DESIGN A/E NOTE - GUIDE SPECIFICATION CONVENTIONS
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Rev 19JUN09 j:\Projects\Active\com-deca_design_criteria_revisions-04071\Guide Specifications\TJG Innformation
SECTION 16640
CATHODIC PROTECTION
Verify that Section titles referenced in this Section are correct for this Project's Specifications; Section titles may have changed.
PART 1. GENERAL
1.1 RELATED DOCUMENTS
1.1.1. Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division1 Specification Sections, apply to this Section.
1.2 SUMMARY
1.2.1. This Section includes Cathodic Protection for underground or submerged structures of ferrous metal.
Adjust list below to suit Project; delete all that are not applicable.
1.2.1.1. Buried ferrous metal pipelines for [natural gas] [water] [<insert other>] service, including valves and fittings.
1.2.1.2. Valves or fittings of ferrous metal on buried nonmetallic pipelines for [natural gas] [water] [<insert other>] service.
1.2.2. The structures to be cathodically protected are shown on the contract drawings.
If the project includes no more than 800 LF of coated pipelines (all services combined), and no bare structures to be cathodically protected, delete Article 1.3 and its subparagraphs (for extensive cathodic protection), and retain the Article following 1.3 (for minor cathodic protection installations).
Retain the Article and subparagraphs below for EXTENSIVE cathodic protection installations.
1.3 CATHODIC PROTECTION INSTALLATION AND PERFORMANCE REQUIREMENTS
1.3.1. Qualified Individual: Design, construction supervision, and testing of the cathodic protection and associated bonding, isolation, and coating of the structures shall be accomplished by an individual qualified under one of the following:
1.3.1.1. A Professional Engineer Registered or Licensed in one of the United States or Puerto Rico in the field of Corrosion Engineering, specializing in cathodic protection;
1.3.1.2. An individual Accredited by the National Association of Corrosion Engineers (NACE) as a Corrosion Specialist or as a Corrosion Technologist specializing in cathodic protection.
1.3.2. Design appropriate and economical cathodic protection for each structure in accordance with the NACE Recommended Practice for Control of Pipeline Corrosion. Include all bonding and isolation, and appropriate test stations. Design for not less than 20 years anode life expectancy.
1.3.2.1. Investigate existing conditions on site that affect cathodic protection, and research utility records of the Host Military Installation to determine the existence of other utilities and cathodic protection systems in the area that may influence, or be influenced by, the new protected structure(s).
1.3.2.2. Conduct any tests that may be required in the design of the cathodic protection, furnishing all equipment, supplies, and labor for the tests. (Examples of tests that might be required are soil resistivity, current requirements tests, structure continuity tests, stray current tests.)
1.3.3. Furnish and install the cathodic protection equipment and materials as designed by the Qualified Individual, under his supervision.
1.3.4. Test the completed cathodic protection to demonstrate acceptable protective structure-to-soil potentials of not less than -0.85 volt, nor exceeding -2.0 volts, (Cu/CuSO4 electrode); with anode current flows not exceeding the current as designed for anode life expectancy.
1.3.5. Test the protected structure for “hot spots”, unprotected areas of structure, or interference from stray currents.
1.3.6. Check for cathodic interference on other structures in the vicinity, if deemed necessary by the Qualified Individual.
1.3.7. Make any adjustments or corrections that may be required to bring the protected structure to acceptable protection, or to eliminate interferences, and retest.
1.3.8. Furnish full reports of all tests, prepared and signed by the Qualified Individual.
1.3.9. SUBMITTALS
1.3.9.1. Qualifications and Credentials of the Qualified Individual. Submit verifiable evidence of the required engineering registration/license or NACE accreditation, for approval.
1.3.9.2. Design calculations supporting the cathodic protection design, and sketches indicating the proposed cathodic protection installations, for approval and record.
1.3.9.3. List of materials and equipment proposed for the cathodic protection installation, for approval and record.
1.3.9.4. Results of all tests performed before and after installation, in clear, typewritten tabular form, certified by the Qualified Individual, for permanent facility records.
1.3.9.5. Operation and Maintenance information. Include detailed recommendations for adjustments, maintenance testing and full descriptions of all parts for replacement purposes.
1.3.9.6. As-Built drawings: Record the locations of all wiring, connections, equipment and components of the cathodic protection system on the As-Built record drawings required under Division 1 Section, “Phase Turnover and Contract Closeout”.
Retain the Article and subparagraphs below for MINOR cathodic protection installations. Do not retain both Cathodic Protection Articles in the same project.
1.4 CATHODIC PROTECTION REQUIREMENTS
1.4.1. General: Provide galvanic anode cathodic protection for the structures indicated on the drawings to receive cathodic protection. Apply anodes to each separate continuous structure in accordance with the table below.
