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Pipeline corrosion is a growing problem in the oil and gas industry. In this interview Prof. Dr. Eng. Moustafa Mohamed El-Gammal is Emeritus Professor, Faculty of Engineering University of Alexandria, Egypt and Consultant Engineer, Marine Approved Surveyor, describes the cause of pipeline corrosion and what can be done to remedy the situation.
Describe some of the different types of pipelines.
Pipelines are considered the main source for keeping the continuation and progress of the served community. Look at the human body and you will be surprised to know that it consists of several huge pipelines with different sizes. The lengths of each can reach several thousand kilometers! Veins and arteries are pipelines within the human bodies. The colon is another type of cascaded pipelines. Furthermore, pipeline leak detection systems mimic the human body animation. If one of the veins or arteries explodes or is blocked then can a human being survive for long? The jamming of these pipelines causes blocking and death could result.
So to start with one should be aware of a pipeline definition that is found in most current practice. A pipeline comprises of all parts, as well as branches, of the physical facility through which liquids (crude oil, petroleum products) or gases (natural gas, carbon dioxide) are transported, including pipe, valves and other equipment and accessories attached to the pipe, e.g., compressor units, pump stations, metering stations, regulator stations, delivery stations, holders and fabricated assemblies.
Pipelines are the safest and most efficient means of transporting crude oil and natural gas from producing fields to refineries and processing plants and of distributing petroleum products and natural gas to the consumer. Pipelines in domestic daily use as well as commercial and industrial projects are composed of several families which can be categorized into sub families. The main fields of pipeline uses as such are composed of:
- Oil and gas industries both upstream and those of downstream
- Product pipelines in refineries, terminals and petrochemical and fertilizing industries
- Water siphons both for waste drain and freshwater
- Feeding liquids pipelines
- Pipelines for heating and cooling media transportation
- Reclamation and irrigation pipelines
- Compressed air pipelines
Why is it important for people to know where pipelines are located? How can their locations be identified?
People must be aware of the importance of knowing pipelines locations for their interchanging safety problems. Also to experience means and to recognize ways of prevention of environmental hazard pipelines problems. The identification of pipelines can be related to colourdefinition for all pipelines route. The pipeline route is influenced by such factors as:
- environmental protection and preservation
- stakeholder input
- operating environment
- location of existing corridors
- control points
- regulatory matters
- land acquisition
How long to pipeline pipes last before they need replacing?
It depends on the maiden lifetime of pipelines; if known then one can work out a time plan to handle pipeline replacements before leaks or explosions. Generally design parameters specifying working conditions depending on anchorage, hammering forces and cavitation as well as bent erosion problems.
The time a part needs to be replaced depends on digging as well as monitoring and inspection, and thus academic and theoretical equations based on probabilistic fatigue and reliability analyses need to be implemented.
The type of flow, the inside pressure and the internal speed of the flow are some of the dominating parameters need to be defined in order to know when replacement is needed. Also, environmental changes, kinetics and computational fluid dynamics of the flow motion which takes variations in viscosity, Reynolds Number and Stock’s formulas must be applied to know the exact the erosion, and hence corrosion rates are all to be harmonized to assess the lifetime integrity of a pipeline.
In global words the contingent plan of replacement varies from site to site and from the used material in the pipeline manufacturing as well as the sequence of assembly. That means what could be applied to a pipeline should be changed and tailored to the surrounding circumstances. Thus reliability and risk analysis play major roles in the estimated pipeline lifetime and are the most dominating factors implemented in the estimation of lifetime cycles of pipelines. Because of this we can tell within a certain percentage of confidence and assurance limits when that part of pipeline should be replaced.
What is causing the corrosion in the pipelines?
Corrosion is a natural process by which a corrosion current is formed with a flow of electrons from a high potential anode to a lower potential cathode material. The formed resulted hydroxyl leads to ionized medium through which the increase in loss of electrons can increase the rate of escaping of electrons. The primary driving force of corrosion is based upon the transformation of iron from its natural state to steel. The refining of iron ore into steel requires the addition of energy. Steel is essentially an unstable state of iron and corrosion is the process of iron returning to its natural state. The energy used in the refining process is the driving force of corrosion. Therefore, corrosion is considered to be a process of deterioration and degradation to an embedded pipeline.
Corrosion cells are established on underground pipelines for a variety of causes. A primary cause of corrosion is due to an effect known as galvanic corrosion. All metals have different natural electrical potentials. Where two metals with different potentials are connected to each other in a common environment, current will flow causing corrosion to occur. The coupling of steel to a different metal, such as copper, will cause a corrosion circuit to be established. Direct coupling of copper to steel will cause the steel to corrode much faster than normal. Another form of this is the coupling of rusty pipe to new, clean steel. The natural difference in potential causes the new steel to corrode more rapidly than the old steel. Other causes of pipeline corrosion cells include the effect of different soil types, oxygen availability, stray current interference and microbiological growth.
