Describe the inspection techniques and standards used for assessing the integrity of storage tanks in oilfield facilities.

The integrity of storage tanks in oilfield facilities is crucial for ensuring safe and reliable operations. To assess their integrity, various inspection techniques and standards are employed. Here is an in-depth answer describing the commonly used inspection techniques and standards for assessing the integrity of storage tanks in oilfield facilities:

1. Visual Inspection: Visual inspection is a fundamental technique used to assess the overall condition of storage tanks. It involves a comprehensive examination of the tank's external and internal surfaces, including welds, supports, fittings, and coatings. Visual inspection helps identify signs of corrosion, leakage, structural damage, or coating deterioration. It also involves the use of advanced techniques such as remote visual inspection (RVI) using specialized cameras or robotic crawlers to access hard-to-reach areas.
2. Ultrasonic Thickness Testing (UTT): Ultrasonic thickness testing is a non-destructive testing method that measures the thickness of the tank walls. It helps identify any localized corrosion or metal loss, ensuring that the remaining wall thickness meets the required standards for structural integrity. UTT is typically conducted at various locations on the tank, providing valuable information about wall thickness variations and potential areas of concern.
3. Magnetic Flux Leakage (MFL): Magnetic flux leakage is a non-destructive testing technique used to detect corrosion or metal loss in the floor and bottom plates of storage tanks. MFL tools generate a magnetic field and analyze the magnetic flux leakage caused by any defects or discontinuities. This technique can identify internal corrosion or pitting, particularly in the tank bottom where corrosion is more likely to occur.
4. Ultrasonic Testing (UT): Ultrasonic testing is commonly used for detecting flaws and discontinuities in storage tank welds. It involves the use of high-frequency sound waves to penetrate the material and provide information about the weld quality, including the presence of cracks, lack of fusion, or other defects. UT can be performed both externally and internally, depending on the accessibility of the welds.
5. Radiographic Testing (RT): Radiographic testing utilizes X-rays or gamma rays to examine the internal structure of storage tanks. It is effective in detecting volumetric defects such as cracks, porosity, or inclusions in the welds or the tank shell. RT requires specialized equipment and trained personnel to ensure proper radiation safety procedures are followed.
6. Liquid Penetrant Testing (LPT): Liquid penetrant testing is a surface inspection method used to detect surface-breaking defects in storage tank surfaces. It involves applying a liquid penetrant solution to the surface and allowing it to seep into any surface cracks or discontinuities. After a specified dwell time, excess penetrant is removed, and a developer is applied to visualize the indications. LPT is particularly useful for detecting surface cracks or defects that may compromise the tank's integrity.
7. Magnetic Particle Testing (MPT): Magnetic particle testing is another surface inspection technique used to detect surface and near-surface defects in storage tanks. It involves applying magnetic particles to the surface and creating a magnetic field. If there are any surface defects or cracks, the magnetic particles will gather and create indications that can be visually inspected. MPT is effective in identifying surface cracks, weld discontinuities, or other defects that may affect the tank's structural integrity.

In addition to these inspection techniques, storage tank integrity assessments adhere to several industry standards and guidelines. These standards provide guidelines for tank design, construction, inspection, and maintenance. Some common standards include:

* API 653: The API 653 standard outlines the inspection, repair, alteration, and reconstruction requirements for aboveground storage tanks. It provides guidelines for assessing tank integrity, evaluating corrosion rates, conducting thickness measurements, and establishing maintenance and inspection intervals.
* API 650: The API 650 standard focuses on the design, fabrication, and construction of atmospheric storage tanks. It provides