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Electrical Engineering Cathodic Protection

Kayıt: 27 Oca 2008
Mesajlar: 183

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Tarih: 19 10 2008 12:19

electrıcal engineering cathodic protection

electrıcal engıneerıng cathodıc protectıon
contents
page
section 1 ıntroductıon
1.1 scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 cancellation. . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 related technical documents. . . . . . . . . . . . . . . . . 1
section 2 cathodıc protectıon concepts
2.1 corrosion as an electrochemical process. . . . . . . . . . . 3
2.1.1 driving force. . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2 the electrochemical cell. . . . . . . . . . . . . . . . . . . 3
2.1.2.1 components of the electrochemical cell. . . . . . . . . . . . 3
2.1.2.2 reactions in an electrochemical cell. . . . . . . . . . . . . 3
2.2 the electrochemical basis for cathodic
protection. . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.1 potentials required for cathodic protection. . . . . . . . . 4
2.3 practical application of cathodic protection. . . . . . . . . 5
2.3.1 when cathodic protection should be considered. . . . . . . . 5
2.3.1.1 where feasible. . . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1.2 when ındicated by experience. . . . . . . . . . . . . . . . . 5
2.3.1.3 as required by regulation. . . . . . . . . . . . . . . . . . 5
2.3.2 functional requirements for cathodic protection . . . . . . . 8
2.3.2.1 continuity. . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2.2 electrolyte. . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2.3 source of current. . . . . . . . . . . . . . . . . . . . . . 8
2.3.2.4 connection to structure. . . . . . . . . . . . . . . . . . . 8
2.4 sacrificial anode systems. . . . . . . . . . . . . . . . . . 8
2.4.1 anode materials. . . . . . . . . . . . . . . . . . . . . . . 9
2.4.2 connection to structure. . . . . . . . . . . . . . . . . . . 10
2.4.3 other requirements. . . . . . . . . . . . . . . . . . . . . . 10
2.5 ımpressed current systems. . . . . . . . . . . . . . . . . . 10
2.5.1 anode materials. . . . . . . . . . . . . . . . . . . . . . . 10
2.5.2 direct current power source. . . . . . . . . . . . . . . . . 10
2.5.3 connection to structure. . . . . . . . . . . . . . . . . . . 10
2.5.4 other requirements. . . . . . . . . . . . . . . . . . . . . . 11
section 3 crıterıa for cathodıc protectıon
3.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 electrical criteria. . . . . . . . . . . . . . . . . . . . . 13
3.3 ınterpretation of structure-to-electrolyte
potential readings. . . . . . . . . . . . . . . . . . . . . . 13
3.3.1 national association of corrosion engineers
(nace)standard rp-01-69. . . . . . . . . . . . . . . . . . . 13
3.3.1.1 criteria for steel. . . . . . . . . . . . . . . . . . . . . . 15
3.3.1.2 criteria for aluminum. . . . . . . . . . . . . . . . . . . . 15
3.3.1.3 criteria for copper. . . . . . . . . . . . . . . . . . . . . 15
3.3.1.4 criteria for dissimilar metal structures. . . . . . . . . . . 15
3.3.2 other electrical criteria. . . . . . . . . . . . . . . . . . 15
3.3.2.1 criteria for lead. . . . . . . . . . . . . . . . . . . . . . 16
3.3.2.2 nace rp-02-85. . . . . . . . . . . . . . . . . . . . . . . . 16
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3.4 failure rate analysis. . . . . . . . . . . . . . . . . . . . 16
3.5 nondestructive testing of facility. . . . . . . . . . . . . . 16
3.5.1 visual analysis. . . . . . . . . . . . . . . . . . . . . . . 16
3.6 consequences of underprotection. . . . . . . . . . . . . . . 17
3.7 consequences of overprotection. . . . . . . . . . . . . . . . 18
3.7.1 coating disbondment. . . . . . . . . . . . . . . . . . . . . 18
3.7.2 hydrogen embrittlement. . . . . . . . . . . . . . . . . . . . 18
section 4 cathodıc protectıon system desıgn prıncıples
