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 inititives for properly risk mitigation actions.

INSPECTION 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, a 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.

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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