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Corrosion Inspection of Power Transmission Structures

Corrosion of structures in electric power transmission and distribution lines is a primary cause of in-service equipment degradation. When a power transmission structure corrodes to the point where it starts experiencing structural corrosion and material loss, the risk mitigation practices cannot be effectively applied and the structure repair/replacement remains as the only viable option.

 

Severly corroded legs of galvanized latticed towers
Severely corroded legs of galvanized latticed towers in a corrosive soil environment.

 

tower_atmospheric_corrosion
Atmospheric corrosion of galvanized members in transmission structures.

If corrosion is not addressed at its early stages, shortly it can affect system reliability and will lead to expensive repair and replacement of corroded structures, beside substantial costs of power shut down, possible environmental damages, injuries, and fatalities. Accordingly, corrosion inspection and risk assessment is the key to identify corrosion related issues and take initiatives for properly risk mitigation actions.

Here are services we provide for corrosion risk assessment and corrosion mitigation of T&D structures

* Drone Inspection and Thermographic Imaging for Tower Condition Assessment
* Paint Coating Selection for Above Ground and Underground Applications
* Custom-designed cathodic protection systems with deep well design for tower facilitie* Monopole Fatigue, Fatigue Sensor and Fatigue Mitigation
* How Team Matergenics differ from other inspection companies
* Why stray current is an important issue in corrosion and How to detect it?
* Corrosion Engineering Training

We also provide GIS Corrosion Mapping: Atmospheric and Soil Corrosivity, Remaining Life Modeling and Estimation for Underground Assets

STAGES

MATERGENICS’ corrosion inspection for transmission structure, including line and substation assets, involves three different stages:

Desk Study

Prior to site visits and field measurements, based on the project requirements,  pre-assessment (desk study) must performed to complete the following tasks:

  • Mapping out the location of structures and reviewing terrain conditions for site accessibility,
  • Reviewing geotechnical reports,
  • Reviewing structural drawings,
  • Reviewing the previous reports on corrosion inspection, maintenance/repair, and all other relevant information including service history,
  • Database analysis for climate data and soil characteristics such as pH level, soil resistivity, water content,
  • Prioritizing structures for field inspection.

Field Survey

Our professional inspectors collect the key corrosion indicator data at each structure footing, and perform site-specific tests to characterize the service environment, including:

  • Soil-to-structure electrochemical potential mapping,
  • Soil resistivity tests (ASTM G57 and ASTM G187),
  • Soil pH tests,
  • Cathodic protection current requirement tests,
  • Visual inspection of buried members,
  • Coating inspection and dimensional measurements,
  • Concrete inspection and hardness test (ASTM C805),
  • AC and DC interference corrosion investigation and source determination,
  • Photographic documentation of all tests and key measurement readings.


OLYMPUS DIGITAL CAMERA

Laboratory Investigations

All inspection findings and recommendations are included in a comprehensive report, that includes:

  • Corrosion risk factor (CRF) for individual structures,
  • Recommend corrosion mitigation methods,
  • Remedial actions,
  • Repair recommendations.

Documentation & Reporting

All inspection findings and recommendations are included in a comprehensive report, that includes:

  • Corrosion risk factor (CRF) for individual structures considering underground and atmospheric risk factors,
  • Recommend corrosion mitigation methods,
  • Remedial actions,
  • Engineering analysis and repair recommendations.

We also provide the following services:

* GIS Corrosion Mapping and Drone Inspection and Thermographic Imaging for Tower Condition Assessment
* Paint Coating Selection for Above Ground and Underground Applications
* Custom-designed cathodic protection systems with deep well design for tower facilities
* Remaining Life Modeling and Estimation for Underground Assets
* Monopole Fatigue, Fatigue Sensor and Fatigue Mitigation
* Why stray current is an important issue in corrosion and How to detect it?
* Corrosion Engineering Training

Our condition assessment considers:

  • High Elevation Atmospheric Corrosion
  • Low Elevation Atmospheric Corrosion
  • Ground Level
  • Shallow Burials
  • Deep Burials due to low pH (not considered by many)
  • Concrete Degradation
  • Coating Degradation
  • Stray Current Corrosion
  • Copper Grounding

Condition Assessment By Climbing Inspection

Inspection Overview and Procedures

The overall condition of the tower structural members, climbing facilities, fasteners, and other components are evaluated as outlined in this section. Visual and physical checks are performed to ensure that the tower and subsystems are structurally sound and functional.

