Category Archives: Corrosion

Understanding AC Corrosion Criteria

AC Corrosion Implications for New and Existing Pipelines

Pipeline AC Corrosion
AC corrosion is a threat for both new and existing pipelines.

AC inference can result in significant and rapid corrosion and is a threat that must be considered for both new and existing pipelines. NACE provides a detailed standard practice to specifically address the threat of AC corrosion; however, it is very important for corrosion professionals to understand the guidelines and their implication for pipeline design, monitoring and risk assessment.

Criteria for Control of AC Corrosion

Approved in December of 2017, NACE SP21424-2018-SG “Alternating Current Corrosion on Cathodically Protected Pipelines: Risk Assessment, Mitigation, and Monitoring” provides supplemental guidance for the control of corrosion for cathodically protected pipelines that are subject to influence from close proximity high voltage AC transmission systems. This standard practice expands significantly on the earlier standard SP0177 “Mitigation of Alternating Current and Lightning Effect on Metallic Structure and Corrosion Control Systems” and introduces new criteria for addressing AC Interference for cathodically protected pipelines.

The criteria detailed in Section 6 of SP21424 allow for two means of assuring that effective AC corrosion control has been achieved:

  1. Document that the corrosion rate is less than the common benchmark for effective corrosion control of 0.025mm/y (1 mil per year). This can be achieved using weight loss coupons, corrosion rate probes or through in-line metal loss inspection tools—provided the inspection tool resolution is sufficient to detect small-diameter attacks such as AC corrosion. This approach is great for areas where AC corrosion risk is considered minimal. Essentially this says we don’t expect AC corrosion and we will demonstrate that AC corrosion is not occurring with a modest testing program. In those areas where AC corrosion can be reasonably anticipated; however, a second criteria is provided.
  2. For areas where AC corrosion mitigation can be anticipated, the criteria for effective control is based on reducing the time weighted average AC current density below a specific threshold that varies depending on the DC cathodic protection current density as follows:
    • Where the DC current density is controlled to less than 1A/m2, the AC current density should be controlled to less than 100 A/m2
    • Where the DC current density is not controlled to less than 1A/m2, the AC current density should be controlled to less than 30 A/m2

This first criteria, much like the first criteria for cathodic protection in SP0169-2013, allows for a prove-it type criteria based on documenting that corrosion is not occurring.  

The second criteria, unlike the criteria for cathodic protection, is not based on a measured potential, but is instead based on measuring current density on a time weighted basis. Not just one type of current density must be considered, but instead the criteria requires evaluation of the time weighted average of both AC and DC current densities.

Current Density vs. Polarization

While conventional criteria associated with control of corrosion through the application of cathodic protection is based on shifting potentials on the pipeline, the control of AC induced corrosion is based on limiting current density criteria on a time weighted basis. These requirements are quite different—and when AC corrosion control is a concern this will require a change in how pipelines are monitored, a shift in CP design philosophy in those areas where AC corrosion is a concern and some understanding of the impact of AC mitigation.

Pipeline Monitoring

Pipelines are typically designed to monitor polarization levels with the installation of test stations at frequent intervals to support measuring polarization levels at the test station and to facilitate continuous close interval polarization surveys.  When AC corrosion is a threat, the monitoring provisions need to shift from providing connections to the pipeline for polarization measurements to the installation of coupon test stations to facilitate current density measurements.

CP System Design Philosophy

The primary concern with cathodic protection design is typically making sure that more than enough current is available to ensure minimum polarization levels (either 100mV shift or -850mV off potential) are met along the length of the pipeline. This often means the CP system is over-designed and overdriven—there is little cost associated with over-polarizing some segments of the pipeline to ensure that the entire pipeline meets the minimum requirements. If the pipeline does not meet criteria in some locations, the first step was to push more current over the entire system until those low potential sections also met the polarization criteria. Little consideration is given to concerns with areas receiving too much current.

However, when we overlay the concerns with AC induced corrosion and the desire to control the DC current density below 1A/m2 or face the requirement to mitigate to a much lower threshold for AC current density, it becomes a more challenging CP system design. Now the CP system designer must:

  • Understand the interaction between cathodic protection system design and its impact on AC mitigation requirements
  • Provide provisions to monitor (on a time-weighted basis) both AC and DC current densities
  • Give consideration to being able to intentionally control DC current densities in those AC corrosion risk corridors—this might require additional CP stations to reduce over-polarization, the strategic use of isolation devices to create DC current density control zones, and the use of auto-controlled rectifiers to vary current output to control DC current densities. Improving the control of DC current density can significantly reduce the amount of AC mitigation that might be required.

