sp60-18 rev3 cathodic protection

7/21/2019 SP60-18 Rev3 Cathodic Protection

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SPECIFICATION

SP-60-18 Revision 3

CATHODIC PROTECTION

VALIDITY OF SPECIFICATION

This document will be valid by directly printing the document from Sasol Intranet and

validated by a registered Sasol Intranet user by completing the table below.

Validity automatically expires 3 months after verification. Reinstatement of a document

takes place by verifying pertinence and completing the next line in the table. If the

document is found to be obsolete, it shall be destroyed or marked as such.

It is forbidden to use obsolete or expired documents.

Sequence

Number

Control

Number

Initials

and

Surname

Signature

Date

of

Verification

Expiry

Date

1 2003-12-12

2

3

4

5

6

7

8

This Specification is protected by copyright and is the sole property of Sasol. The information is proprietary to Sasol and is for the sole useof the identified project or defined scope of work. Any unauthorised use, disclosure or copying or any other means of duplication orreproduction, is prohibited.Copyright 2003. Sasol. All rights reserved.


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SASOL SPECIFICATION SP-60-18

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Originator : (SIGNED)

DG ROSS

Reviewer : (SIGNED)

DFM GOODWIN

Approved by : (SIGNED)JP NELL Date : 16 MARCH 1988

ISSUE DATE: APRIL 1988

For interpretation of the Specification, the following person(s) can be contacted:

GH Mller, BAR Machado, J Piorkowski, T Erasmus

SUBSEQUENT REVISIONS

A Revision Description sheet is included to assist in identifying the changes.

Rev No Issue Date Proposed By Reviewed By Approved By Date

2 Aug 2000 DG Ross BAR Machado C Thirion 5 June 2000

3 Oct 2003 T Erasmus BAR Machado C Thirion 26 Nov 2003

This Specification is protected by copyright and is the sole property of Sasol. The information is proprietary to Sasol and is for the sole useof the identified project or defined scope of work. Any unauthorised use, disclosure or copying or any other means of duplication orreproduction, is prohibited.Copyright 2003. Sasol. All rights reserved.


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TECHNICAL COMMITTEE OF SPECIFICATION SP-60-18, Revision 3

NAME DEPARTMENT AND / OR COMPANY

BERGH, G (Gerhard) Sasol Infrachem Water Systems

COOKE, JH (Jack) Electrical and Integrity, Natref

ERASMUS, T (Theuns) Electrical Engineering, Sasol Technology

HAYNES, GJ (Gerald) Sasol Technology Consultant

HOLLER, RK (Rolf) Electrical and Integrity, Natref

LOMBARD, ER (Sias) Electrical Engineering, Sasol Technology

MACHADO, BAR (Tony) Electrical Engineering, Sasol Technology

MLLER, GH (Grant) Electrical Engineering, Sasol Technology

OOSTHUIZEN, PC (Pieter) Sasol Oil

WILKINSON, W (William) Reliability, Sasol Synfuels

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Copyright 2003. Sasol. All rights reserved.


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REVISION SHEET

REVISION 3

Specification SP-60-18, Revision 2 is revised in its entirety.

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Subject to SASOLs review of the report and acceptance of the conceptual design proposal, the design

specialists scope of work should then be extended to cover:

a. The additional site survey in order to permit the preparation of a detailed cathodic protection

design complete with a detailed technical specification and bill of quantities. The latter shall

permit the procurement or a Request For Quotation (RFQ) document to be issued to enable

cathodic protection construction contractors to carry out the cathodic protection installation.

b. The necessary liaison with the engineering contractor of the process plant, transmission or

distribution pipeline which is to be cathodically protected, so as to ensure the inclusion of all

cathodic protection field installation details in the final plant / pipeline engineering drawings.

c. The site supervision, quality control and commissioning of the completed cathodic protection

system.

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PAGETABLE OF CONTENTS

PAGE

1 GENERAL.............................................................................................................................. 1

1.1 SCOPE ........................................................................................................................ 1

1.2 LEGAL REQUIREMENTS........................................................................................ 2

1.3 ABBREVIATIONS .................................................................................................... 2

1.4 DEFINITIONS............................................................................................................ 9

1.5 PRECEDENCE......................................................................................................... 17

1.6 MATERIAL REQUIREMENTS .............................................................................. 17

1.7 GUARANTEE PERIOD........................................................................................... 17

2 REFERENCE DOCUMENTS............................................................................................ 18

2.1 SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTH

AFRICAN BUREAU OF STANDARDS (SABS) CODES OF PRACTICE AND

SPECIFICATIONS................................................................................................... 18

2.2 SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTHAFRICAN BUREAU OF STANDARDS / INTERNATIONAL

ELECTROTECHNICAL COMMISSION (SABS IEC) SPECIFICATIONS.......... 21

2.3 SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTH

AFRICAN BUREAU OF STANDARDS / INTERNATIONAL

ORGANISATION FOR STANDARDISATION (SABS ISO) STANDARDS....... 21

2.4 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)

STANDARDS........................................................................................................... 22

2.5 AMERICAN SOCIETY FOR THE TESTING OF MATERIALS (ASTM)............ 222.6 AMERICAN PETROLEUM INSTITUTE (API)..................................................... 23

2.7 NATIONAL ASSOCIATION OF CORROSION ENGINEERS (NACE)

RECOMMENDED PRACTICES............................................................................. 23

2.8 BRITISH STANDARDS INSTITUTION (BS) SPECIFICATIONS....................... 24

2.9 RAL DEUTSCHES INSTITUT FR GTESICHERUNG UND

KENNZEICHNUNG RAL-FARBEN ................................................................... 25

2.10 DEUTSCHES INSTITUT FR NORMUNG (DIN)................................................ 25

2.11 INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC)PUBLICATIONS...................................................................................................... 25

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PAGE2.12 INTERNATIONAL ORGANISATION FOR STANDARDISATION (ISO)

STANDARDS........................................................................................................... 25

2.13 SWEDISH STANDARDS INSTITUTION (SIS) STANDARDS............................ 26

2.14 SASOL SPECIFICATIONS, DATA SHEETS AND STANDARD DRAWINGS.. 26

3 CP SYSTEM REQUIREMENTS....................................................................................... 28

3.1 SPECIALIST CP CONSULTANT AND CP CONTRACTOR ............................... 28

3.2 ON SITE INVESTIGATIONS / SURVEY .............................................................. 29

4 CATHODIC PROTECTION DETAILED DESIGN REQUIREMENTS...................... 39

4.1 GENERAL CONSIDERATIONS ............................................................................ 39

4.2 COATINGS AND CP............................................................................................... 39

4.3 CHOICE OF CP SYSTEM....................................................................................... 41

4.4 DETAILED CP DESIGN CALCULATIONS.......................................................... 42

4.5 SPECIAL DESIGN CONSIDERATIONS ............................................................... 47

5 CONSTRUCTION, DRAWINGS, RECORDS AND COMMISSIONING.................... 48

5.1 CONSTRUCTION, TESTING AND INSPECTION ............................................... 495.2 COMMISSIONING, AS-BUILT DRAWINGS AND RECORDS .......................... 51

5.3 SPARE PARTS......................................................................................................... 55

5.4 INSTALLATION, OPERATION AND MAINTENANCE MANUALS ................ 55

6 CP ACCEPTANCE CRITERIA ........................................................................................ 55

6.1 ACCEPTANCE CRITERIA..................................................................................... 55

6.2 ASSESSING THE IR FREE STRUCTURE-TO-ELECTROLYTE

POTENTIAL............................................................................................................. 57

7 OPERATION AND MAINTENANCE OF THE CP SYSTEM ...................................... 59

8 CATHODIC PROTECTION MATERIALS AND THE INSTALLATION

THEREOF............................................................................................................................ 61

8.1 GENERAL................................................................................................................ 61

8.2 MANUAL TAP CHANGE AND AUTOMATIC THYRISTOR CONTROLLED

TRANSFORMER RECTIFIER UNITS ................................................................... 61

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PAGE9 ELECTRICAL CONSTRUCTION ................................................................................... 63

