Chimney Journal 1
Chimney Journal 1
Chimney Journal 1
R L Dinesh1, E R K Nishok2
1
Discipline Head,Civil Engineering -Technology Vertical, Tata Consulting Engineers Limited, Bangalore, India
2
Assistant General Manager, Civil Engineering -Power Business Unit, Tata Consulting Engineers Limited, Bangalore,
India
Abstract
In Modern Power plants are constructed with Chimneys of 275m tall for discharge of hot waste gas at high altitude level. Hot
waste gas is carried through flues made up with either brick or steel material supported on RCC wind shield. Construction of
RCC shell and flues are challenging due to its height. Quality issues due to dragging in slip forming, improper flue can
installations are the major problems faced in chimney construction works. Rectification of these problems are time consuming and
very expensive. This paper high light on the quality issues faced in few chimneys, mitigations and rectification of these problems.
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Volume: 05 Special Issue: 20 | ACCE : REDECON-2016 | Nov-2016, Available @ https://www.esatjournals.org 87
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
Exhibit-1
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Volume: 05 Special Issue: 20 | ACCE : REDECON-2016 | Nov-2016, Available @ https://www.esatjournals.org 88
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
g) Any small steel component of shuttering arrangement outer radius of flue) are to be used to get better joints.
projecting beyond shuttering sheet shall cause dragging. Continuous inspection of quality of work is very important
Therefore this is to be checked at initial stage of slip to achieve better quality of work. In order to achieve this it
form work progress and at intervals. Any such things is necessary to have suitable access arrangement for
noticed shall be rectified immediately. Components inspection team to reach the working level at any time of
poses such problems are twisting cleats, stiffeners
construction. Therefore a access opening/ manhole at every
provided for shuttering plate.
h) During construction of chimney if dragging occurs it is platform level is to be provided along with a temporary rack
essential to stop the concreting and check the quality of & pinion lift to approach these openings quickly & safely
concrete using non-destructive testing like Ultrasonic for inspection team.
pulse velocity test. If the velocity of wave found to be
less than 4000m/sec but greater than 3000m/sec, it is 4.3 Steel Flues
necessary to rectify the quality of concrete. If the Flues are fabricated in circular segments (cylinder) and
measured Velocity of wave less than 3000m/sec it erected from top to bottom. A bigger opening is provided in
indicates that the quality of concrete is poor. chimney at bottom for transportation of segments inside
chimney and erection. For convenience in fabrication,
3.5 Rectification Of Concrete
handling, transportation and erection the length of the flue
Concrete having UPV of 3000 to 4000m/sec indicates ‘CAN’ is to be limited to 6000mm.The cans are to be
presences of porosity in the form of voids, cracks and in classified as typical flue cans, support cum restraint flue
some places loss of integrity. These areas shall be pressure cans, restraint flue cans and S.S. flue cans.
grouted using epoxy or polymer grouts to ensure structural
integrity. For areas where reinforcement is exposed, weld
Typical flue CAN will have stiffener angle 130x130x10 at
mesh to be tied to reinforcement and micro concreting to be
top and bottom with outstanding legs in horizontal plane
performed. For areas where reinforcement is not exposed,
area is to be plastered with repair mortar. UPV tests shall be serving as flanges for bolted connection.
re-conducted for acceptance.
For the concrete where the UPV is less than 3000m/sec, Support cum restraint flue can is provided at the top of each
further core test samples shall be taken at adequate number unit of flue between expansion joints. This flue can supports
of locations across full depth to study the quality and the total weight of this particular unit and transfer the load to
compressive strength for acceptance. If the strength is within the support beams through four brackets. This ‘can’ also
the acceptable limits, grouting, as mentioned above is accommodate restraint buffers for the top restraint bracket
carried out. UPV tests shall be re-conducted for acceptance. of the unit. At the end of this can, where the bracket /
If the core test results are not satisfactory, Concrete shall be
restraint buffers are provided, stiffness of CAN is increased
removed and re-done.
by providing stiffeners and local higher thickness for CAN.