AC Mitigation

For existing pipelines, the AC mitigation requirements should be based on some actual data on the CP current density in specific areas of concern. Current densities are typically highest closer to a CP station and in areas of low soil resistance. Another factor that can impact current density is the quality of the coating. Poorly coated pipelines have more uniform and lower CP current densities while well coated pipelines may have higher localized current densities because of the small size and infrequent nature of the coating defects. For new pipelines, the AC mitigation designer should be careful to presume that the higher AC mitigation threshold based on controlling DC current density can be applied without consultation with the CP system designer to assure that the design provides for sufficient control of CP current density.

Coupons

Remote monitoring units can record and transmit AC and DC current density information from AC coupon test stations to support the prevention of AC corrosion.
Mobiltex Cathodic Protection Test Station Remote Monitoring Unit

The use of AC test stations with specific AC and DC current density coupons is necessary to ensure that localized conditions do not exist where AC corrosion risk is not properly being controlled. These coupon test stations should be equipped with remote monitoring to allow for data polling at regular intervals to allow for time-weighted averaging of the current density data. Mobiltex recently introduced a new series of Test Station RMUs specifically designed to be installed in a conventional cathodic protection test station. These remote monitoring units can record and transmit AC and DC current density information from AC coupon test stations.

The frequency and location of these coupon test stations is a design issue. It is critical to note that within areas subject to AC corrosion risk, coupon test stations should be installed at all significant “inflection” points where predictive modeling and/or AC mitigation design experience would dictate elevated risk including:

  • Entrance/exit points for HVAC / pipeline collocations
  • Low soil resistivity areas or areas with notable differential soil resistivity changes within the collocation
  • HVAC phase transpositions
  • Pipeline crossovers

Conclusions

The criteria for AC corrosion control are different than those typically associated with conventional cathodic protection to control corrosion.  The requirements for monitoring both AC and DC current densities are interrelated and can have a significant impact on the AC mitigation requirements and on the cathodic protection system design and operation.  Understanding this relationship between AC and DC current density and properly controlling each is critical to properly controlling AC corrosion risk.


For information on MATCOR’s AC mitigation solutions or for assistance setting up testing to prevent AC corrosion, please contact us at the link below.

Contact a Corrosion Expert

Pipeline Corrosion — All You Need to Know

This article provides an overview of pipeline corrosion in the United States, the two categories of corrosion in pipelines and the primary methods of prevention.

Corrosion of Pipelines in the United States

pipeline corrosion prevention

The United States has over 2,225,000 kilometers of pipelines, the vast majority of which are transporting oil and natural gas. No other country comes close—Russia is a distant second with approximately 260,000 km of pipelines.  The US Pipeline network consists of hundreds of public and private companies that own and operate these pipelines within a national regulatory framework managed by the US Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA).  While pipelines have proven to be exceptionally efficient and very safe—pipelines are roughly 70 times safer than trucks1 and 4.5 times safer than rail2—the aging network of pipelines continues to be of concern because much of the nation’s pipelines are at least 50 years old and getting older.

Pipeline Corrosion Prevention Mitigates Devastating Failures

Corrosion is one of the biggest problems contributing to leaks and ruptures of pipelines. Corrosion is the natural process where materials made from metal electrochemically react with the environment and deteriorate.  Without proper engineering and preventative maintenance, this deterioration from the natural process of corrosion will result in an increasing frequency of pipeline incidents.  The good news is that with proper pipeline monitoring and maintenance, corrosion is completely manageable. Operators can utilize existing technologies to ensure the integrity of these critical assets and prevent damaging failures.

Two Categories of Corrosion in Pipelines

Pipeline corrosion can be broken down into two primary categories.  Internal Corrosion, which causes approximately 12% of all incidents, occurs on the inside of the pipeline, while External Corrosion, which results in approximately 8% of all pipeline incidents, occurs on the outside of the pipe. 