9.1 GENERAL................................................................................................................ 63

9.2 OUTPUT CONTROL............................................................................................... 65

9.3 METERS AND MONITORS ................................................................................... 66

9.4 SURGE PROTECTION............................................................................................ 67

9.5 WIRING AND BUSBARS....................................................................................... 68

9.6 COLOUR CODING AND LABELLING................................................................. 69

9.7 CABLE ENDS AND TERMINALS......................................................................... 71

9.8 EARTHING .............................................................................................................. 72

9.9 SPARES.................................................................................................................... 72

9.10 COMPONENT LAYOUT ........................................................................................ 73

9.11 AUXILIARY AC SUPPLY...................................................................................... 74

9.12 CABINET CONSTRUCTION.................................................................................. 74

9.13 COATING................................................................................................................. 76

9.14 INSPECTION AND TESTING ................................................................................ 76

9.15 DOCUMENTATION................................................................................................ 78

9.16 GUARANTEE .......................................................................................................... 78

9.17 MANUFACTURER QUALIFICATIONS ............................................................... 78

10 CONCRETE PLINTHS ...................................................................................................... 78

11 CORROSION RESISTANT SILICON IRON ANODES ................................................ 79

11.1 GENERAL CONSIDERATIONS ............................................................................ 79

11.2 GENERAL ANODE DETAILS ............................................................................... 80

11.3 CHEMICAL COMPOSITION.................................................................................. 82

11.4 QUALITY CONTROL AND TESTING.................................................................. 82

12 TYPICAL IMPRESSED CURRENT ANODE INSTALLATION DETAILS............... 83

12.1 DEEP VERTICAL AND SHALLOW VERTICAL ANODE GROUNDBED

SYSTEMS................................................................................................................. 83

12.2 HORIZONTAL AND DISTRIBUTIVE ANODE GROUNDBED SYSTEMS....... 84

12.3 MIXED METAL OXIDE (MMO) / PRECIOUS METAL OXIDE (PMO)

ANODES .................................................................................................................. 85

12.4 ANODE DIMENSIONS AND TITANIUM SUBSTRATE GRADES.................... 86

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PAGE12.5 ANODE LOADING AND OPERATING PARAMETERS..................................... 88

12.6 ANODE CABLE CONNECTION............................................................................ 89

12.7 CHEMICAL AND PERFORMANCE TESTING OF ANODES............................. 90

13 IMPRESSED CURRENT CARBONACEOUS ANODE BACKFILL MATERIAL .... 91

13.1 INTRODUCTION AND GENERAL CONSIDERATIONS.................................... 91

13.2 CHEMICAL COMPOSITION.................................................................................. 92

13.3 PARTICLE SIZE DISTRIBUTION (PSD) .............................................................. 92

13.4 SHIPPING AND PACKAGING............................................................................... 93

14 CATHODIC PROTECTION CABLING.......................................................................... 93

14.1 INTRODUCTION .................................................................................................... 93

14.2 GENERAL PROPERTIES OF INSULATING COMPOUNDS.............................. 94

14.3 CABLE AND CABLE INSULATION COMPLIANCE.......................................... 95

14.4 CP CABLE REQUIREMENTS................................................................................ 96

14.5 CABLE INSTALLATION AND IDENTIFICATION............................................. 97

15 EXOTHERMIC WELDING / PIN BRAZING CABLE CONNECTION DETAILS ... 9715.1 CABLE CONNECTIONS TO PIPES AND REPAIR TO COATINGS .................. 97

15.2 SURFACE PREPARATION.................................................................................... 98

15.3 PIN BRAZING / EXOTHERMIC WELDING......................................................... 98

15.4 TESTING.................................................................................................................. 99

15.5 WELD POWDER / CABLE COMBINATION........................................................ 99

15.6 PRECAUTIONS..................................................................................................... 100

15.7 REINSTATEMENT OF THE COATING SYSTEM ............................................. 101

16 PERMANENT REFERENCE ELECTRODES.............................................................. 101

16.1 GENERAL CONSIDERATIONS .......................................................................... 101

16.2 MANUFACTURER QUALIFICATIONS ............................................................. 101

16.3 PERMANENT REFERENCE ELECTRODE (PRE) CONSTRUCTION ............. 101

16.4 PERMANENT REFERENCE ELECTRODE (PRE) STABILITY........................ 103

17 CATHODIC PROTECTION TEST POINTS................................................................. 103

17.1 INTRODUCTION .................................................................................................. 103

17.2 LOCATION OF TEST POSTS / STATIONS ........................................................ 10417.3 TYPICAL CP TEST POSTS .................................................................................. 105

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PAGE18 SOLID STATE DC DECOUPLING DEVICES ............................................................. 108

18.1 INTRODUCTION .................................................................................................. 108

18.2 ELECTRICAL CONSTRUCTION ........................................................................ 109

18.3 ENCLOSURE CONSTRUCTION ......................................................................... 111

18.4 INSPECTION AND TESTING .............................................................................. 111

18.5 DOCUMENTATION.............................................................................................. 112

18.6 GUARANTEE ........................................................................................................ 112

18.7 MANUFACTURER QUALIFICATIONS ............................................................. 112

19 INSULATING FLANGE MATERIALS ......................................................................... 113


19.2 MATERIAL SPECIFICATIONS ........................................................................... 113

19.3 IDENTIFICATION / LABELS, OPERATING INSULATING FLANGE, NO

ATTACHMENTS TO PIPEWORK PERMITTED .............................................. 115

19.4 MONOLITHIC INSULATING JOINTS................................................................ 115

19.5 INTERNAL PIPE LINING FOR COOLING WATER SERVICE ........................ 116

20 HIGH POTENTIAL SACRIFICIAL MAGNESIUM ANODES (SOIL USE)............. 120


20.2 MAGNESIUM ANODE CHEMICAL COMPOSITION....................................... 121

20.3 HIGH POTENTIAL MAGNESIUM ANODE PHYSICAL PROPERTIES .......... 121

20.4 ANODE CABLE AND CABLE CONNECTION.................................................. 122

20.5 ELECTROCHEMICAL PROPERTIES ................................................................. 123

20.6 TESTING AND REVIEWAL................................................................................. 123

20.7 TYPICAL INSTALLATION DETAILS ................................................................ 123

21 AC MITIGATION EARTH ELECTRODE.................................................................... 124

21.1 ZINC TUBE MATERIAL SPECIFICATION........................................................ 124

21.2 ZINC TUBE DIMENSIONS .................................................................................. 125

21.3 ZINC TUBE CHEMICAL COMPOSITION.......................................................... 125

21.4 HARDNESS MEASUREMENTS.......................................................................... 125

21.5 METALLOGRAPHY............................................................................................. 126

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1

1.1

1.1.1

a.

b.

c.

d.

e.

1.1.2

1.1.3

GENERAL

SCOPE

This Specification defines the minimum and mandatory requirements governing the design,

application, installation and commissioning of a Cathodic Protection (CP) system for the

following:

Pipelines, process, fire water, cooling water and utility piping, as well as pipes located

inside chambers;

Pipeline casings (cased crossings);

On-grade storage tank bottoms and the internal surface of storage tanks;

Well casings;

Water boxes of heat exchangers,

installed inside and / or outside the SASOL plant(s) battery limits.

In the event of any detail that is not fully addressed in this specification and that is warranted

to be carried out by the contractor, the work shall be performed in accordance with the

relevant applicable codes and best recognised engineering practices in the CP industry. The

contractor shall develop detailed specifications, procedures and method statements required

to perform the CP design during the engineering phase of work and this shall be submitted to

SASOL for review and approval prior to construction, supply and / or installation work.

The specification covers the general requirements of the CP system. CP may be achieved

through the use of Sacrificial Anode CP (SACP) or Impressed Current CP (ICCP).

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1.1.4

1.1.5

1.2

a.

b.

c.

d.

e.

