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Small write up about cathodic protectionFull description
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Deepwater offkhore structures am now quite corumom however a deep water development project still &uims significant capital investment on the part of the operator. Corrosion failure is not …Full description
Cathodic Protection ReportFull description
Cathodic ProtectionFull description
cathodic protection spec
Cathodic ProtectionFull description
Cathodic Protection Report
Parsons Document Number EGP3-07-SP-040-403-030
CHEVRON NIGERIA LIMITED ESCRAVOS GAS PROJECT – PHASE 3 DEVELOPMENT - ONSHORE SPECIFICATION NUMBER EGP3–02.01 CATHODIC PROTECTION
Issued for ITB
January 22, 2004
Revised for ITB3
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REVISION RECORD SHEET
Revisions numbers shall be A, B, C, etc. up through the issue for Invitation to Bid.
The issue for Invitation to Bid shall be Revision 0.
iii.) Revisions after the issue for Invitation to Bid shall be 1, 2, 3, etc. Any revisions made after Revision 0 shall be denoted by a vertical line in the left hand margin against the revised text. iv.) A brief description of the key changes made in each revision shall be included on this page.
DESCRIPTION OF REVISION
Based on Chevron Specification 02.01
Updated for EGP3 standards and definitions.
Removed cathodic protection for piles thoughout spec
Changed from zone to division type area classification.
Changed oil filled transformers to dry type.
Issued for Parsons Review/CNL Review and Comments
Issued for ITB
Revised for ITB3 – no changes
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TABLE OF CONTENTS PAGE
1.0 SCOPE & DEFINITIONS
2.1 Industry Codes
2.2 Project Specifications
2.3 Standard Drawings
3.0 RESPONSIBILITIES AND PRECEDENCE
4.0 GENERAL DESIGN PHILOSOPHY
4.2 Protection Method
4.3 Temporary Protection
4.4 Protection Criteria
5.2 Soil Surveys
5.3 Water Circulation and Storage Systems
6.0 DESIGN CONSIDERATIONS
6.1 Electrical Isolation
6.2 Design of Electrical Isolation for Pipework
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6.4 Monitoring Facilities
7.0 ELECTRICAL CABLING AND CONNECTIONS
7.1 Cable Requirements
7.2 Junction Boxes
7.3 Cable Connection Requirements
8.0 SPECIFIC REQUIREMENTS FOR IMPRESSED CURRENT SYSTEMS
8.2 Backfill Material
8.4 Installation Requirements
9.0 SPECIFIC REQUIREMENTS FOR SACRIFICIAL ANODE SYSTEMS
10.0 AVOIDANCE OF ELECTRICAL INTERFERENCE AFFECTS
11.0 INSPECTION AND TESTING OF EQUIPMENT
11.2 Impressed Current Anodes
11.3 Sacrificial Anodes
11.4 Transformer – Rectifiers
11.5 Isolation Joints
11.7 Junction Boxes and Surge Arrestors
12.0 SITE ACCEPTANCE TESTING AND COMMISSIONING 12.1 General January, 2004
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12.2 Transformer – Rectifiers
12.3 Isolation Joints
12.4 Cable Connections
12.5 Pipe Sleeves
12.6 Buried Structures
13.1 Design Specification
13.2 Installation and Commissioning Procedures
13.3 Operating and Maintenance Manuals
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SCOPE & DEFINITIONS 1.1
Scope The purpose of this Engineering standard is to define the minimum requirements for the design, manufacturing, inspection, testing, installation and commissioning of the cathodic protection systems for the ESCRAVOS Gas EGP3 Project. This Engineering Standard covers the following items:
● All direct buried or immersed metallic pipework ● All direct buried metallic vessels and tanks ● All above ground, storage tank base plates in direct contact with backfill materials ● Internal surfaces of water tanks Exceptions to the scope on the basis of high soil resistivities or other factors that indicate corrosion rates would be minimal, and/or cathodic protection would not be economical, and alternative corrosion protection systems would provide adequate life shall be subject to COMPANY review and approval on a case-bycase basis. CONTRACTOR shall notify COMPANY of any conflicts between this specification and other project documents or referenced industry standards.
Definitions Definitions used in this specification are as follows: "COMPANY" is defined as CNL "CONTRACTOR" is defined as EPC Contractor "SUPPLIER or SUB-CONTRACTOR" is defined as companies supplying material, equipment or services to the CONTRACTOR. "FEED CONTRACTOR" is defined as Parsons "PROJECT" is defined as the EGP3 Onshore Project
REFERENCES The following documents are hereby referenced and are considered part of this specification:
Industry Codes NACE RP0169
Control of External Corrosion on Submerged Metallic Piping Systems Specification EGP3-02.01
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Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems
External Cathodic Protection of On-Grade Metallic Storage Tank Bottoms.
Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks
Corrosion Control of Underground Storage Tank Systems by Cathodic Protection
The Electrical Isolation of Cathodically Protected Pipelines
Impressed Current Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks
Design, Installation, Operation and Impressed Current Deep Groundbeds
Standard Specification for Titanium and Titanium Alloy Strip, Sheet and Plate.
Cathodic Protection of Aboveground Petroleum Storage Tanks.
