p.1 

OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

222) 11-1-2 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:51:02 AM Sheet 222 of 276 
P.2 

II-I-2 

IFE EXTENSION - A GLORIFIED MAINTENANCE PROGRAM? 

by 

. A. Derdiger, R. J. Hollmeier, and G. Shibayama 

Many life extension programs have been developed over the last few years. Since 

systematic problem solving techniques can be applied just as easily to life 

extension as to any other business or engineering problem, it is not surprising 

that most of the programs are similar in concept. Because most programs are 

tailored to a specific application, the differences among the programs are in the 

details, as would be expected. Before discussing our program, we will first 

define life extension and discuss the confusion surrounding it. 

Plant Life Extension (PLE) needs to be clearly defined because the term is often 

misinterpreted and abused. There are as many definitions of PLE as there are 

programs, but there is a great deal of similarity among the better ones (those 

that agree with ours, of course). Another thought as to why PLE is diversely 

defined is because it is a new concept or thought process that looks suspiciously 

like a lot of other things that have been done in the past. To determine a good 

definition, therefore, one should start by differentiating PLE from everything 

else. This brings to mind the position of marketing some twenty years ago. At 

that time, marketing professors and professionals spent much of their effort 

trying to differentiate marketing from sales so that the rest of the world would 

appreciate that marketing is a more advanced concept. 

Admittedly, PLE, like marketing, needs differentiation and definition, and not 

just for the nonbeiievers, but to keep us focused on the real objective: lowering 

generating cost. Accordingly, Fluor has defined PLE as "an organized program to 

investigate, evaluate, and plan for prolonged utilization of existing generating 

units in order to satisfy future system electric load." 

This definition embodies a commitment to determine whether and how existing units 

can be better utilized, rather than replaced, to lower future generating cost. 
P.3 

ar, 

ii 

In its most restricted application, PLE involves the determination of the remaining life of critical components, and the economic feasibility of reliable, extended plant operation beyond either the original design life or the currently 

planned retirement date. PLE also includes identification of plant upgrades and 

operating and maintenance techniques required to extend life. 

More generally, however, increased utilization through PLE means taking a new look 

at the existing assets of the plant to determine how to cost-effectively meet 

future generating requirements. Depending upon specific utility needs, these 

requirements may be met by: 

• Recapturing lost efficiency 

• Improving availability 

• . Modifying for cycling 

• Improving operating and maintenance techniques 

t Repowering 

• Converting fuels 

To determine which course of action is best for a particular utility, an integrated approach to: develop an organized data base, evaluate options, and develop 

an implementation plan is required. Four major activities are addressed in 

Fluor's programmatic approach. These activities are as follows: 

• Plant assessment. A quick, low-cost assessment of the overall condition, 

operations, and availability of a plant. 

System planning. Conceptual evaluation of future system configuration 

options, particularly the economic value of extended life and enhancement of 

existing generating units. 

Detailed inspection, testing, and evaluation. An intensive inspection of 

plant systems and components to determine condition, estimate remaining life, 

and calculate cost for upgrade or replacement. 

Implementation plan. An integrated long-term plan involving upgrades, 

training, and ongoing monitoring. 
P.4 

Our approach emphasizes close coordination between maintenance and operations 

practices. Fundamentally, some PLE activities are closely related and may overlap 

into the maintenance arena while others are quite independent. The scope of 

activities which fall under the category of maintenance varies from utility to 

utility depending on factors such as economics, accounting methods, or operating 

philosophy. For example, while most utilities include boiler tube repairs in 

their PLE programs, some exclude it, categorizing these repairs as normal maintenance. From our viewpoint, when the decision to replace tubes is dependent solely 

on history (i.e., current and past tube leaks), this can be considered to be 

corrective maintenance. Where tube sample analysis and high-stress-point engineering are performed, these activities may be considered predictive maintenance, 

and fall under the category of plant life extension. 

Let's now review the distinctions between maintenance and life extension in a few 

general areas. 