1.3

AC interference mitigation may be achieved through the use of pipeline-earth grounding

systems, in conjunction with solid state DC decoupling devices. It must not adversely affect

or interfere with the CP system.

The details and extent of the plant or structure equipment required to be cathodically

protected, the site / locality and the meteorological data shall be both specified and supplied

by SASOL and / or the main contractor.

LEGAL REQUIREMENTS

The SASOL factories are subject to the statutory requirements of the following Acts and all

CP installations shall meet the requirements of these Acts:

The National Environmental Management Act (NEMA) - Act 107 of 1998;

The Occupational Health and Safety Act with Regulations - Act 85 of 1993;

The Mine Health and Safety Act - Act 29 of 1996;

The Minerals Act - Act 50 of 1991;

The National Water Act - Act 36 of 1998.

ABBREVIATIONS

The following CP abbreviations have been used:

A Ampere

A / m Ampere per metre square

AC Alternating Current

AFC Approved For Construction

A.hr / kg Ampere hours per kilogram (Electro-chemical Consumption Rate)

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Al Aluminium

API American Petroleum Institute

A.y Ampere-years

AQL Acceptable Quality Level

ASME American Society of Mechanical Engineers

ASTM American Society for the Testing of Materials

Br Bromine

BSI British Standards Institute

C Carbon

CD Current Drainage

CIP Close Interval Potential

COC Certificate of Compliance

CP Cathodic Protection

Cr Chromium

Cu Copper

CuSO4 Copper Sulphate

Cu-Ti Copper - Titanium

DB Distribution Board

DC Direct Current

DCVG Direct Current Voltage Gradient

DIN Deutsche Institut fr Normung

ECTFE Ethyl Carbo Tetra-Fluoro-Ethylene

EPR Earth Potential Rise

ETFE Ethyl Tetra-Fluoro-Ethylene

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Ex Hazardous Classified Equipment

EXW Exothermic Welding

F Fluorine

FBE Fusion Bonded Epoxy

Fe Iron

Fe-Si Silicone Iron

FDU Forced Drainage Unit

GC Grounding Cell

g / ml grams per millilitre

GIS Geographical Information System

GPS Global Positioning System

H2SO4 Sulphuric Acid

HDPE High Density Polyethylene

HMWPE High Molecular Weight Polyethylene

HVTL High Voltage Transmission Line / High Voltage Power Line

Hz Hertz

ICCP Impressed Current Cathodic Protection

ID Inner Diameter

IEC International Electrotechnical Commission

IJ Insulating Joint

IF Insulating Flange

IP Ingress Protection

IR Ohmic Voltage Drop

ISO International Organisation for Standardisation

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IrO2 Iridium Oxide

kg kilogram

kg / m kilogram per cubic metre

kPa kilopascal

kV kilovolt

kV / mm kilovolt per millimetre

kW kilowatt

LCD Liquid Crystal Display

LMPE Low Molecular Weight Polyethylene

m metre

mA / m Milli-ampere per Square Metre

Mg Magnesium

mH Milli-henry

m Milli-ohm

mA Milli-ampere

MIC Microbial Induced Corrosion

Mil Thousandth of an Inch

MMO Mixed Metal Oxide

MMP Maximum Meter Point

MMWPE Medium Molecular Weight Polyethylene

Mn Manganese

Mo Molybdenum

MON Monitor

MOV Metal Oxide Varistor

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MPa Megapascal

mV Milli-volt

mV / C Milli-volt per Degree Celsius

NACE National Association of Corrosion Engineers

NDU Natural Drainage Unit

NDT Non Destructive Testing

NPS Nominal Pipe Size

OD Outer Diameter

OMM Operation and Maintenance Manual

OWS Oily Water Sewer

PC Printed Circuit

PCB Polycarbonate Based

PDF Portable Document Format

PE Polyethylene

pH Level of Acidity or Alkalinity

PIV Peak Inverse Voltage

PMO Precious Metal Oxide

PO Purchase Order

PPI Probable Performance Index

PPM Parts Per Million

PRE Permanent Reference Electrode

PSD Particle Size Distribution

psi Pounds Per Square Inch

P-TP Plant Test Post

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PTFE Poly-Tetra-Fluoro-Ethylene

PVC Poly-Vinyl-Chloride

PVDF Poly-Vinylidene Fluoride

QCP Quality Control Plan

Pub Publication

RE Reference Electrode

RFQ Request For Quotation

RMS Root Mean Square

RP Recommended Practice

R-TP Recording Test Posts

SAACE South African Association of Consulting Engineers

SABS South African Bureau of Standards

SACP Sacrificial Anode Cathodic Protection

SANS South African National Standards

SEM Scanning Electron Microscope

Si Silicon

SI System International

SIS Swedish Standards Institution

SP Specification

SPIR Spare Parts Interchange-ability Record

SRB Sulphate Reducing Bacteria

SS Stainless Steel

SS-DCD Solid State - Direct Current Decoupling Device

STDD Standard Drawing

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SWA Steel Wire Armour

Ta Tantalum

Ta2O5 Tantalum Oxide

TDS Technical Data Sheet

Ti Titanium

TP Test Point / Test Post

TP-R Reference Monitoring Test Post

TRU Transformer Rectifier Unit

V Volt

+VE Positive Terminal

-VE Negative Terminal

XLPE Cross-linked Polyethylene

Zn Zinc

% IR Percentage Ohmic Voltage Drop

% Percentage

C Degrees Celsius

F Degrees Fahrenheit

micro

m micro metre

s micro second

.m micro Ohm metre (unit of measurement for resistivity)

Ohm

cm Ohm Centimetre

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1.4 DEFINITIONS

ANAEROBIC Oxygen deficient environment.

ANAEROBIC BACTERIA Also called sulphate reducing bacteria. A type of bacteria

which corrodes steel and is present only in the absence of

oxygen (anaerobic). When they are present, the protective

potential must be raised to -0,95 V.

ANODE DISTRIBUTIONCABINET

A steel cabinet containing a bulbar to which is joined theanode cables as well as the main anode groundbed ring main

cable(s).

ANODIC GRADIENT Gradient arising in the soil due to the current flow through

the soil from the anode(s).

ANODE GROUNDBED An anode groundbed consisting of a number of impressed

current anodes joined to a common positive rectifier cable.

The anodes are encapsulated in coke to increase their life and

decrease the resistance to earth. The anode groundbed is onaverage 100 m to 150 m long and a minimum of 2,5 m deep.

APPROVAL OR

APPROVED BY SASOL

Written agreement or authorisation by SASOL. All requests

for approval shall be submitted in writing and any proposed

deviation from the specified requirements shall be fully

explained and motivated.

ANODE (IMPRESSED

CURRENT)

Any buried or submerged metal (or graphite) which is

connected to the positive terminal of a transformer rectifier

and serves to introduce current into the earth. CP anodes

normally consist of a silicon iron alloy, containing 14% to

17% silicon, and measuring 1,1 m long and 0,075 m

diameter. Centrifugally cast tubular anodes have proven to

be the most reliable and effective anodes at SASOL.

Generally an anode is defined as any metal in which current

flows from it to the electrolyte.

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ANODE (SACRIFICIAL) A metal which is more electro-negative in potential than

steel and which when buried or immersed confers protection

to the latter when electrically connected to it. For buried

pipelines sacrificial anodes generally consist of magnesium.

ANODIC AND CATHODIC

AREAS

See Corrosion.

BONDING CABINET A steel cabinet used to bond two or more pipelines

electrically.

BYPASS CURRENT The current drained from a pipeline to a railway line, when

the latter is at very negative potential. Under such conditions,

the transformer rectifier temporarily shuts down.

CATHODE (IMPRESSED

CURRENT)

Any buried or submerged metal which is connected to the

negative terminal of a transformer rectifier. Generally a

cathode is defined as any metal in which current flow is

always from the earth to the cathode.

CATHODIC PROTECTION An active electrochemical method of corrosion protection in

which all areas of a metallic surface are rendered cathodic.

