p.1 

OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

221)11-1-1 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:51:02 AM Sheet 221 of 276 
P.2 

, U , D »W 

\'~r 

I!'—, 

UJlO, 

II-I-l 

A COMPARATIVE STUDY OF 

PLANT AND EQUIPMENT LIFE EXTENSION STRATEGIES 

BY S. A. PATULSKI 

WISCONSIN ELECTRIC POWER COMPANY 

MILWAUKEE, WISCONSIN 

JUNE, 1986 

i),tiil 

ErAASRDOCXEF 

Presented at EPRI/EII - Conference on Life Extension and 

Assessment of Fossil Plants June 2-4, 1986, Washington, D.C. 1986 
P.3 

INTRODUCTION 

Some may argue that the utility community, owner/operators, original 

equipment manufacturers, consultants and specialty contractors, have 

been engaged in life extension practices for a long period of time. 

Early 1983 marks the period during which these efforts become formally 

recognized as "life extension". Organizational structures have been 

adopted, and technologies enhanced to more directly address the 

issues surrounding life extensions. 

The fourteen technical papers that embody the consultant's approach 

to life extension draw on experience gained since 1983. 

I have not attempted to analyze the technical merit or critique the 

various approaches or techniques discussed in these papers. Comments 

are offered on the constants reflected in the papers, the similarities 

in approach, components investigated, and the failure mechanisms of 

greatest concern. The nondestructive techniques used in approaching 

the life extension goal, and some obvious anomalies are also touched 

on. 

Included is a summary of the more important items to be considered by 

the owner/operator of a generating unit when managing a life extension 

effort. 

I. CONSTANTS 

A number of constants appear in the approaches to life 

extension being considered. Some of these constants are: 

1. Modern generating units - those built with final 

steam temperatures of 900 F and above and operating 

over 1600 psig have design lives in the range of 

30-40 years. 
P.4 

Little information is available in design documents 

regarding any originally intended life spans. 

Failure mechanisms encountered in bench mark surveys 

indicate that the engineering standards used in the 

1950's and early 1960's will provide unit life spans 

in this range. Operation signficantly in excess of 

these time spans requires additional technical, and 

economic effort. 

2. Overall objectives driving life extension: While 

they vary from utility to utility, all include at 

least some of the following items: 

deferral of capacity additions 

reduced financial risk when compared to 

other alternatives 

regulatory prudency actions 

uncertain load growth (ability to respond 

rapidly to forecast changes) 

capacity recapture and/or repowing 

cost effectiveness (this is not the same as 

reduced risk) 

improved thermal efficiencies/thermal 

efficiency recapture 

increased availabilities 

decreased operations and maintenance costs 

programs can tailor cash flows to available 

corporate resources 

cycling capability 

changes in fuel soruce or type 

obsolescence • 

3. To formulate, guide, analyze and implement a 

successful life extension program the utility 

needs to commit a diversified group of in-house 

expertise. The following disciplines should be 

included: 
P.5 

Corporate planners 

Engineering personnel (Central Office) 

Operating personnel (Plant inputs) 

Financial managers 

Environmental analyst 

Legal staff 

4. Life extension is a flexible program. It can 

accommodate: 

A small utility with one or two candidate units 

or a large utility with dozens of units. 

It can be timed to occur over a short period, 

with analysis and the start of implementation 

occurring over three years or less; or it can 

be extended over a decade or more. 

The number of units considered and the timing employed are 

often driven by the utility's objectives as discussed in item 2 

5. Life extension is not a glorified maintenance program. 

Some activities can accompany and complement 

maintenance. Others are unique. Life extension is 

defined in many different ways. One of the more 

concise statements of the difference between life 

extension and maintenance that I have run across is 

forwarded by Westinghouse: 

"Good maintenance programs are essential 

to ensure reliable life extension; however, 

they cannot ensure that critical components 

will not fail due to age related phenomenon." 

"Life extension is proactive." 

In the proactive mode, life extension not only identifies 

problem areas but also identifies plant upgrades, timetables, 

and the operating and maintenance techniques required to 

extend plant and equipment life. 
-1§L 

••"*?*•-

•0-

If1 

II PROGRAM STEPS 

Beyond the agreement that surrounds the constants, there 

exists reasonable agreement as to what steps or divisions of 

effort are included in the life extension program. 

fr 

The first step involves a general review of the "supply side" 

options open to the utility. During this step the utility 

must come to grips with its system load growth, its sources 

of supply and what units are reasonable candidates for life 

extension. Many of the benefits are weighed during this 

stage. 

