A common cathodic protection system approach is the use of a shallow horizontal anode bed. These are typically defined as an anode system consisting of a series of multiple individual anodes installed either vertically or horizontally at a depth of less than 15m (50ft) and connected to a single power source. These are particularly effective in areas where drilling deep anode beds is not feasible or practical.
The typical anode used in shallow anode bed applications is an impressed current anode. These can be high silicon cast iron, graphite anodes or mixed metal oxide tubular anodes. The anodes may be pre-packaged in a canister filled with coke backfill, or they can be installed in a vertically drilled/augured hole or a continuous horizontal trench with backfill installed around the bare anode. The anodes can be installed in parallel to a common header cable or can have individual leads all routed to a cathodic protection junction box and connected in parallel inside the junction box.
A New Approach: Continuous Linear Anodes
Another approach that is gaining acceptance in the corrosion industry is the use of a single continuous linear anode as an alternative to multiple individual discreet anodes that are field connected to form an anode bed. There are several advantages to using a single continuous linear anode to create a shallow horizontal anode bed:
Advantages of linear anodes for shallow horizontal anode beds
Ease of installation The use of a single continuous linear anode assembly can significantly reduce installation time by eliminating numerous field splice connections of multiple individual anodes to a header cable.
Reliability The entire linear anode assembly is factory manufactured and tested with internal factory connections that are more reliable than a field connection. The assembly is designed with an internal header cable for redundancy and can be manufactured with an integral external return header cable, eliminating all field splicing and connections.
HDD Installation The use of a linear anode for shallow anode bed design allows for the use of HDD (horizontal directional drilling) to install the continuous anode assembly. This can significantly minimize the installation footprint and greatly reduce installation time and costs. This also allows for a deeper installation to facilitate locations where surface activities such as deep tilling farming operations might preclude a shallower anode system installation.
Cost Effectiveness The use of linear anodes can be extremely cost effective, resulting in a much lower cost installation. This is especially true when considering the overall cost per amp year given the longer design life of mixed metal oxide based linear anode systems.
MATCOR has extensive experience designing and installing shallow horizontal anode beds, including the use of our HDD installation crews and state-of-the-art equipment to minimize surface impact in sensitive areas.
Contact us at the link below to find out if a linear anode cathodic protection system is right for your application.
Last month, MATCOR successfully completed the first ever HDD tank cathodic protection system installation in the Middle East, utilizing a replaceable anode system.
Background—Initial Recommendation for HDD Cathodic Protection System
Equate Petrochemicals is one of the world’s largest producers of Ethylene Glycol. They initially contacted MATCOR in 2012 to discuss options for cathodic protection on a critical service Ethylene storage tank at their flagship Kuwait petrochemical facility. This tank was originally constructed in 1995, and the initial CP system installed with the tank was no longer providing sufficient current to achieve NACE Criteria. At the time, MATCOR suggested installing anodes directly under the tank using horizontal directional drilling technology. The plant’s engineering and operations team had significant reservations about this approach. The tank was critical to the plant’s operation and could not be taken out of service. Should the HDD operations result in damage to the structural integrity of the tank, the results would be catastrophic.
Perimeter Anodes—An (Unsuccessful) Alternative Approach
As a result of Equate’s concerns in 2012, they attempted an alternate approach, suggested by others, using perimeter anodes. Discreet anodes were installed offset around the perimeter of the tank—thus avoiding any possible risk to the tank during the anode installation. The use of perimeter anodes around larger diameter tanks is generally not a good idea. This is because it is very difficult to drive current to the center area of the tank, often resulting in adequate protection levels only for the outer edges of the tank bottom. For the Ethylene Storage Tank, the presence of heating pipes below the tank bottom only exacerbated the current distribution challenges. Ultimately, the results were not satisfactory.
In 2018, the plant engineering team reached back out to MATCOR to discuss our HDD solutions.
Replaceable Anode System Solution
MATCOR provided the plant with a detailed proposal to design and install a complete cathodic protection system using MATCOR’s Replaceable Tank Anode system. The RTA system is based on installing MATCOR SPL linear anode assemblies in a series of parallel slotted PVC pipes that have coke backfill pneumatically blown into the PVC pipe as part of the anode system installation. In addition to the linear anode segments and coke backfill, the slotted PVC pipes have a venting system to allow gases produced during the cathodic protection reaction to vent. This prevents gas buildup and blockage inside the PVC anode pipe.
One of the key advantages of the RTA system is that once the PVC tubes are installed, it is possible to flush out the anode assemblies and coke backfill should the anode assemblies fail and/or they are at the end of their design life making this a replaceable anode system that will assure cathodic protection for the entire service life of the tank.
