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Automatic inspection systems for industrial chimneysPgina 1 de 9

Miguel ngel Parrn Vera y Carlos Martn Daz deEspada

AUTOMATIC INSPECTION SYSTEMS FOR INDUSTRIAL CHIMNEYS

Miguel ngel Parrn Vera (1) Carlos Martn Daz de Espada (2)

(1) University Professor of Continuum Mechanics & StructuresIndustrial & Civil Engineering Department

Escuela Politcnica Superior de Algeciras, Cadiz UniversityAvda. Ramn Puyol s/n, 11202 Algeciras, Cdiz (Spain)

e-mail: [email protected], web: http://www2.uca.es/escuela/politecnica_alg/(2) Associate Professor of Industrial & Civil Engineering Department

Escuela Politcnica Superior de Algeciras, Cadiz UniversitySecurity and Research Director, La Lnea Vertical S.L.

Camino Ancho de la Atunara 36, 11300 La Lnea, Cdiz (Espaa)e-mail: [email protected], web: http://www.lalineavertical.com

1. SYNOPSIS:The automation of the industrial chimney inspection tasks has led to significant improvements in the safety of the inspectors and therepeatability of the obtained results. A high number of devices have been designed during the past few years, and in this paper we will try to

describe and classify them, according to their most outstanding features, trying also to analyse the main advantages and drawbacks of the

different solutions.

2. INTRODUCTION:Industrial chimneys [3] convey the flue gas from fired heaters, boilers or any other combustion facility into the atmosphere. Furthermore, they

provide the draught necessary for the combustion process and take the gases to the appropriate height to minimize their effects on the nearby

ground-level areas. Nowadays they are built using reinforced concrete (cast-in-situ or precast) or steel as a structural basis. Brickwork

chimneys can also be found; they were very widely used some decades ago, but they are no longer built due to their poorer self-bearing

capacity and higher costs compared with other options. In some particular cases, plastic material chimneys are used, but their application

range is very limited.

These self-bearing structures are usually calculated as big cantilever beams; in some cases, specially the steel ones, they can lean on adjacent

structures, or be supported with guy ropes bolted to the ground. Their main parts are: the foundation, which supports and stabilizes the wholestructure; the shell, outer structure resistant to wind and design loads; the lining, which conveys the flue gas and protects the shell from high

temperatures and acid attack; the auxiliaries, which provide access to all maintenance-related areas; the air-space, empty layer between the

shell and the lining, necessary for isolating purposes, but also used to place the auxiliaries; and the top, chimneys highest end.

These facilities are prone to experience severe damage caused by the high temperature and chemical aggressiveness of the conveyed gases, as

well as heavy climate conditions. In order to ensure their operational and safety conditions during their entire functional life, the chimneys

must be inspected and maintained regularly.

3. MODERN INSPECTION SYSTEMS (STATE-OF-THE-ART)The inspections shall be carried out [1] according to established well-planned systems (except for emergency inspections after failures,

accidents, etc.); the reason for insisting in planning and studying the work is twofold: the tight timing for the inspection (usually coinciding

with a scheduled turnaround) and the extremely difficult access, which limits the resources that can be used. Nowadays some of the following

procedures are normally used in the chimney inspection [2]: visual examination, physical examination, concrete cores, ultrasonic thickness

measurements, and testing of connecting joint bolts.

Focusing on the most widely used procedure [2], the visual examination, we find that it is normally carried out by means of some of the

following options:

o Scaffolding systems: Fixed traditional scaffolding flying scaffolding Hanging scaffolding or hanging platforms , with manual or electric lifting mechanism

o Rope access techniques [16]o Automatic devices

Fixed scaffolding systems are very costly and require long turnarounds to be installed and disinstalled. Their main advantage is the fact that

once they are installed, the inspection works can be carried out very easily. In this type of work, traditional fixed scaffolding are used very

seldom, and hanging scaffolding or hanging platforms are preferred.


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Rope access techniques are nowadays gaining a greater acceptance; climbing equipment, safer and more advanced every day, allows expert

personnel to access any chimney point very rapidly and with reduced effort and tools. Hence, rapidity and versatility constitute their main

advantage, but on the other hand, the limitation to work where the loads to be handled are not too big, and the need for costly skilled labour

are their drawbacks. Their usage and that of the scaffolding is regulated by the European Directive 2001-45-CE Provisions concerning the

use of work equipment provided for temporary work at a height [4].