Cathodic Protection of Underground Petroleum Storage Tanks and Piping Systems.EGP3-12.01 General Electrical
Responsibilities CONTRACTOR shall be responsible for verifying the final scope of cathodic protection and for the final detailed design in accordance with the requirements of this Engineering Standard and industry codes and standards. CONTRACTOR shall identify all metallic, direct buried pipes and pipelines where failure would result in risk to health, safety or the environment and/or plant operability and submit a detailed scope for COMPANY review and approval. As a minimum, all hydrocarbon and closed drains shall be included. CONTRACTOR shall ensure that the requirements specified herein are incorporated into any procurement specifications, material or sub-contract requisitions and/or other purchase documentation produced by, or on behalf of, CONTRACTOR.
Precedence Any conflict between this Engineering Standard, other COMPANY documentation, industry codes and standards and local regulations shall be referred to COMPANY for clarification prior to proceeding. Any deviations to the requirements of this Engineering Standard shall be subject to COMPANY review and approval before proceeding.
GENERAL DESIGN PHILOSOPHY 4.1
The cathodic protection system shall be designed in accordance with the requirements of this Engineering Standard and the applicable sections of the following: Referenced Standards(1)(2)
Component Onshore buried pipework
NACE RP0169, NACE RP0177, BS 7361, Pt.1
Onshore buried vessels and tanks
NACE RP0285, BS7361, Pt.1
Internals of water storage tanks
Aboveground, storage tank base plates
NACE RP0193, API RP651
Standards and other documents referenced within the text of the above standards shall also apply to the design of the cathodic protection system as applicable and shall form part of the CONTRACTOR’s design submission for COMPANY review and approval. Specification EGP3-02.01
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Where the text of the above referenced standards uses the word ”should”, this shall be replaced by “shall” to indicate a mandatory requirement. Any deviation to this shall be subject to COMPANY review and approval.
The cathodic protection system shall be designed to protect each of the structures in paragraph 4.1.1 continuously for a minimum period of 30 years.
CONTRACTOR shall ensure that the design of the cathodic protection system is performed by a competent, experienced person, holding certification by NACE International as a Cathodic Protection Specialist, or equivalent national or international certification. CONTRACTOR shall submit such evidence to COMPANY for review.
Equipment and materials shall be selected, designed and manufactured for continual operation under the applicable site conditions. CONTRACTOR shall ensure that due consideration is taken of the tropical, marine environment with potentially corrosive saline conditions, in the design and specification of the cathodic protection system.
CONTRACTOR shall ensure that the impact of the electrical grounding system is included in the design of the cathodic protection system. Positioning of electrical ground rods in the immediate vicinity of cathodically protected structures should be minimized as much as possible. Ground rods that will be electrically continuous with a cathodic protected structure shall be hot-dipped galvanized steel.
Unless otherwise agreed with COMPANY, the following shall apply:
● For cathodic protection of above ground storage tank base plates, 10% of the base plate area shall be considered to have no external coating to allow for coating damage during base plate installation and welding. The operating temperature of the tank shall determine the appropriate current density to be used.
● For cathodic protection of other buried structures, the calculated current requirement shall be increased by an additional 25% to allow for current leakage
● For cathodic protection of the internal surface of water tanks and vessels, the anode sizing and number shall satisfy both the weight requirement to achieve the design life and the current requirement (i.e. the current demand necessary to achieve and maintain protection).
Protection Method 4.2.1
An impressed current system shall be designed and installed for the following:-
● Buried metallic vessels and tanks
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● Aboveground storage tank bottom plates; firewater and condensate storage tanks, as a minimum, shall be included unless the tank is constructed on a concrete pad. Anodes and header cables shall be installed during the construction of the foundation. Use the largest depth of clean “washed” sand fill as practical - allowing anodes to be placed farther from the tank bottom and requiring fewer anodes. Sand shall be considered “clean” if testing shows that it has a maximum of 50 ppm of chlorides. 4.2.2
As an exception to the above requirements, sacrificial anodes may be permitted for the following, subject to COMPANY review and approval:
● Buried metallic vessels and tanks ● Short, buried sections of normally aboveground metallic pipework, such as at road crossings, piping through bund walls etc.
● To locally supplement impressed current systems in areas of shielding or current drainage 4.2.3
Sacrificial anodes shall be installed for the following. The use of an impressed current system in these instances shall be subject to COMPANY review and approval:-
● The internal surfaces of the firewater tank ● The internal surfaces of sumps and other vessels which will contain water
● Coated metallic buried or immersed pipework
The number, location, and type of anodes shall be sufficient to ensure the required current density is applied in a uniform manner throughout the structure under protection. Details of all positions where anodes are placed shall be indicated on drawings and submitted for COMPANY review.
The use of more specialized cathodic protection techniques shall be subject to COMPANY review and approval.
Temporary Protection 4.3.1
Temporary cathodic protection is required for impressed current systems when the period between installation and commissioning of the system exceeds six months and may be obtained either by installing temporary power to the transformer-rectifier and gradually energizing the impressed current system or by installation of temporary sacrificial anodes.
CONTRACTOR shall advise COMPANY of its proposed method of temporary protection and ensure that suitable provision is made for the installation, operation, and monitoring of this temporary protection prior to commissioning of the permanent impressed current system. The facility Specification EGP3-02.01
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for final isolation of temporary sacrificial anodes shall be provided.
Protection Criteria 4.4.1
CONTRACTOR shall advise COMPANY of the protection potentials, coating breakdown factors, and current densities used for the design of the cathodic protection systems. The values shall take into account metallurgy, protective coatings applied, process conditions, and the surrounding environment.
