of mea­sures:

  • mea­sure­ment of volt­age and flow of cur­rent along the sheaths of the main cables;
  • deter­mi­na­tion of the poten­tial dif­fer­ence between con­tact rails and pipelines locat­ed in the soil;
  • check­ing the lev­el of insu­la­tion of rails from the ground cov­er­ing, using a sec­tion of the track for the exper­i­ment;
  • esti­ma­tion of the den­si­ty of ener­gy leak­age from the cable sheath into the ground.

To per­form mea­sure­ments, a spe­cial device is used, if activ­i­ties are car­ried out on rail­way tracks, it is nec­es­sary to choose the rush hour of traf­fic.

Mea­sur­ing tools

To check, trans­form­ers and sub­sta­tions are used near the line of move­ment — the elec­trode con­nect­ed to the device is con­nect­ed to the charg­er and stuck 10 meters from the sub­sta­tion. All the result­ing dif­fer­ence is fixed by the device.

If it is nec­es­sary to lay a line of pipes for water sup­ply, it is impor­tant to iden­ti­fy the loca­tion of stray cur­rents, for this pur­pose the poten­tial dif­fer­ence between two sam­ple points of the earth­’s sur­face, placed per­pen­dic­u­lar to each oth­er with an equal dis­tance, is deter­mined. It is impor­tant to car­ry out such a deter­mi­na­tion sys­tem­at­i­cal­ly with a gap of a kilo­me­ter.

In this case, the devices used must nec­es­sar­i­ly have an accu­ra­cy class of at least 1.5, and the resis­tance of the equip­ment from 1 MΩ. The use of mea­sur­ing elec­trodes with a poten­tial dif­fer­ence above 10 mV. The time of one mea­sure­ment must pass with­in 10 min­utes, and the gap between the process­es is 10 sec­onds.

Conclusion

The cal­cu­la­tion of the poten­tial and the deter­mi­na­tion of the loca­tion of the stray elec­tri­cal par­ti­cles should not be neglect­ed, since the qual­i­ty of the oper­a­tion of the plumb­ing sys­tem depends on this, in addi­tion, both pro­tec­tion meth­ods should be used simul­ta­ne­ous­ly, which will reg­u­late the result­ing volt­age and ensure com­plete pro­tec­tion of the pipeline.

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