Category Archives: Pipeline

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.

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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.

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Case Study: AC Mitigation Design Criterion – It Matters

This case study highlights some of the challenges associated with choosing AC mitigation design criterion for a new pipeline construction project.  The specific project consisted of approximately 200 miles of pipeline with another 35 miles of lateral lines and included compressor stations, metering valves and a valve station.  The final approved right of way consisted of 41 identified transmission lines spanning 5 different utility owners.  MATCOR’s scope of work included designing both the CP system and modeling and designing an AC Mitigation system to address the extensive HVAC colocations.

For the AC Mitigation effort, MATCOR performed extensive field data collection along the right of way and MATCOR sent requests for utility operating data for AC Mitigation Design purposes.  After 6 months of requests from the various utilities, the results were inconsistent with some utilities providing only emergency and peak data, others provided seasonal average data and one utility would not provide any data.  Ultimately, modeling was performed based on actual data wherever possible, supplemented by assumptions based on experience from other AC Mitigation designs projects.

While this engineering project was being started, NACE was adopting its latest version of SP 21424-2018-SG “Alternating Current Corrosion on Cathodically Protected Pipelines: Risk Assessment, Mitigation, and Monitoring”.  This latest version presented an updated criteria standard based on DC Current Density.  Basically, if you can assure that the CP Current Density along the length of pipeline is controlled to below 1 A/m2 then you can tolerate a much higher AC Current density threshold of 100 A/m2 requiring less AC mitigation.  If you are unable to control CP Current to the 1 A/m2 level, then the acceptable AC current density drops to a much lower 30 A/m2 threshold often requiring more extensive mitigation.

For the initial AC modeling effort, MATCOR based the AC Current Density limit to the lower, more stringent, 30 A/m2 criteria that assumes that the CP Current Density could not be controlled to below 1 A/m2.  The modeling, given all the assumptions that we had to make, came back with:

  • Numerous locations where Step and Touch Potential concerns required mitigation
  • No concerns over fault current given the separation distances and fault currents presumed
  • A very significant mitigation requirement to bring the induced current densities below the 30 A/m2 criteria including approximately 81 miles of parallel mitigation and 8 x 600ft deep grounding wells.

These results warranted additional review given the extensive AC Mitigation requirements from the initial modeling.

After some sensitivity assessments, a second modeling effort would be taken based on some revisions to the HVAC operating data based on updated information and some revisions to the input assumptions.  This new modeling effort would also be run using 50 A/m2 as the AC Current Density limit.  Additionally, based on input from operations, it was determined that all deep grounding wells would be limited to 200 ft depth.  The new modeling effort resulted in a significant reduction in AC Mitigation required eliminating almost 50 miles of parallel mitigation.

The dual modeling efforts showed that there were numerous locations that were only slightly above the 30 A/m2 threshold but below that of 50 A/m2.  In those areas, the owner opted to install additional monitoring systems but forego the initial installation of AC Mitigation and instead focus on those higher risk AC Interference areas by installing AC Mitigation.

This case story highlights the role of AC mitigation design criterion selection and the complexity around the current criteria that correlates CP Current Density levels, which are not typically controlled, to the AC current design threshold to mitigate the induced corrosion AC Interference risk.  With judicious design decisions and a healthy amount of monitoring systems, there is significant value in your modeling criteria.


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 +1-215-348-2974.

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PHMSA Mega Rule Update

PHMSA Mega Rule
The PHMSA Mega Rule significantly impacts the US pipeline industry.