The cathodic protection systems shall be designed so that the measured structure-to-electrolyte potentials fall within the following recommended ranges:-
The above values are based upon protection of iron and steel
2. CONTRACTOR shall check the values against the coating systems chosen and submit for COMPANY review. 4.4.3
The following current density values are the minimum recommended values for design of cathodic protection systems for buried or immersed metallic pipework, vessels, internal surfaces of water tanks, and aboveground storage tank bottom plates: Protective Coating
Notes:1. The above values of current density do not account for coating breakdown during the design life. 2. CONTRACTOR shall check minimum values against the coating systems chosen and soil resistivity and submit for COMPANY review.
For marine steel structures, coating breakdown factors and current densities shall be per DNV RP B401. CONTRACTOR shall clearly specify coating breakdown factors and the initial, mean, and final current density values and submit for COMPANY review and approval.
CONTRACTOR may recommend lower values of current density where they are supported by established data from systems of similar design, coating system, and environment, and offer economic advantage in the design. Any recommended values shall be submitted to COMPANY for review and approval.
CONTRACTOR shall handle and install materials in such a manner that coating damage is minimized. CONTRACTOR shall ensure that any anticipated coating damage because of handling and installation is included in the design of the cathodic protection system as bare metal surface.
General CONTRACTOR shall perform surveys in those areas where the protected structures and cathodic protection systems are to be situated. The surveys shall be performed such that the most severe environmental, seasonal, and tidal conditions are accounted for.
Soil Surveys 5.2.1
For buried equipment and aboveground storage tanks, the soil surveys shall be performed per ASTM G57, and include the following measurements as a minimum:
CONTRACTOR shall conduct soil surveys over a representative sample of the anode installation locations. If a remote surface anode bed design is proposed, soil surveys at 10m intervals over the full length of the proposed location shall be performed.
For aboveground storage tanks that have a flexible membrane installed as part of the foundation design, resistivity measurements of the sand foundation fill shall be performed to support calculations regarding impressed current systems. CONTRACTOR shall ensure that these resistivity measurements are performed sufficiently well in advance of the installation of the foundation fill to permit design of the impressed current system and shall be re-confirmed once the cathodic protection system is installed and the foundation backfilled but prior to installation of the tank base plates.
Resistivity measurements shall be made using a non-contact electromagnetic instrument (e.g. Geonics), to a depth commensurate with the burial depth, for soil resistivities in excess of 1000 ohm-cm and the Wenner 4-pin method for soil resistivities of 1000 ohm-cm or less.
Where it is suspected that conditions may support microbial activity, then the design should be based upon anaerobic conditions. In this case, further detailed investigation is not required. Any further soil investigations to justify a design based upon aerobic conditions (no microbial activity) shall be subject to COMPANY review and approval.
Any specialized soil surveys that may be required shall be performed by a specialist SUB-CONTRACTOR, appointed by CONTRACTOR and subject to COMPANY review and approval. The appointed specialist shall define and supervise any necessary measurements to assess the nature and likelihood of the particular concern. Specialized surveys include investigation of the likelihood and effect of microbial activity and soil conditions that may contribute to the deterioration of concrete. These surveys may include measurement of in-situ soil redox potentials, sulphates, sulphides, carbonate, total dissolved solids, and dissolved oxygen content.
CONTRACTOR shall ensure that any changes to the soil conditions in the areas subject to survey are accounted for in determining the measurements.
Water Circulation and Storage Systems For onshore water based systems, water samples shall be taken to measure the following as a minimum:
● Conductivity ● Dissolved oxygen content ● pH
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DESIGN CONSIDERATIONS 6.1
Electrical Isolation 6.1.1
Installation of isolating devices shall be minimized within the plant facilities due to the risk of arcing and interference problems and shall only be installed where necessary to limit flow of current from cathodically protected structures. Isolating devices shall not be installed in Class 1, Division 1 hazardous areas.
Electrical isolation shall be achieved by use of either monobloc isolating joints, isolating spools, or isolating flanges in accordance with NACE RP0286, and the rules described here within. Pre-assembled and pretested joints should be provided where possible. Any work involving electrical connections should be performed with the cathodic protection power source turned off.
CONTRACTOR shall review the need for electrical isolation at the following locations in its design submission:
● Between buried pipework or equipment and aboveground pipework or equipment
● Between buried pipework and equipment with different external protective coatings
● Between aboveground storage tank nozzles and aboveground pipework
● At the connection to structures protected by a separate cathodic protection system
● Electrical and instrument cable conduit and/or cable armour or lead sheathing
● Reinforcing steel in concrete ● Steel casings at road crossings ● Steel supports ● Electrical earthing systems 6.1.4
Design of Electrical Isolation for Pipework 6.2.1
There may be circumstances where the isolation requirements above may not apply. CONTRACTOR shall clearly define where electrical isolation is to be applied.
Isolating joints/flanges shall not be direct buried, but shall be installed either aboveground or in a dry inspection pit, for ease of inspection and maintenance. Specification EGP3-02.01
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High voltage protection shall be provided by installing zinc earthing cells across isolating joints. These shall be included where there is a risk that the protected structures offer a path for high voltages, sources of which include; local power systems, risk of lightening strikes, and process fluid static build up.
All isolation flanges shall have non-metallic flange covers to protect against ingress of dirt and moisture. The covers shall be of a contrasting color and include a suitable warning sign to identify it as a cathodic protection isolation joint.