4.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 general design procedures. . . . . . . . . . . . . . . . . . 19
4.2.1 drawings and specifications. . . . . . . . . . . . . . . . . 19
4.2.1.1 drawings and specifications for the structure to
be protected. . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.1.2 site drawings. . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.2 field surveys. . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.2.1 water analysis. . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.2.2 soil characteristics. . . . . . . . . . . . . . . . . . . . . 20
4.2.2.3 current requirement tests. . . . . . . . . . . . . . . . . . 21
4.2.2.4 location of other structures in the area. . . . . . . . . . . 22
4.2.2.5 availability of ac power. . . . . . . . . . . . . . . . . . . 22
4.2.3 current requirements. . . . . . . . . . . . . . . . . . . . . 22
4.2.4 choice of sacrificial or ımpressed current
system. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2.5 basic design procedure for sacrificial anode
systems. . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.6 basic design procedure for ımpressed current
systems. . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2.6.1 total current determination. . . . . . . . . . . . . . . . . 24
4.2.6.2 total resistance determination. . . . . . . . . . . . . . . . 26
4.2.6.3 voltage and rectifier determination. . . . . . . . . . . . . 27
4.2.7 analysis of design factors. . . . . . . . . . . . . . . . . . 28
4.3 determination of field data. . . . . . . . . . . . . . . . . 28
4.3.1 determination of electrolyte resistivity . . . . . . . . . . 29
4.3.1.1 ın soils. . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3.1.2 liquids. . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3.2 chemical analysis of the environment . . . . . . . . . . . . 31
4.3.2.1 ph. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.3 coating conductance. . . . . . . . . . . . . . . . . . . . . 31
4.3.3.1 short line method. . . . . . . . . . . . . . . . . . . . . . 33
4.3.3.2 long line method. . . . . . . . . . . . . . . . . . . . . . . 33
4.3.4 continuity testing. . . . . . . . . . . . . . . . . . . . . . 35
4.3.4.1 method 1. . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.3.4.2 method 2. . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.3.4.3 method 3. . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.3.5 ınsulation testing. . . . . . . . . . . . . . . . . . . . . . 35
4.3.5.1 buried structures. . . . . . . . . . . . . . . . . . . . . . 35
4.3.5.2 aboveground structures. . . . . . . . . . . . . . . . . . . . 38
4.4 corrosion survey checklist. . . . . . . . . . . . . . . . . . 38
section 5 precautıons for cathodıc protectıon system desıgn
5.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2 excessive currents and voltages. . . . . . . . . . . . . . . 39
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5.2.1 ınterference. . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2.1.1 detecting ınterference. . . . . . . . . . . . . . . . . . . . 41
5.2.1.2 control of ınterference - anode bed location. . . . . . . . . 43
5.2.1.3 control of ınterference - direct bonding. . . . . . . . . . . 43
5.2.1.4 control of ınterference - resistive bonding. . . . . . . . . 45
5.2.1.5 control of ınterference - sacrificial anodes. . . . . . . . . 47
5.2.2 effects of high current density. . . . . . . . . . . . . . . 47
5.2.3 effects of electrolyte ph. . . . . . . . . . . . . . . . . . 47
5.3 hazards associated with cathodic protection. . . . . . . . . 49
5.3.1 explosive hazards. . . . . . . . . . . . . . . . . . . . . . 49
5.3.2 bonding for electrical safety. . . . . . . . . . . . . . . . 49
5.3.3 ınduced alternating currents. . . . . . . . . . . . . . . . . 50
section 6 ımpressed current system
6.1 advantages of ımpressed current cathodic
protection systems. . . . . . . . . . . . . . . . . . . . . . 53