It has finally landed – the PHMSA MEGA rule has hit and will have a tremendous impact on the US pipeline industry, adding significant scope to the current pipeline integrity management requirements.  Some of the industry impacts that the PHMSA MEGA rule will have include:

  • An approximately 20% increase in the number of regulated pipelines in the United States
    The exact impact depends on some additional details not yet released; however, it is very clear that the addition of 20% more regulated pipelines will have a significant impact on an industry where highly qualified integrity professionals and related services are limited in supply and the industry is already struggling to meet demand.  These additional pipelines will require significant integrity resources.
  • Expedited reporting requirements
    The time restrictions for implementing the new rule have been accelerated, with initial reporting requirements in July, 2020, less than a year away. Time to comply with these regulations has been reduced 20% from the initial draft order timeline.
  • Increased cathodic protection requirements
    Many pipelines that previously were not regulated and have not had proper CP will now require a properly designed, maintained and tested cathodic protection system.

The PHMSA MEGA rule will be a challenge and an opportunity for MATCOR as midstream pipeline operators will be looking for partners to help them address these new regulations.  MATCOR provides a full range of cathodic protection and pipeline integrity services including:

  • Field Integrity Surveys
  • ECDA
  • CP Assessments
  • CP Design
  • CP Installations
  • Annual Testing Services
  • Test Station Installations
  • Remote Monitoring
  • CP Maintenance
  • AC Interference

It is going to continue to be exciting times in the midstream market.

Learn more about PHMSA regulations.


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.

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Cathodic Protection Remote Monitoring

This article provides a brief overview of the important role of cathodic protection remote monitoring systems in today’s pipeline operations. We will cover the CP equipment and features that can be monitored and how data is transmitted.

cathodic protection remote monitoring
Advanced cathodic protection remote monitoring systems are critical for today’s pipeline operator.

Modern pipeline operations face increasing pressures to incorporate advanced technologies to:

  • Drive down operating costs
  • Improve system reliability
  • Comply with regulatory requirements
  • Monitor the health of their pipeline networks
  • Monitor the critical systems that are integral to pipeline integrity

The use of advanced cathodic protection remote monitoring systems has become a critical component in the pipeline operator’s toolbox to meet these challenges.

CP remote monitoring (and control) has proven to be a reliable and cost-effective means to oversee the proper functioning of cathodic protection systems and AC Mitigation systems that are critical to assuring pipeline integrity and the proper protection against pipeline corrosion. Where operators in the past would have to send technicians out to remote pipeline locations to collect snapshot data on a frequent basis, the smart deployment of cathodic protection remote monitoring systems can provide continuous real time data that can be accessed from any cloud connected handheld or desktop device. Additionally, a remote monitoring unit for cathodic protection is well-insulated; this construction affords them excellent protection against lightning strikes. The financial, environmental and safety impact of eliminating hundreds of thousands of windshield hours is staggering across the vast pipeline industry.

Cathodic Protection Remote Monitoring – What can you monitor?

  • Cathodic Protection Rectifiers – the installation of RMUs with built in interruption capabilities should be standard on all new pipeline installations and retrofitting older units can provide significant cost savings and improve CP system reliability.
  • DC Cathodic Protection Test Stations – with today’s continuing advances in remote monitoring technology and costs, it is quickly becoming very cost effective to install remote monitoring units on all test stations. When combined with the ability to easily interrupt all of the influencing current sources on a pipeline, regularly scheduled testing of the CP system can be performed quickly and at virtually no cost.
  • AC and DC Coupon Test Stations – the latest NACE guidelines for AC Mitigation (SP21424-2018*) emphasize that the localized DC current density has a significant impact on AC corrosion and gathering data on both AC and DC current densities at areas of interest/risk is critical to a successful AC Mitigation strategy. Effectively doing so requires the ability to monitor these values over time as AC loads vary during the day and seasonally.
  • Critical Bonds – monitoring the effectiveness of critical bonds is necessary (and in many cases required by local regulatory bodies) to assure pipeline integrity.

NACE SP21424-2018 “Alternating Current Corrosion on Cathodically Protected Pipelines: Risk Assessment, Mitigation, and Monitoring”

How does a CP remote monitoring system transmit data?

remote monitoring unit cathodic protection
Mobiltex Cathodic Protection Remote Monitoring Unit (CP RMU)

Today’s operators have a range of options to assure that remote monitoring systems can regularly communicate data to their host data collection systems. The availability of conventional cellular networks combined with various commercial satellite systems assures pipeline operators of the ability to communicate with devices in even the remotest of locations. Your monitoring system provider can work with you to select the appropriate communications technology for each cathodic protection remote monitoring unit (CP RMU) location.

