degRATE Corrosion Maintenance

Great news here at SCM – we’ve recently received the trademark certificate for our pioneering external corrosion degradation-rate formula ‘degRATE’ – aptly named!

This is a massive landmark for us at SCM. Our goal with degRATE is to change the way that corrosion maintenance work is planned and scheduled across a range of industries, which is no mean feat. In adopting the degRATE methodology, plant operators will finally achieve cost effective corrosion maintenance, centered around their most appropriate priorities. To put some perspective on that, we applied degRATE across a number of client assets recently and delivered almost an 80% reduction on what was their originally anticipated annual corrosion maintenance load. That resulted in, not only less maintenance work being required, but a massive reduction in material and equipment resources and also more efficient use of personnel resources, not to mention less downtime for plant that needed to be isolated.

We want to support and guide industry professionals away from that dangerous phrase “because that’s the way we’ve always done it” and join us in adopting this new corrosion maintenance methodology which we believe can inspire a hugely positive change in industry, at a time when it is perhaps needed most!

Currently, plant corrosion maintenance is generally planned & scheduled using ‘anticipated’ rates of degradation (RoD). These anticipated rates suggest how quickly a given component’s external condition will degrade per annum (i.e. using SCFM (Substrate Condition & Failure Mode), Re-based or Ri-based scales). They are considered ‘anticipated’ because they offer a subjective assessment of how a given component substrate ‘might’ degrade over time. There is little objectivity applied using these scales alone, and they have been demonstrated to be accurate only for 1, 2 or 3 years’ condition prediction at most, after which they are often grossly incorrect unless re-assessed regularly.

Until now, applying these scales, and attempting to reconcile the expected degradation with Integrity Inspections and Anomaly Reports, has been the most effective way of planning corrosion maintenance – we know that because SCM spearheaded the SCFM scale development in the 1990’s.

Using these ‘coarse’ RoD assessments has allowed for more flexible maintenance plans to be implemented than was previously possible however, it has always had a major failing – as with the RBA process (Risk Based Assessment), it works on the premise that corrosion degradation is uniform across an entire plant.

This uniform external corrosion condition may well be the case on a new-build facility, where external degradation often does appear to take place at a uniform rate over the first 2 -5 years. However, fast-forward 10-15 years, where a plant may be considered ‘mature’ and we quickly realise that this rate of uniform degradation is simply not the case. Some process equipment may still be in an acceptable condition, whereas others, even of exactly the same metallurgy, coating spec, temperatures etc. may be almost at a point of failure. This is where degRATE comes into play…


Take two of the same component – for example a gas pipe – same metallurgy, same protective coating, even the same process. Let’s say the only difference between these two components is that they are installed on opposite sides of the plant – this actually has a significant, though not immediately obvious, impact on the RoD.


 

So what is degRATE and what does it do?

Well, quite simply – and as the name suggests – degRATE calculates specific rates of external corrosion degradation on all plant substrates (pipes, valves, vessels, structures etc.) and it does this by applying a unique ‘factor and weighting’ for every separate impacting criterion.

The reason for differing rates of corrosion degradation is all down to a component’s ‘micro-climate’ in addition to its base factors; metallurgy, temperature, pressure etc. Every single component (or component part) is in a ‘unique’ micro-climate and therefore has its own individual rate of degradation (RoD).

It’s not just about location either i.e. is the component in a windward/leeward zone? Is it beneath an HVAC duct? Is it in a deluge area? There are many impacting factors which may have an effect on a components external corrosion degradation rate, such as its metallurgy, its operating temperature, coating specification, age, insulation specification and so on – in fact, we have identified 15 separate impacting factors – each with sub-sets of their own.

We define these factors as “Semi-Quantitative Substrate Degradation Assessment Factors”, and have applied them within our holistic corrosion, maintenance & integrity technology suite ‘360integrity’ for some time now.

Once all of the degRATE criteria have been assessed, we then have a component-specific RoD, even accounting for corrosion-acceleration once any protective coating has degraded.


 

So how can degRATE be used?

degRATE influences the entire maintenance decision making process. Once we have an understanding of the current condition of all components, an assigned classification and degRATE RoD, it allows facility management to perform all kinds of simple or sophisticated analysis, for example here are just a few;

Deferment analysis – After applying degRATE it may become clear that some components currently planned for maintenance will not degrade to an unacceptable level within 12, 18 or even 36 months’ therefore, we can identify where can we ‘safely’ and cost effectively defer maintenance load.

Fabric Projections – looking forward 2,5 or even 10 years hence, how will this component look ‘when’ will we need to maintain it? Some components may be actually degrading at a faster rate than initially assumed, meaning maintenance needs to be brought forward and can be justified and budgeted for accordingly, often reducing overall costs because of timely planning and execution.

Threat Management – consider all factors that impact risk to safety, function or operability. Tie together disparate Integrity & Maintenance programmes to define the most appropriate prioritisation of workloads, whilst demonstrating correct corrosion control and management.

HSE Compliance – because of the demonstrable nature of the degRATE process and the ‘objective evidence’ of control it brings, one of the main factors demanded by HSE is easily complied with i.e. you could answer yes to each of these three probing questions…

Do you fully understand the corrosion condition of your plant, and can you demonstrate it?

Where plant is in poor condition do you have a demonstrable plan in place to identify and prevent failure?

Where plant is currently in good condition, do you have a plan in place to mitigate future degradation?

These are just four of the tools available within our technology suite, which degRATE facilitates, delivering that much desired visibility of plant condition, potential integrity threats and objective evidence of control, now and into the future.

*Find out more about degRATE at www.stratcorrman.com

References: 360integrity, O_EofC

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