6533 PART2

8/2/2019 6533 PART2

1/25

IS 6533 ( apart 2 ) : 1989

Indian StandardCODEOFPRACTICEFORDESIGNANDCONSTRUCTIONOFSTEEL CHIMNEY

PART 2 STRUCTURAL ASPECT

( First Rev ision )Third Reprint MARCH 1998

UDC 697.8 ( 669.14 ) : 69,001.3

@ BIS 1991

( Reaffirmed 1998 )

8/2/2019 6533 PART2

2/25

Stru ctura l Engineering Sectional Committ ee, CED 7

FOREWORDThis Indian Sta nda rd ( Pa rt 2 ) ( First Revision ) was adopted by th e Bur eau of20 April 1989, after th e dra ft fina lized by t he Stru ctura l Engineering Sectionalap proved by th e Civil En gineering Division Council.This stan dar d _was first published in 1971. on suggestions by pra ctising engineers_ -

Indian Standards onComm ittee ha d been

and representatives ofvarious organ izations in the coun try, the Sectional Committ ee decided to bifur cate t he sta nda rd in twoparts, separ at ing s tru ctura l aspects from th e mechanical aspects as follows:Pa rt 1 Mecha nical aspects, an dPar t 2 Structura l aspects.

In this par t ( Pa rt 2 ), the dyna mic effects of wind h ave been included as a check,for resonan ce oscillations.More accur ate meth od of determ ining the na tur al frequen cy of oscillation ha s been included. Many ol thecommonly known formulae a nd calculation steps for design ha ve been deleted to mak e th e code concise.Fu rth er, since the principal load on the chimney is wind load, no increase in permissible str ess is envisagedin this code aligning with th e present line of think ing for wind loads.Atmospheric pollution regulations necessitat e adoption of tall chimneys which r equire strength ening againststresses caus ed by oscillat ion du e to wind action. Altern at ive procedur es ( a ) ma king an appr opriateincrease in th e design wind loading, an d ( b ) indicating the need of strength ening or incorporation of&vices for suppr essing von-Karma n type oscillations are given in Annex A.Certa in meth ods of stren gthen ing, such as welding or ~bolting h elical stra kes to th e top one-th ird height ofth e chimney an d the inst allation of dam ping devices a re recommen ded ( see A-2.2 ).Design an d const ru ction of chimn eys ha ve become specialized field with a lot of scope for res ear ch an dmodifications. It is, ther efore, at tempt ed in this stand ar d t o cover only th e basic requirement s. Thedesigner should u se his discretion in the u se of resear ch dat a available.In the prepara tion of this sta nda rd, considera ble assist an ce ha s been derived from t he following: -

a) BS 4075 : 1978 Specificat ion for steel chimn eys, an db) Str oiteln y Normi E Pr ovila ( SNI P-II-VI-1974 ) USS R ( Soviet Norms on Loads a nd Actions ).

8/2/2019 6533 PART2

3/25

1 SCOPE1.1 This stand ard ( Part 2 ) covers terminology,iohding, materials, structural design, construction,Inspection, maintenance and painting of bothself-supp ortin? and guyed steel chimneys ( with or5%.ithout ininq ) and their supp orting structures.1.2 The d esign of chimneys of cross section othert!:an circular is not included in this standard .1.3 Chimneys in pairs, row s or group s, and thosenear other structures of comparable height maybe subjected to csceptional wind force and par ti-ct:!arly wind indu ced oscillations greater th an thatallowed for in this standard . Appr opriate expertadv ice should , therefore, be obtained in thesecases.I.4 The p urp ose for wh ich the chimney is requiredw::il determine w hether lining, insulation orcladding is necessary.2 REFERENCES2.1 The Indian Standard s listed in Annex B arenecessary adjuncts to this standard.7 STATUTORY PROVISLONS3.1 Comp liance Lvith this code does not relievea;.;- one from thr respon sibility of observing pro-visions as may have bt:en promu lgated by anys+.~rl~rory body and/ or obsrrvlng provincial buiid-mt: bvelaws an d the civil aviation requirementspe:-mining to such stru ctures.4 TERMINOLOGY4.0 ITor the pu rpose of this st and ard , definitionsgi\ -en in 4.1 to 4.40 shall app ly.4.1 Access Door;I door for the clltry of personn el.4.2 Access HooksFi::ings weld ed to a chimney to perm it th eat:.ichment of steeplqjacks equipm ent.4.3 Access Lac lder

