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xxxxxx unit #4 January 2003Planned OutageExecutive Summary

1United Dynamics Corporation

1345 Old Preston Hwy. N. Louisville, Ky 40229voice 502.957.7525 fax: 502.957.5441 www.udc.net

Date of inspection:

January 6, 2003 January 10, 2003

Technical specifications:

The boiler system consists of an xxxxx Energy, Positive Pressure, Sub critical,

B & W design unit.

Introduction

The inspection was conducted by United Dynamics Corporation (UDC) boiler

inspection team consisting of Jon S. Cavote, John Linder, Dan Wyngarden, and

Marvin Bronson. This inspection effort would not have been possible without

the efforts of Lloyd Weber. UDC provided the inspection services, non

destructive testing, and overall technical support.

Inspection and planning methodology:

Standard inspection and repair guidelines were utilized by the team. These

guidelines were strictly complied with during this outage. All decisions were

data driven backed up by substantial ultrasonic thickness examinations. In

many cases data was reviewed from previous outages.

The suggested repair criteria used on pressure parts during this outage was:

0-%-65% of design minimum wall was replaced.

66%-75% of design minimum wall was pad welded.

76%-85% of design minimum wall was shielded

All repairs were ranked at the time of inspection into two categories:

Priority #1 Item that will in all probability cause a forced outage

before the next scheduled outage, cause potential hazard to humanlife, or cause a financial loss to the operation of the unit.


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Priority #2 Item which poses a possible failure or performance

issue.

Priority #3 Item that under normal operations would not cause a

forced outage although may decrease operations to a degree but of

no significance. The item is typically planned for future work.

Summary and Analysis of Inspections and Repairs:

The process of inspection and repair interdiction is designed to statistically stack

the deck in the plants favor when it comes to availability. This process is not fool

proof although it has been proven over time to be a cost effective tool.

Conclusions and Recommendations:

Rear Screen Tubes:

The screen tube sections are noted for the front tube being a rear wall

hanger tube 2.5 x .220 MWT SA210A1. All

other screen tubes are composed of 2.0 x .220MWT SA209T1A. All items indicated in the

screen tube report are on the bottom level at the

refractory wall. All other items are indicated in

the crossover report.

Only one tube has been noted for replacement,

three tubes have been recommended for

requiring pad welds, and several have been

noted for requiring shield repairs. All shield work is due to soot blower erosion,

and pad welds are a result of gouged tubing from a mechanical source. Ensurethat all shields are installed on the trailing side of tubes and follow the pattern of

the blower across the unit. Ensure that refractory wall is repacked to design form

after all shield repairs are complete.


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Two attachment support lugs have been noted for

requiring re-welding to the tube. Lugs being

detached will allow for tube misalignment.

KEY POINTS:

Complete all shielding work prior to

refractory wall re-construction.

Grant access to the remainder of elements at the right side of unit to

complete inspection at lower level of tubes, element #81 - #114.

Ensure that tubes are clean prior to shield installation.

Total of (4) Priority #1 items were identified.



This makes (62) total observed deficiencies.

Rear Wall Hangers:

The hangers have been noted for numerous

shield repairs on the trailing edge of tubes. Some

shields need replaced and others require re-

alignment and straps. UT verification was noted

in locations accessible, inspection report lists theseresults. Numerous shields are overheated and

fatigued, proper cooling of shield is imperative


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requiring clean tubes and a tight fit of shields to tube surface.

KEY POINTS:

Ensure that tubes are clean and shields fit tight to tube surface prior to

shield installation.

Total of () Priority #1 items were identified.

Total of (2 records) Priority #2 items were identified.Total of (1 records) Priority #3 items were identified.

Secondary Superheat Inlet/Addendum 1:

Only the lower level of the pendant was inspected due to lack of

scaffolding access granted to upper levels. The spacer tube located on the front

side of the inlet has been previously pad welded at the element intersections dueto soot blower erosion. One 10 section of

spacer tube has been recommended for

replacement.

The tier drop wrapper tubes located at the

bottom of the pendants are being washed

from blowing soot, and several are

recommended for replacement and pad

weld installation due to UT verification.

Numerous lower pendant loops are noted for replacement and pad weld

installations on the leading edge of tubes due to soot blower erosion. The

addendum report indicates one pad weld required on the rear of pendant.


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KEY POINTS:

Check IK1&2 soot blowing frequency and sweep, ensure that blowers

are not spraying in addition to what is required.

Grant access to the upper levels of superheater for complete inspection.




This makes (18) total observed deficiencies.

Reheat Inlet:

The front of the inlet pendants has been noted for numerous shields

requiring replacement due to overheat and fatigue, first and second tube in from

the front. There is no scallop bar located on the lugs in front of pendant, however

misalignment is not a problem.

The problem area of the pendant is located

on the trailing side in the IK 25/26 path. Soot

blower erosion is the most common form of

damage found on boiler pressure part

components and can be easily overlooked if

erosion is smooth across the entire surface of

tube. The trailing reheat tubes have shielding

on several elements however erosion is

pushing off the bottoms of the existing

shields causing wash on the outer radius bends of lower loops, others have noshielding at all. Numerous replacements, pad welds, and shields are

recommended in this area.