All isolation joints shall be provided with test stations. These may include bond boxes and/or resistive bonds depending on the purpose of the joint.
Bonding connections shall be used as far as practicable to interconnect isolated metallic structures within the scope of a given cathodic protection system.
Bonds shall be applied across all non-welded joints to ensure electrical continuity of pipes and pipelines.
Bond boxes shall be provided between parallel underground pipelines.
Bond boxes shall be provided between adjacent structures with separate cathodically protected systems.
Bond boxes shall also be provided at isolation joints that are used for separation of adjacent cathodic protection systems or in the management of interference effects.
Monitoring Facilities 6.4.1
Permanent potential test boxes shall be installed at the following locations, as a minimum, to verify the effectiveness of the cathodic protection system:
● Locations as defined in paragraph 4.5 of NACE RP0169 ● Every 500m (or less) for on-plot buried pipework ● At each buried vessel or tank ● At each aboveground storage tank ● At each water tank, if internally cathodically protected 6.4.2
Permanent test points shall be installed at each isolating joint in accordance with the requirements of Section 7.4 of NACE Standard RP0286.
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At least one permanent reference electrode shall be installed for each protected structure. This is in order to provide an easily accessible potential measurement reading. For aboveground storage tanks, the number of permanent reference electrodes shall be in accordance with paragraph 11.2.4 of NACE RP0193.
Additional permanent reference electrodes shall be provided with the potential monitoring stations, where high soil IR drops are encountered, and/or representative protection measurements by portable reference electrode cannot be easily made.
Buried reference electrodes shall be installed in a backfill material, such as gypsum, that provides a stable, uniform environment, capable of retaining moisture.
Separate test polarization coupons should be combined with buried permanent reference electrodes in the following circumstances:-
● High soil IR drop ● Possibility of stray currents ● Monitoring of buried sacrificial anodes 6.4.7
Copper/copper sulphate reference electrode combinations shall be used in combination with soil and fresh water unless otherwise agreed with COMPANY.
The use of alternative reference electrodes shall be subject to COMPANY review and approval.
Each monitoring station shall be given a unique tag number for future identification and reference against monitoring records.
6.4.10 In addition to the permanent reference electrodes for aboveground storage tanks, slotted pipes (50mm diameter) shall be installed across the diameter of the tank foundation. The slotted pipe material shall be suitable for the normal operational temperature of the tank and shall be wrapped with a low weight, water permeable textile to prevent sand entering the pipe during compaction. Permanent access points for the temporary installation of portable reference electrodes beneath the tank periphery shall be installed through the ring wall. CONTRACTOR shall ensure that the slotted pipes and access tubes are installed during the ring wall construction and do not clash or interfere with other structures, pipes etc. and that adequate access is provided for insertion/pulling of the reference electrodes during monitoring activities.
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ELECTRICAL CABLING AND CONNECTIONS 7.1
Cable Requirements 7.1.1
Cables shall be copper, sized to minimize the voltage drop throughout the system to less than 2V. The minimum cable sizes shall be as follows:
● AWG #4 or 25mm² for DC power and bonding cables ● AWG #6 or 16mm2 for anode cables ● AWG #10 or 6mm2 for test cables 7.1.2
Cable insulation shall be suitable for the environment in which it is installed. All cable insulation shall have a 100V rating, as a minimum. DC power cable insulation shall be rated for 600V minimum. The following requirements shall also be met:
● For onshore buried cables, insulation shall be either double layer polyvinylchloride (PVC/PVC), polyethylene (PE/PE), or cross-linked polyethylene-polyvinylchloride (XLPE/PVC) as a minimum. CONTRACTOR shall provide additional protective sheathing for rocky or aggressive soil conditions
● For cables installed in a marine environment, insulating materials shall be resistant to both water and chlorides. Cables shall be either double layer polypropylene (PP/PP), ethylene propylene rubber/chlorosulphonated polyethylene (EPR/CSP), neoprene or chloroprene, and shall be completely waterproofed. Protection shall be provided
● Where cable is buried in congested areas or areas potentially subject to frequent excavation or damage, the cables shall be either run in a conduit, be armored, or be protected by other suitable method
All buried cables shall be installed at least 600mm below grade and without splices. Cable connections shall only be made aboveground and be tagged with identification labels. CONTRACTOR shall install route markers to identify the presence of buried cables at intervals of not more than 100m. Buried cables shall be installed with at least one relief loop underground.
Where underground cable splice joints are unavoidable, then a “Scotchcast” epoxy resin kit, or similar, shall be used for sealing the joint.
All above ground cables shall be encased in armored cable and/or cable trays. If armored cable is used, this shall be isolated from any earthing system.
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Junction Boxes 7.2.1
All connections, including anode cables, above ground splices, test leads, surge arrestors, bonding, reference electrodes, and negative connections, shall be made in junction/test/bond boxes, certified for the hazardous area classification in which they are installed.
Weatherproofing of junction boxes shall meet the minimum degree of protection NEMA 4X/IP56 in accordance with EGP3-12.01.
Junction boxes for plants containing hazardous areas, shall meet the requirements of EGP3-12.01. Junction boxes shall not be installed in Class 1, Division 1 areas.
All junction/test/bond boxes shall be identified by a unique number, shall be accessible at all times, and shall be constructed to prevent unauthorized entry, vandalism or damage.