4 .4 Aer odyn am ic S ta bi l izerA dev ice fitted to the stru ctural shell to redu cewind excited oscillations by mod ifying vertexsheddings.4.5 Anch or for GuyThe touilda tion for the fixing of guy.4.6 Base GussetsA triangular or trapezoidal steel piate tiscd tothe chimn ey shell and to the base plate.4.7 B a s e P l a t eA horizontal steel plate fixed to the base of achimney.4.8 Bas e S too lA construction comprising two vertical plates( base gussets ) w elded to the chimney shell andto the base plate, supp orting a horizontal platethrough wh ich the h olding down bolts pass andagainst wh ich the bolts can be tightened .4;9 B r a c k e tA construction provid ing resistance to lateral dis-placement of the chimney, and/ or supp orting p artor all of the weight of the chimney.4 . 10 Bracke ted Ch im neyA chimney in which not all external app lied loads( nam ely. wind ) are carried exclusively by thestructural shell and for which brackets are provid-ed to elIsure stability.4.11 Clean Out DoorA door, norm ally at the base of the chimney, tc.permit the removal of flue du st and/ or provideaccess.4.12 C o p e B a n dA steel flat or angle attached to the top o! tilecliimney around its perimeter to give add (Qstrength and corrosion resistance at this lcvei.4.13 Cope-Hood

IS 6533 ( Pa r t 2 ) I 1989

Indian StandardCODE OF PRACTICE FOR DESIGN ANDCONSTRiTCTION OF STEEL CHIMNEYPART 2 STRUCTURAL ASPECT

( First Revision /

8/2/2019 6533 PART2

4/25

IS 6533 ( Pa rt 2 ) : 19894 .1 4 Co r r o s io n T e s t P i e c eA fixed or remov able steel plate insert, generallyof lesser thickness than th e shell of the chimney,in contact with the waste gases and fitted at stra-tegic points where maximu m corrosion is expectedto occur.4.15 CowlA conical or dished cap fitted to the top of thechimney to prevent or minimize entry of rainwater.4.16 Cowl StaysSteel stays wh ich connect the cowl to the top ofthe chimney.4.17 C r a v a tAn upstand fixed to the roof of a building or roofplate to prevent the entry of r_ain water into thebuilding.4.18 Dou ble Skin C h i m n e y.\ chimney consisting of an outer load-bearingsteel shell and all inner steel liner wh ich carriesthe flue gases.4 .19 Doub l ing P la teA plate fixed to th C. shell to reinforce it wh ereincreased stresses occur .4.20 FlareThe bottom port ion of the chimney in the formof a tru ncated cone.4.2 1 Ga l l e r yThe p latform around the shaft for observation andmaintenance.4.22 Guy.\ wire rope attached at one end of the chimneyand anchored at the other end so as to provrd eresistance to the latera l disp lacemen t of the topof the chimney.4.23 Guy B a n d.i steel band/ section fitted around the outside of achimney with provision for the attachment ofguys.4.24 G u y e d C h i m n e y.i chimney in wh ich not all externally app lied:oads ( nam ely, wind ) are carried exclusively by:he structural shell and for which guys are provi-ded to ensure stability.