*& -

%'-

***'• 

The second step is to determine the approximate economics of 

life extension; the value of life extended generation, verses 

a probable range of costs. During this step the short and 

long-term economics of life extension for the utility are 

reviewed. The results of this review can lead to a number of 

major variations in the following life extension steps. 

A major decision normally occurs at this point: the schedule 

is defined. One option is the total unit assessment/implementation approach, the second is proceeding in the "phased" 

approach with selected items of equipment examined, assessed 

and projects implemented over a number of successive years. 

-.- • 

For utilities choosing to pursue life extension across a 

large number of units, a sub-step may now be necessary; that 

of selected an order (ranking) for units to be addressed in 

the life extension program. A variety of selection methods 

and criteria are available to accomplish this task. 

X: 

£ 

A. 

1 

:i: 

! 

I 

f' 

Step three is the evaluation of specific components that 

comprise an individual generating unit. Regardless of the 

options selected (for single or multiple units, the total 

unit assessment verses the phased approach) developing a plan 

to determine the unit's physical condition now occurs. 
P.7 

This step is composed of several sub-steps including: 

Design, operating records, and data review 

Site interviews with appropriate personnel 

Visual inspections, walk downs, and confirmation of 

design drawing accuracy with "as is" condition on 

critical systems. 

Nondestructive evaluation - This can be either testing 

or calculations or both. 

Sampling and destructive testing 

Performance testing 

It is generally agreed that data review, personnel interviews 

and some visual inspections should occur when planning for 

the initial unit assessment outage. These activities provide 

a data base upon which an inspection plan can be made. During 

a unit outae this type of plan is needed to assure a smooth 

interface with the normal maintenance work that is to be 

performed during the same outage timespan. 

At the same time, meaningful data must be gathered to arrive 

at accurate conclusions. Excess data is costly in labor and 

outage time. Incomplete information may lead to erroneous 

conclusions. 

In conducting these inspections several options are open to 

the utility. Inspections can be performed by an architect 

engineer, the original equipment manufacturer or the specialty 

contractor. The considerations taken into account for the 

selection of a proper contractor to perform the actual field 

inspection are varied to perform the actual field inspection 

are varied enough for a spearate paper in and of themselves so 

they are not discussed here. Also not mentioned in any great 

details in any of the papers reviewed is the possiblity of 

utility personnel performing this work. 

When choosing methods for the detailed inspection the utility 

must remember that the data gathered will be used to supplement 

and augment known facts in supporting continued unit operation. 
P.8 

Secondly, the data must be assembled to provide information 

needed to identify alternate means of achieving additional 

unit life and other utility specific goals. Lastly, the 

total data base should permit evaluation of the costs of a 

life extension. 

This leads directly to step four in the process, the identification of improvement requirements. This step includes the 

identification of the physical requirements and equipment 

shortcomings identified in the 3 step inspections and embraces 

all economic alternatives for a unit that are not inconsistent 

in goals or are of themselves conflicting. 

Step 5 is the indepth economic analysis of the various projects 

identified as life extension alternatives. 

For large systems (many units) or severely debilitated units 

this can be an arduous task. Objectives developed by the 

utility in steps 1 and 2 must be carefully set to aid in the 

economic evaluation. This step includes: 

Quantifying the benefits from each individual recommendation. 

Determining the revenue requirements these refined estimates place on the corporation. 

Ascertaining how these revenue requirements might impact 

the corporation and the ratepayers. 

Step 6 is the implementation plan. Financial data combined 

with physical information gained via inspection and a timetable, 

result in a plan developed to meet the needs of the specific 

utility. This step should include a continuing review of 

operating data. This review permits reassessment of the 

physical condition of the unit, the utility's needs, and the 

program costs thus arriving at additional items/recommendations 

for action in future years. 

Via this step, limits on unit life become more dependent on 

non-physical factors such as economics, .future regulations 
P.9 

and the like, then on factors resulting from unit generation 

or equipment obsolescence. 

III. FAILURE MECHANISMS 

The physical investigations that accompany the unit condition 

assessment are a critical part of the life extension program. 

These investigations are used in determining the condition of 

the existing components of a generating unit. Further they 

contribute to the engineering information base for extension 

modifications. 

The failure mechanisms of concern during a life extension 

effort are varied. 

1. Creep of high energy piping and major boiler pressure 

parts are areas of prime interest and investigation. 

