This specification covers the minimum mandatory requirements governing the design, materials, installation and pre-commissioning testing of the cathodic protection systems for buried and submerged metallic structures for plant facilities including but not limited to the following:
Cathodic Protection of Plant Facilities | Codes & References | Definitions
a. Pressurized buried pipelines/piping
b. Non-pressurized buried pipelines/piping
c. Buried sections of process, gas, water or liquids pipelines/piping
d. Drain pipes
e. Cement pipes
f. Concrete cylinder pipes
g. Pre-stressed concrete cylinder pipes
h. Vent pipes
i. Pipe casings
j. Bottom or soil side of above ground storage tanks
k. Buried storage tanks
l. Tank Internals
m. Metallic piles
n. Buried or buried portions of valves, monitors, risers, fittings, fire hydrants…etc
o. Submerged metallic structures (sea walls, anchors, gates, screens…etc) in submerged areas of the seawater structures, cooling towers and basins.
Codes & References
L02-S01 Transformer Rectifiers and Remote Monitoring Systems for Cathodic Protection.
L02-M01 Commissioning and Operation of Cathodic Protection Systems of Plant Facilities.
E02-E02 Hazardous Area Classification.
National Association Of Corrosion Engineers (NACE)
RP0169 Control of External Corrosion on Underground or Submerged Metallic Piping Systems.
RP0177 Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems.
PR0186 Application of Cathodic Protection for Well Casings.
RP0193 External Cathodic Protection of On-Grade Metallic Storage Tank Bottoms.
PR0196 Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks.
RP0274 High Voltage Electrical Inspection of Pipeline Coatings Prior To Installation.
RP0276 Extruded Asphalt Mastic Type Protective Coatings for Underground Pipelines.
RP0285 Corrosion Control of Underground Storage Tank Systems by Cathodic Protection.
RP0286 The Electrical Isolation of Cathodically Protected Pipelines.
RP0375 Application and Handling of Wax -Type Protective Coatings and Wrapper Systems for Underground Pipelines.
RP0388 Impressed Current Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks.
3 Definitions
For the purpose of understanding this specification, the following definitions apply.
Anode. The electrode of an electrolyte cell at which oxidation occurs. (Electrons flow away from the anode in the external circuit. It is usually at the electrode that corrosion occurs and metal ions enter solution). In conventional cathodic protection systems, the anodes are buried underground or submerged for the protection of the metallic structure embedded or in contact with the soil or water.
Anode Junction Box. The box connecting the positive cable from the rectifier to the anodes in the anode bed through set of resistors and the shunt. Each anode in the anode bed has its
own set of resistance and the shunt for anode performance evaluation.
Cathode. The electrode of an electrolytic cell at which reduction is the principal reaction (Electrons flow toward the cathode in the external circuit). Typical cathodic processes are cations taking up electrons and being discharged, Oxygen being reduced and the reduction of an element or group of elements from a higher to a lower valence state. In CP system, cathode is the structure to be protected.
Cathodic Disbondment. The destruction of adhesion between a coating and its substrate by products of a cathodic reaction.
Cathodic Protection. (CP) is a technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell.
Congested Area. the structure to be protected is surrounded by obstacles (adjacent piping, concrete foundations…etc) that may affect the current distribution).
Current Distributor / Conductor. An uncoated strip of titanium which is used to feed current to the anode system and connect adjacent lengths of ribbon anodes together
electrically. The current distributor is welded to the ribbon anode in the field, with a portable resistance welder.
Current -ON Potential. The potential when CP system is in operation. This potential includes the polarization potential and other voltage drops resulting from the flow of current (IR drop).
Electrolyte. A chemical substance or mixture containing ions which migrate in an electric field. For example, soil and water are electrolytes.
Galvanic or Sacrificial Anode. A metal which, because of its relative positioning the galvanic series, provides sacrificial protection to metals that are more noble in the series, when coupled in an electrolyte. Sacrificial anodes are Magnesium, zinc and aluminum.
Ground Bed. The anode(s) of a cathodic protection system that provides cathodic protection current to structures in contact with the electrolyte.
ICCP. Impressed current cathodic protection system.
Impressed Anode. A metal, which have a low consumption rate, provides impressed cathodic protection using an external power supply such as a transformer rectifier.
Instant Off Potential. To measure the true polarization potential, the potential is measured with the current turned off instantaneously, thus eliminating the IR drop.
Natural Potential. The potential of a corroding surface in an electrolyte, relative to a reference electrode. Also known as corrosion potential or open circuit potential.
Negative Junction Box. The box connecting the negative cable from the rectifier to the structure to be protected.
Oxidation. Loss of electrons by a constituent of a chemical reaction.
Polarization. When the CP system is in operation, there is a net flow of electrical current between the anodes and the structure to be protected. As a result of this current flow, structure potential is shifted towards more negative potentials. This potential shift from their open circuit corrosion potentials is called ‘polarisation’. This polarization potential can be varied by varying the current flow in the CP system. Accordingly, a desired level of corrosion protection can be selected.
Reference Electrode. A half-cell of reproducible potential, for example copper/copper sulphate (Cu/CuSO4). A standard against which potentials or other electrodes can be measured or compared. Reference electrodes may be portable or permanently installed in the electrolyte (soil or water).
SACP. Sacrificial anode cathodic protection system.
Stray Current. Current flowing through paths other than the intended circuit.
System Negative Connections. Cable electrically connected to the metallic structure needs to be protected. These cables are connected to the negative terminal in the rectifier either direct or through the negative junction box.
Transformer Rectifier. A device used to convert alternating current (AC) to direct current (DC). In a CP system, the transformer rectifier is used to control the voltage, current or potential.
Pipe/pipeline/piping. A cylinder or tube (wheteher inside or ouside the plant battery limit) used to conduct liquid, gas, or solid (All three words have the same meaning).
Cathodic Protection of Plant Facilities General Requirements
Cathodic Protection Pre-Design Survey, Testing and Considerations
Cathodic Protection Design of Plant Facilities
Cathodic Protection Anode Bed Design of Plant Facilities
Current and Voltage Requirements Cathodic Protection of Plant
System Monitoring of Cathodic Protection in Plant Facilities
Cathodic Protection Materials and Equipment in Plant Facilities
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