The impact of Optimised Cathodic Protection 

But what is optimised CP?

OCP can be neatly quantified and described in a small, controlled lab environment. But what about in a large, distributed operational environment? What does OCP of a 1000km long pipeline look like?

Let’s describe a model structure (an imaginary pipeline) so that we can clearly consider the factors which could contribute to less than optimal CP.

Our model pipeline is 1000km long, has an Impressed Current Cathodic Protection (ICCP) unit every 50km and a test point every 2km resulting in roughly 20 CP sites and 500 test points. The pipeline is entirely buried. To inspect any small portion of it is possible, but time-consuming and costly.

Let us first note that corrosion can occur at any point along the structure and that the structure passes through continually changing environments and that the environment at any specified location can change on a continual basis over time.

Let’s also note that CP can be practically monitored only at a relatively small number of discrete locations (the test points) and CP is only applied at a smaller number of discrete locations (ICCP Sites).

It might already be clear that practical, real-life OCP is starting to look different to OCP on a metal sample in a lab that can be:

• Wholly observed,
• is located in a single, homogenous, controlled environment,
• and can have CP applied almost uniformly to the entirety of the sample.

In practice, numerous factors impact CP efficacy, though only a few of these are practically controllable. Thus, these are what will ultimately define the efficacy.

For the sake of keeping this study practical and not entirely academic, we will define practical OCP as:

Cathodic protection, applied to real infrastructure, which is optimised through all practically controllable factors.

The goals are:

1. Meet the protection criteria at the maximum number of test points possible, given the number, capacity and arrangement of TR’s and sacrificial anodes, and
2. Maintain Goal 1 on a time continual basis for the maximum amount of time.

These goals must be achieved whilst ensuring that polarisation limits are not exceeded at any test points.

These goals naturally implicate several operational requirements.

For example, we clearly need to monitor the polarisation at as many locations as possible in order to know if we have achieved Goal 1.

Furthermore, the structure passes through various environments (soil types, PH, moisture levels etc) which each vary continuously over time. So goal 2 implies a minimum sampling rate for polarisation monitoring that should be in line with changing seasons, changing climates, changing environments and aging assets.

CP outages and failures must be rectified as soon as possible to achieve Goal 2. If possible CP outages and failures should be avoided altogether through proactive management (preventative maintenance). A high enough polarisation sample rate may enable the pre-empting of such failures, outages or deficiencies. In fact, machine learning applied to a high sample rate of a comprehensive dataset may allow for the early identification (or possibly pre-empting) of pipeline events such as:

• Sudden changes to the coating condition (e.g. disbondment).
• Sudden changes to the structure’s environment (e.g. flooding).
• Third-party interference (e.g. dig-ups, impacts, new CP/traction/transmission systems).

Continual monitoring and timely response to outages are not enough to maintain OCP on a dynamic, ever-changing, widely distributed system. To ensure the protection has maximum coverage for the maximum time, the CP system needs to be able to respond continually. A system that can automatically respond on a daily basis to the dynamics of the infrastructure, its environment and its applied CP, is a critical requirement of  OCP. Furthermore, any changes to the applied CP should account for the polarisation of the entire asset, not just a single sample point adjacent to the TR.

So what does practical OCP look like?

• Continually sampling the entire alignment of the asset and automatically adjusting the applied CP to ensure the protection criteria is met for as much of the asset as possible at any given time.
• Immediate notification of CP failures or deficiencies, coupled with timely rectification.
• Where possible, the pre-emptive indication of future CP failures or deficiencies with timely preventative maintenance.