Pipeline Corrosion Protection Strategies for External and Internal Corrosion

Two primary mitigation strategies are employed to prevent external corrosion of pipelines:
  1. Pipeline coatings
  2. Cathodic protection

When these mitigation strategies are properly employed, monitored and maintained, steel pipelines can last indefinitely. While this sounds simple, pipeline coatings are never perfect and are themselves subject to damage during construction and degradation over time, while cathodic protection is a complex process that requires continuous monitoring and extensive testing, combined with regular maintenance to be effective.

Internal corrosion, in most cases, is a result of contaminants naturally occurring in the product being transported by the pipeline. Common contaminants include oxygen, hydrogen sulfide, carbon dioxide, chlorides, and water.

Many variables can affect the nature and extent of a particular internal corrosion reaction on a pipeline:
  • Contaminant concentrations
  • The combination of contaminants within the pipeline
  • Operating pressure and velocity
  • Pipeline geometry and holdup points
  • Operating temperature
  • Other factors
The primary pipeline internal corrosion prevention strategies include:
  • Controlling or minimizing contaminants prior to transporting them in the pipeline
  • Internal pipeline coatings
  • Injection of corrosion inhibitors
  • Increased frequency of internal pipeline cleaning to remove the accumulation of contaminants

For controlling both external and internal corrosion, regular monitoring and testing programs combined with the appropriate mitigation strategies, are a critical part of any pipeline integrity management program.  When performed properly, corrosion can be effectively controlled, assuring that pipelines remain safe from corrosion indefinitely.

1 propublica.org – Pipelines Explained: How Safe are Americas 2.5 Million Miles of Pipelines?

2 fraserinstitute.org – Pipelines are the Safest Way to Transport Oil and Gas


To get in touch with our team of cathodic protection and AC mitigation experts for more information, to ask a question or get a quote, please click below. We will respond by phone or email within 24 hours. For immediate assistance, please call +1-800-215-4362.

Contact a Corrosion Expert

Vapor Corrosion Inhibitors

Are Vapor Corrosion Inhibitors Magic Dust or a Viable Corrosion Prevention Tool?

This article is intended to provide a basic primer on vapor corrosion inhibitors for use in corrosion prevention for above ground storage tanks and address where this technology stands.

There has been a significant effort within the oil and gas world to either promote or repudiate the use of Vapor Corrosion Inhibitors (VCIs) for tank bottom plate corrosion control. As a leader in the above ground storage tank corrosion control industry, MATCOR has partnered with Zerust® Oil & Gas to make VCI options available to our customers that are interested in applying this technology as part of their corrosion mitigation approach.

How Vapor Corrosion Inhibitors Work – Video Courtesy Zerust® Oil & Gas


What are vapor corrosion inhibitors and how do they prevent corrosion?

Zerust Vapor Corrosion Inhibitors can be used in conjunction with CP systems.VCIs are chemical compounds that are released into a confined space, such as the underside of a tank bottom, and diffused through the sand pad material to reach the metal surface. These compounds are adsorbed onto the metal surface forming a strong bond that promotes and maintains a passive oxide layer on the metal and blocks other contaminant molecules from reaching the surface.

Are VCIs a non-permanent solution?

Corrosion protection using VCIs requires sufficient chemical concentration to thoroughly diffuse across the entire tank bottom surface area. The VCI has a finite life, after which it ceases to remain active. When this occurs, further chemical is required to replenish the spent VCI. The frequency of VCI replacement will vary depending a range of factors:

  • The rate of leakage through the tank chime
  • The operating temperature of the tank
  • The sand properties
  • The amount of chemical initially applied
  • Other factors

As VCI technology is still in the early phase of adoption, the typical replenishment frequency remains one of the big unknowns. A conservative estimate would be a minimum of 3-5 years’ service life before replenishment although a least one source has reported upwards of 15 years of effectiveness.

How is VCI applied initially for above ground storage tanks?

There are a variety of application technologies depending on the application and whether the tank is new construction, existing tank during inspection, a tank that is in-service or a double floor tank. Other considerations include the substrate material or concrete pad. The VCI chemical can be provided in a powder or liquid form. Whatever system is utilized to deploy the VCI, consideration should be given to how it will be replenished over the life of the tank.

Can vapor corrosion inhibitors be used in lieu of cathodic protection?

Practically speaking, most tank operators are not looking to replace cathodic protection but are considering VCI as a supplement to cathodic protection or as a short-term solution for inadequate or depleted CP systems until a replacement CP system can be installed.

Can VCI be used as a complement to cathodic protection?