Both with scaffolding and rope access techniques, the inspection is performed

manually, without any systematization or automation; the reports, technically

demanding according to the CICIND recommendations [15], depend mostly on the

inspector skills and furthermore, the results can only be verified by the client by

means of isolated photographs or films (generally of poor quality). The people that

carry out the inspections are exposed to significant risks for their physical safety; these

risks can be kept under control by good planning, the correct selection of Individual

Protection Equipment and an adequate Risk Assessment, but nevertheless, the risks

are always present.

The use of automatic devices, which we have mentioned above as the third option for

performing inspections, has the following advantages:

- Dramatic reduction of the inherent risks, because it is a machine andnot a person that performs the inspection, according to the

requirements of the current Prevention of risks at work Act [5]

(European Directive 89/391/CEE).

- Reduction of the time required for people to access and stay at thechimney inner parts under high risk working conditions; once the

automatic system has finished the inspection, the skilled personnel

would only have to work on specific points where a defect has been

identified.

- Cost reduction: An inspection must be carried out by at least 3-4persons, with the permanent presence of the emergency service and the

fire brigade. Automation greatly reduces the impact of the inspection

works on the facilitys daily routine (most likely undergoing a partial

or complete turnaround) because it requires very little supervision

from the Operations personnel. Thus, with less labour and timerequirements, the inspection costs drop dramatically.

- Real-time inspection control by skilled personnel (engineers); prior tothe arrival of these devices, they had no choice but to follow the

maintenance company indications, due to the lack of real-time

information.

- Access to a great amount of technical data on the chimneys currentsituation, very difficult to collect through alternative means: crack

size and location, carbon layer thickness, circuit leaks, explosivity,

etc. depending on the meters installed on the device.

- Inspection data storage on electronic devices, when a recording iscarried out; these data can be accessed from any part of the world if

downloaded on an Internet Server.

A good design should have the following general features:1. Robust mechanical and structural design, so as to withstand air currents andblows while keeping its functionalities and stability.

2. Manufactured with light materials, because it is to be carried to a great height with traditionally scarce means.3. Adaptable to the greatest possible number of chimney types (many diameters and heights).4. Low-cost, so in addition to the aforementioned functional advantages, it is also cost-effective compared with the traditional

systems.

5. Self-powered (batteries), to keep it from depending on the local auxiliaries, given that they tend to be old and not very wellmaintained.

6. Configurable with different meters, according to the current needs to be fulfilled (digital camera, air analyzer, infrared, etc).

4. AUTOMATIC DEVICES FOR CHIMNEY INSPECTIONThere is a wide variety of devices for chimney inspection; our documental search has been carried out on the following sources:

- Patents Register, through the OEPM (Oficina Espaola de Patentes y Marcas; Spanish Bureau for Patents and Brands),

according to the request 49939, in the database WPI, 47 references [6].- Search through the Internet, 3 references [7] [8] [12].- References of published articles in CICIND documents, 3 references [9] [10] [11].

Los Barrios Power Station Chimney


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After the analysis of this important number of references, we propose a classification based on the following criteria (see table 1):

I. Automatic device: Consisting of a metal structure that moves along the chimney and allows collecting the necessary data forthe inspection. It can be arranged in several ways:

a. For internal or external chimney inspection

b. For usage during chimney shutdown or chimney normal operationc. Depending on the driving system location: Boarded, fixed on top or fixed on the ground level

II. Non-automatic device: A metal structure, that moves along the chimney and allows the inspectors to collect the necessary datafor the inspection; most of them are similar to the hanging platforms [6] [16].

It is worth saying that there are also other types of automatic devices intended to carry out chimney maintenance tasks, other than inspection:

- Devices for inner cleaning of the lining. Most of these operate during turnarounds and are equipped with fixed or mobiledriving systems; they have brushes at both ends which rotate around the chimney axis while the whole device moves vertically

[6] [9].

- Debris disposal devices. Very similar to the aforementioned, they can dispose of the contaminated debris as a preliminaryphase for the chimney demolition, thus reducing to a great extent the amount of dangerous waste to be handled [6].