COMPONENTS COVERED 

While corrective maintenance encompasses all plant equipment and preventative 

maintenance covers equipment that requires periodic attention for changeout of 

lubrication, filters, gaskets, etc., life extension focuses on heavy wall components with finite, analytically determinable life along with those elements useful 

in controlling and monitoring plant life. The most important such elements are 

modernized turbine and boiler control systems, which, in addition to making the 

unit easier to operate, permit the operator to better minimize creepand fatiguerelated stresses on the plant systems, thus maximizing unit life. 

PRIMARY FOCUS 

Normal maintenance focuses on corrective and preventative activities, which tend 

to support continued operation of components and subcomponents. Life extension 

programs, on the other hand, focus primarily on predictive activities which ensure 

safe, reliable unit operation. While safety is always a paramount consideration, 

it is not ordinarily a problem during the initial design life, since the heavy 

wall, high-pressure parts were very conservatively designed. However, with 

extended life, we may intrude into the margin of safety or beyond; so it is 

necessary to determine the expended and remaining life of critical components by 

using more accurate techniques. 
P.5 

i:-

With regard to methodologies that are used to determine remaining useful life, 

utilities are sometimes confronted with widely divergent conclusions that are 

drawn from the "experts" who are called upon to evaluate remaining useful life in 

components. 

CONDITION MONITORING 

Condition monitoring on conventional units that are in operation today is usually 

minimal or nonexistent. As previously stated, design conservatism minimized the 

necessity of condition monitoring. 

Extended life can be more cost effective than new generation or wholesale replacement. Detailed inspection and testing serve two purposes tn that end: 

• Establishes an organized data base to supplement existing records 

for use as a basis

 f or continuing unit operation. 

• Establishes a basis to estimate cost and evaluate extended life 

options. 

Figure 1 (see page 5) summarizes the overlapping and mutually exclusive areas of 

maintenance and PLE. Fluor's plant life extension program emphasizes the importance of reviewing and integrating the identified, required PLE inspections and 

activities with the plant maintenance, operations, and reliability/availability 

programs. Some utilities have found that many inspections performed under their 

life extension program were also performed as part of their routine maintenance 

program. This integration minimizes duplicated effort. 

The approach to PLE will certainly be different for a plant that had curtailed 

maintenance

 ror planned unit retirement, from a plant which has operated with 

satisfactory availability and kept up maintenance. For a plant which has been 

operated and maintained as designed (i.e., base load, peaking, load follow), the 

so-called fatal flow approach is appropriate. For this situation, an evaluation 

of the following components may be all that is necessary: 

• Boiler drum, headers and waterwalls 

• Turbine rotor, shell and steamchest 

• Critical piping 

• Structural foundations and supports 
P.6 

MAINTENANCE BOTH PLE 

Corrective/Preventative 

Periodic 

Lubrication 

Cleaning 

Repair 

Replacement 

Annual Operation 

Expense 

Predictive 

Condition Monitoring 

Creep Measurement 

Critical Piping 

Low Cycle Fatigue 

Structural Evaluation 

Capitalized 

Expense 

Figure 1. Overlaps of Maintenance/PLE 

All other modifications could be considered as upgrades or maintenance. 

For a retired unit that is being revived for duty or for a unit that is operated 

with curtailed maintenance, a comprehensive PLE approach would be appropriate. 

There is no doubt that the high level of early attention given to extensive 

detailed inspection-testing programs and to extensive plant rebuilds have caused 

many to label PLE as a glorified maintenance program. Furthermore, it has reached 

the point that some individuals label every valve or pump replacement as plant 

life extension. 
P.7 

Is Plant Life Extension merely a glorified maintenance program? Obviously Fluor's 

answer is "no." Even with a well-operated plant with good maintenance, it is 

prudent to evaluate and monitor the critical, heavy wall components for reasons of 

safety as well as for economics. This evaluation requires activities and capabilities not normally required in plant maintenance programs. On a more typical 

near-end-of-life unit with curtailed maintenance, many maintenance functions 

become a part of the PLE program; for these reasons, an integrated approach makes 

sense. The reader should also keep in mind that in some situations, the expanded 

view of PLE has some additional public relations' benefits. We hope this explanation has helped to clarify the distinctions and overlaps between PLE and maintenance, as well as the need for plant life extension.