Penstock Integrity Guideline

Bridging the gap in penstock integrity international standards, we aim to develop a unified operational guideline covering inspection procedures, timeline and repair methods.

The challenge of hydrpower penstocks

Across Europe, America, and Asia, aging hydropower penstocks remain in operation, many of which were constructed in the early 1900s using now outdated materials and designs. These aging structures face increasing stress due to higher flow rates, more frequent operational start-stop cycles, and evolving environmental conditions. Despite these challenges, there are currently no globally recognized standards governing the integrity assessment and inspection strategies of penstocks. Existing guidelines are often developed at the operator level and may lack a comprehensive risk-based evaluation. This absence of standardization poses potential legal and safety risks for operators, particularly in the event of an accident. The availability and application of an internationally recognized standard could serve as a significant risk mitigation measure, ensuring both safety and regulatory compliance.

Presently, each operator conducts periodic inspections based on internal guidelines, leading to inconsistencies in maintenance practices and reliability assessment.

Objectives

To address these gaps, DNV proposes the development of a Penstock Integrity Guideline through a Joint Industry Project (JIP). This initiative aims to align industry practices, enhance existing standards, and provide operators with a robust framework for managing penstock integrity. The guideline will focus on identifying various penstock types, construction methods, and materials, evaluating and recommending current inspection and repair strategies, and establishing a risk-based framework for integrity assessment. By implementing these measures, the guideline will enable operators to optimize inspection schedules, extend service life, and ensure compliance with industry best practices, ultimately leading to safer and more cost-effective maintenance strategies.

Scope of Work

Work Package 1:
This work package focuses on collecting and analyzing data related to managed assets from JIP participants, with particular attention to penstocks. The assessment will cover both construction and operational data, as well as inspection and maintenance methodologies.

Work Package 2:
This work package aims to develop a methodology to assess the risk level of penstocks by incorporating mechanical risk analysis and failure probability evaluation.

Work Package 3:
This work package focuses on identifying critical locations along the penstock track and assessing their mechanical condition.

Work Package 4:
This work package focuses on defining inspection and maintenance strategies to ensure continuous reliability updates for penstocks.

Participation

Based on work packages 1-4 DNV expects that a participation fee of 30/40 kEUR per participating company will be sufficient. The JIP will be initiated once 75% of the target budget is achieved.

Time Schedule

The JIP will be carried out over a period of 2 years, with the following tentative schedule:

• Definition of JIP Scope of Work : March/April 2025
• Budget definition and project marketing : May/June 2025
• GO/NO-GO GATE: July 2025
• JIP starts: September 2025
• Draft version of the guideline: October 2026
• Official issue of Guideline for Penstock Integrity: December 2026