TYPE OF INSPECTION DEVICE INSPECTIONAREA

INSPECTIONMOMENT

MECHANISMLOCATION

(A) Automatic (I) Interior (O) Normal Operation (B) Boarded

(N.A.) Non-automatic (E) Exterior (T) Turnaround (FT) Fixed on Top

(O) Other devices (FG) Fixed at Ground level

Table 1 Device classification

Fig. 1 Interior Inspection Device with top fixed mechanism for

turnarounds

Fig. 2 Interior Inspection Device with boarded mechanism for turnarounds


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The automatic systems for external inspection have the following general features:

- Intended for metal chimneys.- Self-propelled device, that moves along the wall with the help of wheels, and sticks to it by means of magnetic fields.- Have ultrasonic thickness measurement equipment.

- Driven from a remote control unit on the ground level, to which it is connected through wires.- Advantages:

Allow working at all times, regardless whether the chimney is on normal operation or in a turnaround

Require little personnel to be operated, generally no more than two persons

Usually self-powered, not depending on the clients local auxiliaries.

They bring about a dramatic risk reduction, because in most cases the device climbs from ground level, so the actualwork is not carried out at height.

- Drawbacks:

Not valid for concrete or brickwork chimneys, or for refractory lining (lack of adherence).

Irregular areas (platforms, stairs) make the measurements more difficult.

Some models carry out the inspections from the ground in a telescopic way; they reach up to 300 m, hardly need access to the

facility (risk reduction) and are not limited to metallic structures. On the other hand, they do not allow sample taking and may leave

unmeasured areas when these are hidden.

The automatic systems for internal inspection are designed to be used either during normal operation or in turnarounds. The formers main

advantage is that, allowing the analysis of the chimneys working conditions, they enable us to program the future turnaround in a very

efficient way, knowing the extent of the work to be done ; this information is very important for the management of the power station (or

similar facility) because it allows turnaround time reduction and better resource planning. Nevertheless, due to the extreme working

conditions (high temperature, corrosive environment) these systems have some drawbacks, such as the following:

- They are of great size and weight, because of the protective and insulating casing.- Their manufacturing cost is high, due to the type of materials required and the aerodynamic design.- They require auxiliary elements for the set-up and start-up phases (cranes), which slow down the work and increase the

operation costs. In the case of very high chimneys (> 150 m) the use of cranes is very limited, and it is weather conditions that

set the pace of the work.

- They also need more technical personnel for the inspections, at least 3 or 4 persons.- Other drawbacks that the device designer will have to deal with are:

Film instability, because the flue-gas flow impacts the device and generates vibrations.

Condensation on the camera glass surfaces, whenever the flue-gas conditions remain below the dew point.

All the reviewed devices have a fixed driving system at ground level, none of them have a fixed driving system on top or boarded.

The systems for chimney internal inspection to be used in turnarounds are much smaller than their counterparts for on-stream

inspection, with a simple bearing structure that works only as a rigid framework (it is not necessary for the data acquisition equipment to be

protected from extreme conditions). Hoisting the equipment up to the chimney top entails less difficulties, so in many cases it can be done

manually. Thus, the chimney height is not an actual limiting factor, and weather conditions are less critical. Other advantages:

- Easier filming, as a result of the lack of both strong air currents and condensation on the glass surfaces.- Lower manufacturing costs.The main drawbacks are:

- The information on the chimneys status is received when it has been shutdown for a few days, so there are less available daysfor maintenance prior to the start-up.

- In many cases the system is not suspended but wire-guided, meaning that it is necessary to access the chimneys foundation to

bolt the guiding elements. This is only possible in some types of chimneys.


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External Inspection Systems

3. SCANSITES [12]4. CETA 1 [7]5. CETA 2 [7]

Scaffolding systems

6. Supporting crane

7. External hanging scaffolding8. Traditional fixed scaffolding

3

4

5

6

7

8


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AUTOMATIC DEVICES FOR CHIMNEY INSPECTION ID

INSPEC. INSPECTION MECHANISM

AREA MOMENT LOCATION

SYSTEM NAME

EXTERIOR NORMAL BOARDED - 1 Ceta 1 y 2 (7), fig 4-5

OPERATION / 2 Scorpion DCP (8)TURNAROUND 3 Mobile working vehicle (6/19)

4 Surface traversing vehicle (6/29)

5 Inspection system of stack cylinder (6/33)

FIXED GROUND 6 ScanSites (12), fig 3

INTERIOR TURNAROUND FIXED TOP 7 Internal inspection equipment for tubular structures (6/2), fig 14

