Inspection and Repair of Plant Civil Structures
The integrity of plant infrastructure is a vital component of maintaining safe and reliable operations. During the life of these facilities, infrastructure has been subjected to environmental and process-related elements through the years. However, capital expenditure is typically focused on assets related to increasing or maintaining production rates. Plant structures supporting the miles of piping, process vessels, platforms, and ladders routinely used in daily operations often can be given less priority than production equipment. Having a robust inspection and repair program for plant infrastructure is an important component of a site’s integrity management program.
Having safe and reliable operations is a goal of all manufacturing facilities. Proactively managing risks due to aging civil structural assets plays an important role in ensuring silent running and in minimizing health, safety, and environmental incidents and business interruption.
If most of a plant’s civil structures (“structures”) are the same age and the plant begins a structural inspection and repair program in response to a structural failure, it may require significant investment to restore the plant to an acceptable condition. Annual preventive maintenance plans and repair strategies are less costly over a plant’s life cycle than large projects for infrastructure renewal. A risk-based approach to inspection, repair, and preventive maintenance further optimizes spending allocation over time and ensures integrity is restored or maintained in the most critical areas.
Structures do not have an infinite design life and may pose certain risks as they degrade over time. For sites that have not actively maintained plant structures, significant resources may be needed for structural repairs to keep plants running safely and reliably. Through the development of a risk-based structural inspection program, structural repairs can be planned and prioritized in a systematic way to promote safe and reliable operations.
This book provides a framework for establishing a risk-based inspection (RBI) and repair program for plant structures. This methodology was developed and deployed at a large manufacturing facility in the United States. It was then incorporated into a sustainable inspection and risk assessment program. The creation of inspection templates, the selection and training for inspection contractors, and a means of determining structural risks were essential components of the program. This program provided a quantitative means of demonstrating a reduction in plant structural risks. The RBI and repair program helped the company focus efforts on the most critical repairs and improved its structural repair strategy. Companies can model this RBI and repair program to help promote the integrity and safety of plant structures and other supporting infrastructure at their facilities. This book will discuss this approach and considerations for implementing a similar program at other manufacturing facilities.
Benefits of RBI Programs
There are many benefits to RBI programs. Many manufacturing facilities realize these benefits through the application of an RBI approach for piping and pressure vessels by using the rules outlined in American Petroleum Institute (API) Recommended Practice 580 and in the base resource document API 581. Currently, plant structures do not fall within the scope of these documents. However, there are many benefits to establishing an RBI and repair program to manage structural asset integrity. An RBI and repair program is a highly methodical and structured way to effectively manage a large number of assets. Benefits of an RBI program for structures include the following:
- A risk-based approach to identifying and addressing structural integrity allows for more effective management of the inspection and repair strategy. In most facilities, generally <10% to 20% of equipment or structures represent most of the risk for the site. This is a fundamental principle of RBI methodology, enabling the owner and/or operator to focus on the areas of highest risk. Proper identification of these high-risk areas allows for shifting inspection and maintenance resources and funding to these assets.4 By concentrating inspection resources on areas that pose the most significant risk of failure, resources can be focused on proactive inspection and repair of the highest-risk structures.
- A risk-based structural inspection program can provide an accurate assessment of the structural risks within the facility by giving visibility to the areas of highest risk by producing a risk-ranked list of all structural assets. Focusing repair efforts on the areas of highest risk provides a means of measuring structural risk reduction over time and quantifying the return on investment.
- A risk-based approach enables identification of structures that have a low likelihood , and consequence of failure (COF), and warrant a longer time period in between inspections. The creation of a register of structural assets also helps with identifying structures that do not require further inspection or maintenance because of the structure having an inherent acceptable risk level for the site. For example, abandoned foundations or small electrical support stands for a power switch may be considered out of scope for the program. Such consideration enables avoidance of the unnecessary use of inspection resources and funds when there is minimal value to be gained from the inspection.
- By identifying risk at the structural component level, targeted risk mitigation plans can be developed. Through identification of the most significant defects of a particular structure, targeted repairs can be made to prevent structural failure.
- An RBI program applies a systematic set of rules to a given asset type that can be applied consistently across all asset types. The rules enable systematic evaluation of the probability of failure and COF for a given asset. Such rule-based criteria are less dependent on inspector judgment and provide a more accurate and consistent means of managing risks across a plant.
- \Without established guidelines or repeatable rules, determining which structures require repair may be based on the opinions of many individuals without the full knowledge of the structural risks across the facility. A risk-based approach enables a clear view of risk across the facility and reduces subjectivity and preferential biases toward areas most in need of repair.
- A risk-based approach allows for comparison of risk within the facility. When risk is mapped to the corporate risk matrix, this approach also allows for comparison with other equipment types and can inform project funding decisions by using common corporate risk language.
- Inspection and documentation of medium-risk structures allows risk to be forecasted into the future and allows appropriate preventive maintenance strategies to be used to prevent increased risk.
Many benefits can be realized by the identification, management, and reduction of safety, environmental, and financial risks associated with the failure of plant structures. Implementation of an RBI and repair approach can be accomplished through the development of robust defect criteria, risk prioritization, translation to the standard corporate risk matrix, and the creation of a simple and repeatable process. An understanding of structural failure modes, a basic knowledge of concrete and steel properties, and an understanding of static and transient loading conditions experienced by structures is essential for developing a meaningful risk-based integrity program for plant structures. A licensed, experienced civil engineer plays an important role in supporting the development of such a program for any company.
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