manual inspection of concrete and brick chimneys

CICIND

Manual for Inspection and Maintenance

ofBrickwork and Concrete Chimneys

February 1993

COMITÉ INTERNATIONAL DES CHIMINÉES INDUSTRIELLESINTERNATIONAL COMMITTEE ON INDUSTRIAL CHIMNEYS

INTERNATIONALER AUSSCHUSS FÜR INDUSTRIESCHORNSTEINE

CICIND Manual for Inspection and Maintenance of Brickwork and Concrete Chimneys page 49

ANNEX 1

CHIMNEY RECORD BOOK

For free standing chimneys in industry - shell: concrete, brickwork- lining: steel, brickwork

Identification of the chimney:

DIRECTIONS FOR USE OF THE CHIMNEY RECORD BOOK1. It is advisable to have a separate chimney record book for each free standing chimney.

2. All descriptions concerning the conditions of the plant, civil engineering drawings, calculations, etc., must beincluded in the book.

3. A chimney must be inspected regularly, depending on the requirements of the plant. The results of the inspec-tions are to be entered in the relevant forms and included in the chimney book. Depending on the load of eachindividual chimney, the period between inspections can be extended or shortened.

4. Inspection must be carried out by a specialist.

5. It is important for the correct maintenance of chimneys that chimney record books are kept carefully.

6. The chimney record book consists of the following sections:

a. Chimney characteristicsThis section includes all design data together with all the materials used. This also includes all drawings, cal-culations and specifications. These must be added to the book in the form of an annex.

b. Important static data for the chimneyThis section includes a summary of the maximum stresses which occur in the main components of the chim-ney. The consequences of some types of damage for strength and stability are to be listed in general terms.

c. Changes to the chimneyThis section provides information on all the changes to process management, materials, constructions, etc.

d. Inspection reportThis section gives the report on one inspection. A completely new inspection report is drawn up for each newinspection. The report consists of:

*checklist,listing the parts of the chimney. If damage is ascertained when the inspection is made, then refer-ence is made to an "explanation",

* explanation list, in which all types of damage are described in as much detail as possible. The size of this listwill vary depending on the condition of the chimney

* conclusions listing and summarising the inspection information.

e. Maintenance adviceIn this section, recommendations are made on the measures to be taken and is the result of the inspectionreport. Each inspection report must lead to a maintenance advice.

f. Repair reportThis part contains the report on the repair work carried out. This part is always important, but particularly ifmeasures other than those recommended in the maintenance advice have been taken.

CICIND Manual for Inspection and Maintenance of Brickwork and Concrete Chimneys

CHARACTERISTICS OF THE CHIMNEY SHELL

Height above land level: m

Diameter at top: m

Height supply opening m

LINING

Height total mDiameter at top mLining in section yes/noLoose lining yes/noHeat insulation yes/no

Year of construction:

Year of start operation:

Kind of fuel and quantity per hour:

Flue gas (composition):

Flue gas quantity: N/m3/sec

Temperature at chimney bottom: °C

Temperature at chimney top: °C

Gas velocity in chimney: m/sec

Continuous operation: yes/no . Intermittent operation:

time/periods/year

Changes of chimney loads, (like flue gas, quantity, composition, temperature):

Start operation in new situation from: (date)

Description of changes:

Number(s) of drawing(s):

Number(s) of calculation(s):

Number(s) of specification(s):

DIMENSIONS MATERIAL MANUFACT./TYPE REMARKS

Foundation

Socle

Shell

Lining

Supporting structure of lining

Coverplate

Fluegas inlet

Funnel

Insulation

Top platform

Mortar - lining

Joints - lining

- shell

- shell

- ash- condensate


CHARACTERISTICS OF THE CHIMNEY (continued)

Platforms at level

.............................................m

Electric provisions

- lightning protection

- aircraft warning lights

- earthening

- inside illumination

Measuring arrangements

- temperature

- fluegas

Several

- connection hooks

- climb safety provisions

- straps

- ventilation provisions

- doors/manholes

- duct entries

- drains

- sprayers

- compensators

DIMENSIONS MATERIAL MANUFACT/TYPE REMARKS

Ladders

Coating/plastering

- outside- inside

- outside- inside

-

-

.............................................m

.............................................m

.............................................m

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-

-

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IMPORTANT STATIC DATA OF THE CHIMNEY

Part

Site

Foundation

Socle

Shell

Lining

Supporting structure for lining

MaterialMaximum stress (N/mm2)

concreteact. allow

brickact. allow

steelact. allow

Location

Parts

Shell

Lining

Measured resonance frequency

Year Frequency

IMPORTANT DYNAMIC DATA OF THE CHIMNEY

Remarks:.................................................................................................................................................................

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CHANGES OF THE CHIMNEY

Year of changes:

Reasons for changes:

Description of changes(dimension, material etc.):

Descriptions of changes (others):


INSPECTION REPORT

Number:

Name of inspector:

Company of inspector:

Date:

No Explanationremarks number

CHECKLIST

1. SHELL

1.1 Uniform deterioration

1.2 Local deterioration

1.3 Wear

1.4 Cracks

1.5 Joints

1.6 Coating

1.7 Sweating/colour changes

1.8 Sundries

2. TOP

2.1 Coverage

2.2 Shell

2.3 Lining

2.4 Insulation

2.5 Coating

2.6 Lightning protection

2.7 Top platform

2.8 Cageladder

2.9 Fastening structures

2.10 Sundries


CHECKLIST (continued)

3. INSIDE OF LINING (flue gas side)

3.1 Brickwork

3.1.1 Uniform deterioration

3.1.2 Local deterioration

3.1.3 Cracks

3.1.4 Joints

3.1.5 Expansion joints (including posterior parts)

3.1.6 Cakes of ash

3.1.7 Sweating/colour changes

3.1.8 Sundries

3.2 STEEL



3.2.3 Uniform rust deposit

3.2.4 Local rust deposit

3.2.5 Cracks

3.2.6 Welded seams

3.2.7 Expansion joints

3.2.8 Wall thickness

3.2.9 Coating

3.2.10 Fastening structures

3.2.11 Cakes of ash

3.2.12 Condensate

Noremarks

Explanationnumber



3.2.13 Sundries

4. ACCESSIBLE AIR SPACE

4.1. Inside shell



4.1.3 Cracks

4.1.4 Joints

4.1.5 Condensate

4.1.6 Drains

4.1.7 Movable parts (doors, man-holes, etc)

4.1.8 Ventilation provisions

4.1.9 Sundries

4.2 Outside brickwork lining



4.2.3 Cracks

4.2.4 Joints

4.2.5 Expansion joints (including posterior parts)

4.2.6 Supporting structure

4.2.7 Sweating/colour changes

4.2.8 Condensate

4.2.9 Insulation

4.2.10 Sundries

Noremarks

Explanationnumber



4.3 Outside steel lining

4.3.1 Uniform rust deposit

4.3.2 Local rust deposit

4.3.3 Cracks

4.3.4 Welded seams

4.3.5 Expansion joints

4.3.6 Wall thickness

4.3.7 Coating

4.3.8 Fastening structures

4.3.9 Condensate

4.3.10 Insulation

4.3.11 Sundries

5. PLATFORMS

5.1 Deterioration (uniform, local)

5.1.1 - Upper side (steel) structure

5.1.2 - Lower side (steel) structure

5.1.3 -Grating

5.1.4 -Handrail

5.1.5 - Stays and supports

5.2 Rust deposit (uniform, local)

5.2.1 - Upper side (steel) structure

5.2.2 - Lower side (steel) structural

5.2.3 - Grating

5.2.4 - Handrail

No Explanationremarks number



5.2.5 - Stays and supports

5.3 Cracks

5.4 Welded seams

5.5 Coating

5.6 Fastening structures

5.7 Slope of floors and drains

5.8 Sundries

6 FLUE GAS INLET

6.1 Expansion provisions at inlet

6.2 Supporting structure flue gas ducts

6.3 Compensator

6.4 Condensate and ash funnel

6.5 Condensate collecting spout

6.6 Drains

6.7 Sundries

7. EQUIPMENT

7.1 Cage ladders

7.2 Climb safety provisions

7.3 Connections hooks/fastener

7.4 Tapes and closures

7.5 Coating

7.6 Lightning protection leads

7.7 Aircraft warning lights

7.8 Inside illumination

7.9 Measuring arrangements

7.10 Sundries

Noremarks

Explanationnumber


- The general impression of the condition of a component

- The interpretation of conclusions from investigations and laboratory tests

- Determining the nature and extent of the damage (see figure Annex 1 -1 )