Two other unique (and sometimes related) causes are stress and hydrogen.
- Stress Corrosion occurs when even a very small pit forms in a metal under stress. The concentrated stress either deepens and extends the pit, or cracks the protective film which tends to form. Under continued exposure to the corrosive medium and stress, the crack extends by alternate corrosion and stress failure.
- Hydrogen Embrittlementand hydrogen attack results when atomic hydrogen penetrates into the grain boundaries of steel producing micro-cracks, blistering and loss of ductility. The atomic hydrogen combines into molecules and results in blistering and laminations.
The US Company Enbridge was recently fined $2.4 million because of an oil spill from a pipeline. Do you think pipeline corrosion is a growing problem?
Yes, of course a leak due to corrosion of pipelines now is a recognized problem and on an increasing scale. Environmental global warming will drastically affect pipeline corrosion rates to the extent that whenever ionization occurs you can expect a corrosion current to be generated. More biological corrosion effects are expecting to hit stainless steel structures as well as duplex steels very severely. Thus whatever protection systems are to be implemented, there will be a corrosion deteriorating and degrading periods that will result.
This means that the next coming decades will witness different and unknown corrosion epidemics to be resulted. There will be more collapsing as well as heavy deterioration of expensive protected structures.
The means of protection will be very much different from those being now known and currently implemented. This is mainly due to the non-predicted severity in corrosion rates and consequences. Global warming is the biggest enemy to engineering and industrial productive assets, and thus any means of controlling this phenomenon will keep corrosion fines very low. Also, controlling global warming of the universe toxic gases, e.g., CO2 , will lead to enrich the green environment and thus will increase the lifetime of metallic structures and will play a major role in enhancing well recovery. Re-injecting this gas will improve the reservoir productivity to very high levels.
What are the regulations in regards to pipelines? Who is in charge of these regulations? Are these universal?
There are hundreds of Codes and Regulations towards safety implementation applied to pipelines, the most important of which are as follows:
- U.S.Department of Transportation – PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINSTRATION – PHMSA, which deals with safety problems in pipelines with the following missions. PHMSA's mission is to protect people and the environment from the risks inherent in transportation of hazardous materials - by pipeline and other modes of transportation, you could open their web link at: http://www.phmsa.dot.gov/
ASME PIPELINES CODES, those set of codes are implemented through applying the Role of ASME Codes & Standards in Pipeline Integrity in high pressure pipelines , e.g., boiler cases, you could have a look at their web link at: http://www.asme.org/NewsPublicPolicy/GovRelations/PositionStatements/Role_
- API Pipelines Codes for Oil and Gas Services, could be seen at: http://www.ewura.go.tz/pdf/Standards/Codes%20and%20Standards%20for%20Natural%20Gas.pdf
- SSPC, dealing with safety protection coatings in pipelines, at: http://www.sspc.org/
- DnV RP, Cathodic Protection of pipelines, at: http://exchange.dnv.com/OGPI/OffshorePubs/Members/rp-b401.pdf
- ASNT SNT-TC-1A-2006, dealing with welders qualifications and tests of pipelines, at:http://www.techstreet.com/standards/ASNT/SNT_TC_1A_2006?product_id=1319387
- ISO 8501-1 - In 2007 updated version of the standard measure for the visual evaluation of rust and purity levels of non-coated steel. Also known as the "Swedish steel blasting grades" (Sa). Contains high-quality colour photographs for estimating the rust levels and purity levels after cleaning manually or by machine (also with blasting). Target audience: Blasting and painting companies and their clients, paint technicians, advice bureaux and industrial coating businesses. http://www.tqc.eu/en/products/article/68/
- ASTM A370 - 10 Standard Test Methods and Definitions for Mechanical Testing of Steel Products, http://www.astm.org/Standards/A370.htm
- DnV 1981 Rules for Rules for Submarine Pipeline Systems, http://pdfcatch.net/ebook/dnv+submarine+pipeline/
- AGA- American Gas Association, http://www.aga.org/NR/rdonlyres/B797B50B-616B-46A4-9E0F-5DC877563A0F/0/0603AGAREPORT12.PDF
- ASME B16.5 2009 Pipe Flanges and Flanged Fittings, www.engineeringsky.com
- AWS D1.1-2006, Structural Welding Code—Steel, http://files.aws.org/technical/d1/D1scope.pdf
- OSHA Hazards Associated with De-Watering of Pipelines, http://www.osha.gov/dts/shib/shib062104.htm
Do you think these regulations are too lax? Why or why not?
Even with the presence of those safeties of pipeline codes leak, fire as well as explosion hazards and corrosion are all increasing.
This is mainly due to either one or a combination of the following:
- Lack of information
- Misuse of the pipelines
- Global warming phenomenon
- Application of new materials, applying new fabrication technology and relaxed monitoring and inspection procedures.
- Innovative designs for new structures
- Lack of experience
Exceeding the lifetime replacement period
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