This is where VCI provides an exciting opportunity to supplement cathodic protection. While cathodic protection has a proven track record in corrosion prevention for tank bottoms, there are limits to the effectiveness of cathodic protection. Cathodic protection only works when the tank bottom is in intimate contact with the sand bottom. Localized corrosion can occur wherever there are air gaps under the tank bottom. These can occur due to flexing of the tank bottom, imperfections in the plate steel, lapping of the plate steel, poor compaction of the sand bottom, presence of aggregate or non-conductive materials such as asphalt or oil, and at crevices in the tank ring wall. These are all areas where cathodic protection may not be effective and the proper application of VCI would be an excellent means of providing corrosion protection in these localized areas. Cathodic protection and vapor corrosion inhibitors are symbiotic. CP current distribution has been shown to improve in the presence of VCI.

How do I monitor that the VCI is working?

When applying VCI to a tank bottom, coupons, ER probes or UT probes installed under the tank are used to measure the effectiveness of the VCI and to alert the owner when the VCI requires replenishment. One of the concerns with using ER probes to measure corrosion rates under tanks is that ER probes provide an average corrosion rate and not localized pitting rates. It is understood that pitting corrosion is the dominant factor in tank bottom corrosion related failures and pitting rates can be significantly higher than average corrosion rates. There is a distinct correlation between average corrosion rates and pitting corrosion rates and the ER probes can be used to infer changes in the pitting rates.

Where do vapor corrosion inhibitors stand with industry standards and regulations?

According to API 651, there are several situations where CP is not recommended for specific tank foundation designs. In some of these designs, PHMSA recognizes that CP is not feasible.  In these cases, VCI can be a viable option. API 2610, the Tanks and Terminals standard outlines the use of VCI for tank bottoms in section 12.5. API 651, the CP standard, is being updated currently and VCI is being included as an option in this document. The State of Florida has identified that VCI can be used in tandem with CP or a standalone solution, for more than 6 years. NACE is currently working on publishing a standard “NACE TG543”, which is a comprehensive document on the application of VCI under tank floors. PHMSA is currently reviewing Special Permit requests for the use of VCI without a functioning CP system. If a non-regulated tank’s CP system is not meeting criteria, or has depleted, but the tank is still a few years from its next inspection, VCI can be applied to protect the floor until CP system repairs can be economically accomplished.

What independent published studies exist supporting VCI?

A 2018 study published by PRCI provides the strongest validation of the effectiveness of VCI and concluded that:

  • VCIs were found to be effective in mitigating pitting of steel exposed to corrosive sand but was not as effective as CP for reducing pitting corrosion. The study confirmed the importance of using the manufacturer’s recommended concentrations, as low levels of VCI was found to be ineffective.
  • ER Probes can be used to monitor the efficacy of VCIs
  • VCIs are compatible with impressed current cathodic protection; however, VCIs change the native potential of the steel and this must be considered when selecting CP criteria in accordance with NACE SP0193

Access the full study: PR-015-153602-R01 Vapor Corrosion Inhibitors Effectiveness for Tank Bottom Plate Corrosion Control

In conclusion, the application of VCI is a viable tool in our corrosion tool box that should be considered in conjunction with cathodic protection for critical service applications and as a standalone solution in some applications.


To get in touch with our team of cathodic protection experts for more information, to ask a question or get a quote, please click below. We will respond by phone or email within 24 hours. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

April 24 is Corrosion Awareness Day

Did you know that corrosion costs us an astounding 2.5 trillion dollars globally?

Not to mention corrosion can cost lives and jobs…

Today is corrosion awareness day, so we thought it would be a good idea to reiterate the importance of the NACE IMPACT (International Measures of Prevention, Application, and Economics of Corrosion Technologies) study released in 2016.

According to the study, most corrosion failures, and nearly all catastrophic corrosion failures are preventable. And nearly $875 billion can be saved through the right prevention and risk analysis efforts.

Through the IMPACT study, NACE determined that in order to reduce the astronomical cost of corrosion, we would have to change how decisions are made regarding corrosion. We must not only continue to develop corrosion control methods and technology, but we must utilize organizational management systems and risk tools throughout all levels of an organization to achieve the greatest success in saving lives, jobs and money.

You can learn more by visiting impact.nace.org.