In addition to choosing how the communication is to occur, another key factor to consider is whether the communications are to be one way (monitoring only) or two-way (monitoring and control). For test station applications where data collection is the goal, one way transmission of the monitoring unit’s data is all that is required. For rectifier units, the ability to control the system output and/or the ability to initiate an interruption cycle for close interval surveys or test station polling purposes necessitates the ability of the remote monitoring unit to receive and act on communications as well as to transmit data.

Software Interfaces – Installing the appropriate CP RMU hardware is just one step in implementing a successful remote monitoring (and control) program. The data must be collected, stored, and accessible for the operator. Sophisticated cloud-based interfaces have been developed that incorporate critical features including firewall-friendly, password protected internet browser access. These systems allow for multiple client user accounts with configurable permission levels and automated alarm and status information including email and text alerts for designated alarm conditions.

In summary, the use of remote monitoring technology is a key component to the successful operation of any modern pipeline integrity management program. While MATCOR has extensive experience with all of the major RMU manufacturers, we have recently teamed up with Mobiltex, a leader in the field of remote monitoring, to bring state of the art technology to the pipeline and cathodic protection industry. Mobiltex’s CorTalk® line of CP RMU units combined with their CorView interface offers all the features necessary to implement a comprehensive, cost-effective, and highly robust cathodic protection remote monitoring program.


Please contact us at the link below if you have questions about cathodic protection remote monitoring, or if you need a quote for services or materials.

CONTACT A CORROSION EXPERT

New Pipeline Cathodic Protection Design | 12 Things to Consider

Pipeline cathodic protection design for new pipelines may appear to be a rather easy task for anyone with a basic understanding of cathodic protection. However, as with all design efforts there are a wide number of factors that need to be considered for a sound design that meets generally accepted industry practices.

Pipeline cathodic protection design considerations.

This article highlights 12 things that the pipeline cathodic protection system designer needs to consider when developing a CP system design. This is not intended to be a comprehensive list as every project has its own unique challenges, but these 12 items would all typically have to be addressed during the design phase. It is assumed that the basic pipeline information is already available to the CP designer including pipeline length, pipeline routing and pipeline characteristics (material, wall thickness, coating type, operating temperature, etc.). Armed with this basic information the CP designer should also consider the following in their design efforts.

