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Protectolast Corrosion Monitoring System

Corrosion monitoring is crucial for maintaining the integrity and safety of oil and gas storage tanks, with soil-side corrosion being a significant concern due to its hidden nature and potential for severe damage. Corrosion can lead to leaks, environmental contamination, and costly repairs. This type of corrosion occurs at the interface between the tank’s bottom and the underlying soil, where various factors such as moisture, soil composition, and microbial activity can accelerate the corrosion process. Monitoring soil-side corrosion is crucial to ensure the structural integrity and safe operation of storage tanks.

One of the most effective methods for monitoring soil-side corrosion is the use of Electrical Resistance (ER) probes. ER probes are designed to measure the rate of metal loss due to corrosion by utilizing a metallic element that corrodes at the same rate as the tank’s material. This element’s electrical resistance increases as it corrodes, providing a direct measure of the corrosion rate.

Working of ER Probes

ER probes consist of a metallic sensing element, typically made of the same material as the tank, which is buried in the soil near the tank’s bottom. As the sensing element corrodes, its cross-sectional area decreases, leading to an increase in electrical resistance. This change in resistance is continuously monitored and recorded, allowing for real-time assessment of the corrosion rate.

Protectolast® Corrosion Monitoring System

Protectolast® Corrosion Monitoring System (CMS) are tailor-made corrosion monitoring solutions to providing accurate corrosion monitoring & analysis of the equipment utilizing advanced sensors and real-time data analysis. Protectolast® CMS continuously assesses corrosion levels, detecting early signs of degradation before significant damage occurs. This proactive approach allows for timely intervention and maintenance, minimizing downtime and repair costs. Protectolast® CMS’s precise monitoring capabilities ensure optimal operational efficiency and safety, enhancing the longevity and reliability of critical assets in various industrial sectors.

At present, the techniques used to determine the corrosion rate on the lower plates of an aboveground storage tank (AST) facing the soil involve methods like Saturated Low Frequency Eddy Current (SLOFEC), Magnetic Flux, and Ultrasonic Thickness Scanning System, as per the inspection intervals specified in API 653. These methods typically necessitate taking the tank out of service, resulting in data collection at periodic intervals, often spanning several years.

Given the extended duration required for internal tank scans, it’s advisable to explore alternative online corrosion rate monitoring devices to assess the corrosive nature of the soil-side bottom environment of the tank.

Electrical Resistance Probes (ER Probes)

To establish a reference point for corrosion rates, it is advised to install a combination of ER probes and metallic coupons beneath each tank’s floor, comprising a carbon 1010 steel element or equivalent. This installation is recommended to take place 3 to 6 months before the injection of any VCI. Should this not be operationally available, the first base line readings should be collected from the data taken from the initial installation through the data logger / transmitter.

Collecting data regularly provides the most comprehensive insights into corrosion rates at the measuring element of the probes. Plotting the loss of metal against time can yield the corrosion rate value, represented by the slope of the line between readings. We recommend that the readings be taken at intervals to determine these values. One approach to determine this value involves applying linear regression to a sufficient number of data points over a reasonable timeframe.

Ports through the ring wall of the targeted asset should be used for the installation of these units, and a data logger should be employed post-installation to record data collected from each probe.

In cases where ports for ER probe installation are absent or not usable, it is advised to drill them prior to project commencement by the client and/or contractor.

Data recording and logging once a week using a transmitter to provide continuous update on corrosion rate after the corrosion inhibitor application can be done for a period of almost 8 to 10 weeks considering that ER probes are installed prior to the application of the corrosion inhibitor by 3 – 6 months period. The recorded data should be forwarded to SKPS for analysis.


Advantages of ER Probes for Soil-Side Corrosion Monitoring

  • Continuous Monitoring: ER probes provide continuous, real-time data on corrosion rates. This helps in detecting early signs of soil-side corrosion, enabling timely maintenance and preventing potential tank failures.
  • Ease of Installation: ER probes are relatively easy to install and can be strategically placed in the soil around the tank’s perimeter. This allows for comprehensive monitoring of different areas that might experience varying corrosion rates.
  • Data Analysis: The data collected by ER probes can be transmitted to a central monitoring system for analysis. Advanced data analysis techniques can identify trends, predict future corrosion rates, and suggest appropriate maintenance actions. According to a study by NACE International, proactive corrosion monitoring can reduce maintenance costs by up to 20% and extend the lifespan of equipment by up to 30%.
  • Versatility: ER probes are versatile and can be used in various soil conditions, including highly corrosive environments. This adaptability makes them suitable for different types of storage tanks and soil compositions.
  • Proactive corrosion monitoring using ER probes can lead to significant cost savings. According to the National Institute of Standards and Technology (NIST), implementing corrosion monitoring systems can improve operational safety and reduce unplanned shutdowns by up to 50%. A survey conducted by the Oil & Gas Journal found that more than 70% of industry professionals consider ER probes to be one of the most reliable methods for monitoring soil-side corrosion in storage tanks.
  • In summary, ER probes are an effective and reliable method for monitoring soil-side corrosion in oil and gas storage tanks. By providing real-time data on corrosion rates, these probes help maintain the structural integrity of storage tanks, preventing leaks and environmental hazards, and reducing maintenance costs. Their ease of installation, continuous monitoring capability, and adaptability to different soil conditions make them a valuable asset in the oil and gas industry’s efforts to ensure safe and efficient storage operations.


Enhancing Tank Preservation with Protectolast WS-VCI

The Protectolast WS VCI, is a water-soluble powder designed to create a protective layer on metal surfaces, effectively preventing corrosion. This inhibitor spreads easily and adheres to metals, offering long-term protection without the need for forced drying after pressure tests, thus reducing the risk of issues like valve seizing and pipework blockages. Its versatility allows it to protect metals in hard-to-reach areas, making it ideal for the underside of storage tanks facing the soil. By providing up to 24 months of continuous protection, Protectolast WS VCI ensures the longevity and integrity of storage tanks, reducing maintenance costs and enhancing safety.

What is VCI Technology?

Vapor Corrosion Inhibitors (VCIs) work by releasing molecules that form a protective layer on metal surfaces. When exposed to air, these molecules create a vapor-phase barrier that adheres to the metal, blocking moisture and corrosive agents from making contact. This barrier prevents oxidation and corrosion by interrupting the electrochemical reactions that lead to metal degradation.

ER Probe Data for VCI Replenishment Timeline

An example of how VCI data can be plotted to monitor and determine the replenishment timelines

From ER probe data analysis for underside corrosion protection of above ground tanks using VCI solutions, several key inferences can be drawn:

  • Corrosion Rate Monitoring: ER probe data provides insights into the corrosion rates over time. By analysing this data, trends in corrosion activity can be identified.
  • Effectiveness of VCI Penetration: The data can indicate how well the VCI s olution penetrates and protects the underside of the tanks. Higher corrosion rates may suggest areas where the VCI coverage is insufficient or where moisture ingress is still a concern.
  • Localized Corrosion Areas: ER probe analysis can pinpoint localized areas of accelerated corrosion, which may require targeted application or adjustments in VCI deployment to ensure uniform protection across the tank underside.
  • Long-Term Protection Trends: Trends in corrosion rates over extended periods offer insights into the long-term effectiveness of the VCI solution. Consistent low corrosion rates indicate robust protection, while increasing rates may signal degradation of the VCI layer or other factors affecting protection.
  • Optimization of Maintenance: By correlating ER probe data with maintenance schedules, optimal intervals for VCI re-application or supplementary corrosion protection measures can be determined, optimizing maintenance efforts and costs.
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