CLOSE POTENTIAL

SURVEY

A technique whereby the pipe potential is measured every

metre along the length of the pipeline.

COKE An electrically conducting form of carbon. It is used in

granular form to surround each individual anode in order to

form one long extended anode, termed the anode groundbed.

It decreases the resistance to earth and increases the life ofthe individual anodes.

COKE BREEZE An inferior carbonaceous backfill material generally termed

metallurgical coke or coke breeze. It nominally contains less

than 85% fixed carbon and high amounts of sulphur and ash.

CONTINUITY BOND An electric cable welded to both sides of a potentially

insulating joint, such as a coupling or flange, in order to

ensure the electrical continuity.

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CONTRACTOR /

MANUFACTURER

Company engaged to perform the work covered by the

specification (successful supplier or bidder).

CORROSION An electrochemical process resulting in metal dissolution

and degradation. A buried or submerged metal forms anodic

and cathodic areas on its surface with consequent flow of

electric current between them. Corrosion occurs at the anodic

areas.

DATA SHEETS All necessary drawings, tabulations, sketches and relevant

documentation which SASOL will submit with a RFQ or PO,

to clearly indicate the technical, electrical and physical

requirements of the equipment, together with information

that is required to be submitted by the manufacturer.

DC DECOUPLING

DEVICE

A solid state device used for two main purposes. One is to

disconnect two metal systems, of which one is under CP and

the other is not, while at the same time permitting continuity

in any AC circuit, for example an earthing system connectedto a pipeline via this device. The other use is as a surge

arrester whereby it blocks DC voltages up to several volts,

but readily passes current at higher voltages (e.g. AC fault

currents and lightning). Its operation does not depend on the

moisture content of the soil, is easily inspected, tested and

more reliable than a polarisation cell or grounding cell.

DEEP WELL GROUND-

BED

One or more anodes installed vertically in a column, the top

most anode being at a nominal depth of 15 m or more below

the earths surface.

DRAIN POINT That part of the pipeline connected to the negative terminal

of the TRU.

EARTHING The technique of using a buried electrode in order to

decrease the voltage to earth of a particular structure.

ELECTRODE An electrode is a solid electrical conductor which discharges,

or picks up, current from an electrolyte.

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ELECTRODE

(REFERENCE

ELECTRODE [HALF

CELL])

The voltage difference between an electrode and the

electrolyte cannot be measured in absolute terms, but only

with respect to a special reference electrode, whose own

potential does not alter regardless of the solution in which it

is immersed. A reference electrode is also referred to as a

half cell. In CP of buried pipelines, a copper / copper

sulphate reference electrode (Cu / CuSO4) is used.

It consists of a copper rod in a saturated copper sulphatesolution, all housed in a suitable polymer housing and

possesses a porous plug at the bottom to permit current to

flow, enabling one to take potential measurements.

ELECTROLYSIS

(ELECTROLYTIC

CORROSION)

Electrolysis or electrolytic corrosion refers to the corrosion

caused by stray electric currents flowing in the ground. 1 A

flowing for 1 year corrodes 9 kg of steel.

ELECTROLYTE A medium, usually liquid, in which the flow of electric

current is by means of cations and anions. Typicalelectrolytes are water and its solutions, acids, etc., and the

soil.

EXOTHERMIC WELDING The universal method of welding a copper cable to a steel

surface. The method is quick and simple and generates far

less heat than brazing or arc welding, which would otherwise

damage the coating and lining. Pin brazing / stud welding is

a newer and quicker method, which generates far less heat

than exothermic welding, but is very costly in comparison.

FORCED DRAINAGE

UNIT

A transformer rectifier using the railway line as the anode is

referred to as a forced drainage unit.

FOREIGN SERVICE A structure lying or buried in the ground belonging to

another owner. Typical examples are pipelines, cables,

railway lines and electricity pylons.

GALVANIC CORROSION A form of corrosion caused by one metal in electrical

contact with another and at different natural potentials or

separated in the galvanic series.

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HALF CELL Another name for reference electrode. See Electrode.

HOLIDAY A defect in the structure coating system also referred to as

coating defects.

HOLIDAY DETECTOR An instrument for detecting coating defects.

HYGROSCOPIC A material that has a high affinity for water.

INORGANIC Compounds composed of elements other than carbon. A few

simple compounds of carbon including carbon monoxide,

carbon dioxide, carbonates and cyanides, are generally

considered inorganic.

INSULATING JOINT /

FLANGE

A joint which is electrically insulating. An insulating flange

normally consists of an insulating gasket, insulating bolt

sleeves and insulating washers. An insulating joint is a

complete joint consisting of insulating epoxies embedded in

a spigot and socket type joint. An insulating joint nominally

cost six to eight times more than an insulting flange.

METAL OXIDE

VARISTOR

A metal oxide varistor is an electrical device used as a

voltage arrester. It has a high resistance at low voltages and

low resistance at high voltages.

MONOLITHIC JOINT Immovable (flange-less) electrical insulating fitting rated to

handle the operating pipe pressure.

NATIVE STATE Natural state or potential of a pipeline or structure.

NATURAL DRAINAGEUNIT

A unidirectional bond from a pipeline to an electrifiedrailway line. It permits current flow only when the rail is at

negative potential and consists of one or more diodes, fuses,

surge arresters, etc. It is a passive device requiring no

external source of power.

NATURAL POTENTIAL Also called the corrosion potential. It is the potential of

steel buried in the ground without receiving current from an

external source.

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OVER PROTECTION When the pipe potential is too negative, the coating may be

damaged in the sense that it becomes detached from the steel

pipe, also referred to as cathodic disbondment. There is no

universal agreement as to what the maximum negative value

should be, but the most commonly accepted value of -2,5 V

is used, where no stray currents are present. This potential

must exclude the IR error associated with normal potential

measurements.

PIPE INVERT DEPTH Depth of ground cover from surface to the bottom of the

pipe.

PIPE OVERT DEPTH Depth of ground cover from surface to the top of the pipe.

PIPE POTENTIAL The voltage difference between a pipeline and a reference

electrode inserted in the ground (also known as pipe-to-soil

potential).

POLARISATION The change in metal potential upon passage of current. The

normal potential of steel in the ground is about -0,5 V and if

current enters it via the electrolyte the potential will become

more negative, say -1,0 V.

Polarisation can take place slowly over weeks or months, by

which the potential becomes even more negative and the

current required diminishes. The latter depends on the

coating quality.

POLARISATION CELL A DC electrolytic varistor / decoupling device. It consists of

two metal plates in a suitable electrolyte. The cell passes AC

at all voltages but blocks DC below a certain voltage, but

conducts above a certain voltage limit. By choosing different

metals and electrolytes a number of different blocking

voltages may be achieved. The steady state AC is generally

limited to 0,01% of the maximum surge current. The cells

need constant toping up and cleaning and are not as reliable

as a solid state device.

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PROTECTION LIMITS The limits in pipe potential between which a cathodically

protected pipe should operate. The lower limit is -0,95 V for

complete corrosion protection of the steel substrate, and the

upper limit is -2,5 V in order to avoid coating damage. The

value of -2,5 V is often impossible to adhere to in the

presence of stray currents.

PROTECTION

POTENTIAL

The minimum IR free pipe potential in order to achieve

protection. It varies from metal to metal. The protectionpotential for steel ranges between -0,85 V to -0,95 V

depending on the oxygen content of the electrolyte.

RAIL RECORDING The potential of the rail (fluctuation) recorded over time.

REVIEWED/REVIEWAL A formal 5-day hold period on the planning schedule while

SASOL reviews / considers the relevant information or

proposed deviations; all communication to be confirmed in

writing

SILICON IRON ANODES See Impressed Current Anode.

SOIL AND PIPELINE

VOLTAGE GRADIENTS

The voltage gradients arising in the soil in the immediate

vicinity of coating defects, as the current flows (CP or DC

traction) to the bare steel (coating defect) through, the soil.

