Failure Modes, Effects and Causes of Microbiologically Influenced Corrosion: Advanced Perspectives and Analysis

By Reza Javaherdashti and Farzaneh Akvan

Failure Modes, Effects and Causes of Microbiologically Influenced Corrosion: Advanced Perspectives and Analysis presents academic research about microbial corrosion (MIC), integrating it into engineering applications that result in a more thorough understanding of MIC and how it is recognized and treated. In addition, new concepts that will be useful in understanding integrity and corrosion management practices are explored. This book will be useful for industry professionals, particularly maintenance and operation engineers, corrosion and material engineers, and R&D personnel working in the field of corrosion protection.

• Focuses on the skills and knowledge necessary to understand how (Failure modes) and why (Effects and Causes) materials fail
• Explains why corrosion control measures, such as the use of coatings, cathodic protection and inhibitors are useful
• Discusses the practical side of MIC treatment in terms of fundamental concepts of time and cost of operation

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 22, 2019
• ISBN: 9780128184493

Reza Javaherdashti

Dr. Javaherdashti holds a double degree in materials science and metallurgical engineering. He has more than 20 years of industrial and academic experience. In addition to various research papers and root cause analysis reports, Dr. Javaherdashti has authored several reference books on corrosion. He is an American Society of Mechanical Engineers (ASME)-approved trainer and has designed and executed many international industrial workshops. Furthermore, he has been involved in many consulting and problem-solving activities around the globe and is also a corrosion advisor to internationally renowned companies. Dr. Javherdashti is a veteran member of various well-reputed international corrosion societies such as the National Association of Corrosion Engineers (NACE).

Book preview

Failure Modes, Effects and Causes of Microbiologically Influenced Corrosion

Advanced Perspectives and Analysis

Reza Javaherdashti, PhD

Director, ParsCorrosion, Perth, Australia

Farzaneh Akvan

Industrial Consultant and Lecturer, CA, United States

Table of Contents

Cover image

Title page

Copyright

Dedication

Author Biographies

Foreword

Chapter 1. Introduction

General Rule of Corrosion Risk

Zugzwang Effect and Its Role in FMEA

Fit-for-service and Pseudo-FSS States

Failure Component of FMEA

How Can FMEA Be a Complex Matter in Practice?

Corrosion Management Definition and Javaherdashti Corrosion Management Model

FMEA for Managers, Corrosion Knowledge Management

Summary

Chapter 2. A Touch of Corrosion to Understand Microbial Corrosion

Introduction

Thermodynamics Behind Corrosion and Its Importance in the Management of Corrosion

Three Essentials of Electrochemical Corrosion

Electrochemical Cells

Parallel and Series Corrosion Scenarios

The Role of Design in Corrosion Prevention and Corrosion Control

How Much Electrochemistry Is Needed to Interpret Microbial Corrosion?

Summary

Chapter 3. Microbiologically Influenced Corrosion (MIC)

Introduction

Common Features of MIC Definitions

Corrosion-Related Bacteria and Corrosion-Related Archaea

How can CRB do Damage to Engineering Assets Based on the Environment the Assets Are in

Issues Related to MIC

Monitoring of Corrosion-Related Bacteria

Returning to Complete Some Unfinished Businesses

Summary

Chapter 4. FMEA-MIC

Predominant Failure Modes in MIC

Training

Inspection

MIC Risk Assessment

POF/COF Evaluation due to MIC and Its Evaluation

MIC Risk Matrix Buildup

Choosing Best Treatment Technique(s)

Monitoring MIC and Comparing It With Chosen KPIs

"Result-Ok?’ Step or Overall Performance Evaluation

Does It Make Sense to Talk About Corrosion Prevention and Corrosion Control in MIC Cases?

Effect of MIC in Accelerating the Passage from Pseudo-FFS to Zugzwang State

MIC Failure Analysis in Laboratory

Engineering Analysis of MIC in the Field: Avoiding Pitfalls via Dynamic Checklists

Summary

Chapter 5. Innovation, Uncertainty, and FMEA-MIC and FCP-MIC

Introduction

Theory of Innovation

Uncertainty

Novelty

Future Studies Model of Corrosion and the Place of FMEA-MIC in it

Futures of FMEA-MIC and FPC-MIC of a Wetted Asset

What can MIC Treatment Learn from Fashion and Food Consumption Lifestyle?!

