Cattodic Protection

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12” LINE EXTENSION ENGINEERING DESIGN
CALCULATION REPORT OF CATHODIC
PROTECTION SYSTEM
11-04-2019 0 SENT FOR APPROVAL C. Vázquez
P. Márquez/
M. Guzmán
R. Balderaz
DATE REV. N° REASON FOR REVISION PREPARED CHECKED APPD. APPD.
DOCUMENT NUMBER : CMP-LE-001 JOB NUMBER:

2. CALCULATION REPORT OF
CATHODIC PROTECTION SYSTEM
Sideline Testing LCC
DATE: 11/04/2019
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Disclaimer
While all efforts have been made to exercise due care and caution, Sideline Testing LLC cannot
assume any liability for damage, injury (personnel or plant), leakage, loss of containment,
environmental damage, remediation or the like associated with the subject pipeline. It is
understood by all parties that the measurement techniques used and discussed in this report are
non-invasive, and as such never made actual physical damage with the subject pipeline. As a
result, the data provided may not be indicative of actual pipeline condition and are deductive in
nature. All recommendations are based upon similar experience, standard industry methods
and best engineering practice.

3. CALCULATION REPORT OF
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CONTENTS
LIST OF FIGURES.........................................................................................................4
LIST OF TABLES ..........................................................................................................4
1. OBJECTIVE............................................................................................................5
2. SCOPE OF WORK .................................................................................................5
3. ENGINEERING AND CONSTRUCTION PROJECT OF THE CATHODIC
PROTECTION SYSTEM ................................................................................................5
4. REFERENCE DOCUMENTS................................................................................10
5 CONCLUSIONS AND RECOMENDATIONS........................................................10

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LIST OF FIGURES
Figure 1. Location of anodic beds along the new and existing pipeline................ 11
Figure 2. Typical multiple galvanic anode installation........................................... 12
LIST OF TABLES
Table 1. General information of the pipeline. .......................................................... 6
Table 2. Soil resistivity vs. Degree of Corrosivity .................................................... 7
Table 3. Anode properties....................................................................................... 7

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1. OBJECTIVE
To develop a basic detailed engineering based on instructions and standards that
integrates the technical support for the design and installation of the cathodic
protection system for the project 12 "Line Extension Engineering Design.
2. SCOPE OF WORK
 Design a cathodic protection system by vertical magnesium galvanic
anodes.
 Sheet of calculations.
 Elaboration of drawing with specifications for the installation of the cathodic
protection system including Bill of Materials.
3. ENGINEERING AND CONSTRUCTION PROJECT OF THE CATHODIC
PROTECTION SYSTEM
3.1 GENERAL CONSIDERATIONS
 The type of cathodic protection system was considered by Galvanic
Anodes.
 Once the cathodic protection system was installed the minimum pipeline
potential shall be -0.85 volts with referenced to a saturated copper/copper
sulfate electrode.
 The cathodic protection system is designed for 30 years of life.
 A 0.9% coating damage was considered to determinate the total external
surface area of the pipeline to be protected. It was determined based on the
type of coating and the design life of the system.
 The soil resistivity considered was 500 ohm-cm, along the right of way of
the pipeline. The soil resistivity was considered very corrosive in order to
design in a conservatively way.

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Table 1. General information of the pipeline.
Pipeline ID: 12” LINE EXTENSION ENGINEERING DESIGN
Company: Laredo ENERGY
Diameter: 12 inches
Thickness: 0.375 inches
Length: 1.545 miles
Type of Coating: 3 layer polyethylene
3.2 OBJECTIVES
 Determine the total external surface area to protect.
 Determine the current requirement for an adequate cathodic protection.
 Select the type and size of the galvanic anodes.
 Calculate the quantity of galvanic anodes required.
 Calculate the anode bed to the earth resistance.
 Calculate the current output from the anode.
 Determinate the anode life.
 Distribute in a uniform way the anodes along the ROW of the pipeline.
3.3 DESIGN BASIS
Cathodic protection has been used for the effective control of external corrosion of
submerged or buried metallic structures. For galvanic anode CP systems, the
anode of the electrochemical cell is a casting of an electrochemically active alloy
(normally aluminum, zinc or magnesium based). This anode is also the current
source for the CP system and will be consumed. Accordingly, it is often referred to
as a “sacrificial anode”, as alternative to the term “galvanic anode”. The galvanic
anodes protection consists in electrically joining the metal structure that it is about
protecting with a more electronegative metal than the steel buried in the same
electrolyte. The existence of the electrolyte is completely essential, which
completes the system for the process.