Structure(Coated)Magnesium Anode Weight(Lbs)
Valve or Fitting (Isolated)5
Pipe to 1” – Each 100’5
Pipe 1-1/4” to 2” – Each 100’9
Pipe 2-1/2” to 4” – Each 100’17
Pipe 5” to 8” -- Each 100’32
1.4.2. Coatings: Each structure must be thoroughly coated with a moisture-impervious protective coating tightly adhered to the metal surface. Voids in the coating for joints, fittings, accidental ‘holidays’ and cathodic protection wire connections must be touched up with equivalent coating materials before the structure is covered up with backfill. Use pipeline tape wrapping half-lapped, coal tar enamel, or mastics specifically recommended for corrosion protection. Insulate welded wire connections with mastic-filled plastic weld caps made for the purpose.
1.4.3. Anodes: Anodes shall be standard H-1 alloy magnesium anodes prepackaged in standard gypsum-bentonite-sodium sulfate formula prepared backfill bags for cathodic protection service, of the (magnesium) weights indicated in the Table. Anodes shall have 10-foot insulated #12 AWG copper lead wires.
1.4.4. Wire connections to structure: Wire connections to the protected structure shall be made by an exothermic welding process, such as Cadweld or Thermoweld. Use the tools, molds, accessories, and weld charges recommended by the manufacturer for the specific wire and structure type. Follow all instructions of the manufacturer precisely in making the welds.
1.4.5. Test stations: Provide at least one flush-mounted cathodic protection test station for each separate structure protected, other than isolated valves or fittings on nonmetallic pipelines. For pipeline structures exceeding 200 feet length, provide two test stations. One or more test stations should be installed at anode connection points, with the anode wire as well as two structure contact wires brought into the test station terminals. Provide a separable link to connect the anode lead wire to one of the structure contact wires. Provide additional test stations where indicated on the drawings.
1.4.6. Acceptance Tests: Perform tests listed below on each protected structure, in the presence of the authorized representative of the Contracting Officer and any other government technical personnel responsible for cathodic protection. Provide all equipment, wiring and labor for the tests. The test should be performed not less than two days after the anodes are connected to the structure, to allow time for polarization to stabilize.
1.4.6.1. Using a high impedance voltmeter (50,000 ohms per volt or higher), measure the structure-to-soil potential at the soil surface above the protected structure every 10 feet along its length. Soil contact shall be made with a standard copper to copper sulfate reference electrode designed for soil potential measurements, placed firmly upon slightly moistened soil for good contact. Structure contact shall be made at a cathodic protection test station; or, in the case of isolated valves with no test station, the contact may be made directly to the exposed valve stem or body.
1.4.6.2. Protection is considered to be adequate if the structure-to-soil potential is negative 0.85 volt or greater. Protective potentials exceeding negative 2.0 volts may cause disbonding of coatings, and should be reduced by introducing resistance into the anode connection.
1.4.6.3. Using a sensitive milliammeter, measure the current flow between the anode and the protected structure. Higher current indicates more rapid consumption of the anode material.
a. For Magnesium Anodes: For the desired rated life expectancy of 20 years, this current should not exceed the current shown in the table below corresponding to the anode weight.
Weight (Lbs)Max. Current (mA)
512
920
1740
3275
48120
1.4.6.4. If tests show the protection to be inadequate, or the anode current too high, remedial measures may be required. It may be necessary to introduce resistance into the anode lead connection; or the structure may be electrically shorted to another structure causing a drain on the protective current. Consult with the Contracting Officer’s technical representatives for guidance in correcting the problems. Retest after taking corrective measures.
1.4.6.5. Prepare a clear, typewritten report of final tests showing all structure-to-soil potentials and anode currents. Record location and ohmic value of any resistances that were added.
1.4.7. SUBMITTALS
1.4.7.1. Submit catalog data on all equipment and materials to be provided for the cathodic protection installation, showing conformance to these specification requirements. For Approval.
1.4.7.2. Submit test reports of all tests conducted on the cathodic protection systems. For Approval and permanent facility records.
1.4.7.3. Operation and Maintenance information, including spare parts information.
1.4.7.4. Submit Record Drawings: Record locations and sizes of anodes, test stations, insulators and the like on the record drawings as required in Division 1 Section “Phase Turnover and Contract Closeout”.
Retain the following Parts 2 and 3 for all projects.
PART 2. PRODUCTSÉ
2.1 MANUFACTURERS
2.1.1. In other Part2 articles where titles below introduce lists, the following requirements apply to product selection:
2.1.1.1. Available Manufacturers: Subject to compliance with requirements, manufacturers offering products that may be incorporated into the Work include, but are not limited to, manufacturers specified.
2.2 Sacrificial Anodes
2.2.1. Available Manufacturers
2.2.1.1. HARCO
2.2.1.2. Mesa Products
2.2.1.3. Brance-Krachy
2.2.2. Packaged Magnesium Anodes, H-1 Alloy:
2.2.2.1. Cast magnesium anodes of H-1 alloy, Grade A, in accordance with ASTM Standard B843, Alloy AZ63. Open Circuit Potential not less than 1.53 volts, and Current Efficiency not less than 45%, when tested in accordance with ASTM-G97 procedures.
a. H-1 magnesium alloy, Grade A: Aluminum 5.3-6.7%; Zinc 2.5-3.5%; Manganese 0.15-0.7%; Silicon 0.10% max.; Copper 0.02% max.; Nickel 0.002% max.; Iron 0.003% max.; Other Impurities 0.30% max.; Magnesium – remainder to 100%.