12 Things to Consider for New Pipeline Cathodic Protection Design

  1. Soil Resistivity is a factor in many of the design calculations and assumptions (e.g. current requirement, anode resistance, attenuation, AC interference, etc…) Actual soil resistivity data should be collected along the proposed route. Learn about soil resistivity testing.
  2. Attenuation calculations should be performed in accordance with accepted industry standard equations and practice, such as NACE International CP-4 Cathodic Protection Specialist Course Manual 2000 Figure 2.18.
  3. Design current requirement is selected based on the soil type(s) using some accepted industry guidelines taking into consideration the coating manufacturer’s recommended coating efficiency or other industry accepted guidelines. Additional current requirements for mitigating interference currents should be considered based on the designer’s experience.
  4. Distribution of CP System Stations should take into consideration the total current required, the pipeline attenuation characteristics, the availability of power for impressed current cathodic protection systems, varying soil regimes, isolation valves and other factors to determine how many, what size and where each CP System will be located.
  5. Foreign pipelines and other DC interference sources should be evaluated as part of the CP system design efforts and generally warrant immediate mitigation measures or testing and monitoring provisions for observation and assessment.
  6. AC Interference assessment should be performed to determine if there are one or more high risk categories for AC Interference. Should the initial assessment confirm that there is potential for AC Interference an experienced AC Interference and Mitigation specialist would typically use sophisticated AC modeling to assess the risk and propose appropriate mitigation. From a CP perspective, there is a relationship between DC current density and AC induced corrosion risks where too much cathodic protection accelerates the AC induced corrosion rate so care must be exercised by the CP designer to avoid high DC current densities in AC risk areas.
  7. CP Station design includes the type of anode configuration, anode selection, installation methodology, etc… The CP designer will typically provide detailed Bill of Materials as well as CP System issued for construction drawings and construction details showing the location of equipment and providing installation instructions.
  8. Isolation of MLVs and Stations is a key design criterion that impacts the pipeline cathodic protection system design. Some owners are strongly in favor of isolation of MLVs and Stations from their main pipeline while other owners prefer not to isolate and have to maintain isolation and instead require the that CP system be sized to account for losses to current drains.
  9. Power supply type, sizing and selection is another of the decisions that is determined by the CP designer with consideration given to the pipeline owners specifications and preferences. For most pipeline applications, impressed current systems are typical and these require a DC power source. Electrical AC to DC power supplies (“rectifiers”) are the most common power supply but for remote areas with limited AC power availability, alternate power supplies such as solar, wind, fuel cells, thermo-electric generators or other sources may be required.
  10. Terminal piping is often associated with a new pipeline construction project and the pipeline CP system designer must often provide a supplemental design specifically for the terminal or station piping, or account for these in the primary pipeline CP system design
  11. Use of temporary CP systems is often recommended when permanent power may not be available for some time. These typically involve the installation of galvanic anodes strategically along the pipeline.
  12. Provisions for testing and monitoring are critical components to any successful pipeline CP system design. This often includes the use of remote monitoring systems for all of the system power supplies, specialized test coupons for AC and DC Interference, and numerous cathodic protection test stations placed at the appropriate strategic locations to be able to properly test and monitor the CP system performance.

As noted earlier, this is far from a comprehensive list of all of the factors for a specific pipeline CP System design. Every project may have its own unique challenges; however, the 12 items listed above represent a great starting point for any new pipeline cathodic protection system design challenge.


Please contact us at the link below if you have questions about pipeline corrosion, pipeline cathodic protection design, or if you need a quote for services or materials.

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Zinc Ribbon Installation Projects

MATCOR provides a full range of AC Mitigation capabilities including AC Modeling and Design engineering services, supply of our proprietary Mitigator® engineered AC grounding system, and an entire construction services organization capable of a wide range of AC Mitigation installation services. Two current projects highlight our construction service capabilities with regards to AC Mitigation. The first project involves several miles of zinc ribbon installation for an AC mitigation system in a congested suburban and urban environment using horizontal directional drilling (HDD) equipment. The second application is in a highly rocky environment in West Texas that requires the use of specialized rock trenching technology for zinc ribbon installation.

Zinc Ribbon Installation Using HDD in a Congested Environment

Zinc Ribbon Installation - HDD
Figure 1 – Zinc ribbon being installed through HDD bore hole

This project in northwestern Ohio involved the zinc ribbon installation over several miles using one of MATCOR’s in-house horizontal directional drilling crews. The project required horizontal directional drilling to minimize surface disturbances due to the congested area.

With any typical AC Mitigation installation there are numerous precautions that must be taken to assure a safe installation. This starts with a thorough pre-construction safety review to develop the project site-specific health and safety plan. Each crew member participates in a daily safety meeting to review the day’s planned activities and address all safety concerns in advance of performing any work. Each crew member is required to have the appropriate operator qualifications and site-specific safety training as identified by MATCOR and the pipeline owner.

HDD Bore for Zinc Ribbon Installation
Figure 2 – HDD bore in process

Prior to any other construction activities, the first task is to perform a thorough line locating including potholing (excavation of the top of the pipe). This is to physically assure that the location of the pipeline(s) being mitigated is accurately marked to avoid any risks associated with construction activities in close proximity to the pipeline.