A Brief Review on the Economic Models for Estimation of Cost of Corrosion

Summary

Index

Copyright

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Notices

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Dedication

To:

Nicola Tesla

The Child of Light and a lonely Hero

Author Biographies

Dr. Reza Javaherdashti holds a double degree in Materials Science and Metallurgical Engineering. In addition to being an internationally renowned expert on microbial corrosion, he has several internationally referenced books and papers on the subject. He has over 20 years of field and academic experience as both a consultant and a researcher. He is the first scientist who has applied Fuzzy logic in prediction of the risk of microbial corrosion successfully. Although as an engineer corrosion is his passion, as a manager he has grown interest in studies related to the cost of corrosion. He theorized and formulated corrosion knowledge management (CKM) for managers and was the first who applied Future Studies to present a Futuristic model for managers that had corrosion as its integral element.

Farzaneh Akvan has M.Sc. degree in Physical Chemistry with a focus on corrosion. Furthermore, as a graduate of Harvard Business School and an entrepreneur, she has professional interest in corrosion cost analysis and corrosion management. Besides her professional job as a corrosion consultant, she has served as the manager of National Corrosion Association and senior corrosion inspector at SGS Company. She was selected as the Best Young Researcher of all Europe in 2010 and received the award of Honor from Gubkin State University. Along with her associated work with Dr. Javaherdashti on Futuristic models of corrosion management, she has several publications about corrosion, particularly MIC. She has been a veteran member of IES, Young researchers and elites club and NACE.

Foreword

Corrosion has been driven from the Latin word Corrodere that means bitten away. Apparently, the way that a corroded piece looks like gives the impression that it has been bitten away by an invisible monster. In fact, this monster is not invisible at all to those who want to see it: ecological as well as economical consequences of corrosion are quite evident to anyone working in industry. However, let us try to give some facts and figures that may assist in understanding the severity of corrosion even more.

In 2012 (the year that many people around the Globe did believe that it was The End), all disasters resulted in a financial loss of only US$157 billion. ¹ The average global loss due to corrosion in the same year had been estimated to be over US$ 2000 billion. ² This means that the cost of corrosion in the supposedly "Doom's Day was more than 13 times of the cost of the natural disasters all together!

NACE’s (National Association of Corrosion Engineers) famous IMPACT report in 2016 estimated the global cost of corrosion at US$2.5 trillion (US$2500 million). ³ The same report states that 15–35% of this cost could be recoverable by proper using of corrosion control methods.

In addition to economical damage, there is a seemingly never-ending list of ecological disasters (even life loss) due to corrosion. ⁴ , ⁵ In this context, corrosion will appear even more frightening than the usual way of referencing to it by ordinary people (even some professionals as rusting or wear and tears.

A very important practical aspect of engineering is concerned with how failures happen, why they happen, and when they do as well as what the consequences and effects are that they create. This can be collectively referred to as Failure Modes, Effects and Causes and Analysis (FMEA). When FMEA focuses on microbiologically influenced corrosion (MIC), we designated it as FMEA-MIC. Perhaps if our attention was on another corrosion process such as atmospheric corrosion or corrosion under insulation (CUI), instead of MIC, we could have come up with FMEA-atmospheric corrosion or FMEA-CUI.

While FMEA is rather a useful tool for us to deal with the how/why questions about failures, it is also essential to know what mechanism(s) have been operating that eventually resulted in failure.

There are various kinds of corrosion processes. The very fact that an asset/equipment is corroding does not necessarily mean that it has failed. This is a very important point that in this book we will discuss in detail: there are mainly three stages of service life of any asset through which its reliability for the job it does starts to expire due to corrosion. These three stages are to be understood very thoroughly by the way we will explain. We will get back to this a few paragraphs below.

Microbial corrosion (MIC) is a wide-spread electrochemical corrosion affected by the presence and activity of living organisms, both micro- and macroorganisms. MIC could be the root cause of posthydrotest failures as well as failures observed in hydrants/sprinklers/fire water rings and cooling towers, heat exchangers, thickeners, etc.

Dealing with MIC is a practice that in many industries rests upon applying some rules of thumb and, unfortunately, misunderstandings and mistreatments that come with it. The share of MIC in the economic damage imposed by corrosion can reach to 40%, and this alone is enough for any integrity and corrosion engineer as well as any manager to contemplate about the effects that MIC can have on weakening the functionality of assets and equipment.