- Determining the rate of ageing of the damage parts

- The probable cause of damage- The probable cause of damage- The anticipated development of damage and the residual life

required of the part which is damaged- The residual life required- Possible repairs and anticipated life- Short-term and long-term costs- Planning- Recommendation with reasons

INSPECTION REPORT

Number:

Name of inspector:

company of inspector:

Explanation number:

Item:

Remarks:

Item:

Remarks:

INSPECTION REPORT

Number:

Name of inspector:

Company of inspector:

Conclusions

Explanation:This must include all the information obtained from the investigations and laboratory tests so that it is possible toissue a maintenance advice on the basis of this information. This must at least include the following

Date

MAINTENANCE ADVICE

Number of inspection report:

Name of consultant:.

Company of consultant:

Advice

Explanation:The maintenance advice is the result of the inspection report in which recommendations are made with regard tothe measures to be taken. This must contain at least the following:

Date:


Utilities Chimney : concrete shell

Plan of damages

Figure annex 1-1

crack through the concretecrack at the inner sidecrack at the outer sideposition ot corecorroded steel


REPAIR REPORT

Number of inspection report: Date:

Name of inspector/supervisor:

company of inspector/supervisor:

Report

Explanation:The repair report is a report on the repair work carried out. This must at least include the following:

- Repair methods- Extend of repair work

- Quality of the result

- Conditions during the work

- Costs of the repair work


ANNEX 2

Demolition of chimneys

Contents:

1. Introduction

2. Restriction

3. Technical aspects

4. Decision to use method A or B

5. Method A

6. Method B

7. The demolition of huge chimneys

8. The demolition of chimneys in a poor condition.


1. IntroductionIt is inevitable that chimneys have to be demolished.The main reason is that their service life endsbecause of the cessation of the operational unit(s) towhich they are connected. It is rarely that chimneyshave to be demolished for construction or safety rea-sons.

The existing condition of the chimney is relative to itsmode of demolition.

A brickwork chimney could have an impressiveappearance and an architectural beauty. Happilyenough there are still several chimneys preservedand well maintained for that beauty, but as far asknown it never happened to a concrete chimney.

Sometimes a chimney makes news, that is especiallythe case when something goes wrong, especially if itfalls in the wrong direction. Shortcomings in prepara-tion and/or investigations, by the demolition teamcould be the cause.

We have to deal with two main methods of demolition:

A: to demolish a chimney piece small,B: to demolish a chimney by making it fall over in an

indicated direction.

2. RestrictionsThis article deals with reinforced concrete and brick-work chimneys only and is meant as a guide and notas a complete manual. In general, brickwork chim-neys have a height of 30 to 100 metres and rein-forced concrete chimneys of 60 to 210 metres.

Because of its height, safety plays an important rolein the demolition of a chimney. Safety aspects andmeasures to be taken must be fully considered andnot be sacrificed due to expense, which in somecases are considerable.

Some technical safety details are given in the nextchapters, each belonging to the subject discussedand adding in some cases to the restrictions.

Chimneys higher than 130 metres are a real chal-lenge to demolish. The manner of execution is partic-ularly restrictive to the top part (higher than 130 m)and its costs could equal the erection cost. To datelittle experience has been obtained.

When working on any height of chimney, weatherconditions and emissions of nearby chimneys mustbe evaluated.

3. Technical aspects3.1 GeneralIt is necessary to deal with some technical aspects ofthe chimney which are important demolishing is con-sidered.

3.2 Demolishing the internal construction.3.2.1 A internal construction consisting of the liningeither without or with a small (narrow) cavity can inmethod A be demolished at the same height as theshell or with a platform hanged from the top of theshell and going down with lining level demolition.

Attention must be paid to the result and dust (whichcan be polluted) and protective measures must betaken on behalf of the operatives. In method B itgoes down with the shell.

3.2.2 An internal construction consisting of a broadcavity, in most cases accessible, and regularly pro-vided with reinforced concrete platforms supportingthe lining and the steel structures with ladders.

In carrying out method A it is rather difficult to reachthe internal construction from the working platformoutside, with pneumatic tools.

In some cases the insulating materials are so weakthat they can just be pushed down with stakes.

Otherwise, the best method is to install a scaffoldingconsisting of small elements because of the narrow-ness of the cavity and manholes in the supportingconcrete platforms, starting at the top.

The lining materials to be demolished, using suitableequipment, can be pushed inwardly. When work pro-gresses the scaffolding is dismantled and be usedagain on a lower level. We assume that the lowestpart of the chimney has no lining; generally, the liningstarts at a higher level, somewhat below the level ofthe (first) flue gas inlet.

In this way the falling debris cannot damage thelower lining causing it to collapse in an uncon-trolled, manner If a lining is present in the lowest part,it is advisable to pull this lining down first, so creatingspace for the work to be carried out and storage forthe debris.

The foundation floor is to be cleared away regularly.The falling debris can form a compact heap of rub-ble, difficult to remove and thus it could block theexit. For several reasons, it is not recommended todemolish with explosives the inner construction.

For B is advisable to dismantle the steel steps withits supporting constructions first, because it can addan unbalancing factor.

3.2.3 The internal construction with a broad accessi-ble cavity is provided with ladders, platforms and insome cases a lift, together with the lining construc-tion, with an insulation at the cavity side.Followingeither method A or B the whole inner constructionand lining must be dismantled first.

The ladders and platforms could be of value anduseful in case method A is followed, provided that


this construction can be protected from damage byfalling debris.

3.3 The external shapeThe external shape of a chimney is to be consideredwhen deciding upon the manner of its demolition (figannex 2-1).

Some details are outlined in the following chapters.

4. Use of method A or B4.1 It is necessary to decide which of the two meth-ods is either possible or desired. This decision issimple for felling a chimney. If method B is chosen itis essential to consider the following aspects:

an adequate and totally empty area must be avail-able including a margin (as advised by an expert ofthe blasting company) for angle and landing.

the chimney must have a sound condition and notbe badly cracked.In case the chimney has no stability, it may not fallin the correct direction.an opening at the bottom can play a decisive role(see fig annex 2-4).

environmental objections and unknown (not calcu-lable) vibrations of the subsoil affecting nearbybuildings.after felling the debris must be cut into removablepieces and be carted away by heavy equipmentwith suitable access.

generally, it is difficult to keep spectators away, sothe whole area must be made secure.

4.2 ConclusionIf any of these conditions are not available, possiblenor desired, it is necessary to abandon method B.

5. Method A (see conditions 4.1)

Demolishing a chimney piecemeal from top to bottomis possible for all types (I,II,III and IV, fig annex 2-1).

5.1 The use of method A makes it necessary to usea working platform. This can be achieved in two dif-ferent ways:5.1.1 - using a complete scaffold around the shell,suitable for all the types (I,II,III and IV, fig annex 2-1).

5.1.2 - using a flying scaffolding for the taperingtypes i.e. only for I and IV/I

ad 5.1.1 Demolishing a shell when using a completescaffold around the shell is a good solution, it pro-tects the workers, the environment and supervision,however it is expensive.

Platforms can be arranged wherever needed usingwooden or metal (aluminium) planks. The originalladder and platforms on the outside can also be

used, provided they are approved for that purposeand that they run from bottom to top.The demolishingwork can start as soon as all equipment, tools andsafety precautions is installed and approved.Theironcap on the chimney-top must be dismantled firstand hoisted down.Then the demolishing can startusing pneumatic tools or other methods such as aconcrete saw and the debris simply be thrown downthe bore.The reinforcement bars must be cut regular-ly and be thrown down internally or hoisted down insecure bundles.

