Pipeline Internal Corrosion Case Study
The Excalibur Shield provides the world’s most accurate assessment and monitoring of internal pipeline conditions using a weight loss coupon, solid and liquid sample collecting. The Excalibur Shield is easy to install, cost effective, and provides highly accurate pipeline corrosion rates, assessment, monitoring and risk management.
For more information, please see our 5-minute video on the Excalibur Shield.
In this case study, the Excalibur Shield was employed at a West Texas facility to collect solid samples, monitor MIC and weight loss coupon at a worst case scenario on a 20-mile long, 10” carbon steel condensate pipeline operating at 700 PSI with a 50% shut down rate.
The internal pipeline conditions were ideal for bacteria growth and induced corrosion. The weight lost coupon was being monitored by a retriever style coupon (Figure 1). The pipeline segment was suffering from a lack of internal monitoring, corrosion rate monitoring at the most severe locations, insufficient solid sampling, and water analysis.
The pipeline operator was injecting biocide and corrosion inhibitors with minimal opportunity to monitor the effectiveness of the chemical treatment because sample gathering was only available while operating a solid urethane cleaning pig. The cleaning pig cycles were also not consistent with best practice for monitor scheduling, and there was no coordination between the field technician and corrosion technician during the pig run. The corrosion technician was only notified weeks after sample collection, and the corrosion control program lacked proper corrosion identification, mechanisms and optimization of chemical treatment programs.
The only effective analysis was the retriever style coupon (Figure 2). The coupon weight was measured with a 2” x ¼” diameter, installed, exposed to the internal pipeline for 117-days, and resulting in a 0.17 MPY. The corrosion rate of a coupon is expressed in mils per year (MPY), or millimeters per year, or number of one-thousandths of an inch of metal loss from the coupon surface over a 1-year period.
The localized average corrosion and pitting rates from the coupon are categorized as low, moderate, high, and severe in accordance with NACE classification SP0775-2013 (Table 1). Ideal insertion of the coupon is at the 12 o’clock position and lowered to the 6 o’clock position in a horizontal pipeline. The placement of the coupon is often the most critical decision in obtaining meaningful internal corrosion information. In this case, only the tip of the coupon was exposed to the worst conditions in the pipeline.
After discussion, our clients and operators agreed to select both a representative location and the most severe location with respect to corrosion. Many operational and environmental conditions influence the optimal selection of location, thus, this decision is best served by the entire team. We installed the Excalibur Shield at the worst case scenario, or low lying area of the carbon steel condensate 10” pipeline, and again at the end of the 20-mile segment where the pig receiver is at the six o’clock position (Figure 3 and Figure 4).
The Excalibur Shield was easily installed on the existing infrastructure, requiring 13″ minimum clearance and no welding. The existing sump tank drainage piping system (Figure 3) was also used to install additional fittings to accommodate for the Excalibur Shield (Figure 4). After installation, we now had the capability of acquiring solids, liquids, and weight lost coupon at the worst case scenario.
The Excalibur Shield has a primary filtering system at the mouth of the 100 ml cavity, a coupon was installed inside the cavity with a secondary filter system surrounding the coupon. The outer portion has an octagon shape for easy removal, and includes a drain with ventilation valves for easy collection of fluids inside the cavity. The base adapter is outfitted with an O-ring seal for easy removal and secure sealing capability using a 316-L stainless steel body, mop 2000 PSI (Figure 4).
After 30-days exposure to the internal pipeline, the Excalibur Shield registered a 1.28 (MPY) at six o’clock, compared to the 0.17 (MPY) on the previous 117-day exposure using the retriever coupon (Figure 2), mincing a low lying area of worst case scenario. We also acquired fresh solid samples from inside the pipeline (Figure 5) and liquid samples (Figure 7) to establish the presence and concentration of bacteria colony counts in mm and grams, within the corrosion sampling location.
In this case, tests for acid producing bacteria (APB) and sulfate reducing bacteria (SRB) measured very low. Going forward, our clients now have the capability of collecting fresh liquid and solid samples internal to the pipeline.
After a second 30-day exposure, and the optimization of the pipeline inhibitor resulted in a 0.08 MPY (Figure 8). This case study demonstrates the retriever style coupon and irregular sampling prior to the Excalibur Shield was insufficient. Fundamental awareness and involvement were lacking and highlighted the need for education on all levels of the internal corrosion program.
In Summary, acquiring samples at regular intervals, corrosion rate monitoring with a coupon in a worst case scenario, fluid sampling, solid sampling and inhibitor treament all under the umbrella of the Excalibur Shield provided our client with a vastly improved corrosion control, assessment and monitoring program. Also, using the new wealth of data analysis, our client, technicians and chemical operators are much more confident in the internal pipeline corrosion program and optimization.
Microbiological Influenced Corrosion (MIC) refers to corrosion caused by the presence and activity of microorganisms such as microalgae, bacteria, and fungi. Microorganisms do not produce unique types of corrosion, however, accelerate and shift the corrosion mechanism.
Microbial action contributes to the rapid corrosion of metals and alloys exposed to soils, seawater, distilled water, freshwater, crude oil, hydrocarbon fuels, processed chemicals, and sewage. Many industries and infrastructure are affected by MIC, including oil production, power generation, transportation, and water and waste water.
Techniques to identify MIC are nonstandard and subject to interpretation. The areas we suspect MIC are at interfaces where scale, wax, and other solids can settle or precipitate. Areas downstream of welds, where cleaning pigs have difficulty removing deposits, dead legs, low-velocity areas, and tank bottoms where solids, bacteria and biofilms can accumulate, are also susceptible. Pitting is often isolated, with one hole surrounded by a number of shallower pits.
Offshore and Onshore Pipelines
You can find the Excalibur Shield in both onshore and offshore pipeline installations. Please contact us for more information on this case study.