MMO Anode Technology: The latest in Cathodic Protection

MMO anode technology has taken over the cathodic protection industry and MATCOR has been on the forefront for the last 20 years. Ted Huck, our VP of International Sales was interviewed at the recent NACE Corrosion Conference. In this video he discusses MMO anode technology for cathodic protection systems and the importance of reliable anode to cable connections.

MMO Anode Technology

MMO anodes, or mixed metal oxide anodes are the latest technology in the corrosion industry. Mixed metal oxide anodes are lightweight and durable with a very low consumption rate. 

MMO anodes are a mix of metal oxide electrocatalysts. In the presence of a DC voltage source they cause an electrical reaction that generates cathodic protection current. Unlike conventional impressed current anodes that physically consume as part of the cathodic protection reaction (at rates measured in kg/amp-year), MMO anodes are dimensionally stable and do not consume. Instead, they have a long and predictable catalytic life. MMO anodes consist of a thin coating of the MMO catalyst over an inert lightweight titanium substrate and are available in a wide range of shapes and configurations.

Why Cathodic Protection Systems Fail

Waterproof Anode to Cable Connection to protects MMO anode cathodic protection systems
Kynex® Patented, Waterproof Anode to Cable Connection

The most critical component to any cathodic protection anode system is the connection of the anode to the cable that runs back to the power supply. Because the cable is part of the anode system, if it has any nicks or defects or is not water tight, that cable can become part of the anode and will very quickly consume. When that happens, the anode fails. So, with cathodic protection systems it is imperative to have the highest quality connections.

Typically, when a cathodic protection anode system fails, it is not the anode that fails, it is the anode connection that fails. MATCOR has developed a proprietary technology for connecting wire anodes to cable, called Kynex®. Wire anodes are the heart of a lot of our products and this proprietary anode technology is a huge leap forward in the reliability of these connections.

Cost-effective, Reliable Cathodic Protection Solutions

At the end of the day, for our clients, it’s all about delivering value. It’s providing a cost effective solution that’s going to serve them for a very long time. As a designer and manufacturer of cathodic protection anode systems, we are able to specifically address client needs with customized corrosion prevention solutions that provide:

  • Long life
  • Great economic value
  • Superior reliability

MATCOR Products and Services

MATCOR is one of the world’s leading cathodic protection companies. We design, manufacture, install and service cathodic protection systems for clients worldwide. MATCOR provides services to the pipeline, midstream and oil & gas industries, protecting assets such as pipelines, storage tanks, and compressor stations. We also do a lot of work in the power industries, petrochemical, and chemical industries. Anywhere where you have buried steel structures, we are there to stop corrosion.
We encourage you to contact MATCOR through our website where our corrosion specialists and engineers can provide a solution tailored to your needs.

MATCOR Profiled in India Corrosion Publication

MATCOR Profile in Coatings and Anti-Corrosion Engineering Review, Apr/May 2015 issueThank you to Abraham Mathai at Coatings and Anti Corrosion Engineering Review for the profile about MATCOR and our 40th anniversary in the April/May 2015 issue!

MATCOR was founded in 1975 by William R. Schutt when he set out to develop a high quality, reliable source for cathodic protection products and equipment. The company designed and provided the first commercial cathodic protection system for reinforced concrete bridge decks that same year. The company has grown to offer a broad portfolio of proprietary cathodic protection and AC mitigation products, in addition to complete corrosion engineering services.

In March of 2015, MATCOR was acquired by Brand Energy & Infrastructure Services (Brand). Brand also owns CP Masters, Inc., a leader in the design and construction of cathodic protection and corrosion control prevention in the North American energy markets.

READ THE COMPLETE PROFILE

MATCOR Celebrates 40 Years Protecting the World’s Infrastructure from Corrosion

Chalfont, PA (Jan 16) – MATCOR, Inc. the trusted full-service provider of proprietary cathodic protection products, systems, and corrosion engineering solutions is celebrating its 40th anniversary throughout 2015.

matcor-40th logoIn 1975, William R. Schutt founded MATCOR, setting out to develop a high quality, reliable source for cathodic protection products and equipment. That same year, the company designed and provided the first commercial cathodic protection system for reinforced concrete bridge decks. Today, Mr. Schutt serves as MATCOR’s Chairman.

MATCOR has built a broad portfolio of proprietary products. The company received its first patent in 1984 for its deep anode cathodic protection system, the predecessor to today’s Durammo™ Deep Anode System. Other patented products include Kynex® waterproof anode to cable connection technology, the SPL™-INT-Anode for internal pipeline cathodic protection, the ORB™ Marine Anode and a precast anode plate system for use in steel-in-concrete applications.

