WATER MAIN BREAKS, FAILURE ANALYSIS, ENGINEERING SOLUTIONS & CORROSION RISK ASSESSMENT
Team Matergenics will be at the site of water main break immediately for failure analysis, to determine if it is due to corrosive soil, water main material or stray current corrosion. Soil analysis, failure analysis and corrosion risk assessment will be performed after the onsite investigation and collection of samples
Water Main Breaks
Water main failures are very expensive for municipalities because they typically result in expenses associated with repair costs, flood damage, and loss of revenue to affected businesses.
Water main failures also interrupt the operation of vital services, such as medical care and fire fighting operations. Currently, millions of dollars are spent annually by industry and by municipalities on the repair of failed components of the water distribution infrastructure, such as components that are made from gray cast iron or “gray iron” pipe.
The rate of municipal water main failure is expected to increase as the existing gray iron infrastructure continues to age. The cost of repairing damages caused by broken water mains (and subsequent flooding damage) may become an important item in many municipal budgets. The development of a non-destructive sensing technique to detect defects in the water distribution infrastructure to prevent catastrophic failure of water distribution infrastructure components would result in tremendous savings.
Galvanic Corrosion: Copper Service Line and Cast iron Water Mains
Copper pipes in contact with ductile or cast iron water mains can result in accelerated corrosion of cast iron pipe in corrosive conductive soils due to galvanic action. Team Matergenics can identify the corrosion mechanism responsible for the leaks and mitigate corrosion in your system by coating and cathodic protection
Soil Testing
Based on soil chemistry and corrosivity we can determine an estimated remaining life by predictive modeling.
Corrosion Risk Assessment And Corrosion Mitigation
Our overall approach to corrosion risk assessment, locating “hot spots” and corrosion mitigation:
Pre-assessment stage
This would involve a “desk study” of soil types (USGS data) in the area encompassing the affected water district. This tells us about the likely level and variation in soil corrosivity that can affect and accelerate external corrosion or internal corrosion followed by graphitization and “breaks.”
Indirect assessment stage
This involves desk study, review of inspection and failure reports and pre-assessment
- Collection of soil samples in areas with a higher concentration of breaks or corrosive soils
- Chemical and corrosivity analysis of soil samples in Matergenics soils lab and modeling for remaining life
- Electrochemical potential measurements in areas with higher and lower concentration of water main breaks
- Look for correlations among the above data to identify “hot” areas for the direct assessment stage.
Direct assessment stage
This involves the condition assessment of cast iron water mains through on site examination
- Schedule excavations in identified hot areas to perform direct observation and visual observation of pipe condition, with a major goal of determining whether the primary corrosion losses are internal (water side) or external
- Take physical measurements including wall thickness and pit depth
- Measure level of graphitization – which is basically the corrosion-related deterioration of the cast iron microstructure which severely weakens the pipes – using a proprietary sensor device
Recommendations & remediation
Matergenics will develop specific, practical mitigation strategies based on findings and data from the direct and indirect assessment phases. This will be performed by an experienced NACE Certified Cathodic Protection Specialist.
Corrosion Risk Mitigation Strategies and Practical Solutions For Water Mains
- Construct soil corrosivity maps for water lines
- Prioritize pipelines for corrosion risk assessment based on corrosion. Map, age, criticality, materials and consequence of failure
- Evaluate existing aging assets in order of highest priority, perform failure analysis and assess corrosion
- Perform indirect assessment at sites identified through the above criteria.
- Direct assessment (digs and focus measurements). Determine acceptable or unacceptable risks and provide engineering solutions
- Install test stations and sensors for high corrosion risk areas
- Engineering solution: cathodic Protection, coating, backfill or replacement.
- Develop a long-term corrosion mitigation maintenance program to cost effectively extend the life of the water lines and prevent failures. Improve and update periodization based on test results, scheduled maintenance, and maintenance already performed
Our soil lab performs more than four thousand soil corrosivity measurements per year. Based on soil chemistry and corrosivity we can determine an estimated remaining life by predictive modeling.
On-site Investigation, Inspection, and Failure Analysis of Water Main Break and Measurement of Graphitization
Team Matergenics will be at the site of water main break immediately for soil analysis, failure analysis and corrosion risk assessment due to stray current that may cause the water line break. We also design and install cathodic protection systems to protect these assets, which can add 20 years to their remaining life.
The properties of iron that could be used to detect graphitization or other localized corrosion phenomena include ductility, electrical resistivity, or acoustic properties, such as ultrasonic sound velocity or attenuation. However, assessing ductility, by nature, involves destruction of the sample. Acoustical methods cannot be used with coated pipes due to the fact that it requires surface contact with bare, clean metal.
The publication entitled “Development of a Cast Iron Graphitization Measurement Device,” NYGAS Technology Briefs, Issue 99-690-1, January 1999, discloses a meter that uses eddy currents to measure the electrical resistivity of a sample surface. Eddy current methods require sophisticated control circuitry and precisely tuned components. The eddy current device necessarily consumes a considerable amount of power to generate the RF signal that it uses to induce eddy currents in the sample.
Ultrasonic measurement of acoustic properties requires a very clean interface between the probe and the pipe for purposes of acoustic transmission and impedance matching, so that it is poorly suited for use with exposed, buried pipe which is often wet or dirty. Accordingly, there is a need for an improved non-destructive testing method and apparatus for detecting the graphitization of gray iron. The sensor development in in progress at Matergenics corrosion testing laboratories.
