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Electrical Design of Cathodic Protection

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CHAPTER 1. INTRODUCTION TO CATHODIC PROTECTION
Purpose . 1-1 1-1
References . 1-2 1-1
Corrosion 1-3 1-1
Cathodic protection 1-5 1-1
Types of cathodic protection systems
2. CATHODIC PROTECTION DESIGN
Required information . 2-1 2-1
Determining the type and design of cathodic protection system 2-2 2-3
APPENDIX A SOIL RESISTIVITY MEASUREMENT . A-1
B CURRENT REQUIREMENT TESTING B-1
C EXAMPLES OF GALVANIC CATHODIC PROTECTION DESIGN . C-1
D EXAMPLES OF IMPRESSED CURRENT CATHODIC PROTECTION DESIGN D-1
E SPECIFICATIONS FOR CERAMIC ANODE E-1
F RECTIFIER CURRENT INTERFERENCE F-1
BIBLIOGRAPHY BIBLIO-1
GLOSSARY GLOSS-1

LIST OF FIGURES

1-1 Corrosion of a pipeline due to localized anode and cathode sites 1-1
1-2. Galvanic and impressed current systems for cathodic protection 1-2
2-1. Design sequence for cathodic protection systems 2-3
A-1. Wenner four-pin method for measuring resistivity A-1
A-2. Soil box for soil resistivity measurements A-2
B-1. Current requirement test on pipelines . B-1
C-1. Galvanic anode cathodic protection for hydrant refueling system C-1
C-2. Galvanic anode cathodic protection for underground steel storage tank . C-4
C-5. Layout of gas piping in residential district C-5
D-l. Cathodic protection system for gas main . D-l
D-2. Impressed current cathodic protection for heating conduit system . D-4
D-3. Cathodic protection for black iron hot water storage tank D-7
D-4. Fringe factor for stub anodes D-9
D-5. Dimensions for an elevated steel water tank D-10
D-6. Cathodic protection for tanks using rigid-mounted button-type
anodes and platinized titanium wire . D-12
D-7. Segmented elevated tank for area calculations . D-13
D-8. Anode spacing for elevated steel water tank D-15
D-9. Anode suspension arrangement for elevated steel water tank . D-17
D-10. Equivalent diameter factor for anodes in a circule in water tank . D-18
D-l 1. Elevated steel water tank showing rectifier and anode arrangement D-24
D-12. Hand hole and anode suspension detail for elevated water tank . 9-25
D-13. Riser anode suspension detail for elevated water tank . 9-25
E-1. Ceramic anode specifications E-l
F-1. Structure-to-soil potential versus distance from foreign structure F-1
F-2. Cathodic interference testing F-2

LIST OF TABLES
2-1. Corrosivity of soils on steel based on soil resistivity 2-1
2-2. Typical current density requirements for cathodic protection of uncoated steel . 2-2
2-3. Weights and dimensions of selected high-potential magnesium-alloy anodes . 2-4
2-4. Weights and dimensions of selected circular high-silicon chromium-bearing cast iron anodes . 2-6
2-5. Shape functions (K) for impressed current cathodic protection anodes where L is the effective anode length and d is the anode/backfill diameter 2-6
2-6 Anode paralleling factors (P) for various numbers of anodes (N) installed in parallel 2-6
C-1 Outside area of liquid fuel pipes C-2
C-2. Requirements for anode spacing C-5
C-3. Dimensions for finding outside area of pipe . C-6
C-4. Galvanic anode size factor If) C-7
C-5. Structure potential factor (y) . C-7
C-6. Dimensions for finding anode division . C-8
D-1. Dimensions for finding steam conduit area: heat distribution system . D-5
D-2. Dimensions for finding condensate return conduit area: heat distribution system D-5
D-3. Conduit area: heat distribution system . D-6
D-4. Anode division: heat distribution system . D-7
D-5. Technical data: commonly used HSCBCI anodes D-1