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DEHN protects Pipelines

Protection solutions for cathodic corrosion protection systems. DEHN protects Pipelines from damage caused by interference voltages. Pipelines: Secure transport - non-stop supply

Safe for people and the environment. Pipelines are the most secure means of transport for flammable liquids and gases. They represent a seamless, reliable supply of oil and gas. In Germany alone, around 40,000 kilometres of pipelines are laid in the ground.

To ensure permanent safety, protection against corrosion constitutes the greatest challenge. Various techniques are deployed to this end: a passive approach, with enclosures for coatings on the one hand, and an active approach on the other, with cathodic corrosion protection systems and decoupling devices.

The problem: Interference voltages

Pipelines are very well insulated. They can therefore pick up interference voltages. This mainly happens when they share routes with railway lines or high-voltage transmission lines. Another cause of interference voltages is lightning strikes. Surges triggered this way spread out quickly throughout the pipeline network.

The damage resulting from this is enormous:
- Environmental damage: Interference voltages lead to corrosion, resulting in leaks.

- Breakdowns: Damaged gas pressure control and measurement system, slide gate valve and compressor stations disrupt transport.

- Threat to human life: Touch voltages on freely accessible system parts during maintenance work could lead to an electric shock.

Provide permanent safety

Safety for pipelines and people is the top protection goal of operators. To this end, interference voltages must be discharged to earth at the correct points.

Suitable measures for this are, for example, robust decoupling devices or spark gaps, as well as special surge protection solutions for cathodic protection rectifiers or field instruments. Operators frequently use remote monitoring systems for particularly sensitive pipeline sections.

Protection solutions are demanded here that are not only robust but above all smart. For the operator, the integration of decoupling devices into the cathodic corrosion protection and management systems means being notified of the status of the pipeline at all times - making everyday work considerably easier.

Electric railways

Electric railways produce galvanically injected stray currents which enter the pipeline via the ground through defects, thus changing the potential of the pipeline by means of interference voltages.

High-voltage transmission lines

High-voltage transmission lines generate electromagnetic fields which are injected into parallel pipelines and usually occur in the form of permanent interference voltage.

Interference voltages threaten people and materials

Interference voltages are non-system voltages that are triggered by sources of interference, such as electrified railway lines, high-voltage transmission lines, earth faults and lightning strikes.

Overvoltages are referred to as being transient, temporary or long-duration depending on the duration of the interference voltages. Stray currents that are injected through the earth and electromagnetic fields change the potential of the pipeline.

This results in material erosion due to stray current or alternating current corrosion (AC corrosion), which regularly leads to material damage to the pipeline, economic damage and environmental damage due to leaks.

Yet interference voltages can also threaten humans, because of the high touch voltages involved. With freely accessible system parts or during maintenance work, these dangerous overvoltages constitute an enormous risk to people.

Integrated protection concepts, consisting of earth electrodes, decoupling devices and surge protection measures (e.g. spark gaps) can limit interference voltages to levels below the specified limit values. Consequently, pipelines and the people working on them are protected in equal measure.

Earth faults

An earth fault causes a potential gradient area in the surrounding soil whose potential affects pipelines located in this area. This potential gradient area thus spreads over to the relevant pipeline network in the form of interference voltage.

Lightning strike

Lightning-induced surges generate transient interference voltages towards unaffected systems. Injected via a potential gradient area, they spread over the entire pipeline network.

Earthing systems - discharge surges safely
The earthing system is the basis for the safe discharge of interference voltages.

To dimension the system, how intensive the interference from interference voltages is must first be determined.

This is usually performed by service providers. Protective measures are deduced from measurements and calculations. This will determine how many earth electrodes are required and where they are placed.

In the area surrounding pipelines, it must be ensured that the materials used for the earthing system meet the particular requirements. This means they must have sufficient current-carrying capability and be corrosion resistant.
Dehn Italia - http://www.dehn.it
Redazionali o presentazioni di prodotto/di azienda
Pubblicato il 15 novembre 2022
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