Additionally, a slotted Reference Cell Tube would be installed to allow for two calibrated fixed cathodic protection reference electrodes to be inserted for full polarized and non-polarized potential measurements across the entire tank bottom. This would allow for testing of the CP system with calibrated reference electrodes for the life of the tank.
Experienced HDD Installation—Assuring a Safe Installation
While the plant conceptually agreed with MATCOR’s solution from a technical perspective, there remained a significant concern within the plant’s operation and safety groups about drilling under this critical service tank and the possibility of a catastrophic event should the drill head drift up to the tank bottom. MATCOR put together a thorough installation procedure including detailed information on the sophisticated drill head tracking systems being utilized to assure that the drill head location was being continuously monitored throughout the bore. Utilizing an experienced local HDD drilling sub-contractor, MATCOR deputed its senior HDD installation drilling supervisor to Kuwait for the installation. Our Senior HDD Drilling Supervisor has completed hundreds of tank HDD installations in the United States and his on-site presence, along with the advanced electronic tracking package being used, assured that each bore went as planned.
Replaceable Anode System Installation Complete!
In December of 2019, MATCOR, working with our local Kuwaiti sub-contractor and the client’s engineering, construction and safety teams, successfully completed the installation of the replaceable anode system. The initial commissioning results showed that the anodes were installed properly. Each anode was distributing current as expected, and the polarization levels were meeting appropriate NACE criteria. The system has been left to operate and fully polarize. A subsequent visit by MATCOR’s technical team is scheduled in early 2020 to make final adjustments to the anode system current output and to confirm that the system continues to meet NACE criteria.
MATCOR’s successful installation in Kuwait of a horizontal directional bored CP system under an existing critical service tank is a first for the Middle East Region. The innovative MATCOR design, combined with the technical knowledge and operational expertise, makes this an interesting and viable option for other tank owner/operators worldwide to consider for their existing tanks with CP systems that are not performing properly.
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.
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
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.
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
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
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.
As the world’s leading manufacturer of linear anodes, and the only manufacturer of a linear anode specifically designed for use with horizontal directional drilling installations, we thought it would be appropriate to discuss various anode options for HDD installation.
Can any linear anode be used in conjunction with horizontal directional drilling?
An engineer’s favorite answer to any question is “It depends” and this is certainly the case with HDD installations. The important thing to note is that when attempting to pull a linear anode through a bore hole, there is a chance that the pulling forces on the anode will exceed the strength of the anode and cause the anode to break. Even if the anode does not break completely, stretching of the anode can weaken or damage the internal header cable or anode to cable connections.
There are a lot of variables that can impact the success of any linear anode HDD installation. The short answer is yes, with the right bore hole, any linear anode can be pulled successfully. Conversely, with the wrong bore hole, any linear anode can be pulled apart during installation.
What are the key factors to consider when planning an HDD linear anode installation?
The key factors include a site geotechnical investigation, terrain and route mapping, and bore planning.
Site Geotechnical Investigation
Any discussion about HDD installation planning starts with a site geotechnical investigation. Obtaining a geotechnical survey or as much geological information about the respective jobsite is very important. A great amount of record information is available through sources including:
United States Geological Society (USGS)
National Geological Map Database
Publications of the US Army Corps of Engineers
The National Soil Survey Center (NSSC) a division of the US Department of Agriculture
State Departments of Transportation
Original construction records
In addition to record information, site-specific investigations (soil bores and soil sampling) by trained geologists and geotechnical service companies can provide valuable detailed data on the planned bore area geology. The geotechnical analysis should identify several relevant items including:
Soil identification along the bore route to locate rock, rock inclusions, gravely soils, loose deposits, discontinuities and hardpan
Soil strength and stability characteristics
Local drillers with experience in the identified area can often provide valuable insight based on similar projects in the same area.
Terrain and HDD Route Mapping
Collecting accurate topographical information of the bore route is another critical component in the planning phase. Terrain and HDD mapping includes determining HDD bore hole entrance and exit locations, identifying and mapping elevation profile changes, ensuring that other utilities are appropriately identified and avoided, assessing the need for traffic control, evaluating any environmental considerations or limitations that might impact the use of drilling muds and hole conditioners.