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3.4 SOIL RESISTIVITY
The soil considered for the design of the cathodic protection system was 500 ohm-
cm, considering a very corrosive soil along the ROW of the pipeline, according the
Table 2.
Table 2. Soil resistivity vs. Degree of Corrosivity
Soil Resistivity Degree of corrosivity
0-500 Very Corrosive
500-1000 Corrosive
1,000-2,000 Moderately corrosive
2,000-10,000 Mildly corrosive
Above 10,000 Negligible
3.5 CALCULATIONS
- CURRENT OUTPUT FROM THE ANODE
Current Output for One Anode
I = Current output of one anode in amps 0.363
Ec = Cathode potential in volts (potential to which
the pipe is to be polarized)
-0.85
Ea = Anode potential in volts -1.55
Ra = Groundbed resistance in ohms 1.93
Table 3. Anode properties
H-1 Alloy Cast Magnesium Anode
Current density 3.25 mA/ft²
Dimension 5 x 5 x 21 inches
Theoretical Amp Year per Pound 0.116 Amp-yr/lb
Potential with ref to CuSO4 -1.55 volts
Electrochemical capacity of Anode 500 Amp-hour/lb
Current Efficiency (%) 50
Weight of anode 32 lbs
Utilization 0.85

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- ANODE LIFE
ANODE LIFE
V = Life in years. 4.34
C = Theoretical Amp Year per Pound 0.116
P = Anode weight in lbs 32
R = Efficiency 0.50
U = Utilization 0.85
I = Current output of the anode in amps 0.363
- SURFACE AREA TO PROTECT
TOTAL EXTERNAL SURFACE TO PROTECT
AB = surface area in sq. ft. 245.07
f = coating damage factor 0.009
π = 3.1416 3.1416
D = Diameter in ft. 1.0625
L = lenght in ft. 8157.6
- CURRENT REQUIREMENT
CURRENT REQUIREMENT
I = current requirement in amps 0.80
AB = surface area in sq.ft. 245.07
ID = current density in mA/sq.ft. 3.25

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- REQUIRED ANODIC MASS
MASA ANÓDICA REQUERIDA
W = total wegiht of required anodic mass in lbs 454
I = current requirement in amps 0.80
DR = Anode consumption lbs/yer 19
DL = CP system design life in years) 30
- NUMBER OF REQUIRED ANODES
NUMBER OF REQUIRED ANODES
N = Number of required anodes 14
W = total weight of required anodic mass in lbs 454
WA = weight of one anode in lbs 32
- GROUND BED RESISTANCE
Ground bed Resistance for Multiple Vertical Anodes in Parallel
(Sunde’sFormula)
R = resistance in ohms 1.93
ρ = soil resitivity in ohm-cm 500
L = anode lenght in feet 1.75
d = anode diameter in feet 0.417
S = anode spacing in feet 13
N = number of anodes 2
*ln is the natural logarithm function

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4. REFERENCE DOCUMENTS
The documents listed below are an integral part of the calculation report.
 Control of Pipeline Corrosion, A.W. Peabody Edited by R. L. Binchetti.
 Cathodic Protection Survey Procedures, Second Edition, W. Brian
Holtsbaum.
 CP-1 Cathodic Protection Tester Course manual, NACE International.
 CP-2 Cathodic Protection Technician Course manual, NACE International.
 CP-3 Cathodic Protection Technologist Course manual, NACE
International.
APPLICABLE CODES & STANDARDS
• NACE SP 0169 Control of External Corrosion on Underground or
Submerged Metallic Piping Systems
• ISO 15589-1:2015. Petroleum, petrochemical and natural gas industries –
Cathodic protection of pipeline systems - Part 1: On-land pipelines.
5. CONCLUSIONS AND RECOMENDATIONS
It is recommended to install seven anodic beds along the right of way uniformly
distributed, located as follows in progressive mileage, see Figure 1 for more
details:
- Bed 1, mile 0.85, two vertical galvanic anodes. The progressive mileage is
considered from the zero in the interconnection point with the new pipeline to
the end of the existing pipeline.
- Bed 2, mile 0.59, two vertical galvanic anodes. The progressive mileage is from
the zero in the interconnection point with the new pipeline to the end of the
existing pipeline.
- Bed 3, mile 0.33, two vertical galvanic anodes. The progressive mileage is from
the zero in the interconnection point with the new pipeline to the end of the
existing pipeline.
- Bed 4, mile 0.08, two vertical galvanic anodes. The progressive mileage is from
the zero in the interconnection point with the new pipeline to the end of the
existing pipeline.

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- Bed 5, mile 0.176, two vertical galvanic anodes. The progressive mileage is
from the zero in the interconnection point with the existing pipeline to the end of
the new pipeline.
- Bed 6, mile 0.43, two vertical galvanic anodes. The progressive mileage is from
the zero in the interconnection point with the existing pipeline to the end of the
new pipeline.
- Bed 7, mile 0.68, two vertical galvanic anodes. The progressive mileage is from
the zero in the interconnection point with the existing pipeline to the end of the
new pipeline.
Figure 1. Location of anodic beds along the new and existing pipeline.
The anodes should be H-1 Alloy Cast Magnesium Anodes, 32 lbs. in weight and
will be buried at a depth equal to or greater than the pipeline depth and should be
separated at a minimum distance of 10 feet from the axis of the pipeline, the
spacing between anodes should be 10 feet at least. The connection of the
HMWPE 12 AWG Cathodic protection cable from the anode to the pipeline must
be joined by exothermic welding and shall be properly insulated. A test station
should be placed in each anodic bed for potential reading in order to determine
effectiveness of the cathodic protection system.

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Figure 2. Typical multiple galvanic anode installation.