All cables being brought above ground shall enter a junction box via a buried conduit or other suitable protective shroud, and entrance shall be by a COMPANY approved fitting/gland.
All cables inside junction/test/bond boxes shall be identified with suitable tags or labels to indicate the structures to which they are connected.
Cable Connection Requirements 7.3.1
Connection of cables to structures shall ensure that an electrically conductive and mechanically secure bond is made. The following are acceptable methods of connection:-
The minimum welded plate size shall be 50mm x 50mm x 6mm.
All connections shall be made a minimum of 50mm from other welded joints.
Thermite brazed connections shall be limited to 15gramme cartridge size with a maximum cable size of AWG #6 or 16mm². Multiple cable connections will be necessary for negative connections. Thermite brazing shall not be used with austenitic stainless of duplex steels.
The connection method shall take into account metallurgical, welding, and inspection requirements for the base material. Specific attention shall be paid to satisfying the base metal hardness limits. Specification EGP3-02.01
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Connections shall be made prior to testing of pipe, as far as practically allowed by the pipe spool fabrication method and testing sequence.
Where connections are to be made to internally lined piping, they shall be made prior to the installation of the internal protective coating/lining, or by low heat input methods that ensure no damage occurs to the internal lining. Alternative methods shall be submitted to COMPANY for review and approval.
Coating repairs to structures after installation of cable connections shall be performed in accordance with the original protective coating specification. Epoxy resin cast seals may be an acceptable alternative method to repair coating damage. All alternative methods shall be subject to COMPANY review and approval.
SPECIFIC REQUIREMENTS FOR IMPRESSED CURRENT SYSTEMS 8.1
Anodes shall be selected from the following types:-
● High silicon cast iron, with chromium ● Mixed metal oxide (MMO)on a noble metal (such as titanium or platinum),
● Platinized titanium or niobium 8.1.2
For aboveground storage tanks that have a flexible membrane installed as part of the foundation design, MMO/Ti anode systems shall be installed with the following requirements:
● For MMO/Ti systems, all titanium ribbon, conductor bars and connector assemblies shall be manufactured from ASTM B265, Ti, Gr.1 or COMPANY approved equivalent. The titanium ribbon anode, with the exception of the titanium conductor bar, shall be coated with a mixed metal oxide layer. CONTRACTOR shall confirm the minimum dimensions of the ribbon and conductor bar during detailed design.
● Multiple power feed cables from the anode junction box to the central conductor bar shall be provided and the central conductor bar shall be interconnected to the other conductor bars. The connections between the cables and the central conductor bar shall be factory made, tested and epoxy encapsulated for water tightness. No field joints/splices shall be permitted below the tank base plates.
● A secondary, complete, redundant MMO/Ti anode grid with power feed cables shall be installed during foundation construction.
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The number, size and spacing of MMO/Ti grid anodes shall ensure a sufficient structure-to-soil potential is met over the entire surface area of the base plates. Maximum spacing between the ribbon anodes shall not exceed three times the actual distance between the anode grid and the tank base plates or 1.75m, whichever is less, unless otherwise recommended by the anode manufacturer and agreed with COMPANY.
Alternative anode selections shall be subject to COMPANY review and approval.
Anode lead wires shall be one continuous length with no breaks. Splicing shall be avoided.
Backfill Material 8.2.1
Backfill for anode beds shall be calcined petroleum coke breeze, with a low sulphur content (4% or less).
For deep groundbeds, calcined fluid petroleum coke breeze in accordance with the minimum requirements of NACE RP0572 shall be used.
Other low resistivity back fill materials may be proposed for COMPANY review and approval, where the ground conditions dictate.
Pre-packaged anodes, where used, shall be supplied with pre-compacted calcined fluid petroleum type coke breeze.
Backfill under aboveground storage tanks shall be clean, “washed” sand with a maximum of 50 ppm of chlorides.
Transformer-rectifiers (T/R’s) shall be specifically designed for cathodic protection duties, and shall meet the minimum requirements of this Engineering Standard.
The T/R shall be dry type for outdoor applications, with double wound transformer and silicon diode rectifier, and supplied with sunshade for outdoor installations. Dry type T/R’s may be used for indoor installations. Electronic switched mode T/R’s shall be subject to COMPANY review and approval.
T/R’s shall be installed in non-hazardous areas wherever possible. If this is not practicable, the T/R shall be an oil immersed type and shall meet all hazardous area classification requirements for the area into which it is installed. T/R’s shall not be installed into Class 1, Division 1 areas. The T/R shall have a minimum degree of protection of NEMA 4X/IP56 in accordance with EGP3-12.01. In all cases, T/R’s shall be protected from damage by vehicular traffic by four concrete-filled steel posts or COMPANY approved alternative.
The rectifier shall comply with the requirements of EGP3-12.16. Specification EGP3-02.01
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The T/R shall be sized to provide a minimum 25% spare capacity of both voltage and current requirement determined during detailed design of the cathodic protection system.
The T/R unit shall be designed to withstand power surges, lightning strikes, and short circuits of up to 15 seconds duration.
The rectifier output current RMS ripple shall be limited to less than 5% of the DC output current, through the range 5% to 100% of the full rated current output.
The current rating of silicon diodes shall be at least 1.25 times the full current rating of the rectifier.
