5F1: Penstock Assessment and Refurbishment
July 14, 2022
Operations and Maintenance
Penstocks are essential components for hydroelectric facilities. Penstock reliability is critical for maintaining power generation, flow passage and overall dam safety; however, assessing and maintaining aging penstocks presents challenges. A typical maintenance program requires monitoring, periodic maintenance, condition assessment, and rehabilitation or replacement if needed. Klohn Crippen Berger (KCB) is currently working on a variety of penstock maintenance and life extension projects for multiple clients. This presentation will focus on condition assessment and evaluation of rehabilitation vs. replacement options for aging penstocks. Typical procedures for condition assessments will be presented, including: Detailed structural assessment and design review of aging penstocks in accordance with industry standards including ASME Boiler Pressure Vessel Code, ASCE No. 79 Steel Penstocks, ASME-B31-G Corroded Pipelines, and other industry standards Corrosion assessment based on non-destructive testing (NDT) thickness testing Demand-Capacity analysis, Finite element modelling, fatigue assessment, vibration analysis and service life estimates Completion of condition assessments are used to inform decision-making for long-term asset management. Evaluation of replacement versus refurbishment options will be discussed using examples from recent projects. The presentation will also touch on a multi-year, multi-facility program of work related to penstock recoating. These projects involved the design of penstock modifications, which include the addition of new penstock access hatches and anchor points to facilitate automated, robot-assisted recoating of the penstocks. At each facility, enhanced access provisions were tailored to facilitate using automated recoating technologies, meet ventilation requirements, and provide safe access and rescue, while minimizing the time workers spent inside the penstock. Consideration was given to structural limitations of the penstock, constraints due to available road access, cost, and constructability.