SOIL RESISTIVITY The specific electrical resistance of the soil. The lower the

resistivity, the higher the corrosivity of the soil. It is

commonly measured on site by a technique called the

Wenner Four method.

STRAY CURRENTS (DC) The flow of DC electric currents in the ground which follow

a course other than that intended. The most frequent cause of

DC stray currents is from electrified railway lines, and of a

fluctuating nature. Another source is that from adjacent CP

systems.

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TEST POINT Consists of a cable welded to the pipe or cleated to the

inside of a chamber wall and connected to an insulated

stainless steel stud protruding through the wall. It permits a

quick and vandal resistant method of measuring the pipe

potential. The potential measurement will however, contain

the IR error.

TEST POST A free standing post protruding about 0,6 m above the

ground and containing a cable welded to the pipe andextending to the top in a suitable terminal. It permits the

ready determination of the On pipe potential at any

location.

TRANSFORMER

RECTIFIER UNIT

An electrical apparatus which converts AC voltages to low

DC voltages.

UNDER- PROTECTION When the pipe is only partially protected, which is indicated

by a potential of between -0,7 V to -0,85 V.

VIKING JOHNSON

COUPLING

A flexible coupling used to mechanically join two sections

of steel, plastic or concrete pipe materials.

VOLTAGE SURGES Also called voltage transients. A voltage, higher than

normal operating voltage, generally of short duration, which

enters the transformer rectifier or natural drainage unit

(NDU), either from the AC or DC side. It does great

damage unless measures are taken to contain it.

WENNER FOUR

ELECTRODE METHOD

A soil resistivity test method covered in ASTM G57,

utilising four electrodes spaced equidistant to one another.

The electrode separation distance equates to the average

depth measured in the soil. Current is injected into the outer

two electrodes and the potential drop is measured between

the inner two electrodes and the resistivity is then calculated.

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1.5 PRECEDENCE

Any conflict between the technical requirements stated in the RFQ or PO and the technical

requirements of this Specification shall be referred to SASOL for clarification. The

precedence of purchase documents is as follows:

a.

b.

c.

d.

1.6

1.7

The technical requirements specified in the RFQ or PO including terms, conditions

and legal requirements;

Data sheets;

This Specification;

Documents referenced in this Specification.

MATERIAL REQUIREMENTS

The material requirements shall detail all of the necessary drawings, tabulations, sketches,

technical data, materials specification and relevant documentation which will be issued with

a RFQ and / or PO.

The latter shall clearly indicate the technical, electrical, metallurgical and physical

requirements of any equipment, together with the information that is required to be

submitted by the manufacturer.

GUARANTEE PERIOD

The contractor shall guarantee the CP system for a 36 month period, which shall commence

from the date of commissioning.

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2 REFERENCE DOCUMENTS

Where reference is made to a code, specification or standard, the reference shall be taken to

mean the latest edition of the code, specification or standard, including addenda,

supplements and revisions thereto.

2.1 SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTH AFRICAN

BUREAU OF STANDARDS (SABS) CODES OF PRACTICE AND SPECIFICATIONS

SANS 10086-1 / SABS 086 The installation, inspection and maintenance of

equipment used in explosive atmospheres Part 1:

Installations including surface installations on mines

SANS 10089-2 / SABS 089-2 The petroleum industry Part 2: Electrical

installations in the distribution and marketing sector

SANS 10108 / SABS 0108 The classification of hazardous locations and the

selection of apparatus for use in such locations

SANS 10121 / SABS 0121 Cathodic protection of buried and submerged

structures

SANS 10142-1 / SABS 0142-1 The wiring of premises Part 1: Low-voltage

installations

SANS 10199 / SABS 0199 The design and installation of an earth electrode

specifications

SANS 122 / SABS 122 Pressure-sensitive adhesive tapes for electrical

purposes (Metric units)

SANS 1700-7 /SABS 1700-7 Fasteners Part 7: External drive hexagon bolts and

screws Section 1 - 10: Hexagon head bolts - Product

grades A and B

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SANS 1700-14 / SABS 1700-14 Hexagon nuts Section 1: Style 1 - Product grades A

and B

SANS 1700-7-2 / SABS 1700-7-2 Fasteners Part 7: External drive hexagon bolts and

screws Section 2: Hexagon head bolts - Product

grade B - Reduced shank (shank diameter

approximately equal to pitch diameter)


screws Section 3: Hexagon head bolts - Product

grade C


screws Section 4: Hexagon head screws - Product

grades A and B

SANS 1700-7-5 / SABS 1700-7-5 Fasteners Part 7: External drive hexagon bolts andscrews Section 5: Hexagon head screws - Product

grade C

SANS 1700-14-1 / SABS 1700-14-1 Fasteners Part 14: Hexagon nuts Section 1: Style 1 -

Product grades A and B

SANS 1700-14-2 / SABS 1700-14-2 Fasteners Part 14: Hexagon nuts Section 2: Style 2 -

Product grades A and B

SANS 1700-14-3 / SABS 1700-14-3 Fasteners Part 14: Hexagon nuts Section 3: Product

grade C

SANS 1700-14-4 / SABS 1700-14-4 Fasteners Part 14: Hexagon nuts Section 4: Hexagon

thin nuts (chamfered) - Product grades A and B

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SANS 32 / SABS EN 10240 Internal and / or external protective coatings for steel

tubes - Specification for hot dip galvanized coatings

applied in automatic plants

SANS 1411-1 / SABS 1411-1 Materials of insulated electric cables and flexible

cords Part 1: Conductors


cords Part 2: Poly-Vinyl-Chloride (PVC)


cords Part 3: Elastomers


cords Part 4: Cross-linked Polyethylene (XLPE)


cords Part 5: Halogen-free, flame-retardant materials


cords Part 6: Armour

SANS 1507-1 / SABS 1507-1 Electric cables with extruded solid dielectric

insulation for fixed installations (300 / 500 V to

1900 / 3300 V) Part 1: General


insulation for fixed installations (300 / 500 V to 1900

/ 3300 V) Part 2: Wiring cables



/ 3300 V) Part 3: PVC distribution cables

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1900 / 3300 V) Part 4: XLPE distribution cables



1900 / 3300 V) Part 5: Halogen-free distribution

cables



/ 3300 V) Part 6: Service cables

SANS 555 / SABS 555 Unused and reclaimed mineral insulating oils for

transformers and switchgear

SANS 1149 / SABS 1149 Flat and taper steel washers

2.2

2.3

SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTH AFRICAN

BUREAU OF STANDARDS / INTERNATIONAL ELECTROTECHNICAL

COMMISSION (SABS IEC) SPECIFICATIONS

SANS 60079-10 / SABS IEC 60079-10 Electrical apparatus for explosive gas

atmospheres Part 10: Classification of

hazardous areas

SOUTH AFRICAN NATIONAL STANDARDS (SANS) AND SOUTH AFRICAN

BUREAU OF STANDARDS / INTERNATIONAL ORGANISATION FOR

STANDARDISATION (SABS ISO) STANDARDS

SANS 121 / SABS ISO 1461 Hot dip galvanized coatings on fabricated iron and steel

articles - Specifications and test methods

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2.4 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) STANDARDS

ASME B31.4 Liquid transportation systems for hydrocarbons, liquid petroleum gas,

anhydrous ammonia and alcohols

ASME B31.8 Gas transmission and distribution systems

2.5

AMERICAN SOCIETY FOR THE TESTING OF MATERIALS (ASTM)

ASTM A325 Standard specification for structural bolts, steel and heat treated, 120 /

105 psi minimum tensile strength

ASTM A694 Standard specification for carbon and alloy steel forgings for pipe

flanges, fittings, valves and parts for high-pressure transmission

service

ASTM B265 Standard specification for titanium and titanium alloy strip, sheet andplate

ASTM B338 Standard specification for seamless and welded titanium and titanium

alloy tubes for condensers and heat exchangers

ASTM A518 Specification for corrosion resistant high silicon iron castings

ASTM B571 Standard practice for qualitative adhesion testing of metallic coatings