Once the pipeline has been physically located and properly flagged, each individual bore must be planned. The route of the bore is assessed prior to boring activities commencing. The bore planning includes:

  • Identifying entry and exit points
  • How the bore is to be tracked
  • Special precautions that might be needed to maintain the bore during the ribbon installations
  • How the cuttings will be captured, stored and removed

Texas AC Mitigation Installation
Figure 3 – Zinc Ribbon Bore – AC Mitigation design detail – note rail line to the South

As with any construction project, logistics and project management are key to the successful execution of the project. Working in conjunction with the owner and their designated project inspector to assure that the work is performed safely and in accordance with the AC Mitigation design requirements. For the project in Ohio, some additional complications included difficult weather conditions and working in close proximity to a railroad which requires additional permitting and coordination with the railroad. In some locations, traffic control was also required during the installation work.

Rocky Conditions in West Texas

Rock Trenching | AC Mitigation Installation
Figure 4 – Rock trenching in a difficult West Texas environment

Another project that MATCOR is currently completing involves the installation of approximately 15 miles of zinc ribbon in West Texas. The original installation plan called for the use of a cable plow to install the zinc ribbon mitigation wire; however, for large stretches of the installation, the rocky conditions forced MATCOR to switch from the planned cable plow to a high-powered rock trencher to cut through the difficult rocky terrain. This project illustrates the importance of using the right equipment to overcome difficult installation challenges. In some cases, being able to adapt to adverse conditions requires a change in construction methodologies and for this project, MATCOR’s ability to react and make equipment changes allowed the project to proceed on schedule with minimal customer impact.

This project also requires the use of HDD for one specific mitigation segment, as the pipeline traverses a cotton field which includes a buried drip irrigation system. The use of HDD is required to prevent any damage to the drip irrigation system during the AC Mitigation zinc ribbon installation. Coordinating the installation schedule around the cotton crop cultivation added another logistical challenge to the project.

Whatever your AC Mitigation challenge might be, MATCOR’s construction teams are able to work with our clients and their project needs to assure a safe and cost-effective installation project.


Have questions about zinc ribbon installation, or need a quote for AC mitigation materials or services? Contact us at the link below.

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PHMSA Rule Making Updates – a look at what is ahead on the US Regulatory Front

See our October 2019 Update on the PHMSA Mega Rule.

Overall
The US Pipeline regulatory environment is poised to see several new rules implemented to expand the scope and effectiveness of pipeline regulations with a goal to improve the integrity and safety of hazardous material pipeline. These rule changes were all initiated years ago and have been winding their way through the regulatory process, soliciting input from the industry and from concerned citizens, environmental groups and other interested parties.

The Liquids “Final Rule”
In January of 2017 in the last few days of the Obama Administration, the Department of Transportation’s Pipeline and Hazardous Materials Safety Administration issued a final rule amending its Rule 49 CFR 195 that among other things expanded integrity management and leak detections beyond high consequence areas (HCA’s). The Final Rule tightened standards and broadened data collection and monitoring requirements for pipeline operators. A few days into the Trump administration, the White House issued a directive to federal agencies to freeze sending new regulations to the Office of the Federal Register (OFR) and withdrawing any regulations sent to the OFR. Thus the liquids “Final Rule” that was 6 years in the making was withdrawn and is awaiting resubmittal by the new administration.
While the exact requirements of the Final Rule may be changed, some of the key changes from the withdrawn rule included:

• Assessment of non-HCA pipeline segments every 10 years in compliance with provisions of 49 CFR Part 195.
• Increased use of inline inspection tools for all hazardous pipelines in HCA.
• Requirement for leak detection systems for covered pipelines in both HCA and non-HCAs.

PHMSA anticipates coming out with their revised “Final Rule” in the Fall of 2018.