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The second tube in from the rear is showing significant signs of erosion however

tubes are composed of .220 MWT. No

repairs have been noted during this

overhaul, however if soot blowing

continues at the same rate, this will

become a high priority area during future

overhauls.

Shield work on the back of this pendant

will include lower radius bends of tubes,

as well as 3 straight sections.

One bulged tube was found on the back side of this component and will need to

be monitored during future overhauls.

KEY POINTS:

Check blower frequency and pressure, do not run blower more than

necessary.

Grant access to elements #91 all the way to the right wall. It is

imperative that the remainder of these elements be inspected and

repairs are made accordingly. PSH work is in progress preventing

further inspection at this time.

Grant access to the upper elevation on the rear of pendant for

inspection during a future overhaul.

All front upper level repairs are indicated in the crossover report.

Ensure that tubes are clean and shields fit tight to tube surface prior to

shield installation.


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Total of (4 Records) Priority #2 items were identified.


Reheat Outlet:

Please note that all repair identified in the upper rear levels will be

indicated in the crossover report.

Two tubes have been noted for replacement onthe back side of the pendant, and two tubes

have been noted for requiring pad welds in the

IK33 path.

Numerous handcuff supports have been noted

for re-welding the end weld due to cracking.

Numerous shields have been recommended

for installation as well, due to overheating of existing shields, Ensure that tubesare clean prior to new shield installation.

Several support lugs have been found to be broken and elements misaligned.

Ensure that pendants are re-aligned and new support lugs are installed. Broken

lugs are found on the lower level as well as the upper level of pendants. The

upper support/alignment lugs will require re-attachment because not only do

they align the pendants, they provide structural support. The top portion of the

pendants will sag forward causing the bottoms of pendants to kick back if upper

support is lost.

Elements 48 68 are showing moderate signs of overheating, no significant sign

of exfoliation or creep is evident. It has been concluded that the tubes are

suffering from long term overheat, not abnormal for a component of this vintage.


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After discussions with plant personnel it has been concluded that tube surface

temperature in the reheat crossover is running around 1,100 degrees F. This is an

average tube surface temperature for this component, and would not expect that

this would cause any short term overheat issues. It has also been noted that this

component is run in excess of 1150+ degrees, this is the leading contributor to

signs of long term overheat. Other factors can come into play to cause short term

overheat in this component:

1. Plugging patterns (will increase gas velocity and temperaturethrough open areas

2. ID blockage (if reheat has had a water filled static test, ensurethat lower loops are cleared prior to unit returning to service.Tube surface temperature will reach excessive temperature before

reheat loops clear enough to allow steam to circulate. This can

cause excessive spaghetti like bowing as well as creep and

exfoliation.)

3. Crushed tubes (flow restriction is the quickest way to overheat atube in a short period of time.)

4.

Sudden increases in steam temperature and surface temperaturedue to excessive slagging in the fire box (The more slagging and

insulators on the water walls will increase the superheat and

reheat temperatures due to less heat transfer in the fire box)

KEY POINTS:

Grant access from elements 72 113 on the rear of pendant to

complete inspection in the lower level.


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To Reduce Superheat and Reheat temperatures

(The removal of refractory that covers studded tubes in the

fire box will decrease Superheat and Reheat temperature due to

more heat transfer in the fire box. Too much heat transfer is also

bad, not allowing superheats and reheats

to reach necessary temperature. UDC

recommends that if this process is to take

action, that only 10% of the refractory is

removed from the top of stud section.

Ensure that exposed studs are removed

from tubes to prevent heat absorption on

tubes.)




Furnace Floor:

The furnace floor has been noted for

impact gouging requiring pad weld repairs.

Refractory and other has been removed for re-

studding and inspection, pad welds are to be

completed before re-studding and refractoryare re-installed.

The rear bends are planned for replacement


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over the next several overhauls. No repair items have been noted

for that location.


Total of ( Records) Priority #2 items were identified.


Econ Gas outlet:

The ductwork was noted for numerous casing cracks that will require seal

welding, and the removal of ash and debris throughout the ducts.




Upper dead air space:

Upper dead air space was noted for casing cracks requiring seal welding.Upper casing at the upper slope has been removed for reheat components

replacements. Ensure that this casing is replaced after slope tubes are replaced.





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Steam Drum:

Steam drum was noted for requiring the removal of debris including

excessive amounts of magnetite and remains of doors gaskets.

The drum shell was found to be in good condition as found. No stress cracking

in shell and corrosion was found at a minimum.

KEY POINTS:

Removal of debris is imperative due to the affects it can have on

the blocking lower inlet header orifices. Over time, debris that isrun down the down comers will accumulate in the lower inlet

headers and block orifices. If possible, UDC recommends that a

lower inlet header inspection be performed by means of Bore

Scope for debris accumulation.





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Secondary Air duct:

No action items have been found.




Air Heater Gas Outlet:

No action items have been found.




Air Heater Gas Inlet:

The right rear corner was noted for an expansion joint replacement.