The scaffolding and the original parts of the laddermust be taken down as work proceeds. The planksof the working platform must be lowered likewise fora floor on a lower level.

ad 5.1.2 Demolishing a shell using a hand operatedflying scaffolding is only possible for tapering chim-neys. It is necessary that the original ladder with plat-forms on the outside of the chimney is in good condi-tion. For installing the equipment at the top, a hoist-ing gear is necessary. First a firm flat working plat-form at the top of the chimney must be installed.Next 3 cables can be assembled around the top,each provided with a hand operated pull lift installednear the ladder. Then the separate yokes are hoistedup to be suspended onto the 3 cables. The numberof yokes must be sufficient to be able to work later onat lower height as diameter of the chimney increas-es, taking into account the distance between eachyoke and the carrying capacity of the planks. Thecables are now drawn tight and the platforms can becompleted. The tension of the cables is converted byhard wood rolling clamps into a horizontal force onthe shell which ensures that the cables do not sag.By stretching the cables, one at a time, by one pullonly on the pull lift, it allows the scaffolding todescend at a steady rate. This amount descentdepends on the angle of the taper. The top platformand iron cap can now be lowered down. Apart fromthe movement of the platform the demolition work isabout the same as described in 5.1.1

5.2 Notes on safety.It is necessary to fix the planks on the working plat-forms, to prevent them from blowing away whenbad weather conditions occur.

Using the flying scaffolding, the fixed planks haveto be loosened when descending. After reachingthe new level the planks must be refixed at the endof each working day.When mounting the flat working platform on top,the workers must use safety belts firmly attachedat the top of the ladder. When assembling thecables around the top and when placing yokes, thesafety belts must be attached at a fixed point in themiddle of the flat working platform.


Tarpaulins are useful when used upon workingplatforms and also mounted on the railings to pre-vent the debris from falling and spreading around,also they create better conditions for the workers.A disadvantage is that tarpaulins catch a lot ofwind thus forming a danger. Spread on workingplatform floors they not only cause a lot of work butalso hide the location of the planks.

When throwing down debris from any height it isnecessary to close the door opening at the bottomsecurely. If all openings are not closed, pieces ofstone, concrete and iron can escape through theopening and could harm (even kill) passers by.It is also very necessary that a suitable areaaround the chimney is covered with wooden safetyshields. Moreover, this area must be made out ofbounds for all except the workers involved.

The workers must be experienced craftsman used towork at any height, willing to follow the safety instruc-tions and regulations it is essential that they use thesafety equipment which is available for them. It isnormal to permit them to carry out a safety audit.

6. Method B (refer to the conditions of chapter 4.1)To demolish a chimney by making it fall in an indicateddirection.

6.1 Introduction.For the execution of this method B, it necessary, todiscuss technical details, (see chapter 6.2) mainly tobe sure the chimney will fall in the correct directionand also because chimneys always break into sec-tions while falling. It is generally not known, that theintroducing of a concrete chair for the chimney to siton at one side, is the safest way in making a chim-ney fall in the correct direction. The best knownmethods to make a chimney to fall are:(6.3.2)- to blow it up after inserting explosives of dif-ferent forces and explosive time at either side of thebase,(6.3.1)- to blow it up at one side only after demolish-ing a calculated part of the concrete at the other sideand providing the chimney with a concrete chair to siton at the other side,(6.3.1)- to make it fall after demolishing a calculatedpart of the concrete at the bottom of one side, to pro-vide the chimney with a concrete chair to sit on atthat side and finally demolish the concrete at theother side. The calculated part must be accompaniedby a stability calculation.

6.2 There are some technical details to be investigatedfirst in order to maintain the surveyability.

6.2.1 The concrete chair (see fig annex 2 - 2 and 3).

Point 1 (see fig annex 2 - 21) is the chosen point onthe chimney circumference just opposite to the fellingdirection. To make a concrete chair, the demolition

must start in the axle at point 1, marked and num-bered clearly with paint on the chimney wall. Thepoints 2,3 and 4 are also to be painted and num-bered clearly. At either side of point 1 the demolitionstarts proceeding only up to the points 2. The verticalreinforcement is to be cut. The first part of the chairis to be poured using rapid hardening cement. Afterthe concrete has hardened (say after 2 days) bothparts between points 2 and 3 must be demolishedsimultaneously up to the point 3. The chair concreteis to be completed, after cutting the vertical reinforce-ment, (see fig. annex 2-2.2)

The parts on both sides between the points 3 and 4must be left untouched. The height of the chairdepends on the height of a gate when situated in thispart. The best idea is to give the total chair the heightof that gate in order to maintain a good and neces-sary balance. The concrete must be poured at least100 mm higher than the upper side of the cut-awayconcrete, also allow the concrete to rise sufficiently atthe inward side. In this case the gate is incorporated,so the inner side of the chimney is not accessible.

6.2.2 The situation of a gate in the circumference atthe bottom part of a chimney.

When studying figures annex 2-2.1 and annex 2-2.2again, it is impossible to have a gate between thepoints 3 and 4 (see fig annex 2-2.1). This could benamed "neutral zone" or the "required balancing part"Fig annex 2-4 explains the effect of this situation,causing two NO options.

The place of the bottom gate, as sketched preventsthe possibilities of falling in the directions "NO" with-out any precaution.

The directions noted "NO" can however be overruledby creating another opening symmetrically on thedesired axis of fall. In every case the bottom of theshell must be symmetrical (figure annex 2-4-A)

6.3 Causing the chimneys to fall over.6.3.1 Having seen the details of 6.2 it is easier to dis-cuss the last details. After making the concrete chairfor the chimney to sit on, two possibilities remain:

a To blow up the chimney, by inserting explosives atthe opposite side. These explosives have to be cal-culated for weight, force and timing by the expert ofthe blasting company, and inserted in holes in theconcrete of sufficient diameter and depth, evenlydistributed between the points 4. (fig annex 2-2.1,2.2,3) After detonating the explosives the chim-ney will fall in the correct direction.

b To make it fall over by demolishing the concrete atthe opposite side, between the points 4. (fig annex2-2.1,2.2,3). We have to introduce point 5 (see figannex 2-5) as the starting point of the demolition of


the concrete by the use of hand operated pneu-matic tools. The system is, to work in the directionof the points 4, maintaining on both sides of thenewly made gap exactly the same distance to thepoints 4, doing the same work on both sides suchas cutting the same amount of vertical reinforce-ment bars. Maintaining this balance, proceeding tothe points 4, it is necessary to stop and listen fre-quently during the demolition work. When a crack-ing sound is heard (even faint) the work is ready,leaving the workers enough time to leave the area,(at right angles to the axis of fall). After a while thechimney will fall in the correct direction.

6.3.2 To make it fall by blowing it up.It is necessary to insert explosives on both sides.That means total dependency on the skill of theblasting team and experts( see figure annex 2-6).The direction of the fall must be discussed first, thenit must be indicated with painted points on the chim-ney-surface, giving the directions of axes A-C and B-B. The expert has to calculate the amount of explo-sives (see 6.3.1) etc. There will be a difference inexplosives inserted in parts BAB and BCB. (see fig.annex 2-6) If direction A is wanted. Then part BABgets the heaviest load, causing the concrete almostto powder and the reinforcement to break. Part BCBwill get a far lesser load with an explosion detonatinga fraction of time later, causing the reinforcement tobreak and leaving the concrete crumbled. The chim-ney will over after detonation in direction A.

6.4 During the felling, a chimney, it will break. Somedetails are given in fig. annex 2-7,8,9.

The chimney will always break at least into two parts.The upper part cannot follow the falling-velocity of thelower part, (see fig. annex 2-9). It is often the spotwhere a double vertical reinforcement is changed intoa single or a reduced double reinforcement.