4 .26 Hold in g Down Bol tsBolts built illto a concrete found ation or sup por t-ing framew ork to prov ide anchorag e at the b:scof the chimney.4.27 I n l e tAn opening in the side ofa chimney to permit rheentry of exhaust gases from connecting flue duct.4.28 Joint FlangeA steel section fitted to the end of a chimney sec-tion to enable section to be connected together4.29 Lateral Supp ortsSupp orts positioned at app ropriate levels withinthe structu ral shell to locate the liners and toallow for their independ ent expansion.4.30 LinersFlue ducts contained within a structural shell.4.31 M u l t i f l u e Ch im n e yA group of two or more chimneys within a struc-tural framework or a group of two or more linerswithin a structural shell.4.32 N o m i n a l C h i m n e y D i a m e t e rInternal diam eter at the top of the steel shell.4.33 Ro o f P l a t eA plate wh ich follows the contou r of the roarround th e chimneys where it passes through theroof. It is also know n as flashing arou nd thechimney.4.34 Se l f - Su p p o r t in g Ch im n e yA chimney in which externally app lied loads( nam ely, wind ) are carried exclusively ~by thestructural shell and wh ich together with thefoundation, will remain stable und er all designconditions w ithout add itional sup port.4.35 Sta c kNormally the straight portion of the chimney.4.36 S t a yA rigid member providing both tensile and com-pr essive resistance to the lateral disp lacement otthe chimney.4.37 S t a y e d C h i m n e yA chimney in wh ich not all externally app :lpdloads ( nam ely, wind ) are carried exclusively bythe structural shell and for which stays are pru vl-ded to ensure stability.

8/2/2019 6533 PART2

5/25

4 .39 S t ru c tu ra l S h e l lThe main external steel plate of the chimneyexclud ing any flanges.

5 .7 Guy Ropes an d F i t t ingsGu y rop es sha ll conform to IS 2141 : 1979 andIS 2266 : L970 and sh all be galvanized or protec-ted from corrosion by other su itable m eans.

4.40 W e a t h e r H o o dA hood designed to shed rain water clear of thecravat and prevent its entry into the building.5 MATERIALS

5.8 Other mat erials used in association with steelworks shall, wh ere app ropriate Indian StandardSpecitication for the ma terial exist, conform tosuch specification.

5.1 P l a t e s a n d S e ct i o n s 6 LOADING AND LOAD COMBI NATIONSSteel plates an d sections used in the constructionsof chimneys shall conform to IS 226 : 1975,IS 961 : 1975, IS 2062 : 1984 or IS 8500 : 1977,wh ichever is app ropr iate. Suitable stainless oralloy steels may be used in special circum stances,such as, when the gases are of an extremelyaggressive nature or are at a temperature higherthan 480C bu t the thickness shall otherw ise com plywith the requirem ents of this specification.

6.1 Dead LoadsWhere the unit weight of materials are not known,the dead load shall be calculated according toIS 875 ( Part 1 ) : I987.

5.2 Rive t sRivets used in the constructions of chimneys shallcomp ly with IS 1929 : 1982 ,and IS 2155 : 1982,as app ropr iate. Rivets mad e of high tensile steel,if used , sha ll conform to IS 1149 : 1982.5.3 W e l d i n g C o n s u m a b l e s5.3.1 Covered electrodes shall conform to IS 814( Part 1 ) : 1974, IS 814 ( Part 2 ) : 1974 orIS 1395 : 1982, as appropriate.5.3.2 The bare. wire electrodes for subm erged arcweld ing shall conform to IS 7280 : 1974. Thecombination of wire and flux shall satisfy therequirem ents of IS 3613 : 1974.5.3.3 Filler rod s and bar e electrodes for gas sheil-ded metal arc weld ing shall conform to IS 6419 :1971 and IS 6500 : 1972, as appropriate.5.4 B o lt s a n d N u t sBolts and nu ts shall conform to IS 1363 : 1984.1364 : 1983, IS 3640 : 1982, IS 3757 : 1972, IS6623 : 1972, IS 6639 : 1972, and IS 7002 : 1972as app ropriate. Foundation bolts shall conform toIS 5624 : 1970.5.4.1 Supp ly conditions of thread ed fastenerssha llconform to IS 1367 ( Par t 1 ) : 1980, IS 1367( Part 3 ) : 1979 and IS 1367 ( Par t 6 ) : 1980, asappropriate.5.5 W a s h e r sWash ers sha ll conform to IS 5369 : 1975, IS 5370:1969, IS 6610 : 1972 and IS 6649 : 1972, asappropriate.