Expansion joint in the right front corner will need to be patched due to open

holes.

Remove ash from expansion joint flex points , to allow for proper expansion.


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Turning vane support struts are noted for repair as well.




Reheat Crossovers:

The crossover section is the highest priority pressure part area of this

overhaul. Numerous tubes have been noted for replacement, pad welding, andshielding. These repairs include the front

side of the inlet, back side of the outlet, the

crossovers themselves, and the rear screen

tubes that intersect the crossovers.

IK 23/24 is severely eroding reheat outlet

tubes with a rough eroding surface. It

appears that the steam is not completely

superheated, saturated steam will erodesharp jagged edges and can cause tubes to

reach quick failure. Numerous tubes have

been previously pad welded and are now eroded through the pad weld and back

into the tube.

Screen tubes have been noted for shield, and pad weld repairs from blower wash

and detached welds. 7 tube U straps at the upper level have been marked for

replacement due to overheat and failure, install new strap 6 above or below

previous strap to help prevent welding on the same heat effected zone.

Numerous outlet tubes have been noted for existing horizontal weave pad welds,

we need to plan to have these tubes replaced. During this overhaul, the thin

tubes are a much higher priority to replace.


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KEY POINTS:

Prevent Saturated Steam:

1. Ensure that blower lance has

weep holes located in the

bottom of lance, and that lance

is rested in its proper position.

2. Ensure that all steam piping is

insulated properly to

minimize condensation.

3. Ensure that all steam piping isat least at a 30 degree pitch to help drain access moisture.

Check soot blowing frequency (Only blow when necessary)

If any of the replacement recommendations are not completed

during this overhaul, ensure that they are completed during the

next scheduled overhaul.





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Furnace Tube Sample:

One tube in the fire box was pulled for metallurgical analysis per plant

personnel request. Right sidewall tube #70, elevation 658.




PSH Bank 1, 2, 3:

The primaries are noted for elements falling off of their saddle lugs at the

front of the banks.

The right half of the primaries are being replaced during this overhaul, and the

left half of the primaries have been replaced

last year.

Debris has been noted for accumulation at the

front of the bank from deteriorated refractory

wall and slag. This will need to be cleaned out

to prevent eddying channels for fly ash to

erode, as well as allowing gas velocity to pass

through component at an even pattern with no

restrictions.

A few scallop bar support have been noted for repair. Bank 3 was noted forrepairing two support guides on the rear wall, and for the removal of loose

debris.


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UT verification surveys have been performed at the base of the riser tube sections

to help project tube wastage rates during future overhaul. UT survey has also

been performed on the dogleg sections between banks.

KEY POINTS:

Review weld X-rays for a percentage (of plants request) of butt

welds made on new PSH bank tubes (If greater than 10% of x-

rays reviewed fail, UDC recommends that a minimum of 50% of

all welds be X-rayed and approved by contractor QC and an

Alliant CWI.

Air Heater Gas Outlet:

No action item have been found.





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SSH Outlet:

This component was noted for three pad welds on the front of the pendant

on the spacer tube due to soot blower erosion.

A 100% visual was not possible due to the excessive amount of slag build up on

the tube surface.

KEY POINTS:

Grant access to the upper levels of pendants for inspection.




Furnace Grinds:

The furnace was laid out with 6 bans for grinding to record accurate 3-

point UT verification. Discussions with plant personnel indicate that the unit

may run with low oxygen if not negative in the fire box. No exact numbers or

facts have been concluded as to stokemetric measures at and or below burner

elevation.

For a 100% water wall inspection, it is recommended to pressure wash or sand

blast the water walls.





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Penthouse:

The penthouse was noted for numerous floor casing cracks, as well as

holes in the side casings. Due to excessive cracking in the floor casing, there is

approximately 8of ash build up on the floor. Ash build is a result of gases

passing through the cracks and entering into the penthouse. Gases from the

boiler below will elevate the penthouse temperatures which are not designed to

exceed limits of structural steel integrity.

SSH headers are noted for missing insulation; this will also elevate temperature

and potentially affect carbon steel supports in the general vicinity of headers.

KEY POINTS:

Excessive temperatures in the penthouse can contribute to

structural degradation of support rods and other carbon steel

structures.

If interlocking tiles are used for isomembrane installation

(Ensure that roof tube below are properly supported by means of

support clips that should be connected to the collector barsrunning left to right at the front and rear of high crown seal

boxes. Improperly supported roof tubes can sag at a greater rate

due to additional tile weight.)

If roof tubes are not supported properly (Install 8 fire

blanketing in place of the interlocking tiles to reduce weight. Fire

blanketing is effective however, is more of a short term fix than a

permanent fix. Plan on additional repairs in less than 10 years if

fire blanketing is used.)





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Economizer:

The economizer banks were in good condition as found.

Retractable blower lances have been noted for minor abrasion, no action is

required.




Items not inspected:

DA Tank

De-Superheat sprays

Reheat De-superheat sprays

Reheat Pendant (Upper level rear of inlet)

Superheat Pendant (Upper levels)

Fire Box (UT survey only)

Cyclone Burners

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