In this book, we bring a new look to the way MIC is to be treated in industries by redefining MIC within the discourse of FMEA-MIC.

The essence of FMEA, however, is describing the mechanism(s) by which the failure has occurred in the first place. From a corrosion specialist point of view, as we cannot stop corrosion due to its very nature which is thermodynamically driven, it is failure that marks the disastrous end of any corrosion process, whether MIC, CUI, or else. In other words, while there is no way to stop corrosion, there could exist many ways to contain, control, or even prevent failure. (We once again want to emphasize upon the terminologies here: prevention of a failure which is being caused by corrosion is far different from prevention of corrosion itself. In Chapter 2, we will discuss the discrepancies existing between corrosion control and corrosion prevention.)

In failure analysis context, we have been used to thinking of FMEA within the tight, predefined mindsets that make it, more or less, a postmortem practice: we analyze why and under what conditions such-and-such failure occurred, and we try to explain it by adapting one or more of the corrosion processes templates we can choose from as a corrosion expert (and for that matter, as an RBA ⁶ ) and consultant. For one case, we may see SCC ⁷ as being the main failure contributing mechanism and attribute it to a range of certain corrosion factors such as the detrimental impact of sulfur or chloride or bacteria on enhancing corrosion combined with the effect of tensile strength and for another case, we may see CUI as the main culprit. But this postmortem analysis is just one stage of a three-stage process that, when completed, could assist in containing or, even much better, prevention of failure.

The above-mentioned three-staged process consists of the followings:

I. Understanding and highlighting what caused the failure

II. Analysis of failure

III. Defining conditions under which failure will not likely to happen again

The contributions coming from nonengineering parameters related to the first and third steps are never discussed in their required length in any corrosion book we know about. We would like to draw the attention of our readers to the point that nonengineering in this context does not necessarily mean nontechnical: a nonengineering yet technical parameter refers to a parameter that require management skills to control the working conditions suitable enough not to be leading into failure or conditions prone to failure. An example of such is that in the case of hydrotesting, all the required logistics will be made available and ready to carry out the practice: from the management of the cost of the equipment to the man-hour required to actually carrying out the job (this is the management side that does not require high engineering skills), but the technicalities involved in the process of hydrotest (from selection of the water source to chemically conditioning it and monitoring it from a microbiological point of view) is an engineering job. It is true that even for the engineering part of the practice we need management of costs and it is a management decision ⁸ most of the time instead of being a technical decision, yet the core of the job in this context will be engineering.

Two very important aspects of CM (corrosion management) that we take as an engineering tool to deal with corrosion are that neither do they belong to a specific industry nor a specific company. These features give enough flexibility to corrosion engineers to develop their own CM model to be adapted by various industries and companies other than and in addition to what BP, TOTAL, PETRONAS, and many other well-recognized companies have for their own. These models are similar in their underlying principles but differ from each other according to the specific working conditions in a given industry or company.

Based on this flexibility of CM and 20+ years of experience, we have presented a CM model that we humbly call it Javaherdashti Corrosion Management Model, and we have shown an example of applying it for considering the corrosion (in the form of MIC) in a fire water ring to specify how Javaherdashti CM model can be applied in practice.

In addition to CM, we have also introduced and defined CKM (corrosion knowledge management) for managers who know nothing or just a little about the technicalities involved in corrosion. CKM will allow a manager to look at corrosion in general and MIC in particular from the higher grounds of a manger.

The third stage (stage III) we mentioned previously also consists of very important contributing factors and parameters not all of which being engineering. For instance, management of environmental impacts that could have a potential influence on enhancing corrosion: a few months back, it was found that an underground pipeline carrying gasoline had been leaking for over 10 years, polluting cultivation lands and underground water sources of many villages nearby a refinery. ⁹ On the hand, research shows that mixture (blend) of ethanol and gasoline can easily absorb relatively huge amounts of water (0.3–0.5 v/v %) without phase separation. ¹⁰ It may not be a far-fetched scenario to assume that the water absorbed over all these years have done a lot of harm in the form of enhancing external corrosion of the pipe, maybe in the form of persuading and enhancing microbial corrosion for which the nutrients from both the leaking fuel and its components as well as from the soil have been readily available. It is of great significance to contemplate over environmental impacts of corrosion as these impacts are often being neglected. ¹¹

Stages I and III could become very hard to be distinguished from each other: in case of microbial corrosion, which is the main topic of this book, training of the personnel for technicalities related to MIC, management for providing enough tools and resources for inspection, monitoring and treatment of MIC can in fact contribute to both prefailure as well as postfailure logistics management.