IS 6533 ( Pa r t 2 ) : 1989

6.1.1 In calculating dead load s, the weigh t olchimney shell, permanen,t fixtures such as, ladders,platforms, baffles, and gu ys ( if any ) shall be in-cluded . The w eight of flue lining shall he treatedas a separ ate load for the pu rpose of JlJacicombinations. The flue lining shall not be assum edto increase section mod ulus of th e shell nor resistovertur ning du e to its lateral bending stiffness orstrutting action.6.2 I m p o s e d L o a d sImposed loads on platforms shall be taken at therate of 300 kg/ m2.6.3 Wind LoadsThe w ind loads shall be calculated in accordancey$; the provisions contained in IS 875 ( Part 3 ):

6.3.1 Wind force on ladd ers and other fixture:fixed to a chimney shall be determined and addedto the force on the chimney.6.4 E a r t h q u a k e L o a d sUnless otherw ise specified, the provision containedin IS 1893 : 1975 sha ll ap ply .6.5 Load CombinationFor the design of chimney and its found ation, anyof the followin g load combinat ions wh ich producrmaximu m forces and effects and consequen tl!maximu m stresses shall be ~chosen:

a) Dead load + wind load,bj Dead load + earthquake load,C) Dead load -+ load d ue to lining + impu -sed load on service p latforms + windload, or

8/2/2019 6533 PART2

6/25

I S 6 5 3 3 ( Pa r t 2 ) : 1 9 6 97 DESIGN7.1 Ge n e r a lFor the design of chimney shell and other com po-nents o f chimney in steel, the relevant pro visionscontained in IS 8 0 0 : 1984 shall he ap plicable inconjunction with the provision of this standard.7.1.1 The pr ovision s covered in IS 800 : 1984regard ing the following shall, how ever, be sup er-seded by the requirements of this standard:

a)bjC)4e)

Minimum thickness,Allowable deflection,Allowan ce for corrosion,Allowance for temperature,Allowable comp ressive stress in circularshells due to direct force a nd bendingmoment, and

f ) Stresses du e to earthqu ake.7.2 Basic Dim e n s io n s7 .2 .1 The basic dim ensions of the chimney,nam ely, clear diam eter, height, etc, are decidedon considerations of temp eratur e, compo sition offlue gases, ad jacent structu res, pollu tion control,dr aft requirem ents, etc, with Part 1 in accord ancewith this stand ard . Neverth eless, certain recom-mended proportions should be maintained for thestrength and stability of the chimn ey.7.2.2 The clear diameter of the chimney is thenom inal d iameter of the shell if the chimn ey isun lined or par tially lined. For fully lined chimn eythe clear diam eter shd ll be th e clear diam eter ofthe lining at the top. The fully lined chimn eyshall have a minimum clear diameter of 500 mm.If, for technological reasons, it is necessary tohave a smaller diameter, the top opening shall beredu ced by constricting the passage locally.7.2.3 A self-supp orting chimney of height 43 mand above shall be p rovided with a flare at thebase to achieve better stability.7.2.4 Propor tions of the basic dim ensions of aself-supp orting chimney shall conform to thefollowing:

a)b)

Minimu m height of flare be equal to one-third the height of the chimney.Minimum outside diameter of unlinedchimney shell at top be equal to one-twentieth of the height of cylind ricalportion of chimney and for lined chimneyit shall be one-twenty fifth of the height ofthe cylind rical por tion.

7.3 Min im u m T h ic k n e ss o f S t e e l?.3.1 Chimney ShedThe minim um thickness of the stru ctural chimneyshell in single or mu ltiple shell constructions, shallbe the calculated thickness obtained fromstress and deflection considerations plus thecorrosion allowan ce ( see 7.5 ), ;but shall not beless than 6.0 mm nor less than l/ 500 of theoutside d iameter of the chimney at the consideredheight.7.3.2 Chimney LinerThe minim um thickness of the steel liner in adou ble skin or mu ltiple construction shall be thecalculated thickness obtained from stress conside-rations plu s the corrosion allowance, but shall benot less than 6.0 mm .7.3.3 Supporting SteelworkThe minim um thickness for hot rolled sectionsused for external construction exposed to theweath er shall be 8.0 mm , and for constru ctionsnot so exposed and ancillary steelwork, 6.0 mm .These provisions do not apply to the webs ofIndian Standard rolled steel sections or to pack-ings. The min imum thickness of hollow sectionssealed at the ends, used for external constructionsexposed to the weath er or other corrosive influen-ces shall be 4 mm , and for constructions not soexposed shall be 3 mm.