In addition to pressure parts, creep can have a 

significant effect on turbine rotors and casings that 

are exposed to operating temperatures in the range of 

concern for materials of their manufacture. 

2. Erosion is a second failure mechanism associated with 

life limiting conditions. It is of concern in such 

areas as high energy piping elbows, heat exchanger 

tubing, (both condensers and feedewate heaters) turbine 

blades, and boiler heat transfer surfaces. 

3. Corrosion: The chemical dissolution of power plant 

components can be a long term failure mechanism for 

many areas of the plant. Condensate cycle equipment 

such as deareators, condensers, and feedwater heaters 

are affected as well as boiler steam generating 

surfaces. 

Other failure mechanisms of concern are high cycle and low 

cycle fatigue. These failure modes are particularly sensitive 

to past and future operating practices. Stress corrosion, 
P.10 

temper embrittlement and insulation breakdown round out the 

failure modes most often considered in life extension studies. 

To ascertain the level to which equipment has been damaged 

by these failure mechanisms the contribution of mechanism 

suggest the need for a variety of destructive and nondestructive techniques. 

IV. • NONDESTRUCTIVE TECHNIQUES 

Nondestructive and in some cases, destructive techniques for 

equipment condition assessment include the following overall 

areas: 

Records review 

Industry data review 

Visual inspection 

Performance testing 

Mathematical modeling 

Nondestructive examination 

Destructive testing 

Nowhere else in the literature comprising this group of 14 

papers such diversity of opinion abound. This diversity 

includes the areas of nondestructive/destructive testing, 

mathematical modeling (finite elements and crack propagation 

analysis) and to some lesser extend performance testing. 

The disagreement includes, what method of analysis to use, 

when these methods should be applied, who is best to apply 

each method, and lastly, who and what type of interpretation 

should be employed. 
P.11 

V. ANOMALIES 

In all well ordered groups there appears the exception to that 

order. Not necessarily wrong, but different, I prefer to 

refer to these cases as the anomalies. 

1. Life assessment efforts can be quite different for 

minor power generating facilities, less than 25 MW, 

(typical of small municipal or industrial plants). 

These facilities usually have signficant systems of 

support, that is larger utilities from which energy can 

be purchased at an economically competitive level. 

For this type of situation, records review, industry 

data review and visual inspections have been employed 

to determine the plant status, expected remaining life 

and projected costs/benefits for life extension. This 

approach provides useful information to the plant's 

owner/operator without more lengthy and costly physical 

investigation and planning phase. 

2. Equipment Population Prediction - This approach permits 

an assessment of unit condition based on past performance 

of other similar units. Economics are based on improved 

maintenance performance and thermal performance of the 

equipment involved. 

3. Fatalistic Approach - Ties into the equipment population 

approach to some extent and says that after a predetermined 

time period an orderly replacement program is needed. All 

that remains to be determined is how to do the replacement 

work on an economical basis. 

4. Other Plant Upgrades - The belief that any long term confidence in the life extension technology is flawed and postulates that this belief is born out by short term failures in 

younger plants. This belief is coupled with concentrating 

on design upgrades in the areas of controls, turbine water 

induction prevention and water and steam chemistry control. 
P.12 

VI. SUMMARY 

A majority of approaches to the life extension question follow 

a common approach. Variations that exist are on the whole, 

not substantial, and are the result more of the needs of an 

individual utility. 

While unanimous voice cannot be given to the life extension 

technology, most contributors believe that factors other than 

physical limits will determine the future end of lives for 

generating units as long as a continuing and proactive life 

extension effort remains in place. 

The continuing effort in life extension by the utility 

community has lead to a rapidly evolving technology and 

continuing competition amongst the AE's/OEM's/and specialty 

contractors. This situation is good for the power generation 

industry. 

Finally, the utilities themselves must continue to respond 

to the challenges that unit life extension presents. Realistic 

goals for the program must be established in concert with the 

regulatory pressure and financial demands on the corporation. 

Project management must be and remain innovative, challenging 

to its staff and contractors, and entrepreneurial in its 

approach to solving technical problems, meeting regulatory 

limits and achieving financial goals. 

Lastly, as the life extension effort comes of age as a 

technology, all parties concerned, utility, AE, OEM and 

specialty contractors, should be cognizant of the fact that 

continuing equipment management is needed to optimize any 

life extension effort. Life extension does not end with 

project implementation, it really begins there anew.