Comprehensive Cathodic Protection Solutions for Oil and Gas Pipelines: Equipment, Methods, and Technologies

Corrosion protection is crucial for oil and gas pipelines, as structural failure due to corrosion can result in catastrophic consequences. Alongside insulation coatings, cathodic protection is widely used for pipeline systems at industrial sites and residential areas.

Impressed Current Cathodic Protection (ICCP) for Oil and Gas Pipelines

Key components include the cathodic protection power supply (transformer rectifier unit), anodes, and reference electrodes. The objective of cathodic protection is to provide a negative potential shift relative to the natural steel potential on the pipeline.

Electrical energy enters the transformer rectifier and is converted into a regulated protection current. This protective current circulates between the anode and the pipeline, flowing from the anode into the soil and onto the pipeline, protecting it from corrosion.

Transformer rectifiers (TRU) include pulse rectifiers and single-phase AC transformer rectifiers. TRUs should be positioned closer to the midpoint of the pipeline, based on the calculated number of stations and power source locations. PSS Corporation manufactures a wide range of transformer rectifiers varying in power, characteristics, and data transmission capabilities.

Anodes are another essential CP element, functioning as sacrificial material. High silicon cast iron alloys and conductive polymer materials are widely used, with titanium anodes coated with platinum-group metals also highly effective. The main requirement for anode groundbed is a low dissolution rate. The anode layout scheme depends on the protected structure's configuration. CP systems cannot function without additional switching and measuring equipment.

To verify cathodic protection operation, polarization and total potentials of the pipeline must be measured. Copper/copper sulfate reference electrodes such as copper/copper sulfate ENES-4M-RE and PSS-ESTD are used. Reference electrodes can be copper-sulfate or steel portable or permanent, with solid-state or liquid-state electrolytes. To monitor corrosion rates on pipelines, corrosion rate sensors should be utilized. PSS Corporation manufactures several sensors, such as Anode Ladder Corrosion Control, a corrosion rate indicator unit.

At drainage points, measuring and power cables are thermite-welded to the pipeline. For enhanced safety, magnetic contacts are available, eliminating the need for thermite welding and allowing easy removal. These cables are connected to the test stations, where potential measurements are taken. Data from test stations is transmitted via cable lines or wirelessly to the CP station. Test stations have been developed with data transmission equipment, CP separator units, and autonomous power sources.

The essential CP system kit can also include:
- Diode-Resistor Blocks — to protect several metal objects from one source, non-interconnected structures, to prevent negative interactions.
Automaic Reserve Switching System switching main CP devices to reserve systems.
High- and Low-Voltage Distribution Cabinet for receiving and distributing electrical energy from high- and low-voltage transmission lines to CP converters.
Coke breeze backfill — filled in trenches with anodes, reduces soil resistance drawbacks and extends anode life.
CP cables designed for protection system power transmission withstand loads and resist aggressive environments.
Data is transmitted through wired and wireless communication channels.
"PSS.CP-Analytics" software processes and analyzes collected data, predicting equipment maintenance and replacements.

Sacrificial Anode Cathodic Protection (SACP) for Oil and Gas Pipelines

Sacrificial anode protection was humanity’s first cathodic protection method. By connecting metals with different potentials, the more negative potential metal—acting as an anode—dissolves in place of the pipeline. Once fully dissolved or disconnected, the anode must be replaced.

Magnesium, zinc, and aluminum alloys are primarily used. Magnesium-based alloys, like prepackaged magnesium anode PSS-PM-U, are preferred for pipelines.

Sacrificial protection is ideal when CP power supply is unavailable or for shorter, smaller diameter pipelines. In remote, inaccessible areas lacking power lines, sacrificial anodes are buried individually or in groups, connected to the pipeline via cable, and linked to CMP. To ensure even dissolution and reduced resistance, anodes are packaged with a coke breeze backfill.

Stray Current Mitigation and Induced Current Protection from Power Lines

Drainage in electrochemical protection theory and practice refers to stray current removal. Stray currents originate from electrified railway rails or power lines and can be direct or alternating currents.

To protect pipes from electrified transportation:

• Polarized stations (EDP, DRP) directly divert current to rail networks or traction substations.
• Automatic drainage transformer rectifiers (SAUD-I, SAUD-C) provide stray current protection and cathodic protection by creating protective potentials, manufactured with analog or digital control units.

For pipelines near high-voltage power lines, AC Mitigation Devices are used to divert currents induced by electromagnetic radiation from high-voltage power lines. These devices do not affect the pipeline's protective potential maintained by cathodic protection systems.