In 1987, MATCOR experts served as part of the White House delegation to the Soviet Union under Ronald Reagan, invited for their expertise in concrete and construction infrastructure. The company has also received numerous safety, technical and industry awards in its 40-year history.

The company has grown from manufacturing and supplying cathodic protection products to offering a full array of turnkey cathodic protection and AC mitigation services and products.

William Schutt Web-1MATCOR is located in a state-of-the-art ISO 9001:2008 certified facility in Chalfont, PA. With a service office in Texas since 2006, an office opened January 2015 in India and a growing list of international distributors, MATCOR has established global reach in the corrosion industry. In 2014, the company delivered products and services to over 25 countries.

MATCOR Chairman William Schutt said, “MATCOR’s 40th anniversary is a tremendous milestone for the company. We’ve succeeded not only in our vision to become a reliable source of cathodic protection products; MATCOR has become a trusted global leader for both products and engineering services throughout the corrosion industry.”

ABOUT MATCOR

 

Chief Big Dig engineer is fired over light fixture controversy

Helmut Ernst, the embattled chief engineer of the Big Dig, has been fired, the state transportation secretary said today, as the fallout continued from the controversy over a light fixture collapse earlier this year in one of the project’s tunnels.

Ernst had already been reprimanded and suspended for his role in the state’s failure to notify the public for more than a month after a corroded 110-pound light fixture collapsed onto the highway in the O’Neill Tunnel on Feb. 8.

Transportation Secretary Jeffrey Mullan said the department had finished a review of Ernst’s performance on Friday and concluded he could no longer serve as the District 6 highway director, the former title for his job as a top engineer in charge of the Big Dig tunnels.

Mullan said he offered Ernst other jobs in the transportation department, but Ernst, who has worked as an engineer for the state highway system for two decades, declined to take them.

“As a result of that, we terminated Helmut’s employment at the DOT today,” Mullan told reporters at the state’s highway operations center in South Boston. “It was clear that we lost confidence — I lost confidence — in him, and given some of the issues, someone in a leadership position like that, I would expect more,” Mullan said.

Tom Broderick, currently the chief engineer in the highway division, will replace Ernst while the department searches for a permanent replacement.

The collapse revealed widespread corrosion in lights throughout the 7.5-mile Big Dig tunnel system — and the delay by state officials in notifying the public sparked outrage and concern about the tunnels’ safety.

In an interview in July with the Globe, Ernst said his team of engineers filed no written report about the collapsed light fixtures despite state policy requiring documentation of safety issues. Ernst admitted his engineers had been wary about writing things down since the 2006 collapse of a Big Dig ceiling panel that killed a woman.

“After all the depositions in the ceiling collapse case, we just meet and talk about it … What’s the point of putting it in writing?” he said. He said engineers had been “trained not to.”

Ernst claimed he had called his boss, Frank Tramontozzi — who was forced to resign in March as highway administrator for his own role in mishandling the light fixture collapse — the day after the collapse. Tramontozzi said he didn’t learn about the collapse until Feb. 28.

Ernst also claimed he brought up the collapse at a Feb. 14 senior staff meeting. But seven other staffers, questioned by a staff lawyer at Mullan’s request, said they didn’t remember him mentioning it.

Mullan said he was not pushing out a whistleblower, who had spoken out about problems in the Big Dig. “I don’t think that’s related to it all,” he said.

He said there would not be a chilling effect on other employees, discouraging them from speaking out. “No,” he said. “It just didn’t work out, and sometimes it doesn’t work out.”

Mullan has said he plans to leave his own job by the end of the year, but said today he has not settled on the exact date when he plans to step down.

SOURCE: http://www.boston.com/Boston/metrodesk/2011/08/chief-big-dig-engineer-forced-out/XXfFA4dQ3daU1pNdCO4KHJ/index.html

Oil sands critics target a new concern – pipelines

The crude oil that is pulled from Canada’s oil sands is thick and heavy, a black tar-like substance that takes large amounts of energy and effort to make into end products like gasoline and diesel. Even some people in the Alberta energy industry describe it as “nasty” stuff.

But is it also dangerous?