6.2 determination of circuit resistance. . . . . . . . . . . . . 53
6.2.1 anode-to-electrolyte resistance. . . . . . . . . . . . . . . 53
6.2.1.1 effect on system design and performance. . . . . . . . . . . 53
6.2.1.2 calculation of anode-to-electrolyte resistance . . . . . . . 54
6.2.1.3 basic equations . . . . . . . . . . . . . . . . . . . . . . . 54
6.2.1.4 simplified expressions for common situations. . . . . . . . . 55
6.2.1.5 field measurement. . . . . . . . . . . . . . . . . . . . . . 57
6.2.1.6 effect of backfill. . . . . . . . . . . . . . . . . . . . . . 58
6.2.2 structure-to-electrolyte resistance. . . . . . . . . . . . . 59
6.2.3 connecting cable resistance. . . . . . . . . . . . . . . . . 59
6.2.4 resistance of connections and splices. . . . . . . . . . . . 59
6.3 determination of power supply requirements. . . . . . . . . . 59
6.4 selection of power supply type. . . . . . . . . . . . . . . . 60
6.4.1 rectifiers. . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.4.2 thermoelectric generators. . . . . . . . . . . . . . . . . . 60
6.4.3 solar. . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.4.4 batteries. . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.4.5 generators. . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.5 rectifier selection. . . . . . . . . . . . . . . . . . . . . 60
6.5.1 rectifier components. . . . . . . . . . . . . . . . . . . . . 61
6.5.1.1 transformer component. . . . . . . . . . . . . . . . . . . . 61
6.5.1.2 rectifying elements. . . . . . . . . . . . . . . . . . . . . 61
6.5.1.3 overload protection. . . . . . . . . . . . . . . . . . . . . 61
6.5.1.4 meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.5.2 standard rectifier types . . . . . . . . . . . . . . . . . . 63
6.5.2.1 single-phase bridge. . . . . . . . . . . . . . . . . . . . . 63
6.5.2.2 single-phase center tap. . . . . . . . . . . . . . . . . . . 63
6.5.2.3 three-phase bridge. . . . . . . . . . . . . . . . . . . . . . 63
6.5.2.4 three-phase wye. . . . . . . . . . . . . . . . . . . . . . . 65
6.5.2.5 special rectifier types . . . . . . . . . . . . . . . . . . . 65
6.5.3 rectifier selection and specifications. . . . . . . . . . . . 68
6.5.3.1 available features. . . . . . . . . . . . . . . . . . . . . . 69
6.5.3.2 air cooled versus oil ımmersed. . . . . . . . . . . . . . . . 69
6.5.3.3 selecting ac voltage. . . . . . . . . . . . . . . . . . . . . 70
6.5.3.4 dc voltage and current output. . . . . . . . . . . . . . . . 70
6.5.3.5 filters. . . . . . . . . . . . . . . . . . . . . . . . . . . 70
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6.5.3.6 explosion proof rectifiers. . . . . . . . . . . . . . . . . . 70
6.5.3.7 lightning arresters. . . . . . . . . . . . . . . . . . . . . 71
6.5.3.8 selenium versus silicon stacks. . . . . . . . . . . . . . . . 71
6.5.3.9 other options. . . . . . . . . . . . . . . . . . . . . . . . 71
6.5.3.10 rectifier alternating current rating. . . . . . . . . . . . . 71
6.6 anodes for ımpressed current systems. . . . . . . . . . . . . 73
6.6.1 graphite anodes. . . . . . . . . . . . . . . . . . . . . . . 74
6.6.1.1 specifications. . . . . . . . . . . . . . . . . . . . . . . . 74
6.6.1.2 available sizes. . . . . . . . . . . . . . . . . . . . . . . 74
6.6.1.3 characteristics. . . . . . . . . . . . . . . . . . . . . . . 77
6.6.1.4 operation. . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.6.2 high silicon cast ıron. . . . . . . . . . . . . . . . . . . . 78
6.6.3 high silicon chromium bearing cast ıron
(hscbcı). . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.6.3.1 specifications. . . . . . . . . . . . . . . . . . . . . . . . 78
6.6.3.2 available sizes. . . . . . . . . . . . . . . . . . . . . . . 79
6.6.3.3 operation. . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.6.4 aluminum. . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.6.5 platinum. . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.6.6 platinized anodes. . . . . . . . . . . . . . . . . . . . . . 79