ASTM D149 Standard test method for dielectric breakdown voltage

ASTM D229 Standard test method for rigid sheet and plate material used for

electrical insulation

ASTM D293 Standard test method for sieve analysis of coke

ASTM D709 Standard test method for laminated thermosetting materials

ASTM D732 Standard test method for shear strength of plastics by punch tool

ASTM D785 Standard test method for Rockwell hardness of plastics and electrical

insulating materials

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ASTM D1248 Polyethylene plastic moulding and extrusion materials

ASTM D2000 Standard classification system for rubber products

ASTM D3222 Standard specification for unmodified Poly-Vinylidene Fluoride

(PVDF) moulding extrusion and coating material

ASTM E186 Standard reference radiographs for heavy walled (51 to 114 mm) steel

castings

ASTM G57 Method for field measurement of soil resistivity using the Wenner

Four Electrode method

2.6

2.7

AMERICAN PETROLEUM INSTITUTE (API)

API Std 620 Design and Construction of Large, Welded Low-Pressure Storage

Tanks

API Std 650 Welded Steel Tanks for Oil Storage

API RP651 Cathodic Protection of Aboveground Petroleum Storage Tanks

API RP1632 Cathodic Protection of Underground Petroleum Storage Tanks and

Piping Systems

API RP2003 Protection against Ignitions Arising out of Static, Lightning and Stray

Currents

NATIONAL ASSOCIATION OF CORROSION ENGINEERS (NACE) RECOMMENDED

PRACTICES

NACE RP0169 Control of external corrosion on under ground or submerged, metallic

piping systems

NACE RP0177 Mitigation of alternating current and lightning effects on metallic

structures and corrosion control systems

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NACE RP0186 Application of cathodic protection for well casings

NACE RP0193 External cathodic protection of on-grade carbon steel storage tank

bottoms

NACE RP0285 Corrosion control of under ground storage tank systems by cathodic

protection

NACE RP0286 Electrical isolation of cathodically protected pipelines

NACE RP0388 Impressed current cathodic protection of internal submerged surfaces

of steel water storage tanks

NACE RP0572 Design, installation, operation and maintenance of impressed current

deep groundbeds

NACE RP0575 Recommended practice for design, installation, operation and

maintenance of internal cathodic protection system in oil treating

vessels

NACE Pub10A190 Measurement techniques related to criteria for cathodic protection of

underground or submerged steel piping systems

2.8

BRITISH STANDARDS INSTITUTION (BS) SPECIFICATIONS

BS 171 Specification for power transformers

BS 1016 Method for analysing and testing of coal and coke

BS 1591 Specification for corrosion resisting high silicon iron castings

BS 1872 Specification of electroplated coatings on tin

BS 6001 (ISO 2859-1) Sampling procedures for inspection by attributes

Part 1: Specification for sampling plans indexed by acceptable quality

levels (AQL) for lot-by-lot inspection

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BS 7361 Cathodic Protection

Part 1: Code of practice for land and marine applications

2.9

2.10

2.11

2.12

RAL DEUTSCHES INSTITUT FR GTESICHERUNG UND KENNZEICHNUNG

RAL-FARBEN

RAL Specification for Colours for Identification, Coding and Special Purposes

DEUTSCHES INSTITUT FR NORMUNG (DIN)

DIN 30676 Design and application of cathodic protection of external surfaces

DIN 50918 Corrosion of metals, electrochemical corrosion tests

DIN 50925 Verification of the effectiveness of the cathodic protection of buried

structures

DIN 50929 Probability of corrosion of metallic materials when subject to corrosion from

the outside

INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC) PUBLICATIONS

IEC 60038 Standard voltages

IEC 60144 Degree of protection of enclosures for low voltage switchgear and control

gear

INTERNATIONAL ORGANISATION FOR STANDARDISATION (ISO) STANDARDS

ISO 2325 Method for analysing and testing of coal and coke

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ISO 2859-1 Sampling procedures for inspection by attributes

Part 1: Specification for sampling plans indexed by Acceptable

Quality Levels (AQL) For Lot-by-Lot inspection

ISO 8501-1 Preparation of steel substrates before application of paints and

related products

Part 1 to 3 and supplement 1994

ISO 13 623: 2000E CP monitoring plan

2.13

2.14

2.14.1

SWEDISH STANDARDS INSTITUTION (SIS) STANDARDS

SIS 05 59 00 Pictorial visual standards for surface preparation for the painting of steel

surfaces

SASOL SPECIFICATIONS, DATA SHEETS AND STANDARD DRAWINGS

Specifications

SP-40-3 Spare parts requirements

SP-50-6 Coating and wrapping of under ground steel pipe

SP-50-7 Design of under ground gravity sewers

SP-60-1 General electrical specification

SP-60-4 Low voltage switchgear and motor control centres

SP-60-10 Power and control cables rated 600 / 1000 V

SP-60-35 Earthing systems

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SP-60-37 Classification of hazardous locations and the selection of apparatus for use in

such locations

SP-60-47 Requirements for electrical engineering documentation

SP-90-32 Minimum requirements for SASOL engineering drawings

SP-90-37 End of job documentation deliverables

2.14.2

2.14.3

Data Sheets

E979 Spare Parts and Interchange-ability Record (SPIR)

Standard Drawings

STDD-6005CA Electrical CP general assembly G-026 to G-028

STDD-6005CB Electrical CP general assembly G-030

STDD-6005CD Electrical CP connection assembly G-034 to G-036

STDD-6005CN Electrical CP manual output transformer rectifier

STDD-6005CP Electrical CP details of thermit weld

STDD-6005CQ Electrical CP insulating flange

STDD-6005CR Electrical CP junction box test point

STDD-6005CS Electrical CP cabling at tanks located in tank farms

STDD-6005CT Electrical CP schematic diagram of variable voltage DC decoupler

STDD-6005CU Electrical CP encapsulating of anode head

STDD-6005CV Electrical CP electronic controller

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STDD-6005CW Electrical CP data logger post

STDD-6005CX Electrical CP potential test point details

STDD-6005CY Electrical CP insulating joint details

STDD-6005CZ Electrical CP high potential magnesium and cable connection details

3

3.1

3.1.1

3.1.2

3.1.3

CP SYSTEM REQUIREMENTS

SPECIALIST CP CONSULTANT AND CP CONTRACTOR

SASOL and / or the main contractor shall appoint a specialist sub-consultant in order to carry

out a detailed site survey, to permit the drafting of both a conceptual and detailed CP design,

should they be warranted. The detailed design shall only be carried out upon the reviewal of

the conceptual design by SASOL.

The design of the CP system shall be carried out by a SASOL approved consultant. The CP

consultant shall be completely independent as defined by the Southern African Association

of Consulting Engineers (SAACE). The main contractor shall assist the CP consultant with

drawings to permit the AFC drawings to be issued. The CP consultant shall prepare and

submit to the main contractor / SASOL a detailed list of all materials and equipment required

permitting the relevant RFQ document to be formulated.

The CP construction contractor shall install the CP field installation elements, concurrently

with the construction of the associated process plant and / or pipeline. The CP consultant

shall provide field engineering support and site supervision necessary to ensure the integrity

of the as-built CP installation. The CP consultant shall prepare a quality control plan for the

progressive checkout and acceptance of the CP installation and assist the main contractor in

its implementation.

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3.1.4 The CP consultant shall assist in the checkout, testing and commissioning of the installation

and the marking-up of AFC drawings to reflect the as-built status. He shall also submit a

final commissioning report in accordance with the requirements stipulated below.

3.2

3.2.1

a.

i)

ii)

iii)

iv)

ON SITE INVESTIGATIONS / SURVEY

The following surveys shall be carried out by the CP consultant prior to commencing with

the design:

Soil Corrosivity Survey

Distribution / transmission pipelines

Soil resistivity measurements shall be conducted nominally every 250 m along

the pipeline route in accordance with the Wenner Four Electrode Method, as

stipulated in ASTM G57 at pipe invert depth. Where corrosive areas are

encountered or at locations where temporary CP will be required or where it isto be anticipated, measurements will be conducted every 50 m or as required.