Tower load bearing members , conduits, ladders, stairways. fasteners, and all load bering primary and secondary members will be checked, documented and severity of corrosion will be reported by our experienced climbers and NACE certified corrosion engineers. Corrosion mitigation: coating selection, surface preparation and application of coating per SSPC and NACE specifications will be provided for the Client’s review.

Physical inspections and UV thickness measurements  are performed  to determine steel member thickness using Ultrasonic Thickness Gauge. All corners of the towers are checked at the ground level and at any location that appears questionable with a three-point check that covers the leg and the braces on either side of it Coating thickness is also checked at these points using an Elcometer 456 Coating Thickness Gauge. ASTM A-123A is referenced for coating thickness requirements. Galvanized Thickness and protective organic coatings are measured as well.

Concrete foundations and anchoring hardware are visually checked for wear and damage.Concrete hardness tests are performed using  Digital Concrete Test Hammer. Two hardness measurements are taken per foundation corner – one set of four readings on the top of the foundation (vertical reading) and one set of four readings on the side (horizontal reading).

MATERGENICS provides corrosion inspection/monitoring services, and corrosion risk assessment for different types of telecom structures including:
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  • Guyed-wire towers,
  • Self-supporting towers,
  • Tapered steel monopols.

If corrosion is not detected and mitigated at its early stages, shortly it will lead to expensive refurbishment of corroded members, while in a longer time it can affect tower safety and increased risk for injuries, and fatalities. Periodic corrosion inspection and risk assessment is a cost-effective method to bring certainty to core asset safety. Team Matergenics can assist you on these tasks. At your request we can provide a comprehensive.  presentation on our approach and experience in this important field

We can assist you with the following important tasks:

  1. Construct soil corrosivity maps for  sites for system-wide corrosion risk assessment and maintenance
  2. Prioritize towers for corrosion risk assessment based on corrosion map, age, design/material, tower criticality, consequence of failure (high consequence areas- HCA)
  3. Evaluate existing aging assets (based on prioritization order) and assess corrosion damage in high elevations, low elevations, ground level, and underground and for guy wires through visual examination, drone inspection and NDT techniques
  4. Perform indirect assessment of towers, and galvanize anchors
  5. Perform condition assessment of concrete foundations by inspection and petrographic analysis
  6. Perform direct assessment (excavation/climbing and focus measurements)
  7. Measure grounding resistance and document grounding components
  8. Evaluate tower coating systems and select coating for various environments
  9. Perform failure analysis root cause determination for accidents and incidents
  10. Determine acceptable or unacceptable risks and provide engineering solutions for risk mitigation
  11. Engineering solution for material selection, coating, cathodic protection, structural repairs
  12. Sensor development and corrosion activity monitoring
  13. Post assessment and development of tailored inspection program for long-term cost-effective corrosion mitigation and maintenance

Why Matergenics

Team Matergenics is able to provide many unique services to assess the corrosion risk and to determine the remaining life of towers and anchors. We are also able to provide best-in-class CP design for helical anchors and special situations where installation of galvanic anodes is not feasible. What distinguishes us from our competition are the following:

  • We are trained, academic-disciplined corrosion engineers and we have four top level certifications from NACE; our competition does not have high-level corrosion certifications
  • We have successfully completed thousands of corrosion assessments projects for telecom structures to predict and quantify the corrosion rate and determine their remaining in-service life
  • We have developed patent pending GIS soil corrosivity mapping for corrosion risk assessment as a system-wide maintenance tool
  • We can provide computer-aided anode bed designs for optimum cathodic protection at tower foundations―we are NACE-Certified Cathodic Protection Specialists (CP4)
  • Every year we perform thousands of inspections on transmission lines and communication tower foundations buried in corrosive soils, identifying deep burial corrosion where competition is unable―thickness measurements at shallow burial is not necessarily representative of the integrity of the structure
  • We have a modern materials and soil testing laboratory and can perform failure analysis root cause investigation for different modes of failures at tower component
  • We have published many technical papers that have been reviewed and cited by experts in corrosion field (most recently regarding galvanized anchors, which is attached for your review)
  • We have repeat clients and can provide references form SBA Communications, Crown Castle, Southern California Edison, Consumer Energy, Valmont Industries, to name a few
  • Our corrosion risk assessment includes grounding evaluation, concrete inspection, and petrographic analysis
  • We understand budget limitations and can provide options to fit your budget if you wish

Items 1, 3, 4, 5 and 6 are unique to team Matergenics and we do not know of any other firm performing these tasks. Please see the onsite photos attached to this document for examples of our work.

