Static equipment, such as pressure vessels, tanks, and piping systems, plays a critical role in industrial operations. Over time, these assets are subjected to mechanical wear, environmental stresses, and most notably, corrosion. Ensuring the integrity of these systems is paramount to prevent failures, optimize safety, and maintain operational efficiency. Central to this process is the practice of mapping thickness measurements throughout the equipment’s lifetime, which allows engineers to assess its condition and perform accurate calculations for fitness for service (FFS).
Importance of Mapping Thickness Measurements
Corrosion is a natural phenomenon that can significantly reduce the thickness of materials, especially in equipment exposed to harsh operating conditions. As equipment ages, its material strength can degrade, leading to weakened structural integrity. Regularly mapping the thickness of the equipment during its service life provides essential data on how much corrosion has occurred.
Thickness measurements are usually taken at various points on the equipment, especially in areas where corrosion is more likely, such as low-flow zones, welds, or surfaces in contact with corrosive substances. By tracking these measurements over time, engineers can observe trends in corrosion rates and identify potential areas of concern before they become critical.
Mapping also enables engineers to determine the remaining useful life (RUL) of the equipment, helping to schedule maintenance, repairs, or replacements in a timely manner. This proactive approach ensures that the equipment operates within acceptable safety margins and prevents unexpected failures that could disrupt operations.
Fitness for Service (FFS) and Calculations
Once thickness measurements have been taken, engineers must perform a fitness for service (FFS) assessment. This process evaluates whether the equipment is still safe and capable of performing its intended function despite material loss. The FFS evaluation typically follows established standards such as the ASME (American Society of Mechanical Engineers) code or API (American Petroleum Institute) guidelines.
The FFS analysis involves several steps. First, the current state of the equipment is compared against its original design specifications. Calculations are performed to determine if the equipment can still withstand the stresses and pressures it is exposed to. This includes assessing the remaining wall thickness, the corrosion rate, and the operating conditions. If the thickness falls below a certain threshold, the equipment may be deemed unsafe for service, requiring repairs or replacement.
Advanced FFS methods also consider factors like localized corrosion, material degradation, and potential fatigue failure. Engineers use sophisticated software and simulation tools to model the behavior of the equipment under varying conditions. By inputting factors such as operating pressure, temperature, and corrosion rates, these calculations provide a detailed picture of the equipment’s condition and help in making informed decisions about its continued use.
Conclusion
Regular mapping of thickness measurements and performing fitness for service calculations are essential for maintaining the safety and reliability of pressure equipment. By carefully tracking corrosion and assessing the integrity of the equipment (typically using dedicated software), engineers can ensure that equipment continues to perform safely, minimizing the risk of catastrophic failures while optimizing maintenance schedules. Properly executed, these practices allow for the extended life of critical infrastructure, helping industries remain efficient and secure.