7. The demolition of huge chimneys

7.1 Huge reinforced concrete chimneys are consid-ered to be higher than 130 metres. These objectsbelong to important capital investments and conse-quently they are well maintained.

7.2 However, in present times several reinforcedconcrete chimneys with a height of 130 up to 150metres have already been demolished. The demol-ishing work is executed in a suitable modern way,strongly different from what has been discussed inthe previous chapters. In principle, two huge hoistingcranes are erected and are made stable for opera-tion. One crane is used for the operator having hisseat in a cabin hanging on the first crane, which isprovided with modern electronically operated steer-ing gear and transmitters. The operator in his cabin,is able to bring himself in a good working positionand is able to operate the second crane, which

remains unmanned. The second crane equipped withelectronic receivers conducting the modern hydraulicequipment is able to bite, to snip, to cut etc., withenough energy to demolish thick reinforced concrete-structures. The demolished pieces must be lowereddown. In case the lining construction is of steel, it isadvisable to remove that inner lining first (as earlierdescribed). Generally there is no problem to demol-ish an inner brickwork lining at the same time as thedemolishing of the shell. It is inevitable that bits ofrubble will fall uncontrolled from any height. Whenfalling from a height of 140 metres it has a velocity of187 km/h when landing. The impact of this is enor-mous. Consequently corresponding safety measuresmust be taken. With the use of this kind of modernequipment it is no problem to pick up the debris andto load trucks for its removal.

7.3 The demolition of chimneys higher than 150metres.

What has to be done and which method have to befollowed to pull them down is a problem for the futureand it is suggested that this is a subject of later dis-cussion.

8. The demolition of old chimneys in a badstructural condition.

When touring around a country, several chimneyscan be found having a bad structural condition,sometimes amidst abandoned factories, for examplebrick factories. Most of them are made of brickworkand not higher than 60 metres. When pulling downcomes into discussion, it is likely to be impossible todo it the way, described in the foregoing chapters.The blowing down using evenly distributed chargesof explosives around and into the base, could be thebest solution, causing the chimney to collapse.Another possibility is to execute the demolition workby means of adjusted modern equipment, asdescribed in chapter 7, being safe, no workersaround, and reasonably rapid.


THE BEST KNOWN TYPES OF CHIMNEYS-FORMS ARE GIVEN BELOW:

I Tapering II Straight

III Kinked IV+ 1 , 1 1 or IIIwith services

basement

V Huge (> 130 metres)with services

basement

FIG. ANNEX2-1


FIG. ANNEX 2_2.2

Secondly

Blasting chargesor to demolish withpneumatic handtools

FIG. ANNEX 2.2.1

Firs t ly

Concrete chair ( u n r e i n f o r c e d

To be left intact for stabilityon either side of thecircumference

UNREINFORCED CONCRETE CHAIR


FIG. ANNEX 2-2.2a


FIG. ANNEX2- 4a

Limit of chargesor demolishing

UNREINFORCED CONCRETE CHAIR

FIG. ANNEX 2-3

The situation of the bottom gate as sketched preventsthe possibilities of falling in the directions "NO"


You create on opening s y m m e t r i c a l l yand you con use this f a l l i n g direction

FIG. ANNEX 2.4b

If you are in this case


FIG. A N N E X 2 _ 5

FIG. ANNEX 2 _6

D=simu1taneous

demolishing

from point 5

to point 4

Falling

direction


This crack will often arise

on the spot where the

original double vertical

reinforcement is changed

into single or reduced

double reinforcement

FIG. ANNEX2-7

fierce blow(to come)

Collapsing of shell causesfierce blows at both ends.

Brickwork chimneys are likely to break while fallinginto more than two parts due to the absence ofreinforcement.FIG. ANNEX 2-8

Fierce blowof blackdusty air.


Graphical approach of the behaviourof a falling chimney.

FIG. ANNEX 2-9


ANNEX 3

DRYING. PRE-HEATING AND COOLING OF CHIMNEYS FOR START UP. MAINTENANCE.PROCESS STOPPAGES AND SHUTDOWN

1. INTRODUCTIONWhen preparing schedules for drying, heating, cool-ing or shutting down chimneys, all relevant factorsmust be taken into account, the most common ofwhich are described in clauses 2 and 3 below.

Chimneys are sometimes pre-heated, but are usuallydried and fired. The main aim of pre-heating is to cre-ate a draught in the chimney before start up. The aimof drying and firing is to dry the materials from whichthe chimney duct is constructed and prevent inad-missible stresses as a result of fast temperaturechanges or high water vapour pressures.

The drying, firing, and cooling period for a chimneynormally to coincides with that of furnaces or boilers.These periods are usually different for chimneyscompared with furnaces or boilers so that specialfacilities, such as valves, shut off valves, dampers,etc. are necessary in order to control the temperaturein the chimney.

Practice has shown that the life of a chimney can beincreased considerably if drying, firing and coolingprocedures are planned and carried out properly.

2. INFLUENCE OF THE INSTALLATION2.1 FurnacesA furnace installation, including the correspondingheat-exchangers, usually constructed with withdense, brickwork, has to be fired and cooled slowly.Heat absorption and heat emission are greatly influ-enced by whether there is a charge (for instance inmetallurgic and ceramic industries) in the furnace ornot. The presence of water or steam cooled partsalso has an effect.

2.2 BoilersA boiler installation usually has no lining, or only athin brick-layer, and therefore has a small heat con-tent. Also, apart from the medium in the pipe system,there is no charge. Bearing in mind the properties ofthe lining material, firing and cooling of the installa-tion can take place relatively quickly. Shutdowns,occur more frequently with boiler installations thanwith furnaces. Consequently, facilities must be avail-able at the inflow aperture of the chimney in order toprevent rapid temperature changes (e.g. in the formof valves or draught apertures, see figure annex 3-1).During cooling of the chimney, back-up firing may benecessary to prevent a too rapid temperature drop.

3. EFFECT OF THE OPERATING MODEIt is clear that the frequency of shutdowns and thecorresponding cooling and firing period greatlyaffects the life of the lining and shell of the chimney.The construction of the lining, the choice of material

and also accessibility, must suit the type of operationconcerned, taking unexpected shutdowns and tem-perature deviations into account. This applies in par-ticular if there is no possibility for "keeping hot" thelining system (see 4 below). It is evident that thereare design and material differences between a chim-ney in continuous operation at a constant tempera-ture of approximately 250°C and a chimney with sev-eral shutdowns a year.

Shutdowns may be necessary for inspection andrepairs. However, more frequently they are the resultof the shutdown of other installation parts.Consequently, the length of the shutdown may rangefrom a few hours to a few months. In the case of thelatter, special measures have to be taken as dis-cussed in point 6.

4. GUIDELINES4.1 Keeping hotKeeping the installation hot, for both short and longdowntimes, ensures the least risk. Condensation anddamage to both construction and material will be pre-vented at a temperature of approximately 100°C,measured at the outlet. If sulphurous fuel is usedthen the'temperature must be approximately 150°Cbecause of the potential for the condensation of SO3.The energy costs for keeping the installation hot maybe very high. Therefore, a temporary reducing of theoutlet aperture is recommended, as is the use ofwaste heat from nearby installation.

4.2 Pre-heatingPre-heating can be used for a new construction orafter a long down time, but contributes very little tothe drying of the chimney. The principle aim of thepre-heating process is to create a draught in order toexpel the cold air.

The minimum capacity of burners in furnaces or boil-ers is usually much too high to achieve the relativelylow temperatures in the chimneys for pre-heatingand drying. Consequently, the use of auxiliary burn-ers or hot air heaters is recommended. These can beinstalled in front of a man hole or draught aperture atthe bottom of the flue gas duct (see figure annex 3-1). It is necessary to measure the temperature of thecovering in the vicinity of these burners in order toprevent overheating. The temperature must not behigher than 100°C - 150°C. The gate valve or valvesin the furnace or draught aperture must be slightlyopen. When a draught is detected (usually within afew hours), the pre-heating process is stopped andthe installation or chimney is then dried and fired. It isimportant for the mortars used to be completely setbefore drying and firing.