In this book, we will focus on all the three stages mentioned earlier. We will describe why MIC-related failures could be expected to happen mainly by looking at corrosion mechanism scheme from a wider angle and its links to parameters that can promote MIC. We will show why corrosion and MIC must be considered to be of engineering importance in the first place. To define it in more accurate terms, we introduce for the first time in corrosion management nomenclature the three stages of service life of an asset as Fit-For-Service (FSS), pseudo-FSS and Zugzwang state (or Zugzwang Effect state). These three stages are essential, in our opinion, to enable us to define what failure really means: arriving at Zugzwang effect state of the service life of an asset.

We will mention MIC and its various aspects in some details and the length that could be accommodated to a book that undertakes to give its readers a relatively reasonable description of the matter. During this, we will address some of the myths and misunderstandings about MIC which are still common even among corrosion experts. ¹²

We are after establishing a logical mindset for our readers about how corrosion can be interrelated to MIC and via what mechanism(s) these are related to the concept of FMEA-MIC. This is a significant effort because in almost all works written about MIC, it is the technical core of the issue that is of interest to the author(s), and this interest is assumed to be the same as that of the reader as well. This is a wrong assumption: the reader could have chosen another book or another source of information over this or that particular book and if it is the matter of technicality, as the results by the biblometric study that we will mention in Chapter 5 suggest, nothing seems to become augmentable to the main body of knowledge that has already been formed around MIC over decades so far. Based on this, it is expected for MIC research and investigation just to grow in size and in the quantity of the data gathered and/or the information processed by which these data would fall into a certain categorical classification. Therefore there must be a reason for the readers to look at what is being offered to them other than tricks such as compiling the papers that have been presented in the past by some author(s) and now—with adding some dressing—has taken the shape of a book.

It is quite unfortunate that we engineers (and researches for that matter) have grown to think that our mental model and assumptions about the technicalities of a subject are the only alternatives that can be offered and only a few of us have tried to look at the matter from all possible aspects of view. This is particularly true for MIC and many books and publications (both web-based blogs and webinars). However, as just mentioned, there are still a handful of corrosion specialists who have tried to see out of the box.

The above essentially covers the contents of the first three chapters of this book. In Chapter 4, we explain FMEA-MIC in the length required, and, to further furnish the idea with novelty, various aspects of FMEA-MIC in Chapter 5 will be introduced and discussed. In Chapter 5, we introduce new challenges and ideas about the feasibility and possibility of using techniques such as Fuzzy logic and TRIZ in dealing with MIC as the main cause of failure in any FMEA-MIC approach. We will also introduce corrosion management, and for that matter, MIC management in a holistic Future studies management plan. To add more to the surprising aspects that can accompany our approach toward FMEA-MIC, we also study how slow fashion can be taken as a role model for environmentalists who want to deal with MIC-related failures and their environmental impacts.

We believe that in today's interwoven network of multidisciplinary skills and knowledge as well as technicalities, FMEA-MIC has no other way but to adapt its own paradigm of research into more innovative fields. In addition to that, FMEA-MIC has to be nurtured from various disciplines and sciences to become more equipped in dealing what it expected from it to do.

We hope that our readers will find this book as an introduction to the realm of MIC and its importance. Our book also aims at filling the gap that exists between research at universities and the practice needed by industry. MIC is one of the fastest growing areas in research and perhaps one of the slowest in adapting and accepting industrial practices: we still run intelligent pigs without really caring about the possibility of increasing the risk of MIC and we still apply hydrotest in the same way we have been taught to do without thinking much about posthydrotest possible MIC scenarios. We still believe in many myths!

We would like to end this chapter by a Farsi short poem by Reza Javaherdashti:

A rather free translation of the poem is as below:

[Come and see] how I have removed rust from iron but have not been successful in removing the rust of grief of your love from my own mournful heart!