The Gas “Mega Rule”

On the gas side of the pipeline regulatory environment, 49 CFR Parts 191 and 192, several public meetings have been held regarding PHMSA’s proposed gas rules, often referred to as the Gas Mega Rule. The rulemaking changes originally recommended would have nearly doubled the current number of pages in the regulations. PHMSA has announced that instead of one Mega Rule, the effort would be broken into three separate rules that are expected to be introduced in 2018 and to go into effect in 2019. Part 1 addresses the expansion of risk assessment and MAOP requirements to include areas in non-High Consequence Areas (HCAs) and moderate consequence areas (MCAs.) Part 2 of the rule making focuses on the expansions of integrity management program regulations including corrosion control to gathering lines and other previously non-regulated lines. Part 3 of the gas rule making is expected to focus on reporting requirements, safety regulations and definitions to include expanding into related gas facilities associated with pipeline systems.

Pipeline Cathodic Protection Design for New Transmission Stations

Technological advances in horizontal drilling and fracking have changed the oil and gas production landscape that propels the US Pipeline industry. This combined with an increasing demand for natural gas and the promise of larger export markets for both LNG and US crude oil have led to a surge in new pipeline construction. As a result, pipeline corrosion prevention, including cathodic protection design and engineering expertise is critical as the industry adapts to a changing production landscape and new distribution challenges.

Cathodic Protection Engineering Capabilities

MATCOR has been heavily involved in several key engineering projects including pipeline cathodic protection design for new transmission stations. Whether these are compressor stations for gas pipelines or pump stations for liquids pipelines, pipeline owners appreciate MATCOR’s innovative application of linear anodes when designing new construction stations.

Pipeline Cathodic Protection Design with Linear Anodes

The advantages of using linear anodes in a new pipeline station environment include:

  • pipeline cathodic protection design for new transmission stationInstallation in the same trench as the buried piping during initial construction greatly reduces installation costs
  • Close coupling of the anode to the piping greatly minimizes the current losses of the CP system to the station’s grounding system
  • Utilizes a low anode gradient / low current output anode system that minimizes interference concerns with other structures and with foreign pipelines outside the station area
  • Provides exceptionally long anode life using MMO (mixed metal oxide) anodes operating at mA/ft current output.

MATCOR has successfully pioneered the use of linear anodes in plant environments for two decades. With the recent surge of pipeline projects, the use of linear anodes in stations has gained significant traction in the market. MATCOR design engineers and field technical personnel are uniquely qualified to perform engineering, pipeline cathodic protection design, field installation support, commissioning and testing services for these critical infrastructure projects.

MATCOR also offers a full suite of cathodic protection design and AC mitigation design services for transmission pipeline and oil and gas production pipeline gathering systems.


Have questions or need a quote for engineering and design or materials for your pipeline cathodic protection system? Contact us at the link below.

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AC Mitigation: 4 Approaches

AC mitigation is the process of designing and applying pipeline grounding systems to:

  • Prevent voltage spikes during fault conditions
  • Reduce AC current density to protect against AC induced corrosion
  • Maintain AC step and touch potentials below 15 Vac to protect personnel from shock hazards

AC mitigation prevents voltage spikes and corrosion and protect workers
AC mitigation prevents voltage spikes, protects pipelines from corrosion and protects workers in areas where the pipeline parallels high voltage transmission lines.

Pipelines that parallel overhead high voltage AC transmission power systems are subject to AC interference. AC interference has several potential adverse impacts on the safety of personnel and pipeline integrity. Assuming that these conditions exist, there are several measures that can be taken to mitigate the AC interference present on a pipeline. These AC mitigation strategies are detailed in various international standards including NACE SP0177-2014 Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corrosion Control Systems.