Over the past few months, critics of the oil sands have taken a new tack. They are now arguing that oil sands crude, which contains more contaminants than traditional sources of crude, poses a risk to pipeline safety – and they’ve linked the recent spate of North American oil pipeline spills to what they say is the corrosive content of oil sands products.

It’s an argument that began with environmental groups, but has now been taken up by legislators. Last week, for example, Alcee Hastings, a U.S. Democratic congressman, warned that “the risk of an oil spill from these tar sands pipelines is very real.”

“The oil eats away the pipelines, compromising them and leading to frequent spills,” he said during a debate on the proposed TransCanada Corp. Keystone XL pipeline, which will bring oil sands crude to the U.S. Gulf Coast if it is approved. That echoes a February report from the Natural Resources Defense Council, an influential U.S. environmental group, which called oil sands crude a “highly corrosive, acidic, and potentially unstable” substance that “may be putting America’s public safety at risk.”

That conclusion has always been contradicted by industry, which has maintained that oil sands crude is safe. TransCanada, for example, has argued that it simply would not place at risk its $13-billion Keystone line by filling it with a dangerous substance. Yet the debate highlights the political obstacles that exist for the project, a crucial piece of infrastructure for getting the ever-rising volume of Alberta oil to market.

The two sides have left little middle ground between them. So who is right?

Interviews with academics, engineers and federal officials make clear that oil sands crude does indeed appear to pose additional risks. But those risks are largely borne by refineries that have had to deal with a dirtier and more corrosive substance than industry has been accustomed to.

In pipelines, independent sources suggest that the danger is substantially lower. Indeed, in decades past, thick bitumen was actually used to coat pipelines as protection against corrosion. And pipelines are partly shielded by the fact that they operate nearer room temperatures. Refineries, in contrast, process crude at up to 400 degrees Celsius, and the fierce heat promotes a series of chemical interactions that don’t happen at lower temperatures.

The corrosion question largely surrounds the properties of diluted bitumen, also called “dilbit.”

Oil sands producers generally produce two different products. One, “synthetic crude,” has passed through a sort of pre-refinery, called an upgrader, to transform it into a lighter substance that contains far fewer impurities. Dilbit comes from producers that don’t run upgraders. Instead, they take the oil sands crude and, with minimal processing, thin it with a lighter oil and pump it into a pipeline. As a result, it contains far higher levels of numerous noxious substances, including sulphur, acids, salts and sediments.

That in itself has raised some concerns.

Take sulphur, for example. Oil sands crude contains sulphur levels up to 10 times higher than other oil. But in dilbit, the sulphur is locked up with heavy oil molecules. As a result, it is largely harmless inside a pipeline, said Harvey Yarranton, a professor of chemical and petroleum engineering at the University of Calgary.

“You’d have to put it into reaction temperatures to release that sulphur – and those are above 300 Celsius,” he said.

Acids and salts are also found in substantially elevated levels in dilbit. But both substances are “not corrosive under pipeline conditions,” according to Natural Resources Canada, whose researchers have studied the corrosiveness of different oils. Acids need temperatures above 200 Celsius for corrosion to occur, the government said in a statement.

One area of concern remains sediments – little bits of sand that are embedded in oil. Industry measures these in pounds per 1,000 barrels. Conventional oil might measure 30 to 50 pounds per 1,000 barrels. Scott Bieber, a marketing manager with oil field services giant Baker Hughes Inc., has seen oil sands bitumen hit 500.

Sediments can contribute to corrosion in pipelines – and they have become a significant menace in refineries, where they have proven difficult to remove and help foul wastewater, Mr. Bieber said.

And environmental critics say that with the expansion in the oil sands, more study needs to be done of the effects dilbit has on pipelines. In particular, the thickness of oil sands crude – it’s far more viscous than conventional oil – creates friction inside pipelines that creates higher temperatures.

With Keystone XL, TransCanada has predicted temperatures as high as 55 Celsius. That remains far from the heat in a refinery, but higher temperatures do speed corrosion, and Anthony Swift, an energy analyst with the National Resources Defense Council, said governments both in Canada and the U.S. should take notice.

“There’s enough information out there about [the risks of] this stuff that merits a study,” he said. “The government should be protecting the public, and it’s a huge concern when they turn a blind eye to a potential danger.”

SOURCE: http://www.theglobeandmail.com/report-on-business/industry-news/energy-and-resources/oil-sands-critics-target-a-new-concern-pipelines/article2116408/

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