Alternatively, an electromagnetic soil conductivity meter may be used, on long

remote pipelines. Measurements shall be carried out every 50 m at pipe invert

and overt depth.

Soil samples shall be taken at pipe invert depth or proposed burial depth along

the pipeline route nominally every 1000 m. The samples shall be analysed and

assessed in accordance with DIN 90529 Part 1 to 3, in order to determine thePPI of the proposed or existing buried steel pipe.

The presence and probable magnitude of SRB shall be assessed every 1000 m

and / or at corrosive locations where the soil resistivity is less than 30 m.

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b. Petrochemical plants

i)

ii)

iii)

iv)

v)

3.2.2

a.

i)

ii)

Soil resistivity measurements shall be conducted accordance with the Wenner

Four Electrode Method, as stipulated in ASTM G57. The measurements shall be

carried out in a 50 m x 50 m grid section at a depth of 0,5 m, 1,5 m, 2,5 m and

3,5 m per grid section.

Soil samples shall be taken at pipe invert depth or proposed burial depth across

the site in accordance with BS 6001: Part1. The samples shall be analysed and

assessed in accordance with DIN 90529 Part 1 to 3, in order to determine the

PPI of the proposed or existing buried steel pipe.

The presence and probable magnitude of SRB shall be assessed per 50 m x

50 m grid section, but only where the soil resistivity is less than 30 m.

Where on-grade carbon steel storage tank bottoms are encountered, all of the

items described in Section 3, of NACE RP0193, shall be evaluated in full for

both new and existing tanks, in order to determine whether or not CP will be

required.

Redox measurements will not be carried out, as they are difficult to perform and

assess under normal site conditions.

Stray Current Survey


The presence and magnitude of DC traction stray currents shall be assessedprior to installation of the pipeline and / or after installation of any transmission

pipeline. In the absence of a pipeline, rail recordings and pipe to soil and

pipeline voltage gradient recordings shall be conducted at the foreign service(s).

This, however, shall only be conducted upon approval from the foreign

service(s) owner.

On long transmission pipelines, the possible presence and magnitude of telluric

(magnetic interference effects from solar storms and flares) effects, shall also be

determined.

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iii) All foreign service(s) shall be identified, as well as foreign CP system(s) which

may influence (positively and / or negatively) the SASOL system. Where

possible, the GPS co-ordinates shall be obtained and the data entered into the

existing SASOL GIS. Operating data shall be obtained from the railway

authority, including the polarity, operating voltage and power of the overhead

catenary.

iv)

b.

i)

ii)

iii)

Where transmission pipelines are located in close proximity of HVTL, where

resistive and / or capacitive and / or inductive coupling may occur, tests shall be

conducted in order to determine the extent of the interference. All of the

relevant data pertaining to the supply authority shall be obtained, as well as the

soil resistivity at a depth in the vicinity of the HVTL towers representative of

pipe invert and overt depths along the affected pipeline route. All data relating

to the power line transpositions shall be obtained, as well as the distance

between the pipeline and HVTL, including angles of convergence, divergence

and all earthing (earth mat or point) details.

Petrochemical plants

Tests shall be conducted to determine whether the adjacent CP systems will

introduce any form of stray current into the new plant.

The tests shall include but not be limited to obtaining natural potentials with all

of the CP system(s) de-energised. Measurements shall also be obtained with the

neighbouring CP systems re-energised one-by-one. The neighbouring TRU(s)

shall also be pulsed at a 1,1 Hz frequency and the pipe potential signal (On -

Off) influence be recorded, mapped and modelled.

Once the above surveys have been carried out, definitive recommendations can

be made as to whether CP is required or not. A conceptual CP design report

shall be issued to SASOL for reviewal, should CP deemed to be required. As

soon as the conceptual CP design has been reviewed by SASOL, the following

additional tests shall be carried out.

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3.2.3

a.

i)

ii)

iii)

iv)

v)

vi)

Anode Groundbed Survey

General considerations

When designing and / or selecting to use ICCP, consideration must be given to the

proper use and selection of the anode groundbed(s).

The groundbed location shall be determined early in the design process because its

location may affect the choice of which groundbed type may be best suited to a

particular application. The following factors should be considered when choosing a

groundbed location:

Soil resistivity and moisture content;

Interference with other structures;

Electrical shielding by structures;

Availability of power supply and site accessibility;

Vandalism or other damage (e.g. operational damage);

Purpose of the groundbed and availability of Right-of-Way or servitudes.

Horizontal (conventional) anode groundbeds are normally used to distribute the

protective current over a broad area of the structure requiring protection. These are

frequently called remote groundbeds because the structure is outside the anodic

gradient of the groundbed caused by the discharge of current from the anodes to the

surrounding soil. They may be continuous or discrete in construction as detailed in

Figure 1 and 2.

FIGURE 1 SHALLOW CONTINUOUS HORIZONTAL ANODE GROUNDBED

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FIGURE 2 SHALLOW DISCRETE HORIZONTAL ANODE GROUNDBED

b.

i)

ii)

iii)

Anode Groundbeds

Distributed Anode Groundbeds (2,5 m to 15 m deep) are used to reduce the

potential for interference effects on neighbouring structures. They are also used

to protect sections of bare or poorly coated structure. They are extensively used

in congested areas where electrical shielding may or will occur, if other types of

groundbeds are considered.

Deep Vertical Anode Groundbeds (30 m deep) are remote to the structure by

virtue of the vertical distance between the anode and structure. Deep anode

groundbeds therefore achieve results similar to remote horizontal (surface)

groundbeds. A deep anode groundbed is an appealing choice when space is not

available for a horizontal groundbed or when the surface soil has a high

resistivity and the deeper strata exhibit low resistivity. They should however,

not be used where electrical shielding can occur in congested plant areas.

Shallow Vertical Anode Groundbeds (15 m but 30 m deep) are commonly

used where space is limited and shielding might occur, as well as to mitigate

costs associated with a distributive anode groundbed system as shown in

Figure 3.

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FIGURE 3: DISTRIBUTIVE, DEEP AND SHALLOW VERTICAL ANODE BED

ARRANGEMENT

c.

i)

ii)


Preference shall be given to remote horizontal continuous or discrete anode

groundbed systems. Where servitude and / or Right-of-Way problems exist,

deep vertical anode groundbed systems shall be employed.

Where horizontal anode beds are to be installed, the soil resistivity shall be

measured at 20 m intervals along the entire length of the active anode bed

length at the proposed anode installation depth.

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iii) Soil resistivity measurements shall also be conducted at two, three, four and

five times the equivalent depth of the proposed anodes, at the beginning, half

way to the centre, centre, halfway between the centre and end and end of the

proposed anode bed, using the Wenner Four Electrode Method, as per

ASTM G57.

iv)

v)

vi)

d.

i)

ii)

iii)

The minimum distance between the pipeline and anode bed shall be two and

half times the length of the anode bed.

Where deep vertical anode groundbeds are required, the soil resistivity shall be

measured at a depth of 2 m, 4 m, 8 m, 16 m, 32 m, etc., until the final depth of

the proposed deep vertical anode groundbed is attained, using the Wenner Four

Electrode Method, as per ASTM G57. The values will be rechecked upon

drilling of the bore hole.

The minimum burial depth of the vertical anode bed (i.e. excluding the active

length) shall be determined according to the resistivity data obtained from the

bore hole, but shall nominally be two and a half times the active length of thebed.

Petrochemical plants

In uncongested areas, deep vertical anode groundbeds shall be the preferred

choice of anode groundbed systems.

In congested areas where electrical shielding can occur, only shallow vertical

and / or distributive anode groundbed systems shall be employed.

In both instances, the soil resistivity shall be measured at the active anode depth

of the proposed shallow vertical / distributive anode groundbed, using the

Wenner Four Electrode Method, as per ASTM G57. The values will be

rechecked upon the drilling of a test hole.