-7.3.4 Angle FlangesThe minimu m thickness of jointing flanges tochimney shall be 6.0 mm .7.4 Allowable DeflectionThe maximu m deflection at the top of the steelchimney prod uced by the wind load withouttaking into account the dyn amic factors, calcula-ted as acting on the circular cross section shall notbe greater than h/200. Where h is the unsuppor-ted height of the chimney.7.5 Allowan ce for CorrosionThe total allowance for corrosion shall be the sumof the extern al ( TBe ) and in ternal ( rCt ) allow-ances given in Table 1. This total allowan ce shallbe add ed to th e thickness of shell obtainedfrom th e calculation s of the stresses and d eflection.Internal flanges shall have corrosion allowan ceI OiP and external flanges corrosion allowan ce T,,except if they are encased.

NOTE - How ever, a lower corrosion allowance ~thanspecified in Table 1 may be ~adopted at the discretionof the designer/owner, if it can be ensured that theproperties of flue gas and its effect on the chimney shell

8/2/2019 6533 PART2

7/25

IS 6533 ( P ar t 2 ) : 1989T a b le 1 Co r r o s io n Al lo wa n c e T ,, a n d T e l ,

( Clause 7.5 )Degree o f C o r r o s i o n E x p e c t e d

a) External, Ire-e1) None ( that is, paint, insulation, cladding orsimilar protection available always )

2) Above average ( that is, unprotected )b) Internal, ICI

1) None ( such as, non-corrosive flue gases or thestructural shells of multiflue chimney )2) Average ( such as, lined, insulated or naturalgas fired )

r-- __h____-7 C----h_- -- _10 yrs 20 vrs 10 yrs 20 yrsNil Sil Nil Nil

1 0 15 3Nil NII Nil NilI 2 1.5 32 2 3 5) Above average ( such as, unprotected coal fired )

KOTES1 The internal corrosion allowance for the exceptional degree of corrosi(,n shall be as mutually agreed betweenthe purchaser and the designer, based on the desired life of thf, chimney.2 No corrosion allowance need be provided if the chimnvv shrli i> mad r of Ltainlr,s steel.3 Partly lining the inside chimney with stainless steel dorb IIU[ elililin,ltl~the condensed cWuent passing down to chimney. :hr possrbility of corrosion because ofThe same is *l,)r I((08fi:111( it>d.

Corrosion Allowance, i n m mc--- ----_--_.*___----__,_____.Copper Bearing Steel Non-copper Bearing Steelr----- *----_7 r____h-__-~Design Life Design Life

T a b le 2 E f fe c t iv e He ig h t o f Ch im n e y Sh e l l( Clauses 7.6 and C-l ;__._.__. _. --.- .--.----. ___

Description Effective Height, he /--.II- elf-supportingchimney

SupportedEhimney,tixed base

Supportedchimney, pinnedbased

For stresses in BCie = bFor stresses in ABie = 085 0

For stresses in BCle = bFor stresses in ABhe = a

8/2/2019 6533 PART2

8/25

IS 6533 ( P ar t 2 ): 1989

7 .7 M a x im u m P e r m i s s i b le S t r e s s i n t h eS h e l lTo control buckling, the compr essive stress causedby the combination of extrrme fibre stresses dueto bending and direct load for the load combina-tion given in 6.5, shall not exceed values specifiedin Table 3 for steels conformin g to IS 226 : 1975and IS ?W2 : 1984. The values shall be reducedfintiler 11nt~~.essary for temperature and calculatedwith tlie corrosion allowance ded uced from thethickners I.7.7.1 For steels other tha n IS 226 : 1 9 7 5 atld1s (JO : 1%; , nt,iximilrll pernlisR:ble stressessh:~ll tic olltarrred b\ . rn;l!tiplyirig the values inT;Il)le : by the facrnr I;,- / J,. \ \ .here I;,. is theguar arlterd yield stress 01 ctt,el u sed and ,,, ~ IS the~ua ra;.trrd vield stres-: 01 stc-cl1c 22(j 15 of6l tlilt is 1-t conforrnirg toI, LbIJ) , &. I Xlla.7.7.2 The ma ximu m pet-rnissil)le stresses given inTable 3 have been lvorktd out in accordarlce xviththe formulne gtven in Anuex C.7.8 Al lo w a n c e f or T e m p e r a t u r e7.8.1 Masimum permissible stresses as obtainedin 7.7 shall be corrected for the most adv ersetemperature conditions to which the mem ber orpart may reasonably be expected to be exposedby multiplying with the appropriate temperaturecoefficient Kt given in Table 4. The expectedtemperature of steel components shall not beallowed to exceed 4 0 0 %.