FIXED GROUND 8 Apparatus for inspecting interior of smoke stacks (6/38), fig 10

BOARDED - 9 Inspection apparatus for wall thickness for chimney (6/24), fig 13

10 Washing/Inspecting apparatus for stack lining (6/25)

11 Observing device for interior of cylindrical body (13), fig 11

INTERIOR NORMAL FIXED GROUND 12 Scanliner (11), fig 11

OPERATION 13 Camera system (6/27), fig 12

14 Hot camera (10)

15 Inspection system (6/4)

16 Device for the recording and simultaneous representation

of the conditions of a building (6/6)

FIXED TOP -

BOARDED - -

Table 2. Summary table on the classification of the automatic devices for industrial chimney inspection

9

9. Chimney inspection by rope access techniques

9


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Automatic Devices

10. Apparatus for inspecting interior of smoke stacks (6/38)11. Scanliner [11]12. Camera system [6/27]13. Inspection apparatus for wall thickness for chimney [6/24]14. Internal inspection equipment for tubular structures [6/2]

14

13

11

10

12


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Other devices

15. Method and device for clearing wall surface insidechimney (6/5)

16. Transportable work platform for shaft inspection [6/39]17. Installation for facilitating inspection and repair of the

interior of chimneys [16]

15

17

16


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5. CONCLUSIONSIndustrial chimneys are to be inspected regularly in order for them to be kept in good operational and safety conditions. Several

procedures have been developed to carry out these inspections, mainly the scaffolding systems, the rope access techniques and

the automatic devices. The latter provide a significant reduction in the risks involved and in the inspection duration and costs,together with an improved quality in the inspection reports.

The internal inspection devices intended to be used during normal operation allow the facilities to benefit from a cost reduction

by means of improving turnaround planning; however the inspection unitary cost is higher due to the specific systems features,

compared to those intended for turnaround usage, with less auxiliary equipment costs.

Nevertheless, the automatic devices do not have the possibility to perform repairs on the chimneys; if a technical problem arose

during a inspection, the only way to access these devices would probably be by means of the rope access techniques. This aspect,

together with the foreseeable need to carry out some maintenance works on the chimneys, suggests to us that a combination of

experts in rope access techniques and automatic inspection systems could turn out to be the best choice in most cases.

6. ACKNOWLEDGEMENTSThis work has been partly funded by theDireccin General de Investigacin of the Secretara de Estado de Poltica Cientfica y

Tecnolgica, Ministerio de Ciencia y Tecnologa de Espaa, under the project Torres Quevedo n PTQ2004-1369.

7. REFERENCES[1] CICIND, Manual for inspection and maintenance of brickwork and concrete chimneys, February 1993.

[2] CICIND, Chimney maintenance guide, January 2006.

[3] CICIND, A customers guide for specifying chimneys.

[4] Official journal of the European Communities, European Parliament and Council Directive 2001/45/EC concerning

Minimum safety and health requirements for the use of work equipment by workers at work, Annex 4 Provisions concerning

the use of work equipment provided for temporary work at a height, 27 June 2001.

[5] Official journal of the European Communities, European Parliament and Council Directive 89/391/EEC concerning

Introduction of measures to encourage improvements in the safety and health of workers at work, 12 June 1989.

[6] Oficina Espaola de Patentes y marcas, Dispositivos automticos de inspeccin interior de chimeneas, Solicitud 49939,

febrero 2006.

[7] Tecnitest, Sistema CETA 1 y CETA 2 www.tecnitest.com .

[8] Silverwing, Scorpion DCP www.siverwinguk.com .

[9] Esparza J., Gonzlez C., New automatic device for clearing the insides of chimneys, CICIND report vol. 15, No. 1, 1998.

[10] Miller J.D., Hot camera chimney inspections, CICIND report vol. 3 No. 1.

[11] Sushchev S., Scanliner diagnoses, CICIND report vol. 21 No. 2, September 2005.

[12] SITES, Ageing diagnosis of structures with SCANSITES process (doc. ref 0173MTC2v02ang), January 2004.

[13] Shingo N., Seiji N., Isamu T., Observing device for interior of cylindrical body, patente nmero JP2146494, Junio 1990.

[14] CICIND, The CICIND Chimney Book, Industrial Chimneys of concrete or steel, 2005.

[15] ANETVA, Manual de Trabajos Verticales, Noviembre 2000.

[16] Prochniak S., Glogowski W., Installation for facilitating inspection and repair of the interior of chimneys, patente nmero

GB2026980, febrero 1980.

[17] Shingo N., Kazuo K., Isamu T., Observing device for interior of cylindrical body, patente nmero JP1295574, Noviembre

1989.

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