6.6.6.1 types. . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.6.6.2 operation. . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.6.7 alloyed lead. . . . . . . . . . . . . . . . . . . . . . . . . 91
6.7 other system components. . . . . . . . . . . . . . . . . . . 91
6.7.1 connecting cables. . . . . . . . . . . . . . . . . . . . . . 91
6.7.1.1 factors to be considered. . . . . . . . . . . . . . . . . . . 91
6.7.1.2 ınsulation. . . . . . . . . . . . . . . . . . . . . . . . . . 92
6.7.1.3 recommended cables for specific applications. . . . . . . . . 93
6.7.1.4 economic wire size. . . . . . . . . . . . . . . . . . . . . . 93
6.7.2 wire splices and connections. . . . . . . . . . . . . . . . . 94
6.7.3 test stations. . . . . . . . . . . . . . . . . . . . . . . . 96
6.7.4 bonds. . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
6.7.5 ınsulating joints. . . . . . . . . . . . . . . . . . . . . . 96
section 7 sacrıfıcıal anode system desıgn
7.1 theory of operation. . . . . . . . . . . . . . . . . . . . . 113
7.1.1 advantages of sacrificial anode cathodic
protection systems. . . . . . . . . . . . . . . . . . . . . . 113
7.1.2 disadvantages of sacrificial anode cathodic
protection systems. . . . . . . . . . . . . . . . . . . . . . 113
7.2 sacrificial anode cathodic protection system
designprocedures. . . . . . . . . . . . . . . . . . . . . . . 113
7.3 determination of current required for
protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
7.4 determination of anode output. . . . . . . . . . . . . . . . 114
7.4.1 simplified method for common situations. . . . . . . . . . . 114
7.4.2 determination of output using
anode-to-electrolyte resistance. . . . . . . . . . . . . . . 114
7.4.2.1 calculation of anode-to-electrolyte resistance. . . . . . . . 114
7.4.2.2 determination of structure-to-electrolyte
resistance. . . . . . . . . . . . . . . . . . . . . . . . . 115
7.4.2.3 connecting cable resistance. . . . . . . . . . . . . . . . . 115
7.4.2.4 resistance of connections and splices. . . . . . . . . . . . 115
7.4.2.5 total circuit resistance. . . . . . . . . . . . . . . . . . . 115
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7.4.2.6 anode-to-structure potential. . . . . . . . . . . . . . . . . 115
7.4.2.7 anode output current. . . . . . . . . . . . . . . . . . . . . 115
7.4.3 field measurement of anode output. . . . . . . . . . . . . . 116
7.5 determination of number of anodes required. . . . . . . . . . 116
7.6 determination of anode life. . . . . . . . . . . . . . . . . 116
7.7 seasonal variation in anode output. . . . . . . . . . . . . . 117
7.8 sacrificial anode materials . . . . . . . . . . . . . . . . . 117
7.8.1 magnesium. . . . . . . . . . . . . . . . . . . . . . . . . . 117
7.8.1.1 composition. . . . . . . . . . . . . . . . . . . . . . . . . 118
7.8.1.2 anode efficiency. . . . . . . . . . . . . . . . . . . . . . . 118
7.8.1.3 potentials. . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.8.1.4 sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.8.1.5 current output. . . . . . . . . . . . . . . . . . . . . . . . 119
7.8.1.6 backfill. . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.8.2 zinc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.8.2.1 composition. . . . . . . . . . . . . . . . . . . . . . . . . 125
7.8.2.2 anode efficiency. . . . . . . . . . . . . . . . . . . . . . . 125
7.8.2.3 potentials. . . . . . . . . . . . . . . . . . . . . . . . . . 125
7.8.2.4 sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7.8.2.5 current output. . . . . . . . . . . . . . . . . . . . . . . . 126
7.8.2.6 backfill. . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7.8.3 aluminum. . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7.8.3.1 composition. . . . . . . . . . . . . . . . . . . . . . . . . 127
7.8.3.2 anode efficiency. . . . . . . . . . . . . . . . . . . . . . . 127
