(178d) Assessment Methods to Prevent Brittle Fracture Failures in Pressure Vessels & Piping Components

In this paper, an overview of the analytical methods available for plant engineers is presented that will determine the brittle fracture susceptibility of existing and in-service pressure vessels and piping components. These methods are described in detail in post construction codes such as ASME/API 579-1 (Fitness For Service). Presented methods are primarily based on ASME Code, Section VIII design philosophy developed to prevent a catastrophic brittle fracture failure. Risk based assessments such as process hazard analyses can identify and avoid process scenarios that may cause brittle fracture. However, there are process scenarios such as pressure relieving events, other valve operations, and blow down events which are necessary and unavoidable, yet need to be addressed in the brittle fracture framework. In these cases, the brittle fracture concern is due to the exposure of the components to low temperatures during such process scenarios. In addition, the fracture toughness rules have evolved over time and the lowest design temperature for a given thickness and material type may not be appropriate for such low temperature excursions. While the analytical methods are fairly easy to implement, care shall be exercised when assessing the individual components. This paper provides an outline of the various levels of such analytical methods, the appropriateness of the method chosen, limitations, and remediation guidelines to prevent brittle fracture failure.