4.3 Drying and firingDrying and firing is necessary after completion of anew-construction or after a long downtime.

Generally speaking, chimneys are dried and fired atthe same time as the installation connected to them.The drying and firing time depends on the degree ofmoisture and the thickness and mass of the materi-als used for the covering, amongst other things. Theratio between shell height and diameter is alsoimportant. It must be remembered that water vapouris released when the installation is being dried. Asthis vapour has to escape via the chimney, there isevery chance that the moisture content of the liningwill increase considerably instead of decreasing.Getting rid of moisture (condensation) is very difficult.First of all, during drying and firing, the moisture willbe displaced towards the coldest part, that is the out-side of the lining. Particularly in the case of olderchimneys, this condensation is highly pollutant andaggressive, so that new damage may occur. An idealmethod is drying from the outside to the inside, butthis can only be done with chimneys which have anopen or accessible cavity between lining and shell.

All brick and ceramic covering materials which willbecome hotter then 100°C must be dried slowly.During the drying, the temperature of the lining mustremain just above 100°C in order to remove themoisture. Only than can the temperature beincreased for firing. It is clear that a drying and firingschedule must be prepared first; this must include allthe necessary measures and provisions.Considerable experience and skill is required forpreparing a schedule of this type.

The diagram of figure annex 3-2 shows the principleof a drying and firing schedule, for which the follow-ing basic parameters have been used:

- the chimney is dried and fired independently ofother parts of the installation,

- the temperature curve applies to the surface tem-perature of the inside of the covering,

- the time required for drying must be long enough sothat no further drop occurs in the moisture contentof the gas (for example, for a chimney 150 metreshigh, with a diameter of 5 metres and a wallthick-ness of 0.2 metres, approximately 15,000 litres to20,000 litres of moisture have to be removed),

- the required setting period depends on the plan-ning and may be much longer than 72 hours.

It is clear that it is not possible to provide a generalschedule for drying and firing because numerous fac-tors and circumstances have to be taken intoaccount.

5. CONTROL MEASUREMENTSIn order to minimise both risk and energy costs dur-ing drying and firing as much as possible, controlmeasurements of the moisture content of the gases

and the temperature of lining should be carried out.The measurements must be made from the begin-ning of the drying period to the end of the firing peri-od. The most important points where the measure-ments are to be made are immediately above theinlet or burner and approximately 2 metres below thetop of the chimney. Additional intermediate measure-ment may also be necessary, depending on theheight of the chimney.

The measured data must be recorded continuously,so that stand-by equipment must be already installedor available. It must be possible to record the mea-sured data by recorders or monitors in a safe place,preferably in a control room. Therefore, it is neces-sary to design provisions for the installation of themeasuring equipment, cables and access to equip-ment before the chimney is built. The moisture con-tent of the waste gases must be measured in the gasflow. The temperature must be measured on or a fewcentimeters from the inside of the lining. In the caseof a very thick or a composite lining, it is recommend-ed that a number of thermo-couples are set in thewall so that the temperature gradient can be con-trolled accurately. At least 2, but preferably 3 mea-suring points near the top, halfway and near flue gasinlet must be included in the circumference of theshell for both temperature measurements at eachlevel in the chimney. (See figure annex 3-1)

6. INFLUENCE OF "SETTING TO COLD"In the case of chimneys which are taken out of oper-ation for a long time, i.e. set to cold, in principle, thesame drying and firing conditions apply as describedabove. However, when chimneys are set to cold,damage may effect the lining and the shell becausethrough the effects of moisture, causing reactionsbetween the used material and the aggressive com-ponents from the flue gases which have penetratedit. Moisture can occur after setting to cold as theresult of condensation, rain or snow.

Protective measures to prevent penetration andattack by moisture and condensation on the brick-worklining, concrete shell or steel lining must betherefore taken immediately after the installation hasbeen taken out of operation. Rain, snow and frostmust be prevented from entering by fitting a topcover. Various solutions are possible and all must beconsidered from the point of view of feasibility andsafety.

Starting up and firing a cold "chimney" involves manyrisks, in spite of all the measures taken.Consequently it is necessary to check the conditionof the lining materials, coating, joints and concrete orsteel walls beforehand.

The measures required may be expensive both interms of money and of time.


Drying- and firing-diagram

Figure annex 3-2


Temperature- and moisture measurements (T and M) must be doneon two or three places along the chimney-circumferenceon a certain height.

Depending on the

height and the construction

of the lining,

more measuring-points

must be installated

(e.g. on each 30 m

of the height)

Figure annex 3-1


ANNEX 4

STRUCTURAL MEASURES CONNECTED WITH CHANGING OPERATION CONDITIONS THROUGH THE

INSTALLATION OF EQUIPMENT FOR THE DESULPHURISATION OF FLUE GASES

1. GENERAL

Chimneys are designed for certain operating condi-tions. If these change, then it has to be consideredwhether the construction is still suitable and if neces-sary changes may have to be made.

As the chimney is usually a part of an existingprocess, and as a rule processes change very little,structural changes occur relatively seldom as theresult of changes to the type of operation.

However, as the result of installations added later,e.g. installing flue gas desulphurisation equipment atexisting power stations at a later date, it is becomingmore and more necessary to adapt the chimneyaccordingly.

2. OPERATING CONDITIONS CREATED BYDESULPHURISATION INSTALLATIONS

In power stations, the flue gas desulphurisationprocess takes place between the fly ash filter and thechimney, on the cold side of the flue gas flow.

Of the various methods available, the so-called wetmethod, based on limestone, is the most common.(The present market share of this method is approxi-mately 90 %.)

Dry or semi-dry methods are usually used in industry,central heating installations and refuse incinerators.

The specific feature of this method is that the desul-phurisation installation is installed upline of the elec-trostatic filter. The desulphurised flue gases passthrough the electrostatic filter first and are only thenintroduced into the chimney. The flue gas tempera-tures at the chimney inlet are 130°C and higher, andthe flue gases contains less water than in the case ofthe wet method.

With the wet method, the operating conditions andthe flue gas characteristics are important for thechimney. They differ fundamentally from the usualflue gases conditions from fossil fuel combustionprocesses.

The most important difference is that during theabsorption process, the flue gases pass the watersaturation point and therefore contain water dropletsin addition to water vapour. This phenomenon occursbecause in addition to high excess air.the remainingsolid particles in the flue gases act as condensationnuclei in the scrubbing process, resulting in waterdroplets.

Well constructed scrubbing towers have double drip

separators which limit droplet formation to 200mg/m3 maximum. The behaviour of the dropletsvaries. Droplets with a diameter of 25μ maximumevaporate relatively quickly to form anwater vapour. However, they can lead to local con-densation. Even after these gases have been re-heated upline of the chimney inlet, the flue gas tem-perature is still close to the dew point. Although theflue gases are desulphurised with the aid of (basic)lime in a water saturated vapour state, the conden-sate reacts in a very aggressive, acid form.

The following details need to be known in order toassess the flue gases:

- the remaining solids (fly ash) in the flue gases, inorder to obtain an idea of the scale and amounts ofwater.

- the minimum and maximum flue gas temperatureof the purified gas at the chimney inlet,

- the relative humidity and the sulphuric acid still pre-sent in order to be able to calculate the dew point.As is known, a small amount of sulphuric acid issufficient to allow the dew point to increase toapproximately 50°C.

Condensation can occur due to droplets in the fluegases or through unfiltered combustion residue orscaling of the drip separator or regeneration of thepre-heaters, released in the course of the scrubbingprocess, leads to congestion or scaling. In the caseof a chimney with a brickwork lining, there is the pos-sibility of attack and moisture infiltration of the brick-work.

