The birth of value-based maintenance

US NUCLEAR UTILITIES ARE STRIVING to enhance economic performance and reduce power generation costs, while maintaining safety and equipment reliability.

The Nuclear Energy Institute (NEI) initiated the Delivering the Nuclear PromiseTM (DNP) initiative. DNP’s mission is to strengthen practices that advance world-class safety and reliability levels, enhancing the economic performance of nuclear plants through innovation and efficiency, and gaining full recognition of the value of nuclear generation in electricity markets.

The industry formed targeted DNP working groups comprising utility, Institute of Nuclear Power Operations (INPO), NEI, Electric Power Research Institute (EPRI), other industry personnel and union representatives to brainstorm and develop numerous improvement initiatives called efficiency bulletins (EB). These bulletins were approved by chief nuclear officers across the USA, and NEI issued them. The goal is to reduce power generation costs by 30%.

The nuclear power industry’s culture of ‘reliability at any cost’ and ‘more is better’ has resulted in unsustainable costs. Generators have focused on eliminating failures with little consideration of the value of the maintenance strategy used. Hence NEI industry bulletins aimed to establish a value-based maintenance (VBM) programme to appropriately balance risk and the consequence of failures with the total cost of maintenance.

The industry developed three supporting bulletins in addition to a principal VBM bulletin. The implementation flowchart (Figure 1) shows how the various VBM strategies and bulletins fit together.

1. Value-based maintenance

Efficiency Bulletin 17-03a: Value-Based Maintenance is the primary efficiency bulletin that expands the guidance in the supporting bulletins and provides a definition for a new, value-based maintenance strategy.

The VBM strategy is one that optimises safety and reliability while weighing the cost of component maintenance. This includes identifying possible adverse costs when a change in maintenance strategy causes an increase in failure rates for a component. Reducing preventive maintenance may not reduce costs if it results in increased corrective maintenance or regulatory scrutiny.

The total costs and impact to the station must be considered when deciding components are noncritical and analysing value-based maintenance strategies for them. This bulletin also discusses value-based maintenance tools to optimise the costs of component maintenance while identifying possible adverse reliability effects using new maintenance strategies.

VBM focuses plant resources on maintenance of critical equipment. Deploying maintenance personnel accordingly saves time and money while improving work efficiency.

Nuclear plants using these tools should begin seeing significantly lower annual maintenance costs by the end of this year, and costs should fall by at least 25% by 31 December 2020.

2. Critical component reduction

Efficiency Bulletin 16-25: Critical Component Reduction was one of the first in a series of VBM related bulletins to focus station equipment reliability processes on critical components. A change to the INPO AP-913 critical component definition supports the framework for consistent implementation of cost-effective maintenance in the nuclear energy industry. It establishes a zero-tolerance policy for critical components whose failure results in unacceptable consequences, while facilitating cost-effective maintenance strategies for noncritical components.

The aim is to focus on components and systems that are critical to safe, reliable plant operation. Components are classified as critical based on the relative importance for maintaining system function, and a thorough process is used to review and document the technical bases of preventive maintenance task deferrals, changes, additions and deletions.

3. Preventive maintenance reduction

Efficiency Bulletin 16-16 is titled High-Cost, Noncritical Preventive Maintenance Reduction. This addresses the extensive high-cost, high-frequency and resource-intensive preventive maintenance performed on noncritical equipment without improved reliability.

Identifying the most expensive noncritical preventive maintenance performed over large populations of components such as air operated valves, and asking how they improve reliability and optimisation of the tasks, reduces their frequency and may reclassify them as run-to-maintenance. Targeting the most expensive preventive maintenance cuts costs immediately.

The desired result is a reduction in labour, parts and planning costs by optimising, reducing and eliminating maintenance tasks. It will help minimise the need for intrusive maintenance and reduce post-maintenance equipment issues.

The expected value is a reduction in the most-costly maintenance on noncritical equipment (or component groups) where the total cost of the maintenance activity does not justify the gains in equipment reliability. This review reduces or eliminates low-value tasks to focus resources on critical equipment or maintenance backlogs. The industry benchmark is that the results do not increase critical component failures or adversely affect the equipment reliability index, and improves labour and material cost savings.

4. Cultural shifts

Efficiency Bulletin 17-03b is Embracing Cultural Shifts For Value-Based Maintenance. Changing the industry’s culture of ‘reliability at any cost’ and ‘more is better’ to one of value-based maintenance is the key to improving safety and reliability in a cost-effective manner. Senior utility leaders drive behavioural changes to support the shift from a culture of zero tolerance for equipment failures to one that is appropriately tolerant for low-consequence failures.

The big picture

Re-scoping component criticality for utility components using the revised definitions in the Delivering the Nuclear Promise EBs 16-25 and 17-03a, and the INPO AP-913 component scoping guidance documents will refine the list of critical and noncritical components, as well as reducing critical components.

Data from the station work management system can be used to identify the highest total cost noncritical maintenance tasks (including those for common components such as air-operated valves). US industry data visualisation tools can assist utilities with this task. Some of the initial components are air-operated valves, relays, and low voltage breakers.

The next task is to establish a technical maintenance strategy (i.e., task and frequency) evaluations and engineering evaluations as required. The latest proven industry approaches that assess age-related degradation and provide a sound engineering technical basis can optimise the maintenance tasks and frequencies.

It is important to establish a cross-functional review team. The team reviews past site-specific performance, historical as-found condition, technician input, resource costs, engineering recommendations and industry operating experience. They will then analyse plans for eliminating or for a reduction in frequency or content of tasks. This process helps establish a sound technical basis for the station’s maintenance strategy.

Industry tools can be used to assist with the evaluation and also address the total cost of maintenance.

Based on Sargent & Lundy’s project experience, the ambitious industry goal can be achieved while improving equipment reliability. This starts with the suggested equipment groups. Wear in these types of equipment makes them prime candidates for innovative approaches, which includes functional and equipment ageing and material analysis, as well as calculations.

O-rings, seals, plastics and diaphragms are especially sensitive to environment and temperature effects over time. These elements are evaluated and maintenance frequencies can be better established using advanced engineering- based ageing evaluations that are consistent with sound industry practices. Enhanced maintenance evaluations can augment the work a client is currently performing in the VBM area and provide a solid and defendable engineering basis for maintenance strategy changes.

Sargent & Lundy’s experience with supporting VBM-type projects has shown that adding engineered ageing and material analysis best reduces maintenance costs without sacrificing reliability. For example, one project for 672 air-operated valves (AOVs) reduced labour costs to less than 50%, while improving safety and equipment.

Sargent & Lundy’s innovative approach have produced short- and long-term cost savings. They have helped minimise the need for intrusive maintenance and reduce post-maintenance issues.

After optimised maintenance strategies and basis are established, a plant expert panel performs a risk and cost assessment review. This challenges classification, value, tasks, frequency, etc. A feedback loop uses value-based maintenance tools and evaluation processes to adjust the maintenance strategies if necessary.

Once the expert panel approves the changes, the projected return on investment and annual O&M cost savings are captured using plant-specific labour and material costs. The technical bases, work management database and other engineering records are updated; change requests are generated, and the appropriate plant procedures are marked-up and updated in accordance with station procedures.

Once the work is performed, lessons are captured, and the feedback is used to adjust the process accordingly.  

Mark Maras is Senior manager at Sargent & Lundy; Steve Malak is Senior project manager at Sargent & Lundy 

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