MLB-MIC-2MLL

Reza Javaherdashti- Farzaneh Akvan

(14 Farvardin 1397)

April 03, 2018

---

¹   https://reliefweb.int/report/world/annual-disaster-statistical-review-2012-numbers-and-trends, Last seen 6th April 2018

²   http://www.usbasalt.com/us-basalt/solution-to-corrosion-problem.htmlm Last seen 6th April 2018

³  G. Koch, J. Varney, N. Thompson, O. Moghissi, M. Gould, J. Payer, International Measures of Prevention, Application, and Economics of Corrosion Technologies Studies (IMPACT), NACE International, March 2016, USA.

⁴  Z.C. Petrovic Catastrophes caused by Corrosion VOJNOTEHNI ČKI GLASNIK/MILITARY TECHNICAL COURIER, Vol. 64, No 4, pp. 1048–1064, Republic of Serbia, 2016.

⁵  R. Javaherdashti, C. Nwaoha, H. Tan Corrosion and Materials in Oil and Gas Industries, published by CRC Press/Taylor&Francis, USA, 2013.

⁶  RBA = Risk-based assessment

⁷  SCC = Stress corrosion cracking

⁸  For instance, if the engineer insists that the total microbiological screening of the hydrotest water (culture dependent and culture independent analyses of both planktonic and sessile CRB/CRA) is needed, management is highly like to refuse it and for this, they will of course have their own excuses the most common of which being others did not do that and they have had no problem

⁹   http://greenreporters.ir/?p=3467, Last visited 6 June 2019.

¹⁰  J. Rawat, P.V.C.Rao, N.V.Choudary, Effect of Ethanol-Gasoline Blends on Corrosion Rate in the Presence of Different Materials of Construction used for Transportation, Storage and Fuel Tanks, SAE Number 2008-28-0125, SAE International, 2008.

¹¹  To the best of our knowledge, one of us (Javaherdashti) for the first time studied the environmental impacts of corrosion. See R. Javaherdashti- H. Nikraz, A Global warning on corrosions and Environment: A new look at existing technical and managerial strategies and tactics, VDM Germany 2010.

¹²  Very recently (third week of April 2019) we received an e-mail about a corrosion training being held in India by two very experienced corrosion management figures. In the outline of this so-called training, microbiologically influenced corrosion had been defined as "types of Corrosion Mechanism— General Corrosion, Oxygen and CO 2 , Sulfide Stress Cracking Corrosion, Chloride influenced Corrosion, Microbiologically influenced corrosion. Assuming that all the technicalities of this training event has been checked by not one but the two experts whom are also themselves the lecturers and each has been in the business of corrosion and corrosion management for at least two decades in addition to that the audiences of this event would be mainly corrosion professionals, this is a serious mistake that has been made. We are not here for quarrelling over words but we do believe that the term type" was important enough that it had been even emphasized upon in the related NACE standard that MIC is NOT a corrosion type.

Chapter 1

Introduction

The main topic of this book, as the title suggests, is to understand (or to understand what we understand!) what is meant by failure modes, effects, causes, and analysis (FMEA) as to be applied to microbial corrosion (MIC) so that we could talk about FMEA-MIC.

Our understanding is simply as below:

1. A failure has happened that we think it is/can be due to microbial corrosion (how do you know=failure mode analysis),

2. We also want to know the way this failure would affect the overall performance of the equipment and the safety of working with that equipment (effect analysis),

3. But, obviously, without knowing what caused the failure and how it caused it, we cannot find a way to control its effect or—even much better—prevent it (causes analysis).

Failure is the very last stage of a relatively slow, yet powerful process that can start with corrosion. In fact, due to thermo dynamical nature of corrosion, it is impossible to have no corrosion. At the best, one can say that corrosion is under control and not that there is no corrosion. However, if it is unattended, then failure will be inevitable. The main focus here is to outsmart failure. In other words, we must not let failure happen in the first place. This will logically require us to answer to the three items we mentioned earlier.

No matter what fancy names we use to address corrosion and corrosion prevention and control, it is always at the heart of the issue of corrosion that it is much more complicated than what we can see on the surface. A detrimental mistake, made particularly by inexperienced engineers, is that they try to estimate the corrosion mechanism by which failure has happened by just looking at the crime scene, that is the failure appearance. This is a wrong approach mainly because of the fact that it assumes that there is only one particular mechanism of corrosion that can be operative: this assumption may not always be necessarily true.