There are four basic approaches to mitigating AC Interference. These mitigation strategies are:

1. Fault Shielding

One of the primary concerns with high voltage AC transmission systems parallel to buried pipelines is the risk that a fault condition at a transmission tower could result in the rapid discharge of fault current near the pipeline. This could lead to direct current arcing in soil – rare but very damaging. More common is the rapid ground potential rise that subjects the pipeline coating to large voltage gradients that result in coating damage. Fault shielding is a suitably designed grounding system that is installed between the tower footing and the pipeline that acts to shield the pipeline and shunt harmful currents away from the pipeline by providing a low resistance path to earth. This typically takes the form of a parallel shielding wire, either copper or zinc, connected to the pipeline.

2. Gradient Control Mats

When high levels of AC voltage are present on a pipeline, either during a fault condition or as the result of an inductive coupling during normal steady-state operations, personnel in close proximity to and/or touching any above ground or exposed appurtenance are at risk for electrical shock step or touch hazards. Installing gradient control mat, which is a system of buried bare conductors, typically galvanized steel, copper or zinc, connected to the structure, provides localized touch and step voltage protection by creating an equipotential area around the appurtenance.

3. Lumped Grounding Systems

Lumped pipeline grounding systems consist of shallow or deep localized grounding conductors that are connected to the structure at strategic locations to reduce the AC voltage level along the pipeline. This provides protection to the structure during steady-state or fault conditions from nearby electric transmission.

4. Gradient Control Wire

Gradient control wire grounding systems function the same as the lumped grounding system. With this type of system, long continuous grounding conductor(s) are installed horizontally and parallel to the pipeline. They are strategically located and sized to reduce the AC induced voltage along the pipeline during steady-state or fault conditions from nearby electric transmission.

For mitigating high levels of AC induced voltage along a pipeline, gradient control wires are the most common form of AC mitigation. Hybrid systems that combine lumped grounding systems with gradient control wires are also common. Regardless of the type of pipeline grounding system used, all of these AC mitigation approaches involve installing a grounding device to the affected structure to allow AC induced current and fault current to be quickly discharged off of the pipeline.

AC Modeling

Prior to installing an AC mitigation system, it is common to use a complex AC modeling software to evaluate the impact of fault currents and estimate the steady state induced currents that can be expected along the pipeline. This information is used to determine the quantity and location of mitigation required based on numerous factors, including the resistivity of the soil, the physical characteristics of the pipeline, the operating parameters of the HVAC transmission system and the spatial distances between them.

Engineered AC Mitigation Systems

Based on a thorough assessment of the pipeline and high voltage AC transmission system interaction, including modeling results when available, an AC mitigation system is designed by experienced engineers familiar with the mitigation strategies detailed above. This engineered AC mitigation system would detail the quantity and location of grounding installations required for a specific application. MATCOR’s MITIGATOR is an example of this type of AC mitigation system.

Other features of an engineered AC Mitigation system include:

Special Backfill

It is quite common to install the grounding conductor in a special backfill material. The purpose of the backfill can vary depending on the conductor material chosen and the type of backfill used. The benefits of various types of AC mitigation backfill include:

  • Enhanced surface area – conductive backfills such as carbon or conductive concrete are used to effectively increase the surface area of the grounding conductor reducing the overall resistance to earth.
  • Corrosion/Passivation Protection – some backfills are designed to protect the grounding conductor from corrosion or passivation of the conductor that could adversely affect the life or impede the performance of the grounding conductor.
  • Hydroscopicity – some hygroscopic backfills readily attract and retain water from the environment, helping to maintain a low uniform resistance around the grounding conductor.

Solid State Decouplers

These devices are almost always used in conjunction with AC mitigation systems and are usually installed wherever the grounding system is connected to the pipeline. These devices are designed to allow AC current to flow off the pipeline during steady-state or fault conditions while blocking all DC current. This effectively isolates the pipeline’s cathodic protection (CP) system from the AC mitigation system, preventing the mitigation system’s grounding conductors from taking CP current from the pipeline.

MATCOR provides complete AC Mitigation solutions including design, supply of materials, turnkey installations and comprehensive testing services.


Have questions or need a quote for an AC mitigation system or services? Contact us at the link below.

CONTACT A CORROSION EXPERT

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