7.8.3.3 potentials. . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.8.3.4 sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.8.3.5 current output. . . . . . . . . . . . . . . . . . . . . . . . 127
7.9 other system components . . . . . . . . . . . . . . . . . . . 127
7.9.1 connecting wires. . . . . . . . . . . . . . . . . . . . . . . 127
7.9.1.1 determination of connecting wire size and type. . . . . . . . 133
7.9.2 connections and splices. . . . . . . . . . . . . . . . . . . 134
7.9.3 bonds and ınsulating joints. . . . . . . . . . . . . . . . . 134
7.9.4 test station location and function. . . . . . . . . . . . . . 134
7.9.5 backfill. . . . . . . . . . . . . . . . . . . . . . . . . . . 135
section 8 typıcal cathodıc protectıon
8.1 diagrams of cathodic protection systems. . . . . . . . . . . 137
section 9 cathodıc protectıon system desıgn examples
9.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2 elevated steel water tank. . . . . . . . . . . . . . . . . . 155
9.2.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 156
9.2.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 156
9.3 elevated water tank (where ıce is expected). . . . . . . . . 173
9.3.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 176
9.3.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 176
9.4 steel gas main. . . . . . . . . . . . . . . . . . . . . . . . 177
9.4.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 180
9.4.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 180
9.5 gas distribution system. . . . . . . . . . . . . . . . . . . 184
9.5.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 185
9.5.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 185
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9.6 black ıron, hot water storage tank. . . . . . . . . . . . . . 187
9.6.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 188
9.6.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 188
9.7 underground steel storage tank. . . . . . . . . . . . . . . . 190
9.7.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 190
9.7.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 192
9.8 heating distribution system. . . . . . . . . . . . . . . . . 192
9.8.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 192
9.8.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 193
9.8.3 groundbed design . . . . . . . . . . . . . . . . . . . . . . 194
9.8.4 rectifier location. . . . . . . . . . . . . . . . . . . . . . 195
9.9 aircraft multiple hydrant refueling system. . . . . . . . . . 195
9.9.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 195
9.9.2 computations. . . . . . . . . . . . . . . . . . . . . . . . . 196
9.10 steel sheet piling in seawater (galvanic nodes). . . . . . . 199
9.10.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 199
9.10.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 201
9.11 steel sheet piling in seawater (ımpressed
current
9.11.1 design data. . . . . . . . . . . . . . . . . . . . . . . . . 203
9.11.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 203
9.12 steel h piling in seawater (galvanic anodes). . . . . . . . . 207
9.12.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 208
9.12.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 208
9.13 steel h piling in seawater (ımpressed current). . . . . . . . 210
9.13.1 design data . . . . . . . . . . . . . . . . . . . . . . . . . 210
9.13.2 computations . . . . . . . . . . . . . . . . . . . . . . . . 210
section 10 ınstallatıon and constructıon practıces
10.1 factors to consider. . . . . . . . . . . . . . . . . . . . . 213
10.2 planning of construction. . . . . . . . . . . . . . . . . . . 213
10.3 pipeline coating. . . . . . . . . . . . . . . . . . . . . . . 213
10.3.1 over-the-ditch coating. . . . . . . . . . . . . . . . . . . . 213
10.3.2 yard applied coating. . . . . . . . . . . . . . . . . . . . . 213
10.3.3 joint and damage repair. . . . . . . . . . . . . . . . . . . 214