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3.2.4 Current Drainage (CD) Survey

a.

b.

c.

d.

e.

f.

g.

A CD test is conducted in order to calculate the total current required to confer

complete protection to the structure / pipeline. This is of utmost importance as the

current requirements determine the rating and number of TRUs required and the size

and rating of the anode groundbed(s). The current required is also used in order to

determine both the number and distribution (in conjunction with the soil resistivity

data) of the sacrificial anodes required.

This survey cannot generally be carried out on new structures / pipelines or during the

construction of a new process plant or during construction of new on-grade steel

storage tank(s), as construction schedules generally preclude such testing.

On existing pipelines and / or tanks the CD survey must be carried out.

During a CD survey, one essentially sets up a temporary CP system and injects a

known current into the structure(s) requiring protection via a suitable anode

groundbed. The latter may be a convenient fence or steel rods driven into the groundand the former may be a portable DC power source such as a car battery, AC

generator connected to a rectifier bridge, etc.

The pipe potential is measured along the pipeline / structure before (natural potential),

and after injection of current (On potential). The current is adjusted until adequate

protection is achieved over a meaningful length of pipe or meaningful area of the

structure requiring protection.

It must also be appreciated that the On potentials of the structure / pipeline will also

vary as a result of temperature variations and due to the fact that the On potentials

also contain a voltage drop as a result of the current flowing through the soil /

electrolyte.

From the magnitude of current required and the length of pipe and / or surface area of

the structure protected and taking into consideration the abovementioned variations,

one may proceed towards preparing a CP design based on the current requirements.

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3.2.5

a.

b.

c.

Electrical Continuity Survey

This survey is generally conducted on old pipelines where the method of construction

may not be fully documented and on newly constructed OWS lines. The survey entails

measuring the voltage drop along the pipeline(s), with CP current flowing.

A break in electrical continuity is indicated by a voltage drop and complete electrical

continuity is indicated by a direct short measured between the two points with

current flowing in the pipeline as shown in Figure 4a and 4b.

This survey is obligatory, as any break in electrical continuity will result in corrosion

occurring downstream of the break.

FIGURE 4a and 4b: CONTINUITY BONDED CHAMBER / FLEXIBLE COUPLING

FIGURE 4a:

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FIGURE 4b:

3.2.6

a.

b.

c.

d.

Other CP Requirements

All other aspects pertinent to the installation of a CP system shall be addressed. Theseinclude, but are not limited to the following:

Location of a suitable power source (public, plant and / or remote);

Location of river, rail and / or road crossing where casing will be required;

Location of test stations / points for CP, AC mitigation, foreign crossings, Insulating

Flanges (IF) or Insulating Joints (IJ);

Location of in-line valves, chambers, block valves, etc., etc., etc.

Once all of the above surveys have been carried out, a detailed CP design report will be

submitted to SASOL for reviewal.

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4 CATHODIC PROTECTION DETAILED DESIGN REQUIREMENTS

4.1

4.2

4.2.1

4.2.2

4.2.3

GENERAL CONSIDERATIONS

CP is perhaps the most important of all approaches to corrosion control. By means of an

externally applied electric current, corrosion may be reduced to virtually zero and the metal

surface may be exposed to a corrosive environment without any deterioration for an almost

indefinite period of time. CP is also one of the most economically viable methods available

in abating the corrosion process of submerged metallic structures.

COATINGS AND CP

Coatings (e.g. tape wrap systems, bitumen fibreglass, Fusion Bonded Epoxy (FBE), etc.)

applied to metal surfaces can be extremely effective in containing the corrosion of the steel

substrate in many environments.

However, no freshly applied coating is entirely free from defects and there will always be

small areas of steel which are exposed directly to the corrosive environment. It is possible to

reduce, but not eliminate these defects, by paying attention to workmanship. In practice it

becomes increasingly expensive to achieve fewer and fewer defects due to the need for high

quality inspection, detection and the repair of individual defects.

The coating provides the initial barrier against the corrosive environment and CP provides

protection at the coating defects. This apparently ideally complementary behaviour occurs as

a result of the low resistance path offered by the defects, as opposed to the high resistance

path offered by the coating.

A coating will deteriorate both chemically and mechanically during its lifetime. These results

in an increase in both the number of defects and the current required in order to protect the

newly exposed steel surface areas (defects).

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The defects will once again provide a low path of resistance and the CP current will flow to

it and provide protection, providing that it is of sufficient magnitude. This naturally implies

that the CP system must be designed such that it has sufficient reserve in order to provide the

necessary additional current.

4.2.4

4.2.5

In general, the choice of the coating system falls outside the scope of the CP Consultant.

However, the coating system must be compatible with the choice of CP utilised to protect the

structure.

Specification SP-50-6 must be complied with in full and any deviations must be reviewed by

SASOL prior to carrying out the work.

As a guideline, the protective coating system efficiencies should comply with the following:

COATING SYSTEM EFFICIENCY (%)

Three Layer FBE / Polypropylene > 98,5

FBE > 97,5

Polyethylene Tapes > 96

Cold Applied Mastics or Enamels > 95

Internal Pipe and Tank Linings > 94,5

Bitumen Fibre Glass Coatings > 92

External Epoxy Paint Coatings > 90

No Coating System 0

4.2.6

The pipeline shall be backfilled in accordance with ASME B31.4 / 8. This implies a selected

pipeline backfill material (size less than 9 mm) free from sharp objects, rocks, stones or any

other material which may damage the coating system. Pipelines located in the same trench

should nominally be separated by at least one and a half times the diameter of the largest

pipe, in order to prevent shielding.

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4.2.7 Where concrete encasement of the pipe is required, such as at river crossings, the reinforcing

steel shall be electrically isolated from the steel pipe. The pipeline shall be wrapped as per

Specification SP-50-6 prior to being concrete encased.

4.2.8

4.2.9

4.2.10

4.3

4.3.1

4.3.2

All buried pipelines when entering, passing through or leaving a chamber, reservoir, or any

concrete structure shall ensure a minimum clearance of 50 mm from the steel reinforcing and

the pipe or pipe puddle flange and shall be completely wrapped / coated as per Specification

SP-50-6 in the concrete covered section.

Pipeline sections which will be located inside chambers that may become flooded from time

to time or which will be continuously flooded, shall be wrapped / coated as per Specification

SP-50-6. Sacrificial magnesium anodes shall be employed to protect the pipeline or pipe

section in these chambers.

A DCVG survey shall be conducted on all transmission and distribution lines afterconstruction, in order to assess the condition of the coating subsequent to construction. The

pipeline construction contractor shall be responsible for the repair of all major defects

identified during the DCVG survey. Some 10 % of the defects will be exposed in order to

delineate defects and compare them to the DCVG % IR values prior to prioritising defects

for repair.

CHOICE OF CP SYSTEM

CP may be achieved by means of ICCP or SACP. The choice of which system to use shall be

based on both technical and economic factors.

ICCP utilises a TRU, which is supplied by a 230 V, 400 V or 525 V AC supply and produces

a low voltage direct current. The negative terminal of the TRU is connected to the structure

(tank / pipe), which becomes the cathode, and the positive terminal to an anode or a series of

anodes buried in the ground. This set-up is generally termed an anode groundbed.

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Current flows from the anode to the cathode through the electrolyte (soil or ground), and

provided it is of an adequate magnitude, protection will be attained.

4.3.3

4.3.4

4.4

4.4.1

a.

b.

c.

d.

e.

f.

g.

h.

i.

A SACP system does not need an external source of power. It exploits the difference in

potential of various metals in the galvanic series and generates its own voltage, much like a

battery. For example, magnesium possess a natural potential of -1700 mV and steel a natural

potential of -500 mV with regard to a saturated copper / copper sulphate reference electrode.

Therefore, the two combined will produce a driving voltage of approximately 1200 mV.

If the structure is subject to moderate to sever