Cathodic Protection Testing for Underground Steel Storage Tanks: Safeguarding Structural Integrity

Underground steel storage tanks are essential for industries that store liquids, from petroleum products to hazardous chemicals. Ensuring these tanks’ longevity and structural integrity is paramount to prevent leaks, corrosion, and environmental hazards. One critical method employed by internal tank and pipeline inspection services companies for this purpose is cathodic protection, a technique that involves applying a sacrificial current to the steel tank to mitigate corrosion.

In this blog, we’ll explore the significance of cathodic protection testing and its role in safeguarding underground steel storage tanks.

What is Cathodic Protection?

Cathodic protection is a corrosion prevention technique that utilizes electrochemical principles to protect metallic structures, such as underground steel storage tanks, from corrosion. A galvanic cell is created by introducing a sacrificial anode material, typically made of zinc or aluminum, diverting corrosive currents away from the steel tank.

The Role of Underground Environment

Underground environments can be particularly harsh due to soil conditions, moisture, and the presence of corrosive substances. When buried underground, steel is susceptible to corrosion, which can compromise the tank’s structural integrity. Cathodic protection is, therefore, a proactive measure to counteract the corrosive effects of the environment.

Importance of Cathodic Protection Testing

While the installation of cathodic protection systems is a crucial step, regular testing is essential to ensure that the system is functioning effectively. Cathodic protection testing involves measuring parameters such as voltage, current, and potential to assess the level of protection provided to the underground steel tank. Regular testing helps identify deviations from optimal performance and allows corrective actions to be taken.

Types of Cathodic Protection Testing

There are two primary types of cathodic protection testing: potential measurement and current measurement.

  • Potential Measurement: This involves measuring the voltage between the steel tank and a reference electrode. The goal is to ensure that the tank’s potential remains within the desired range for effective corrosion protection.
  • Current Measurement: This testing involves measuring the output from the sacrificial anode to the steel tank. Monitoring the current is crucial to verify that the sacrificial anode is providing adequate protection.

Frequency of Testing

The frequency of cathodic protection testing depends on various factors, including the soil’s corrosiveness, the tank’s coating condition, and regulatory requirements. Generally, annual testing is recommended to promptly detect any issues and take corrective actions.

Compliance with Industry Standards

Cathodic protection testing for underground steel storage tanks is guided by industry standards, including those set by organizations like the American Petroleum Institute (API) and the National Association of Corrosion Engineers (NACE). Adhering to these standards by tank inspection company ensures that testing procedures are comprehensive and in line with best practices.

Benefits of Cathodic Protection Testing

Corrosion Prevention: Regular testing ensures that the cathodic protection system is actively preventing corrosion, preserving the tank’s structural integrity.

Environmental Protection: Effective cathodic protection minimizes the risk of leaks, preventing the release of hazardous substances into the surrounding soil and groundwater.

Compliance: Meeting regulatory requirements for underground storage tanks is crucial, and cathodic protection testing is often mandatory to demonstrate compliance.

Cathodic protection testing is crucial to maintaining the structural integrity of underground steel storage tanks. By regularly assessing the effectiveness of the cathodic protection system, industries can ensure that their tanks are safeguarded against corrosion, extending their service life and mitigating environmental risks. Adhering to industry standards and testing at recommended intervals are essential to derive the maximum benefits from cathodic protection systems for underground steel storage tanks.…

Standard Practices for Conducting API 653 Tank Evaluation.

Storage tanks are crucial elements in any industry. Storage tanks allow one to collect and store essential commodities like fuel, gases, water, and other materials. Since storage tanks and containers are susceptible to damage and contamination, they must be regularly monitored—some various standards and regulations guide tank inspection. API 653 is one type of tank inspection undertaken by professionals from worldwide inspection services companies. Any industry using storage tanks must undertake API 653 tank inspection from time to time. 

The time interval between each tank inspection varies according to the nature of the material stored, the type of tank in use, and the inspection’s objective. Internal tank inspection should be conducted within ten years from the last evaluation, while external tank inspection should be conducted within five years.

However, if needed, monthly tank inspection can be considered as per the needs and requirements. Since inspecting a tank requires highly specialized skills and knowledge, it can be performed by someone certified to do the task. Besides conducting tank evaluation, inspectors are required to maintain a log of the test results for further review. 

In this blog, we will look into some essential aspects of API 653 tank inspection in detail. 

Detection of moisture under the insulation

Moisture or vapor can accumulate in the tank due to various reasons. Once the moisture level has reached a particular range, it can lead to water contamination and corrosion. Tank inspection companies are often called to look for the signs of any possible moisture inside the tank. Moisture detection in heated or insulated tanks is often a challenging task. The insulation or metal jacketing covering the outer part of the tanks also prevents detection of corrosion. 

Tank repairing and damage prevention methods

Missing out on any part of the storage tank and accessories while conducting an API test can lead to catastrophic consequences. There are instances when tanks start to leak soon after conducting the inspection. Areas underneath the horizontal insulation panels may go unchecked and start to leak. 

Thus, API tank inspectors ensure that every part of the storage tank and pipes are thoroughly scanned for any sign of damage. Insulation specialists are trained in deducing the area of water intrusion and evaluating corrosion rate. Once the crack or dent is identified, the next step is to prevent corrosion or spill. 

Can You Avoid Hidden Moisture Damage?

The best way to adhere to the API 653 regulation is to adopt a customer’s insulation program. 

Tank inspectors often expose the corners of the tank. This allows the inspectors to monitor the welded part that is hard to reach. Additionally, exposed insulation jackets will enable the detection of moisture that may have entered from the tank’s bottom. To check the condition of the walls, inspectors use inspection ports and ultrasonic thickness meter. 

Insulation Support Systems

Tank operators and owners can comply with API 653 standards by installing an insulation support system. The support system allows proper upkeep of the insulation panels. The support platforms also simplify the task of inspecting critical areas of the tank that may be hard to reach. These support systems come in various sizes and are compatible with most insulation panels. …

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