The installation of flue gas desulphurisation equip-ment causes extra problems for the chimney. Thechimney must always be able to transport theuncleaned flue gases from a conventional unit. Thisoccurs if the scrubbing installation (suddenly) fails asthe result of insufficient maintenance or a fault. In thiscase, just like previously, unpurified flue gases with atemperature of 130°C to 180°C are transportedthrough the chimney. On the other hand, the chimneymust be able to carry the flue gases, which are satu-rated with water, purified and re-heated and have atemperature of 70°C to 90°C, without damage.

These rapid temperature changes cause static forces(alternating compressive and tensile stresses) andthermo-dynamic forces in the brickwork. Watervapour occurs during high temperatures and conden-sation during low temperatures.

The different flue gas characteristics (cold, wet gasesor hot, dry gases) also influence the pressure ratios


in the chimney. These are affected by not only differ-ent flue gas with its different specific gravities butalso the volume at the different temperature gradi-ents are the cause of the fact that different flue gasspeeds, and therefore different pressures, occurwithin the same cross-section.

For example, with a chimney with a diameter of 6.0metres at the top and 8.6 metres at the flue gas inlet,and with a height of 130 metres between the twocross-sections, an underpressure can occur in nor-mal operation with flue gases of 160°C and an over-pressure can occur at a temperature of 70°C whenthe desulphurisation equipment is used.

If desulphurisation equipment is to be installed in anexisting power station at a later date, or connected toan existing chimney which was intended for a con-ventional unit, then the chimney must be adapted tothe new operating conditions.

3. ASSESSING THE EXISTING CHIMNEYIn order to be able to determine which measures arenecessary, the chimney must be inspected verycarefully. An analysis of the chimney and its materi-als is then made on the basis of this. In addition tothe investigations described as necessary in otherparts of this report, the following information is alsorequired:- material test on the brickwork: apart from acid solu-

bility and water absorption capacity, the infiltrationinto the brick caused by the actual operation condi-tions must be analysed and determined.condition of joints. An assessment of the joints isessential. Material tests need to be carried out onthe mortar. Portland cement mortar is unsuitable.

fly-ash deposits, places where fly-ash accumulatesmust be examined. The extent and layer thicknessof these must also be determined. Any caking mustbe analysed.

steel linings which should have a covering (e.g.coating) must be checked very carefully for rustformation, pitting or other forms of damage.

expansion joints, compensators: these structuralparts are to be assessed from the point of view oftheir function, and also for their capacity to with-stand different operating conditions.

exposed steel structures of suspended equipment,straps, auxiliary structures, chimney copings andcap, parts of the lightning protection system, steps,ladders, etc. must be inspected thoroughly,repaired and protected.the strcuture should be assessed with any newconditions in mind. Particular attention must bepaid to the following parts: possibility of inspectingand checking the lining, flue gas speeds, pressureratios and corrosion protection.

4. MEASURES TO BE TAKENAny measures to be taken have to be established onthe basis of the before mentioned investigations andassessments. With the present state of the art, thefollowing are recommended (naturally to be adaptedto the local conditions).

4.1 LiningIn the past, experience with different types of opera-tion has resulted in the opinion that the best materi-als for linings in chimneys are brickwork or steel.

4.1.1 Brickwork liningsIn this case, particular attention must be paid to thestresses and changing pressure ratios caused bytemperature changes. Brickwork constructed withcement or cement-lime mortar is unsuitable for a fluegas desulphurisation installation.

Up to now, potassium silicate cements have provedsuccessful. Synthetic resin cement can also be usedwithin certain temperature limits

Condensation must be drained away properly, partic-ularly at expansion-joints and above the flue gasinlet. The hopper shaped floor of the lining must beacid-proof and provided with an acid drain of morethan 200 mm in diameter.

Old scale, e.g. fly ash, must be removed. It is sug-gested to coat the inside of the lining with a water-repellent coating to prevent condensation penetration.

Expansion joints: it must be assumed that overpres-sure will sometimes occur in the chimney. Therefore,the expansion-joints must be made similar to a com-pensator. Fluorine rubber has been used as an elas-tic material with good results. The material is vulcan-ised on the spot and can be attached by means ofstainless steel strips which are secured to the brick-work with screws and rawl plugs.

4.1.2.Steel liningsUp to now, opinions have differed with regard to theneed to apply a corrosion protection layer. This isbecause the coatings known at the moment are notvery suitable for these conditions. The temperaturesrange between 70°C (wet scrubbing) and 160°C -180°C (normal operation). If the air pre-heater fails,the temperature may even rise to a maximum of250°C. If the maximum fluegas temperature in thechimney can be limited, good results can beachieved with rubber or synthetic resin coatings.

It is extremely important that the substrate is treatedvery carefully by shot-blasting, flame jets, etc. Theatmosphere when the treatment is carried out (tem-perature and atmospheric humidity) is also a veryimportant factor which has to be taken into account.


4.2 Chimney topAs soon as the flue gases leave the chimney at thetop, the cold, purified, supersaturated flue gases con-dense in the atmosphere. This means that the outsideof the part of the shell right at the top also has to beprotected against condensation. If the shell is madeof concrete, the top section must be protectedapproximately 5 to 8 metres below the top of thechimney. Before the treatment, the substrate has tobe treated very carefully by shot-blasting or with aflame jet.

Steam cleaning and cleaning with high pressurewater jets is not recommended. A good form of corro-sion protection is a synthetic resin coating, consistingof an undercoat and a top coat, applied in one or sev-eral (three) layers, based on a 2 pack epoxy resin.Condensation forming at the top may lead to ice form-ing in winter, which can be dangerous if lumps of icefall off The installation of a hot-air jacket, at the top orelectrically heated matresses can be a solution forpreventing this; considering that, up tillnow, a hot-airjacket is a better solution than an electric heating.

In the case of chimneys with an accessible cavity anda brickwork lining, it is recommended that the top isre-built so that the lining is extended to a height equalto at least half the diameter of the shell. The height ofthe shell is then increased to the same extent with theaid of acid resistant brickwork and pointed with syn-

thetic resin cement, so that the outside of the chim-ney-top is also protected against acid attack.

Another advantage of this construction is that theplume of flue gas detaches itself from the chimneymore easily and the condensation can be collectedand removed by means of a drain through the acces-sible cavity. Remember that this drain must be ableto function in winter.

Metal in the vicinity of the top of the chimney, usedfor ladders, vents, steps and measuring points, etc.must be stainless steel.

Up to now, material no. 1.4577 has been used, whichis then also coated with a plastic protective layer.Experience has shown that higher alloys are needed.Tests have already been carried out with Hasteloy.Plastic vents and grids have also proved successful.

5. SUMMARY

When wet desulphurisation plant is installed, fluegases are produced which essentially differ in behav-iour and properties from flue gases in power stations,etc. before installation of this type of equipment.

An exception are chimneys at chemical installationswhich are designed for this type of operation. If anexisting chimney is connected to a desulphurisationinstallation, it must be renovated. The necessary pro-visions or treatments need to be determined and car-ried out on the basis of careful analysis.


ANNEX 5

ANNEX 5. BUILT-IN PROVISIONS FOR INSPECTION AND MAINTENANCE WORK ON CHIMNEYS

GeneralWhen designing chimneys, attention must be paid tomaking provisions which:

allows measured data to be obtained (e.g. flue gascomposition and variations of these) to supportdamage-analysesgives safe, efficient access for people and materi-als/equipment used for inspection and maintenance

limits the period when the chimney is out of use.

The right provisions should be conducive to properand regular maintenance work on the chimney.

In this connection, the following facilities should beconsidered in detail:

ladders and steps,facilities for hoisting work,connections,flue gas detection points,thermocouples for measuring flue gas temperature.

Ladders and stepsCageladders are to be constructed in such a waythat:

the vertical distance between landings and/or hori-zontal balconies is not more than 20 m,

sufficient space is available between laddertreadsand shell for safe use (minimum 20 cm),

above each stop, the cage is partly open over aheight of approximately 2.2 m and is provided witha safety chain(s),

the top of the chimney is also accessible.

