Corrosion of most pipelines occurs due to an electrochemical reaction in the presence of an electrolyte. The electrochemical nature of the process also facilitates the detection and mitigation of this deterioration, which is accomplished by monitoring the voltages and the currents associated with the corrosion rate.

The rate of corrosion of a piping system is generally related to both external and internal factors. External factors include a working environment of pipes, soil chemistry and moisture for buried pipes or water chemistry in the case of submerged pipes

Protection is done by:

• Coating of the metallic surface with plastic (formerly bitumen)
• Active cathodic corrosion protection (CCP):

Using impressed current technology, it supplies a direct current in the low-voltage range. The current flow through and the electrochemical process is reversed having the positive and negative ions balanced back in the pipeline. As a result, the iron ions which moved can no longer cause corrosion. Corrosion is prevented for at least 20 years using impressed current technology. The DC voltage is generated by an AC-powered rectifier. The metal tube is connected to the – pole and the special anode buried deep in the ground with a low resistance, ideal is approx. 1 Ω. with the + pole of the rectifier.

In order to reliably protect the rectifier against the effects of lightning, extensive lightning and surge protection must be provided. Both on the AC side and on the DC side of the CCP caused by the lightning.

The pipeline is divided into sectors in order for the CCP (impressed current) to operate. This requires having insulating flanges to isolate each section.

In the event of lightning, these insulating flanges must be bridged to create lightning protection equipotential bonding and prevent electrical breakdown and destruction of the insulation as well as flash over cause by lightning. This is done by means of special lightning current isolating spark gap which is hermetically sealed. These high-performance isolating spark gaps are filled with inert gas (100kA 10/350µs) with fail-safe function. The fail-safe function prevents mechanical destruction in the event of overload. The second fail-safe function which is in the gas discharge tube (GDT) protects the GDT in electrical faults events which can cause an internal explosion.

If the pipeline carries highly explosive gas, it must be used with an ATEX certified isolating spark gap such as the (TC 100 A) with low response voltage (70V AC / 100V DC) and fail-safe function when laying above ground or underground.

The pipeline acts as a grounding conductor when lightning strikes through the bridged insulating flanges. For long distances, an earthing point can be created either at the station or in between such distances. If it is created in between long pipeline distances, instead of one isolating spark gap, two isolating spark gaps can be used and an earthing point can be created there.

In the case of a high-voltage lines or alternating current lines that run parallel to a pipeline, alternating voltages are injected into the pipeline, which reverse the function of the rectifier and cause alternating current (AC) corrosion. The PLPro 40A will divert the alternating current to earth keeping the DC current in the pipeline supplied into by the rectifier. In this event, the CCPS will function effectively without affecting the performance.

The PLPro 40A is well protected against direct lightning strikes by a TSF 100 (or TC 100 A in the Ex-area) with a 100 kA (10/350µs) isolating spark gap. The derived alternating current can be measured via an integrated current transformer. An integrated HF filter helps blocks the 10 kHz search signal from leak detectors to prevent unnecessary wrong detection. The generously large power capacitors are also protected by fine protection diodes and have an extremely long service life.

The duration of a functional guarantee for the CCP is about 20- 30 years. As long as the lightning and surge protection should remain in operation.

Surge Protection Devices (SPDs) ensures that the CCPS remains in permanent operation and well protected against lightning strikes. The PLPro 40A and TC100A are extremely high quality products manufactured in Germany and perfected over the years to ensure customers enjoy highest reliability and the best solutions deployed.