The T/R shall be provided with continuous reading, flush-mounted DC voltmeter and ammeter for displaying the measured output voltage and current. Meters shall be accurate to within 2% of full scale value and shall be linear from zero to full scale value. Digital meters are also acceptable.
8.3.10 Control switches and meters shall be accessible and mounted as close as possible to eye level. 8.3.11 Stepless adjustment should be used where practical. Stepped manual control may be used for onshore buried structures where a low variation in output current is expected. Where stepped control is used, then this shall be by front mounted switches with a maximum step size of 5% of the full rated voltage. Detachable links or jumps shall not be used. For the T/R of the system for the internal surfaces of the firewater storage tank , the output voltage shall be controlled to provide a constant structure-toelectrolyte potential using an electrical or electronic automatic control circuit. 8.3.12 The T/R shall be provided with an “ON/OFF” timer unit and circuit interrupter on the DC output capable of switching the full output current for 2 minutes ON and 3 minutes OFF. If the system is protected by more than one T/R, then the timer units shall be provided with synchronous switching. The timer unit shall be provided with a bypass for normal operation. 8.3.13 A power failure signal shall be provided from the T/R for feed back to a centralized control room.
Installation Requirements 8.4.1
Impressed current systems shall be installed in accordance with the requirements of the standards referenced in this specification.
Groundbeds may be either shallow or deep. Deep groundbeds shall be installed in accordance with the requirements of NACE RP0572.
For deep groundbeds, the fluidized calcined petroleum coke breeze shall be pumped from the bottom of the hole, and not gravity fed from the top. Specification EGP3-02.01
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Groundbed anodes shall be centered within the coke breeze envelope.
For deep groundbeds, the following additional requirements shall be met:
● Subsurface strata shall be logged at 1500mm intervals and at all formation changes. sediment.
CONTRACTOR shall note the type of rock or
● Before installing anodes, each hole shall be electrically logged at 1500mm intervals, and anodes placed to minimize ground resistance whilst maintaining a balance with the other anodes.
● Surface casings shall be installed and sealed with a bentonite or cement seal plug after loading and testing is completed.
● Each hole shall have a vent tube installed concurrently with the first anode in order to vent dangerous gases that may form due to anode reactions. The vent tube shall be resistant to chlorides and shall be perforated from the top of the bottom anode to 5m above the top anode. It shall extend a sufficient height aboveground to prevent ingress of water and dirt and have a filter and breather cap installed.
SPECIFIC REQUIREMENTS FOR SACRIFICIAL ANODE SYSTEMS 9.1
Sacrificial anodes shall be selected from the following types. Untried or special alloy compositions and/or applications shall require COMPANY review and approval:-
● High purity zinc (99.9% Zn or greater), ● Zinc to US Military Specification MIL-A-18001. ● Magnesium-Aluminum-Zinc alloy ● Magnesium-Manganese alloy
Additions of elements that have a detrimental affect on the anode output, (e.g. iron, copper, nickel) or that are potential carcinogens (e.g. mercury, cadmium, tin) shall not be permitted.
The application of Zinc anodes shall be limited to resistivities less than 2000ohm-cm.
The anode selection shall take into account cost, number of anodes required, ease of installation, lifespan, service temperature, and the risk of any other detrimental effects due to environmental conditions.
CONTRACTOR shall submit full details of anode compositions and proposed inspection and test procedures, for COMPANY review and approval prior to installation. Specification EGP3-02.01
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Cast anodes shall be free from through body and surface inclusions, pores, and longitudinal cracks. Transverse cooling cracks may be permitted. Casting acceptance criteria shall be submitted to COMPANY for review and approval.
Anode steel cores shall be blast cleaned to a near-white metal finish and shall have this finish at the time of casting. Zinc anode inserts may be galvanized. The core shall be centered in the anode and shall extend a minimum of 75% of the length of the anode.
The net mass of each anode shall not be less than 95% of the specified nominal mass.
The anode material shall be bonded to the steel core over a minimum of 90% of the total surface. No individual discontinuity shall exceed 35mm in length.
9.1.10 Dimensions and positions of inserts shall be within +/-2% tolerance of the defined dimensions. 9.1.11 Fabricated inserts shall be subject to 20% MPI inspection of completed welds. 9.1.12 For direct buried anodes, lead wires shall be attached to the core by brazing or silver soldered and sealed with a water repellent, electrically insulating material such as epoxy resin with a heat shrinkable sleeve. The lead wire connection shall have a breaking strength equal to or greater than the anode cable and shall be capable of supporting the full weight of the anode. The lead wire shall be a minimum of 10m in length. 9.1.13 Direct buried anodes shall be pre-packaged with a chemical back-fill of gypsum, bentonite and sodium sulphate, the composition of which shall be suitable for the specific soil resistivities and ground water encountered. 9.1.14 For anodes with a net weight in excess of 100kg, a destructive test shall be performed on one anode to check the strength of the bond between the steel insert and the anode, and the result recorded.
Anodes shall be installed in accordance with the standards referenced in this specification.
Pre-packaged sacrificial anodes for onshore buried structures shall be installed no closer than 1m from the structure to be protected, and for buried pipes and pipelines, the top of the anode shall be below the pipe centerline.
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AVOIDANCE OF ELECTRICAL INTERFERENCE AFFECTS The following general requirements shall be noted 1.