Balconies are to be built in such a way that:

if necessary, aircraft warning lights can be mount-ed and connected,

the tread grids are interchangeable,

the steel ties of both the innermost and outermostpolygon are linked,

if required, lifting gear can be suspended from theradial steel sections,

to guarantee strength/stability diagonal bracingshould be provided,

sufficient working space is created for maintenanceof aircraft warning lighting, flue gas detection andvertical access,

toe boards and handrails are provided.

All the steelwork mentioned above must be properlyprotected, for example by means of hot dip galvanis-ing plus a paint system. Care must also be taken to

ensure that the steelwork mentioned is properlysecured.

For hoistingIt is recommended to attach a (simple) hoisting sys-tem to the shell where balconies are provided. In thiscase, a swivelling davit with lock is usually used,where the suspension point for the pulley usuallyprojects approximately 50 cm beyond the rail. Adevice of this type can be used for the vertical liftingof materials and equipment for inspection and main-tenance work.

Connections (steelwork to concrete)In order to fasten the steelwork to the concrete chim-ney shell, cast-in inserts are preferred in placeswhere forces of any significance need to be transmit-ted. On the other hand, the lightning protection instal-lation for example can be secured by means of post-drill inserts. The cast-in type of insert must be madein such a way that:

a secure connection is made so that tensile forcesare applied behind the external reinforcement. Inthis connection, reference is made to variousreports published about forces transmitted by cast-in inserts.the right choice of materials is made, i.e. withregard to corrosion as a result of flue gases and/oran industrial atmosphere. In practice, bronze orstainless steel (AISI 316) is often used, preferablybronze.the inserts can be properly secured behind thereinforcement in the correct location within toler-ances as specified and, where applicable, can befixed to formwork. In this connection, inserts, pro-vided with anchor bars tied behind the vertical rein-forcement are recommended. The baseplates ofsteelwork for the ladders, steps, davits, etc., needto be provided with slotted holes to give tolerancesto allow for actual position of built-in inserts. Setsof inserts e.g. for fastening one or two baseplates,are often linked together and attached to the rein-forcement as a single unit.

Flue gas detection pointsFlue gas detection points, required by national orlocal environmental organisations, are intended toallow (random) measurements to be carried out fordetermining the flue gas composition. The followingrecommendations apply for the design or implemen-tation of these detection points:

they must be well sealed. Flue gases must not beallowed to escape into the atmosphere. Also, theflue gases must not be able to penetrate into the


insulation and vapour-proof layer as described in Thermocouples for measuringAppendix 5 behind the brickwork (chemical attack, flue gas temperature

"'' In addition to information concerning the flue gasThey must be easy to open, even after long-term composition, information on flue gas temperatureexposure to the atmosphere. The seals must fit and changes is essential for a correct analysis ofproperly and the caps must be greased. They must problems regarding chimney-damage,have good insulation properties. Two insulatedstainless steel sleeves are often used in order to Consequently, thermocouples are often installedprevent overheating (through conduction) of both near the flue gas inlet with continuous temperaturethe insulation layer and the concrete. recording in the control room.

ANNEX 6

DUTCH SAFETY-INSTRUCTIONS FOR EXECUTION OF WORKS

For the execution of civil and architectural work inHolland, there are a number of statutory directives orregulations for control of work practices - the socalled "P-sheets". P-sheets relevant to the executionof chimney maintenance work include the following:

Electric tools, electrical engineering regula-tionsMobile scaffoldingSteel propsHoisting cranes, checking and testingTemporary electric equipmentList of equipment allowed by the workinspectorateSafety at work report•Maximum concentration at workplacevalues - basic data for recommendations

p146

p151p154p156CP4V3

V4OP 20

p79p80

p81p82p83p87p 112-1p 112-3p113p114

p 115-1p 115-2

p 115-3p116p 116-2

p 116-3p117

p119p120p123p125p127p128p131p137p138p144

Requirements for mobile laddersManually operated lifting equipmentincluding tackles, jacks and racksSteeplejacksWinchesDemolition workGoods hoistRespiratory protectionRespiratory protection, choice tableDangerous substances, introduction cardLifts and lifting gear with guides, for thevertical transport of personnelHoist, legal provisionsHoist, construction, strength, testing andmaintenanceHoist and lifting tackles; safety hoistsAsbestos, generalWorking with asbestos in the constructionindustryWorking with asbestos (general)Installation work, fabricating and erectingcomponents**Mobile scaffolding, use and maintenanceMobile scaffolding, design and manufactureConcrete hoistsMobile cranesRail tracks for towercranesErection of steelworkScaffolding fittingsExplosivesHearing protectionWorking from cradles suspended from acrane

-check cables and ropes for kinks and breaks

use only certified ropes and fittings withoriginal parts

use only certified or approved platforms andscaffolding

use electrically operated climbing gear with doublehoist wire and free fall safety protection gear

when using platforms, work always with a sepa-rately attached safety line combined with approvedsafety harness

only transport people using double hoist wirewinches with free fall safety protection gear andwinches with double dead man's switch (hand andfoot) and overload cut-out (thermal)

provide all scaffolding and platforms with adequaterail protection

establish a safety area around the chimney andensure that the entrance to the chimney at groundlevel is covered.

As an example, the most important directives of theDutch P-sheets concerning hoisting activities aregiven in the following:


ANNEX 7

EXAMPLE OF A CHIMNEY REPAIR SPECIFICATION

INTRODUCTIONThe following example of a chimney repair contract isbased on the assumption that the chimney repaircontractor is fully familiar with chimney repair work.

It assumes also that the order issued to the repair con-tractor for the work is based on a performance specifica-tion, rather than on resources employed as the choice ofthese is left to the initiative of the repair contractor.

ExampleThe enquiry documents sent to the repair contractorwill typically include the following:

administrative and commercial contract docu-ments, covering, in particular, guarantees, penal-ties insurance.

The enquiry may also includea technical specification, setting out all technicalrequirements for undertaking the repair of thechimneyquality assurance document concerning the qualityof the supplies and services to be provided,administrative and service specifications, applica-ble to service contracts executed on plant in opera-tion, and including, in particular, all clauses relatingto health and safety.

Apart from the technical specification, the documentsmay not be suitable for international use and must bedrafted specifically taking due account of legislationin force in each couintry concerned.

The only technical document included hereafter istherefore the Technical Specification.

MODEL CHIMNEY REPAIR CONTRACT

DOCUMENT No.1 Contract No.:

TECHNICAL SPECIFICATION

CONTENTS

SECTION I PURPOSEPurpose

SECTION II CHIMNEY CHARACTERISTICSChimney construction details anddimensionsGas analysis and quantityFuel details

SECTION III OPERATING CONDITIONSOperating conditionsEnvironmental conditions and sitespecific criteria

SECTION IV CHIMNEY REPAIR WORKSRepair of external shellRepair of masonry liningRepair of steel liningRepair of paintworkRepair of accessories

SECTION 1 -

1. PURPOSE

1.1 This Special Technical Specificationconcerns repair work on the chimney forunits Nos. and of the power station at

SECTION 2 -

2. CHIMNEY CHARACTERISTICS

2.1 This chapter must define:

chimney characteristics,gas characteristics,fuels usedoperating conditions in the localenvironment.

SECTION 3 -

3. OPERATING CONDITIONS ANDCHIMNEY ENVIRONMENT

3.1 .Operating conditions

Electric power generation plant chimneys areused to carry flue gases for discharge to theatmosphere at a height at which they aredispersed.

The flue gases principally comprise hot air,water and aggressive substances (generallyacids).

Flue gas temperatures can vary according tothe process employed, from a cold level ofabout 30°C, to a hot level of between 140°and 190°C, in some cases up to 200°C.

3.2. Environment

This chapter must define:

environment in which the chimney issituated and which influences thechimney,

chimney design and maintenance workto be executed,

constraints imposed by local admini-stration and which can require theinstallation of instruments for measuringdust, SO2 and NO4 discharge rates,


maintenance according to climaticconditions and the environment inwhich the chimney is located(industrial zone, rural area, sea coast,etc.).