2.2.2.2. Lead wire of #12 AWG copper wire, insulated with type TW insulation or HMWPE insulation, 10 feet long, silver-soldered (45% silver) to the galvanized steel core of the magnesium anode, and sealed against moisture.
2.2.2.3. Anode centered in a cloth bag containing a backfill mixture of 75% hydrated gypsum, 20% bentonite, and 5% sodium sulfate.
2.2.2.4. Packaged for shipping and storage in a multiwall paper sack; palletized, and film-wrapped.
2.3 Test Stations
2.3.1. Available Manufacturers
2.3.1.1. Cott Manufacturing Company
2.3.1.2. C.P. Test Services
2.3.1.3. Handley Industries
2.3.2. Test stations shall be flush-to-grade design with sturdy plastic outer tube and well-sealing top cover, similar to “Fink” test stations by Cott Manufacturing . Terminals and connecting links shall be of nickel plated brass. Provide each test station with a minimum of 3 terminals and one link. Station shall include a locator magnet.
2.3.3. Provide three each of any special tools required for operation and maintenance of the test stations.
PART 3. EXECUTION
3.1 INSTALLATION OF PACKAGED MAGNESIUM ANODES
3.1.1. Handling: Keep packaged magnesium anodes dry and protect from physical damage until ready to install. Remove protective packaging carefully just before installation to avoid damage to the cloth backfill sack or lead wire. Never handle the anode by its lead wire. When lowering the anode into the earth, support its weight with a “sling” of rope or fabric until it is resting on the bottom of the hole.
3.1.2. Location: Space anodes evenly over the extent of the protected structure; if one anode is required, it should be near the midpoint of the structure.
3.1.3. Bell Hole: Provide a bell hole for the anode that is to one side of the structure to be protected, deep enough that the entire anode will be lower than the lowest part of the structure. Minimum separation of the anode from the structure shall be 12 inches. Over excavate sufficiently so that all large rocks and other foreign matter can be removed from the vicinity of the anode. Segregate the backfill so that the backfill close to the anode or its lead wire contains no debris or stones larger than 1/2 inch, to avoid damaging the anode or wire.
3.1.4. Wiring: Anode lead wires and wires for contact to the structure shall be installed with sufficient slack that tamping the backfill will not place strain upon the wires or the wire connections. Place wires in the trench in such a way that they are not likely to be damaged if the structure has to be dug up in the future.
3.1.4.1. Connecting to the Structure: All connections to the structure shall be exothermically welded (Cadweld, Thermoweld) to the structure. The weld and all exposed metal of the structure and the wire shall be thoroughly insulated and protected, using a plastic weld cap filled with mastic. Follow instructions of the weld manufacturer explicitly. The structure wire connections for the anode current and for testing must be separate welds separated by at least 12 inches.
3.1.4.2. Connecting to Test Stations: Connect to test station terminals with at least 10 inches of slack inside the test station, so that the entire terminal board can be removed for servicing or testing. Coil the slack wire compactly below the terminal board. Ensure that all terminal connections are clean and bright, and made up tightly. Expose no more of the copper wire than necessary to make the connections.
3.1.5. Backfilling: When backfilling the anode, after about 12 inches of backfill cover has been placed, activate the anode by pouring 5 gallons of clean water slowly over the anode site to moisten the anode, the prepared backfill inside the cloth bag, and the earth around the anode.
3.2 INSTALLATION OF TEST STATIONS
3.2.1. Avoid placing test stations directly above anodes or directly above the protected structure. Place test stations 18 to 24 inches off the centerline of the protected structure, and at least 5 feet horizontally from the anode. Place the top of the station flush with pavements, or 1/2 inch above grade if unpaved. The earth directly underneath a test station should be native backfill, so it can be used for earth contact for testing purposes in case the surrounding area is paved or covered.
3.3 TESTING
3.3.1. Structure-to-Soil Potential Measurements
3.3.1.1. Be sure your test lead connection to the structure makes good contact to metal. Use abrasive paper or a file to clean tarnish or soil from any connection point. Do not use the anode wire as a structure contact; use an independent structure contact wire at the test station.
3.3.1.2. To insure good soil contact at the tip of the copper/copper sulfate reference electrode, moisten the soil slightly (about 1/2 cup of clean water) at the point of contact. Place the reference electrode on the soil as close to the vertical centerline of the structure as possible.
3.3.1.3. Record the negative potential of the pipe to the soil, to 3 significant figures.
3.3.2. Anode Current Measurements
3.3.2.1. Positive current flow in the anode lead is from the structure to the anode.
3.3.2.2. Record current to 3 significant figures. Record a sample structure-to-soil potential reading taken simultaneously with the current reading, to ensure that the insertion of the ammeter has not altered the protective current level.