10.3.4 ınspection. . . . . . . . . . . . . . . . . . . . . . . . . . 214
10.4 coatings for other structures. . . . . . . . . . . . . . . . 214
10.5 pipeline ınstallation. . . . . . . . . . . . . . . . . . . . 214
10.5.1 casings. . . . . . . . . . . . . . . . . . . . . . . . . . . 214
10.5.2 foreign pipeline crossings. . . . . . . . . . . . . . . . . . 215
10.5.3 ınsulating joints. . . . . . . . . . . . . . . . . . . . . . 215
10.5.4 bonds. . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
10.6 electrical connections. . . . . . . . . . . . . . . . . . . . 216
10.7 test stations. . . . . . . . . . . . . . . . . . . . . . . . 216
10.8 sacrificial anode ınstallation. . . . . . . . . . . . . . . . 216
10.8.1 vertical. . . . . . . . . . . . . . . . . . . . . . . . . . . 216
10.8.2 horizontal. . . . . . . . . . . . . . . . . . . . . . . . . . 217
10.9 ımpressed current anode ınstallation. . . . . . . . . . . . . 217
10.9.1 vertical. . . . . . . . . . . . . . . . . . . . . . . . . . . 219
10.9.2 horizontal. . . . . . . . . . . . . . . . . . . . . . . . . . 219
10.9.3 deep anode beds. . . . . . . . . . . . . . . . . . . . . . . 219
10.9.4 other anode types. . . . . . . . . . . . . . . . . . . . . . 225
10.9.5 connections. . . . . . . . . . . . . . . . . . . . . . . . . 225
mıl-hdbk-1004/10
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page
10.10 ımpressed current rectifier ınstallation. . . . . . . . . . . 225
section 11 system checkout and ınıtıal adjustments
11.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 229
11.2 ınitial potential survey. . . . . . . . . . . . . . . . . . . 229
11.3 detection and correction of ınterference. . . . . . . . . . . 229
11.4 adjustment of ımpressed current systems. . . . . . . . . . . 229
11.4.1 uneven structure-to-electrolyte potentials. . . . . . . . . . 229
11.4.2 rectifier voltage and current capacity. . . . . . . . . . . . 230
11.5 adjustment of sacrificial anode systems. . . . . . . . . . . 230
11.5.1 low anode current levels. . . . . . . . . . . . . . . . . . . 230
11.5.2 ınadequate protection at designed current levels . . . . . . 230
section 12 maıntaınıng cathodıc protectıon
12.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 231
12.2 required periodic monitoring and maintenance. . . . . . . . . 231
12.3 design data required for system maintenance. . . . . . . . . 231
12.3.1 drawings. . . . . . . . . . . . . . . . . . . . . . . . . . . 231
12.3.2 system data. . . . . . . . . . . . . . . . . . . . . . . . . 231
12.3.2.1 design potentials. . . . . . . . . . . . . . . . . . . . . . 231
12.3.2.2 current output. . . . . . . . . . . . . . . . . . . . . . . . 231
12.3.2.3 system settings and potential readings. . . . . . . . . . . . 231
12.3.2.4 rectifier ınstructions. . . . . . . . . . . . . . . . . . . . 232
12.4 basic maintenance requirements. . . . . . . . . . . . . . . . 232
12.5 guidance for maintenance . . . . . . . . . . . . . . . . . . 232
12.5.1 agency maintenance and operations manuals. . . . . . . . . . 232
12.5.2 dot regulations. . . . . . . . . . . . . . . . . . . . . . . 235
12.5.3 nace standards. . . . . . . . . . . . . . . . . . . . . . . . 235
section 13 economıc analysıs
13.1 ımportance of economic analysis. . . . . . . . . . . . . . . 237
13.2 economic analysis process. . . . . . . . . . . . . . . . . . 237
13.2.1 define the objective. . . . . . . . . . . . . . . . . . . . . 237
13.2.2 generate alternatives. . . . . . . . . . . . . . . . . . . . 238
13.2.3 formulate assumptions. . . . . . . . . . . . . . . . . . . . 238
13.2.4 determine costs and benefits. . . . . . . . . . . . . . . . . 238
13.2.4.1 costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
13.2.4.2 benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . 239
13.2.5 compare costs and benefits and rank
alternatives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
13.2.6 perform sensitivity analysis. . . . . . . . . . . . . . . . . 239
