Elevating the Pressure and Temperature

This article discusses the modernization of the rules of Section I of the ASME Boiler and Pressure Vessel Code to better accommodate the challenges of increasing temperature. At very high pressures and high temperatures, the current Section I rules require components to be comparatively thick, but making things thicker is not always better. In thick components, temperature gradients and consequent differential thermal expansion produce large secondary stresses. When pressure and temperature drive a component’s thickness to be very large compared to the size of the component, it can compromise that component’s ability to endure thermal transients that occur in service. One of the biggest challenges in addressing elevated temperature service is understanding creep and fatigue interaction and developing appropriate design rules to manage that. Another challenge is that corrosion mechanisms change with increasing temperature. The push to higher temperatures will spawn development of new materials to meet all the design goals. The BPVI standards committee on Power Boilers will also need to evaluate whether some of the construction details traditionally used will be appropriate at higher temperatures.