SECTION 4

4 CHIMNEY REPAIRThe repair defined in this chapter, and whichtakes due account of the conclusions of theinspection report (referenced) and themaintenance-advice-report, must be executedin accordance with standards and regulationscurrently in force, special rules laid down byowners, national rules (safety) and generalrules as applied in the profession.

Particular the following repairs are described:

external shellinternal masonry lininginternal steel liningrepaintingrepair of accessories

The repair must be executed in compliancewith all clauses of this Special TechnicalSpecification.

4.1 REPAIR OF EXTERNAL SHELLAll repair work undertaken on the concreteshell must ensure:

elimination of all degraded materials,reconstruction of the shell

and concerns the internal and external facesof the shell.

4.1.1 Elimination of degraded materialsFor all parts where:

insufficient cover to the steelreinforcement,corrosion of the steel reinforcement,formation of cracks,inhomogeneity

are observed, the following work must becarried out:

preparation of all degraded parts,elimination of all material degraded asa result of defective adhesion, inhomo-geneity or corrosion of metal parts,brushing and cleaning of all parts(concrete and steel reinforcement).

4.1.2 Reconstruction of the shell

Materials used for the repair of concretechimney shells are as follows:

poured concrete,shotcreting mortar,smoothing mortar incorporating

synthetic resin or not,synthetic resin for injection.

For the selection of repair materials thefollowing parameters must be taken intoaccount:

coefficient of elasticity,coefficient of expansion,shrinkage, creep and relaxation,compressive and tensile strength,waterproof and water-resistantcharacteristics,high and low temperature performance,prevention of corrosion.

The repair work consists of applyingmaterials, suitable for the types of repairinvolved, duly complying with applicableutilisation and application specifications.

Repair of steel reinforcement:passivation of steel elements afterremoval of concrete overlay and rustand smoothing with waterproof mortarincorporating synthetic or compositeresins.

Isolated concrete repair:smoothing with appropriate conventionalmortar.

Surface repair of large areas:shotcreting to obtain:

full adhesion to the sound concretebase structure,

adequate cover to the steelreinforcement.

Major repair (part reconstructed):application of appropriate pouredconcrete.

Repair of cracks:injection or filling.

4.1.3 Preventative maintenance on theconcrete shellFor this purpose, generally the shell iscoated.

4.2 REPAIR OF INTERNAL MASONRY LININGThe repair work must cover:

elimination of degraded material,

reconstruction of the lining

4.2.1 Elimination of degraded materials

Removal of the following:

crumbling, broken or worn bricks,

bricks, where their volume has beenreduced,


brickwork adjacent to cracks,

removal of upper brick-layers tore-establish expansion clearance levewith the expansion joints,removal and replacement of damagedexpansion joints.

4.2.2 Reconstruction of brickworkReplacements of parts or sections ofbrickwork liningReadjustment of expansion joints

Replacement of all expansion joints

Repair of cracks in brickwork:Filling and smoothing of small cracksusing a synthetic resin mortar resistant

to chemicals.Partial repair of the masonry with major,full depth cracks (incorporation of flue gasdetection points in the case of chimneyswith accessible air space).

4.2.3 Repair of thermal insulation of brickworklinings

4.2.4 Preventative maintenance

4.3 REPAIR OF INTERNAL STEEL LINING

4.3.1 Repair of corroded parts

Isolated or minor repairs:repair by welding new sheet sections inthe same grade of steel as the existinglining.

Major isolated repairs:addition of an outer lining comprisingfour segments.

Extensive repairs (loss of shell thick-ness due to intensive corrosion):

reinforcement of the weakened partusing IPN steel girders placed insidethe metal lining, and forming a circularmesh system.

4.3.2 Repair of thermal insulation

4.3.3 Preventative maintenanceCleaning of the internal lining for inspectionpurposes, is completed by passivation(Hutter process), followed by flushing.

4.4 REPAIR OF PAINTWORK

Paintwork repair operations comprise, inparticular:

elimination of defective coatings,

preparation of base structures,application of protective and finishingcoatings in accordance with thespecification, covering coating work,issued by the owner and to which thecontract is subject.

4.5 REPAIR OF ACCESSORIES

4.5.1 Repair of ladders, platforms and stepsThis chapter must define all accessories forwhich the replacement of defectiveelements is required, and all accessoriessubject to maintenance work.

4.5.2 Repair of lightning protection

4.5.3 Repair of beacons

4.5.4 Repair of coping

4.5.5 Repair of ventilation

Cleaning of ventilation orifices andbaffles.

Execution of draught tests.


ANNEX 8

STRAIGHTENING OF BENT BRICKWORK CHIMNEY

The bending of a brickwork shell can have severalcauses. Humidity, resulting in local expansion ofthe brickwork can be considered as the mostimportant cause of the bending phenomenon.

The straightening of bent brickwork shells often isrequired, when - for instance - a new lining or lin-ingsection must be built. This lining or lining sec-tion can consist of steel or brickwork.

The execution of this work requires a specialisedcontractor with extensive experience, in this type ofwork.

The straightening-work starts with the making ofone or more horizontal incisions on the convexside of the chimney (see figure annex 8-1).

In these incisions steel or wooden wedges orhydraulic jacks are placed in order to maintain ver-

ticality during the operation.These wedges or jacks areplaced during the cutting out ofthe incision(s), starting in the mid-dle of the incision(s) and nextalternatingly on the left and theright side of the starting point.(see figure annex 8-1)Next the width of the incision(s) isdiminished by carefully hammer-ing out, little by little, the wedgesor by lowering, little by little, thejacks. This activity will be done inthe reverse sequence as for thatof the placing of the wedges orjacks, (see figure annex 8-1)

Because of the flexibility of thebrickwork, small unequal move-ments of the shell along the inci-sion(s) will not cause damage.

The number of wedges or jacks tobe placed, depends on the per-missible stress of the brickwork.

During the work, steel ring ban-dages around the shell will beinstalled directly above and belowthe incision(s) to limit radial defor-mation during the procedure.

After the straightening work, thewedges or jacks are taken outand replaced by packs of steelplates to fix the position of theshell.

Next the incision(s) is fully closedwith new high quality masonry.

Longitudinal section Bend-Graph

Detail

Brickwork

liningShell

corbel

"A"

View "A"

Top - View

Figure annex 8-1

Area of horizontalincision below the

incision width

steel or woodenwedges

steel or wooden

Start

Bendinq

Horizontal

Finish

Start

start

wedges or jacks1

3

5

7

9

2

4

68

shell

DRAWING OF STRAIGHTENING OF BENDED BRICKWORK CHIMNEYS

incision

corbel

wedges

Finish

Finish

Cutting

direction

Straightening

direction

Straightening

direction

Cutting

direction


ANNEX 9

ADJUSTMENT OF DAMAGED EXPANSION-JOINTS IN BRICKWORKS LINING

Reduction of expansion clearance is due to expan-sion of the masonry cylinders. This expansion caus-es an increase in the height and diameter of thecylinders. Restoration of functional clearancebetween two lining-sections as shown in the exam-ples given in the figures 1,2 and 3, therefore involvesdismantling the brickwork forming the upper part ofeach lining section.

In case of a structure of the type, shown in figures 1and 2 in compliance with the required functional radi-al clearance, over the full height of the joint, must beensured. In the event of unacceptable radial defor-mation, this means that the masonry must be recon-

structed over a height exceeding that of the joint, inorder to obtain a profile compatible with the correctmechanical strength of the cylinder.

Readjustment of clearances is essential, and mustbe conducted on a systematic basis. Clearances aremeasured cold. Where they are held within the toler-ances stipulated by the manufacturer, these clear-ances allow for expansion, without generation ofmechanical stresses applied to the linings, expansionjoints and concrete corbels. Destruction of the joints,brickwork and even the corbels, is consequentlyavoided.

EXPANSION JOINT

Figure annex 9-1

Inside ofchimney


Figure annex 9-2


EXPANSION JOINT

Inside ofchimney

Figure annex 9-3

manual inspection of concrete and brick chimneys

Documents