13.3 design of cathodic protection systems. . . . . . . . . . . . 239
13.4 economic analysis - example 1 . . . . . . . . . . . . . . . . 240
13.4.1 objective. . . . . . . . . . . . . . . . . . . . . . . . . . 240
13.4.2 alternatives . . . . . . . . . . . . . . . . . . . . . . . . 240
13.4.3 assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 240
13.4.4 cost/benefit analysis . . . . . . . . . . . . . . . . . . . . 240
13.4.4.1 cost - alternative 1--steel line without
cathodic protection. . . . . . . . . . . . . . . . . . . . . 240
13.4.4.2 cost - alternative 2--steel line with cathodic
protection. . . . . . . . . . . . . . . . . . . . . . . . . . 242
13.4.4.3 cost - alternative 3--plastic line. . . . . . . . . . . . . . 242
13.4.4.4 benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . 243
mıl-hdbk-1004/10
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page
13.4.5 compare costs/benefits . . . . . . . . . . . . . . . . . . . 243
13.5 economic analysis - example 2 . . . . . . . . . . . . . . . . 243
13.5.1 objective. . . . . . . . . . . . . . . . . . . . . . . . . . 243
13.5.2 alternative . . . . . . . . . . . . . . . . . . . . . . . . . 243
13.5.3 assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 243
13.5.4 cost/benefit analysis . . . . . . . . . . . . . . . . . . . . 244
13.5.4.1 cost - alternative 1--steel line without
cathodic protection. . . . . . . . . . . . . . . . . . . . . 244
13.5.4.2 cost - alternative 2--steel line with cathodic
protection. . . . . . . . . . . . . . . . . . . . . . . . . . 245
13.5.4.3 benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . 246
13.5.5 compare costs/benefits . . . . . . . . . . . . . . . . . . . 246
13.5.6 conclusions and recommendations. . . . . . . . . . . . . . . 247
13.6 economic analysis - example 3 . . . . . . . . . . . . . . . . 247
13.6.1 objective. . . . . . . . . . . . . . . . . . . . . . . . . . 247
13.6.2 alternatives . . . . . . . . . . . . . . . . . . . . . . . . 247
13.6.3 assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 247
13.6.4 cost/benefit analysis . . . . . . . . . . . . . . . . . . . . 247
13.6.4.1 cost - alternative 1--ımpressed current cathodic
protection. . . . . . . . . . . . . . . . . . . . . . . . . 247
13.6.4.2 cost - alternative 2--galvanic anode system. . . . . . . . . 248
13.6.5 compare costs/benefits . . . . . . . . . . . . . . . . . . . 249
13.7 economic analysis - example 4 . . . . . . . . . . . . . . . . 249
13.7.1 objective . . . . . . . . . . . . . . . . . . . . . . . . . . 249
13.7.2 alternatives . . . . . . . . . . . . . . . . . . . . . . . . 249
13.7.3 assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 249
13.7.4 cost/benefit analysis . . . . . . . . . . . . . . . . . . . . 249
13.7.4.1 cost - alternative 1--cathodic protection system
maintenance continued. . . . . . . . . . . . . . . . . . . 249
13.7.4.2 cost - alternative 2--cathodic protection system
maintenance discontinued. . . . . . . . . . . . . . . . . . 250
13.7.5 compare benefits and costs . . . . . . . . . . . . . . . . . 251
13.8 economic analysis goal. . . . . . . . . . . . . . . . . . . . 251
section 14 corrosıon coordınatıng commıttee partıcıpatıon
14.1 ıntroduction. . . . . . . . . . . . . . . . . . . . . . . . . 253
14.2 functions of corrosion coordinating committees. . . . . . . . 253
14.3 operation of the committees. . . . . . . . . . . . . . . . . 253
14.4 locations of committees. . . . . . . . . . . . . . . . . . . 253
appendıx
appendıx a underground corrosıon survey checklıst . . . . . . . . . . . 255
b economıc lıfe guıdelınes . . . . . . . . . . . . . . . . . . 265
c project year dıscount factors . . . . . . . . . . . . . . . . 267
d present value formulae . . . . . . . . . . . . . . . . . . . 269
e dot regulatıons . . . . . . . . . . . .

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Electrical Engineering Cathodic Protection


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