INSPECTION STAGES

MATERGENICS’ corrosion inspection for telecom structure, involves three different stages:

Desk Study

Prior to site visits and field measurements, based on the project requirements, a desk study must performed to complete the following tasks:

  • Review of geotechnical reports,
  • Review of structural drawings,
  • Review of previous reports on corrosion inspection, maintenance/repair, and all other relevant information including service history.

Field Survey

Our NACE certified inspectors collect the key corrosion indicator data at tower base and anchor footings, and perform site-specific tests to characterize the service environment, including:

  • Soil-to-structure electrochemical potential mapping,
  • Soil resistivity tests (ASTM G57 and ASTM G187),
  • Soil pH tests,
  • Cathodic protection current requirement tests,
  • Visual inspection of underground members,
  • Coating inspection and dimensional measurements,
  • Concrete inspection and hardness test (ASTM C805),
  • Photographic documentation of all tests.


Laboratory Investigations

Collected samples during site visits must be examined in a controlled environment to identify:

  • Soil contamination concentration,
  • Microbiologically induced corrosion,
  • Root cause determination.

Documentation & Reporting

All inspection findings and recommendations are included in a comprehensive report, that includes:

  • Corrosion risk factor (CRF) for individual structures,
  • Recommend corrosion mitigation methods such as cathodic protection,
  • Remedial actions,

Engineering analysis and repair recommendations.

Cathodic Protection

Matergenics is able to design, install, test, and monitor cathodic protection systems that prevent any further corrosion and extend the life of buried assets for at least 15 years. Compared to oil and gas industry, the tower industry as a whole is behind on implementation of CP method of extending in-service life of the assets. The oil and gas pipeline industry has been using this method successfully for many years to prevent failures and reduce inspection and maintenance costs.

PhD-level NACE-certified engineers in Matergenics have developed an advance simulation tool to design best-in-class anode bed designs for optimum protection of tower foundation regardless of structural materials and designs.

 

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Related Services


 

We design and Install Cathodic Protection Systems for Tel-communication Towers Based on Corrosion Engineering Principles and By NACE Certified Technical Personnel.

We understand budget limitations and can provide options to fit your budget if you wish.

Coating Selection for Atmospheric, Ground Level  and Underground Zones

Another effective way to protect structures against corrosion attack is to use a coating film to shield it from the environment. However, not all coatings are created equally. Matergenics has several coating experts that are equipped to test and analyze coating quality based on common coating failure modes.

 

Proper coating system and Adequate surface preparation per SSPC and NACE standards are extremely important for atmospheric high elevation zones of the telecom tower. To improve the protection level at foundations of telecommunication structures, Matergenics recommends partial coating application along with CP system installation. This results in improved protection at both deep and shallow burials, also extends the lifespan of anodes. Answers to the following questions are keys for a successful coating application:

  • Coating material – was the coating material suitable for the service environment and the substrate?
  • Surface preparation – was the surface properly prepared to allow for coating adhesion?
  • Application – was the coating applied using proper technique at the correct thickness?
  • Formulation – were the drying and curing specifications followed?
  • Mechanical damage – is the coating susceptible to damage backfilling
  • Cathodic protection shielding – is the coating compatible with cathodic protection?

ASTM, SSPC, and NACE test procedures are followed to assure that the selected coating will survive and protect the structure as intended. These tests include:

  • Accelerated paint exposure
  • Salt spray
  • UV light exposure
  • Tensile and flexural tests
  • Cross section microscopy

Considering our expertise, Matergenics is the only company that can select coatings that work with cathodic protection systems to guarantee maximum protection to extend the life of any structure.

 

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Use our online SERVICE REQUEST FORM or send the same information to  info@www.matergenicsinc.com, and let us know how we can help you.

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