Bore Planning Software
Several commercial bore planning software tools are available to assist in the planning phase. These programs utilize the soil and geotechnical data combined with the terrain and route mapping information to provide a graphic visualization of the job helping the driller more accurately “see” and perform the job from start to finish. These software tools help the contractor select the appropriate drill rig, drill bit type and back reamer based on the anticipated soil conditions and the total bore length. By choosing the drill stem and length, the desired bore path depth, desired minimum cover, diameter and bend radius of the product being pulled, the software plots a proposed bore pitch, calculates setback distances, figures point to point bore paths, estimates hole volumes and calculates pullback time. The software can also provide a fluid–mixing process map that shows how much mud should be used based on soil conditions, drill unit and tooling used.
If a bore planning software package is not used, field calculations should be performed to appropriately choose the correct drill rig, drill bit and back reamer tooling requirements, desired bore path and quantity and type of drilling fluids to be utilized.
What anode should be selected for HDD installation?
MATCOR manufactures two linear anode products (SPL-FBR™ Linear Anode and the Iron Gopher™) that are both, in the right circumstances, suitable for use in HDD installations. The installation contractor, along with the client, must carefully select the appropriate anode and the appropriate anode installation methodology. The two generally accepted methodologies are direct pulling of the anode through the properly conditioned borehole by attaching the anode to the backreamer after the initial pilot hole has been drilled. The second installation methodology involves pulling an HDPE pipe sleeve into the borehole, installing the anode inside the pipe, and then removing the HDPE sleeve. The tables that follow are intended to assist the installer in selecting the appropriate anode and installation methodology. The selection of the appropriate anode type and installation methodology is subjective based on a qualitative analysis.
TABLE 1 – Linear Anode Application Difficulty
• Less than 200 foot pulling length
• Minimal changes in elevation
• No environmental restrictions on use of drilling muds/hole conditioners
• Installation costs and risks are low
• 200-500 foot pulling length
• Moderate elevation change
• No environmental restrictions on use of drilling muds/hole conditioners
• Installation costs are modest and risks are low
• 500-1000 foot pulling length
• Moderate elevation changes
• Some environmental restriction on use of drilling muds/hole conditioners
• Installation costs are higher and risks are moderate
• 500+ foot pulling length
• Extreme or multiple elevation changes
• Restrictive environmental limits on use of drilling muds/hole conditioners
• Critical application with high costs and risks
TABLE 2 – Anode Selection Guidelines
Linear Anode Application Difficulty 1
SOIL TYPE 2
Gravel / Coble
*Anode is to be installed in HDPE sleeve that is then removed
NOTES 1Classifying the linear anode application difficulty using Table 1 is a qualitative analysis and may warrant taking into consideration other risk factors that may be appropriate. In general, the more difficult the application, the more costly the installation component, the greater the case to use the higher pulling strength Iron Gopher and the greater the incentive to use temporary HDPE sleeving to assure the lowest risk installation. 2Soil Types based on the US Department of Agriculture Soil textural classification guidelines. Earth Loams would include the broad range of Sandy Clay Loam, Loam, Silt Loam, and Clay Loam.
What contingency planning is warranted for an HDD installation?
Even with proper project planning and an experienced installation contractor, some consideration should be given to contingency plans if something unforeseen happens during the HDD boring and anode installation.
Are alternate bits available if needed to complete the pilot hole?
Is a larger boring machine available if needed?
If drilling is more challenging than anticipated, do we have ready access to HDPE pipe for sleeving if warranted?
Does the project warrant having one or more spare anode assemblies in the event of an anode breakage during installation?
While these risks can be greatly minimized with proper planning, asking these questions before mobilizing to the site can help solve problems more quickly, saving time and money.
For assistance with linear anode selection for HDD applications, MATCOR’s linear anode systems, project management or installation, please CONTACT US.
Iron Gopher® Impressed Current Linear Anode System designed for horizontal directional drilling (HDD) is installed beneath an above ground storage tank (AST)
Chalfont, PA (May 27, 2015) – MATCOR, Inc. the trusted full-service provider of proprietary cathodic protection products, systems, and corrosion engineering solutions recently released a video showing the installation of the company’s Iron Gopher impressed current linear anode system at the site of an above ground storage tank in Texas.
Trenching to install cathodic protection systems may not be feasible for applications such as cross country pipelines, congested industrial environments and under above ground storage tanks. For these horizontal directional drilling applications, a linear anode with superior mechanical strength is required. The Iron Gopher with Kynex® technology is the only impressed current linear anode designed specifically for cathodic protection in horizontal directional drilling applications.
“As another example, Colonial Pipeline installed several thousand feet of our Iron Gopher® linear anode at an HDD project in NE Georgia,” said Ted Huck, VP of Sales for MATCOR. “With its unique design and greatly increased strength, Iron Gopher is superior to anything seen in the market for cathodic protection in HDD applications.”