Abstract
We will present the results from several projects from the USA and other jurisdictions where ASME B31.1 Ch. VII O&M Covered Piping System (CPS) Programs have been implemented at several types of natural gas-fired CCGT plants. Common elements of programs for different plants will be summarized as well as plant-specific considerations for high energy piping condition assessment for newer plants. Pros and cons between a common program for a thermal fleet and plant-specific programs will be discussed including advantages and disadvantages of each approach. Effective implementation of parts of the Nonmandatory Appendix V guidance within the CPS Program will be described and recommendations for best practices.
A brief overview of degradation-specific mechanisms for high energy piping and approaches for planninng/scheduling NDE inspections will be described. This overview will include: creep, fatigue, corrosion (erosion-corrosion - E/C and flow accelerated corrosion - FAC) as well as mechanisms that are commonly responsible for high energy piping leaks, failures and repairs including thermal quench cracking of HRSG inter-stage, terminal desuperheaters and turbine bypass attemperators. A brief summary of Gr. 91 inspection planning in Ch. VII O&M Programs will also be included as well as corrosion under insulation (CUI) and common inspection scopes for high temperature steam drains.
Resolution of constant force and variable spring pipe supports on high pressure/high temperature piping that are not accommodating thermal expansion as per their engineering design can be evaluated using pre-outage pipe stress models and data obtained from field walkdowns to support rapid decisions for repair/replacement in the field.
Finally, experiences with long term scheduling the need for adaptive management of the CPS Programs will be summarized with typical management oversight actions described for effective implementation.