Failures of components and equipment can have various reasons; some of these failures could have resulted from human errors and some from technical issues. Perhaps among these technical issues, the place of corrosion is quite important: Of the budget to be spent on maintenance in a refinery, about 36% is directly due to the cost of corrosion and more than half of pipeline leaks is also because of corrosion. ¹

The role that human factors play in failures and particularly in corrosion-related failure cannot be ignored: A study ² that analyzed the factors involved in corrosion-related failures between 2001 and 2004 in the oil refining industry revealed that, on the average, 60%–80% of these failures had happened due to human factor. We, however, prefer to concentrate only on corrosion as the main concern for us in analyzing failures. In this respect, we do not prefer a particular industry over another: for us FMEA-MIC in oil and gas industry is as important as it may be in water treatment or food industry. The reason is that we are looking at corrosion per material not per industry.

There are various kinds of corrosion processes that, by the degree of damage they cause, can each be the focus of a book. During our professional life, we observed that it is as if each industry experiences one type of corrosion more than other types and it is like that a particular industry suffers from a main type of corrosion. In mining industry, for example, it is erosion–corrosion that can be taken as the passion mark of corrosion, in oil and gas industries it is sour and sweet corrosion and so on. Even so, in a given industry one can come across segments and parts of the industry that among other types of corrosion, experience one type more: in a thermal power plant working based on water-steam circuit, hot corrosion in boilers (water wall tubes), impingement on the first rack of high power turbine blades and electrochemical corrosion between the condenser and the boiler feed pump could be among the corrosion major players. In metallic fire-water rings and hydrants, it is microbial corrosion that can be the prevailing corrosion scenario. The list can go on and on.

A corrosion per industry approach mainly focuses on corrosion issues that are of interest to a certain industry (which is good) but neglects other industries that could, even by chance, have the same corrosion problems (which is bad). A corrosion per material approach, however, looks at the overall effect corrosion can have on a particular material per se without a particular interest in a given industry.

However, what is interesting here is that despite the confusing picture we may get at the first sight, there are certain general rules that can be applied to any plant, whether a refinery or a power plant or a dairy products plant: we call this as "general rule of corrosion risk" and will explain it later.

General Rule of Corrosion Risk

In any industrial plant, irrespective of the industry, there are three features:

(1) The plant has its own production process or providing services

(2) The dollar's value of the production or services is specific to the plant and the industry the plant belongs to

(3) There is a safety issue to be observed for the industrial activities that are taking place in the plant. This safety issue will provide a safe production/service provision environment.

An example may serve to clarify the three features mentioned earlier: a power plant and an oil refinery and a port are examples of three plants that work in different industries: power generation, oil refining industries, and marine transportation services. Each plant has its own way of production and service provision that is unique to that particular industry pace and what each plant either produces or provides service for has its own market value. However, what is common among all the three is that safety must be provided. No one wants to work in a power plant or a refinery or on a port that is vulnerable to failure and possibly the risk of inducing damage to the environment and, even more importantly, to the personal who work there.

Corrosion is a safety issue. In the context of possibility of a failure being resulted from corrosion, it is corrosion that can be taken as the main culprit and therefore it is corrosion that has to be seriously considered, in terms of its control and possibly prevention (corrosion prevention and corrosion control are two very important instruments in understanding FMEA ion the way we treat it here in this book. We will define, and several times return to the definitions of corrosion prevention and corrosion control and the very important difference they have with each other).

Corrosion having such significance is to be studied in detail in terms of FMEA. We will try to exactly define what we mean by failure of an engineering asset not in terms of what engineering textbooks say but in terms of real life corrosion management. It is also important to clearly understand the causes that may be leading into these failures and how to address them properly by applying the best possible analysis techniques.

FMEA will become even more complicated when it comes to microbial corrosion; therefore, we have to prepare the stage properly for the main concepts that can be listed below as follows:

(i) General rule of corrosion risk

(ii) Corrosion prevention and corrosion control

(iii) Zugzwang effect state

(iv) Fit-for-service (FSS) and pseudo-FSS states

(v) The link between the four elements mentioned earlier.

According to what we call as the general rule of corrosion risk, in any plant one can observe two categories of corrosion scenarios/risks: those related to the main process equipment and those related to the auxiliary equipment.