Flange connection at the end of the CANs as well as
4.0 CONSTRUCTION /INSTALLATION OF
stiffeners will be provided similar to typical flue CANs.
FLUES
Restraint flue can is provided at the bottom of each unit of
4.1 Brick Flues
flue immediately above the expansion joint in the case of
Brick flues are constructed on RC brackets or RC ring hung portion of the flue and at the top of the bottom
beams or on steel beams. In case of RC brackets adequate supported portion of the flue.
openings is to be provided for air circulation if the bracket is
continuous. If the bracket is not continuous, ring beam with
The total length of the Stainless Steel portion of the flue
gap between wind shield and ring beam face is provided for
air circulation. shall normally be fabricated into two cans of equal length.
The top can shall have a box shaped stiffener
4.2 Quaility Issues In Brick Flue Construction And
The supporting / restraining arrangements of the flue/duct
Remedial Measures shall be such that the movement of the flue longitudinally or
Laying of brick masonry joints is very important since they circumferentially is not restrained.
are weak points for gas leakages and joint failure. Joint on
inner periphery of flue is to be kept not more than 2mm and 4.4 QUALITY ISSUES IN STEEL FLUE
on outer periphery not more than 12mm. More the thickness INSTALLATION
more the probability of weak joint and crack may develop
over a long period leading to gas leakage and fall of bricks. It is very important to fabricate the cans with stiffeners,
Therefore skilled labour and adequate time shall be given brackets at exact designed locations and same shall be
checked before shifting to chimney for erection. If bracket
for construction of fire/acid resistant brick work. Also
location is not in proper position and not checked the
shaped bricks with required curvature (matching to inner &
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Volume: 05 Special Issue: 20 | ACCE : REDECON-2016 | Nov-2016, Available @ https://www.esatjournals.org 90
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
4.5 Rectification
Rectification of such dislodged bearings can be taken up
during boiler maintenance period. Additional brackets are
welded to existing brackets and all brackets are lifted
simultaneously using hydraulic jacks. Lift of brackets are to
be within the designed expansion compensation allowance.
After lifting the brackets, support bearings are relocated to
its postion and jacks are released. Sliding arrester in the
form of plate welded to fixed support is suggested to prevent
lateral movement beyond the fixed support.
5. CONCLUSIONS
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Volume: 05 Special Issue: 20 | ACCE : REDECON-2016 | Nov-2016, Available @ https://www.esatjournals.org 91
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
ACKNOWLEDGEMENT
Authors acknowledge the management of TATA
CONSULTING ENGINNERS LIMITED and thankful to
them for giving opportunity to publish this article.
REFERENCES
[1] IS:4998 Criteria for design of reinforced
concrete chimneys: Part 1 – Design
criteria – 1975- Presently under revision
[2] IS:4998 Criteria for design of reinforced
concrete: Part 1 Assessment of loads-
1992 Presently under revision
[3] IS:2062 Hot rolled low, medium and high
tensile structural steel
[4] IS:8183 Bonded Mineral wool
[5] IS:3677 Unbonded rock and slag wool for
thermal insulation
[6] IS:1526 Sizes and shapes for fire bricks
[7] IS:4860 Acid resistant bricks
[8] Manoha Tall Chimneys-Design and
r,S.N Construction", Tata McGraw Hill
Publishing Co.Ltd., New Delhi, 1985
[9] Pinfold, "Reinforced Concrete Chimneys and
G.M Towers", View Point Publication,
Cement and Concrete Association,
U.K., 1975
[10] ACI Standard Practice for the Design and
307 - Construction of Cast-in-place
2008 reinforced concrete chimneys
BIOGRAPHIES
Bachelor of Engineering in Civil
Engineering from Mysore University and
Master of Technology in Industrial
Structures from NIT –Suratkal. Has over 20
years’ experience in Industry and involved
in detail engineering of many power plants.
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Volume: 05 Special Issue: 20 | ACCE : REDECON-2016 | Nov-2016, Available @ https://www.esatjournals.org 92