Corrosion is the biggest enemy of transmission pipelines. According to PHSMA, about 40% of pipeline damage and leakage is the direct result of corrosion, and other types of pipeline damage, such as excavation and natural force damage, are also highly associated with pipeline corrosion and can be easily triggered. Overall, soil corrosivity is the key and influences the degree of corrosion that happens on a pipeline.
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In this section, the objective is to determine the soil corrosivity and assess the corrosion risks of pipelines by developing a continuous soil corrosivity index surface by using ArcMap and ArcGIS Pro in Harris County. Given the fact that soil corrosivity is influenced by a number of different soil properties at different levels, multi-criteria evaluation (MCE) was used as the technique to determine soil corrosivity in Harris County.
Corrosion is the biggest enemy of transmission pipelines. According to PHSMA, about 40% of pipeline damage and leakage is the direct result of corrosion, and other types of pipeline damage, such as excavation and natural force damage, are also highly associated with pipeline corrosion and can be easily triggered. Overall, soil corrosivity is the key and influences the degree of corrosion that happens on a pipeline.
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In this section, the objective is to determine the soil corrosivity and assess the corrosion risks of pipelines by developing a continuous soil corrosivity index surface by using ArcMap and ArcGIS Pro in Harris County. Given the fact that soil corrosivity is influenced by a number of different soil properties at different levels, multi-criteria evaluation (MCE) was used as the technique to determine soil corrosivity in Harris County.
The lack of preparedness of local governments and energy companies led to this serious state-wide power outage and energy crisis. Therefore, to prevent similar series of disasters from happening, it is crucial to ensure and assess the resiliency and integrity of current transmission pipelines in the State of Texas.
In this project, the main objective is to investigate the driving factors of pipeline incidents (failures, accidents) of currently existing pipelines.
The lack of preparedness of local governments and energy companies led to this serious state-wide power outage and energy crisis. Therefore, to prevent similar series of disasters from happening, it is crucial to ensure and assess the resiliency and integrity of current transmission pipelines in the State of Texas.
In this project, the main objective is to investigate the driving factors of pipeline incidents (failures, accidents) of currently existing pipelines.
Result & Discussion
MCE for Soil Corrosivity
Soil Corrosivity
Map 5.1.1: Soil Corrosivity in Harris County
In the map shown above, soil corrosivity in Harris County was calculated and classified, the input parameters were pH level (30%), Electrical Conductivity (25%), Clay Content (15%), Bulk Density (10%), Organic Content (10%), and Drainage (10%). In general, different regions within the county have various soil corrosivities.
The corrosivity was divided into three groups by using Natural Breaks (Jenks). The three groups were Low Corrosivity (0 - 3.25), Moderate Corrosivity (3.25 - 5), and High Corrosivity (5 - 9). Soil with low corrosivity are mostly located at west Harris County, where is mostly dominated by sub-urban areas and ranch land. Soil with moderate corrosivity occupies the central part of the county including most part of Houston. For high corrosivity soil, it is mostly in the northwest and southeast part of the county, where the land is mostly forest and industrial areas respectively. In the left frame of map 1, it can be seen that near the Galveston Bay region, the land is mostly dominated by moderate to high corrosivity soil.
Below is the histogram generated for soil corrosivity index, where "0" stands for non-corrosive soil, and "9" represents highly corrosive soil. By examining this histogram, it can be seen that the soil in Harris County is normally distributed with a mean value of 4.33. However, high corrosivity soil still occupies a considerable area of Harris County, mostly in the southeast part of the county around Galveston Bay.
Histogram for soil corrosivity index
Soil Corrosivity - High corrosivity alone
Pipeline Corrosion Risks
In Map 5.2.2 shown below, all pipelines were overlaid with the soil corrosivity map (map 5.1.1), and the risks of corrosion to pipelines were assessed. The pipelines were mostly concentrated near the southeast corner around Galveston Bay, in the Galveston Industrial Clusters. In other words, a large percentage of the pipelines travel across soil with moderate to high corrosivity in Harris County. On the other hand, although the northwest corner of the county also consists of highly corrosive soil, much fewer pipelines travel right across the region.
Map 5.1.2: Soil Corrosivity with Pipelines
Based on the result of MCE, the risks of corrosion for all the sections of pipelines were assessed and summarized below. As discussed in map 5.1.2, a large portion of pipelines is exposed to high corrosion risk, map 5.1.3 below visualizes the corrosion risks for pipelines specifically. It can be seen that most sections of pipelines near the Galveston Bay are at high corrosion risk. It also should be noted that pipelines in the interior are mostly at lower corrosion risk, despite a small portion of them in the north are facing high corrosivity soil. Overall, although only around 40% of all pipelines are exposed to highly corrosive soil in Harris County, these sections of pipelines are densely concentrated on the southeast part of the county, and they are crucial in transmitting fuels extracted from the Gulf of Mexico and Louisiana to the rest of Texas. Therefore, pipelines in the southeast of Harris County are considered to be at risk of failure, damage, or leakage if no protection plan is implemented.
Map 5.1.3: Corrosion Risk for Pipelines
In the County of Harris, in total 2933 kilometers of transmission pipelines travel across the county. To the left is a bar chart showing the total length of pipelines with three levels of corrosion risk in kilometers, and a pie chart showing the associated percentage for each risk group. In general, over one-third (1108 km) of the pipelines are exposed to highly corrosive soil, forty percent (1190 km) of the pipelines are facing moderate corrosion risk, and 22% of them have low corrosion risk.
Graph 1 & Graph 2: Statistical Summary of Pipeline Corrosion Risks
Pipeline Incidents and Pipeline Corroion
Map 5.1.4: Soil Corrosivity and Pipeline Accidents - A close-up view of 1. Buffalo Bayou and 2 Jersey Village, NW Harris County
An incident is defined as an unplanned event that occurs under a certain degree of randomness. In Harris County, overlaying pipeline incidents with the soil corrosivity and pipelines, it can be concluded that the distribution of pipeline incidents is possibly influenced by the soil corrosivity. In Map 5.1.4 above, two regions within Harris County, Buffalo Bayou Region, and Jersey Village, are shown. Both regions are major junctions for pipelines, while Buffalo Bayou and areas along it have overall relatively higher soil corrosivity than Jersey Village. Similarly, associated pipeline incidents in the Buffalo Bayou region are much more abundant than those in Jersey Village, with 51 and 3 accident records near the centers of those junctions respectively. This result is consistent with the corrosion risk for pipelines discussed above. Therefore, high soil corrosivity is considered to be a driving factor that results in the frequent occurrence of associated incidents in the Buffalo Bayou area and other similar areas.