What we mean by auxiliary equipment is the equipment that is part of the main process equipment but without them the process is highly likely to experience difficulties, sometimes very serious difficulties. A good example of auxiliary equipment is the fire water rings. Another example is the base load power plants that in a steel production complex or a petrochemical complex (any strategic plant that is to work 7/24 and always needs electricity that is not coming from the main grid) is entitled to produce the required power.

Therefore, the aim of a corrosion engineer must not be limited to the corrosion of the assets and equipment directly related to the process but also to the auxiliary assets and equipment that facilitate the main process to happen. Fig. 1.1 shows two examples of the corrosion observed in the main process and the auxiliary equipment. It is to be noted that while these corrosion processes may each have different mechanisms, the result is that the asset that is corroding may sooner or later come to a Zugzwang state (to be discussed in length later). Fig. 1.1B–E also serves to illustrate a state of service that we call pseudo-FSS (pseudofit for service) and we will describe it in full length later in this chapter.

General rule of corrosion risk can also be interpreted as that taking care of corrosion problems in both main and auxiliary equipment is a must unless the function of auxiliary equipment is directly related to the safety of process. It is in this case that understanding the failure mode(s) of the auxiliary equipment will be even more important than that of the main equipment and must be put on priority.

Fig. 1.1 An illustration of the general rule of corrosion risk: (A) to (C) show a cyclone used in a copper refining plant with overall corrosion that, in the case shown by arrow, has caused two through-wall pits. (D) and (E) corrosion (most probably oxygen attack) of a 20 inch water in-let pipe to the same plant. (C) and (D) present examples of corrosion in the main process equipment, and (D) and (E) are examples of corrosion in auxiliary equipment. 

Taken from Dr. Reza Javaherdashti personal collection.

FMEA concentrates on four issues related to failures: understanding its mode, the possible effects that can have, the possible cause (s) for these failures, and the way they must be analyzed.

MIC, based on the industry and the equipment/asset, could be regarded either as a predominant corrosion risk in main process equipment or in an auxiliary equipment: in a post-hydrotested pipe, MIC could be the main corrosion mechanism in action that would deteriorate the material of the asset. MIC can also be the prevailing corrosion mechanism in pipelines that carry fluids such as oil and gas with entrained water phases as well as water and waste water treatment facilities, ports, and jetties and many more main process equipment and assets. On the other hand, in a hydrant and fire water ring, MIC is the main corrosion mechanism and as the safety of operation in a plant has direct correlation with the functionality of the fire water ring, understanding MIC and the way it can become the main failure mechanism is of great importance, as briefly discussed earlier as an interpretation of the general rule of corrosion risk.

Zugzwang Effect and Its Role in FMEA

When failure happens it means that the red part shown in Fig. 1.2 has long been passed:

Fig. 1.2 shows in a schematic way how thermodynamic, ongoing corrosion can reach to a stage that is irreversible failure. To understand Fig. 1.2, one has to have a better understanding of Fig. 1.3:

For each component, there is a set of parameters that are considered dangerous limits because if they are ignored, failure will be inevitable. For example, there is a temperature limit for each material within which it must remain to be in an fit-for-service state. Or, there is a corrosion potential versus pH range, as thermodynamically determined by Pourbaix diagrams, that will allow keeping a certain material within a safe range of these two parameters. As long as the components of the asset are within the safe range, the asset can be expected to be in its fit-for-service state. However, if it enters into the danger zone of that specific parameter (or the set of parameter) that in Fig. 1.2 we have shown with a red arrow, then the equipment must be cared for seriously.

Google defines Zugzwang as "a situation in which the obligation to make a move in one's turn is a serious, often decisive, disadvantage." We believe that as a useful concept, Zugzwang can also be applied to corrosion.

Fig. 1.2 The delicate balance between being fit-for-service and failure. 

Taken from Dr. Reza Javaherdashti personal collection.

Zugzwang Effect in cases related to corrosion can be redefied with the following two criteria:

(1) For the structure/asset that has been exposed to corrosion, thinking of any repair is not economical any more. In other words, the extent of damage is so economically devastating that the management cannot/is not willing to handle any repairs as it will not make economic sense to them,

(2) Even if despite its lack of economic feasibility we decide to do it, corrosion case has become so widespread and hard to cope with that it will make it technically not feasible to even try to mitigate corrosion any more. This means that as the root cause of the problem is not known, even