CONTRACTOR shall ensure that the design of the cathodic protection system avoids stray currents and other electrical interference effects, such as from direct current, AC power cables, train traction power supplies, foreign pipelines, other secondary metallic structures, and neighboring cathodic protection systems.
Where CONTRACTOR can show that avoidance is not practicable, it shall propose mitigating measures to be adopted to minimize the effects on the cathodic protection system for COMPANY review.
The measures adopted by CONTRACTOR shall consider in the first place, maintaining independence of the cathodic protection systems and structures. This should include the selection of high standard/high integrity coating systems. Where this is considered inadequate or impracticable, then consideration may also be given to the following:• •
Resistive bonding Localized sacrificial anodes or impressed current cathodic protection system
Zinc grounding cells
Decoupling devices (specific to AC or DC power sources)
INSPECTION AND TESTING OF EQUIPMENT 11.1
General 11.1.1 CONTRACTOR shall propose the minimum inspection and testing requirements for all cathodic protection equipment and materials for COMPANY review and approval. Inspection and testing shall ensure that the material requirements of this specification and referenced specifications are satisfied prior to dispatch from manufacturers’ works. The following requirements are in addition to any site inspection activities. 11.1.2 All electrical equipment shall be inspected against the relevant requirements of EGP3-12.01. 11.1.3 Final inspection of all equipment described within this section shall include visual checks to confirm compliance with the specified design drawings and details.
Impressed Current Anodes Inspection and testing of impressed current anodes shall include the following activities:
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● Agreed manufacturer standard tests ● Chemical analysis per heat for cast anodes (at least two samples) ● Review of all material certificates for plating materials, substrates, inserts, cables, and any other sub-supplied materials integral to the anode construction
● Visual inspection and measurement of cracking and shrinkage of cast anodes
● Measurement of overall dimensions, thicknesses, weights, and positions on at least a 5% sample basis
Sacrificial Anodes Inspection and testing of sacrificial anodes shall include the following activities:-
● Agreed manufacturer standard tests ● Chemical analysis per heat (at least two samples) ● Review of all material certificates for inserts and cables, and any other subsupplied materials integral to the anode construction
● Visual inspection of steel inserts’ surface preparation and dimensions, on at least a 5% sample basis
● Visual inspection and measurement of cracking and shrinkage ● Measurement of overall dimensions, thicknesses, weights, and positions on at least a 5% sample basis
Transformer – Rectifiers 11.4.1 A manufacturer’s standard Factory Acceptance Test shall be performed to demonstrate the capacity and functionality of the transformer – rectifiers. This procedure shall be submitted by CONTRACTOR for COMPANY review and approval. 11.4.2 Enclosure certification shall be reviewed to confirm compliance with the specified enclosure protection and hazardous classification ratings.
Isolation Joints 11.5.1 Monobloc type isolation joints and isolation spool pieces shall be hydrostatically tested at the manufacturer’s works in accordance with the applicable piping code. 11.5.2 The electrical resistance and resistance to sparking of pre-assembled isolation joints shall be checked using the following tests:-
● Apply 1500V 50Hz AC across the joint for at least 5 minutes without January, 2004
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sparking or insulation breakdown.
● Apply 1000V DC across the joint and measure the resistance. The resistance shall be greater than 1mega-ohm.
Cabling Jun Cabling certificates shall be reviewed prior to shipping to confirm compliance with the specified size, type, rating, and quantity.
Junction Boxes and Surge Arrestors Certification for junction boxes / monitoring stations / bond boxes and surge arrestors shall be reviewed prior to shipping to confirm compliance with the specified enclosure protection and hazardous classification ratings.
SITE ACCEPTANCE TESTING AND COMMISSIONING 12.1
General 12.1.1 Site acceptance testing and commissioning of the cathodic protection systems shall be undertaken in accordance with the standards referenced in this specification and this section, as a minimum. 12.1.2 CONTRACTOR shall ensure that commissioning of the cathodic protection system is integrated into the overall construction and commissioning activities and schedules. 12.1.3 Stable, effective operation of onshore cathodic protection systems shall be achieved within 2-4 weeks of the start of commissioning. Ineffective operation beyond this time shall be investigated and resolved by CONTRACTOR to COMPANY satisfaction. Any necessary remedial measures shall be proposed by CONTRACTOR for COMPANY review and approval. 12.1.4 All measurements, readings, and pertinent data shall be recorded within the final operating and maintenance documentation described in Section 15.
Transformer – Rectifiers Each transformer-rectifier shall undergo a load test prior to initial system energizing. The T/R shall be run continuously for a minimum of 24 hours at the maximum current and DC voltage rating. During this test, calibration checks of the ammeters, voltmeters, and any other instrumentation shall be performed.
Isolation Joints 12.3.1 All monobloc type isolation joints shall be retested immediately prior to welding into the pipeline.
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12.3.2 Insulating flanges and spools should be pre-assembled and tested immediately prior to welding into the pipeline. Where this is not possible, the following checks shall be made to ensure adequate performance of the joint:-
● The individual bolt to flange resistance’s shall be measured prior to energizing the system for the first time,
● After energizing, the current through the joint shall be measured using an ammeter, and recorded.
Cable Connections 12.4.1 Thermite and pin brazing cable connection procedures shall be prequalified by CONTRACTOR by a minimum of three representative connections on a sample plate of the same type and class of material as the actual pipe. Fusion and stud welded connections shall be performed to prequalified welding procedures. The test procedures shall be submitted by CONTRACTOR for COMPANY review and approval. Brazing test welds shall be witnessed by COMPANY. 12.4.2 The following test requirements apply specifically to thermite brazing:-
● A single hammer blow using a 1kg hammer shall be applied without visible cracking or breakage.
● The penetration of the copper joints into the base metal shall be inspected metallographically. Copper penetration into the base metal shall not exceed 0.5mm.
● Transverse Vickers hardness checks shall be made to confirm the relevant base material requirements are satisfied.
Pipe Sleeves The electrically isolation of pipe sleeves from the protected pipe is critical. Visual checks shall be made during installation to ensure satisfactory separation and prevention of accidental in-fills into the sleeve. Measurements shall be made before backfill and after completion and recorded, to ensure satisfactory isolation.
Buried Structures 12.6.1 Prior to energizing the cathodic protection system, the “native” structure to soil potentials shall be measured at the following locations, as a minimum:-
● All test stations ● Locations where buried structures protrude above ground
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12.6.2 The cathodic protection system shall be energized and preliminary adjustments made to balance the distribution of current and satisfy the structure to soil protection potential criteria. “On” and “Instant Off” potential measurements shall be made at the same locations as the “native” potentials, when the system is first energized and then switched off. 12.6.3 The current output and potential of the transformer – rectifier shall be measured and recorded. 12.6.4 The current output from individual impressed current and sacrificial anodes shall be measured and recorded. 12.6.5 Any effects due to stray current and interference between the cathodically protected structures, secondary structures, and neighboring cathodic protection systems shall be determined and corrected as necessary. 12.6.6 Where permanent reference electrodes are installed, the readings shall be compared with measurements obtained using the portable reference electrode, in order to validate the permanent reference electrodes. 12.6.7 After a minimum period of two weeks, but no more than four weeks, the initial polarization testing shall be repeated and system adjustments made as necessary. Both “On” and “Instant Off” potential measurements shall be recorded before and after any adjustments. 12.6.8 For aboveground storage tanks, “native”, “On” and “Instant Off” potential measurements shall be taken utilizing the permanent reference electrodes. 12.6.9 For water tanks, “native” and “On” potential measurements shall be taken using a portable copper/copper sulphate reference electrode. Measurements shall be taken at minimum of three depths, as follows:
● At the tank floor, ● 500mm below the water surface, and ● At a point midway between the two. 13.0
Design Specification 13.1.1 CONTRACTOR shall submit a basic design specification for each cathodic protection system. This shall propose the design philosophies and outline the selected cathodic protection systems for COMPANY review and approval before detailed design proceeds. The specifications shall include the following, as a minimum:
● Design philosophy, including protection criteria, design life, and referenced codes and standards January, 2004
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● Results and assessment of site surveys ● Outline description of the chosen cathodic protection systems, including the size, number, and location of anodes / groundbeds, transformer – rectifiers, as well as control and measurement features, with basic calculations and economic justifications
● Evaluation of any potential stray current and interference effects, and also impact from and to any neighboring secondary structures and other cathodic protection systems
● Definition of the type of isolating joints to be used ● Definition of the type and number of monitoring stations to be used 13.1.2 CONTRACTOR shall provide a detailed design specification for each cathodic protection system as part of its detailed engineering deliverables. This final specification shall contain, but not be limited to, the following:
● Design philosophy, including protection criteria, design life, and referenced codes and standards
● Results and assessment of site surveys ● Definition of the chosen cathodic protection systems (including temporary systems), including selection, sizing, and placement with all necessary calculations and economic justifications
● Evaluation of any potential stray current and interference effects, and also impact from and to any neighboring secondary structures and other cathodic protection systems
● List of all structures to be protected, including identification numbers, locations, and dimensions
● List of all piping and pipelines to be protected, including identification numbers, length, nominal diameter, coating and lining systems, pipe specification, and service
● List of all isolating joints, including associated piping identification numbers, service, type of joint, and calculations for sizing isolating spool pieces
● List of all monitoring stations and junction boxes, including identification numbers, location, and purpose
● List of all negative connection points, including identification numbers and location
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● Detailed system layout drawings, indicating the location of anodes and ground beds, transformer – rectifiers, cable routings, monitoring stations, reference electrodes, negative connection points, and adjacent secondary structures and neighboring cathodic protection systems
● Definition of assigned IP ratings and Hazardous area classifications 13.1.3 The basic and detailed design specifications shall be produced by a specialist cathodic protection engineer.
Installation and Commissioning Procedures 13.2.1 CONTRACTOR shall ensure that full installation and commissioning procedures are submitted by the cathodic protection system design CONTRACTOR, and that they are in accordance with the requirements of this Project Specification and CONTRACTOR’s instructions. 13.2.2 Commissioning procedures shall contain, but not be limited to, the information necessary to perform the tests and system balancing required in this specification. CONTRACTOR shall submit these procedures for COMPANY review and approval.
Operating and Maintenance Manuals CONTRACTOR shall submit operating and maintenance manuals to COMPANY as part of the hand-over documentation. These manuals shall contain, but not be limited to, the following:
● A full description of each cathodic protection system as-installed, including as-built drawings of the system layouts.
● Commissioning report, including a record of all measurements required. ● Maintenance procedures for all equipment items with recommended schedules.
● Monitoring schedules and procedures for each monitoring station. ● Safe operating guidelines for the cathodic protection system. ● Schedule of recommended spares.