In case of steels other than IS 226 : 1975 ,LI;~IS 2062 : 10%:. n~aximu m permissible stresses a\obtaine d from 7.7.1, shall shall be red uced basedon temp eratu re coefficient factor Kt obtairlri! b\dividing yield stress at the operating temprra~ ~rr~-by the yield stress at 20C.7.9 O t h e r S t r e s s e s i n S t e e lAllowable stresses in axial tens.on, shear .,t!clbearing shall be as specified in IS IWO : lS18.1.7 .1 0 In c rea se i n S t r e sse sFdu- load combination involving earthquake, ::?rperm issible stresses ma y be exceeded by 3,:j per-cent provided the steel thickness shall neither beless than the minimu m thickness specified norwhen the earthquake loads are neglected.

7.11 Al lo w an ce fo r La r g e O p en in g s i n sh e l lThe allowable stresses app ly to the shell platesafter due allo\ vance for rivets and bolt holes.LVhere large apertur es are cut in tne shrll pl,?tes,as for inlets or inspection pan els, a strrrl,turalanalysis of the stresses shall be nlade alid ctrm-pensating material provided, as required. toensure that the stresses specified in the standar dare not exceeded. Apertures in the shell plates,other than flue inlets, shall have the cornersrounded to a minimum radius of 10 t, where / isthe thickness of the plate.

T a b l e 3 M a x im u m P e r m i s s i b le S t r e s s f or C i r c u l a r C h i m n e y s( &u s~-.~ 7.7, 7.7.1, 7.7.2 a n d C- l )

Ratio Maximum Permissible S t r e s s in MPa, for D/the/D ~__--___-________-____-*.--_--____----_-_______-_~140 150 160 li0 180 190 200 225 250 301) 350 400 450 500and1CSS

up IO 20 126 124 123 120 118 115 112 105 99 87 78 70 64 5830 108 107 105 103 101 99 96 90 85 75 67 60 55 5040 89 88 86 85 83 81 79 74 70 62 55 50 45 4150 72 71 70 69 68 66 64 60 57 50 45 40 37 :j-cCiO 59 58 57 56 55 54 52 49 46 41 36 33 30 2770 48 48 47 46 45 44 43 40 38 33 30 27 24 280 40 40 39 38 37 37 36 33 31 28 25 22 0 10i)O 33 33 33 32 31 31 30 28 26 23 21 19 17 11;

100 28 28 28 27 26 26 25 24 22 20 18 16 14 I .i110 24 24 24 23 23 22 22 20 19 17 15 13 12 1 II20 21 21 20 20 19 19 19 17 16 14 13 12 11 IO130 18 18 18 17 17 17 !6 15 14 13 11 10 1 ti140 16 16 15 15 15 15 14 13 12 11 10 9 8 7150 14 14 14 13 13 13 13 12 11 10 9 8 7 7

8/2/2019 6533 PART2

9/25

IS 9333 ( P ar t 2 ) x 1999T a b le 4 T e m ie r a tu r e Co e ff ic i e n t , K t 8.2.3 Static wind force acting at the midp oint of

( Clause 7.8.1 ) Ktb zone ( X varying from 1 to r ) shall be cal-culated from the formula,Temperature, C

-L_-_-_-, P--v-m &k - c qk hk dkO-200 250 300 350 400Kt 1.0 0.75 067 06 05 where P&k = static wind load acting at the mid-NOTE - Intermed iate valuea shall b e linearly inter- point of Kth zone, in N;polated. qk = static win d pressu re at the mid-point of Kth zone, in Pa;

7.12 De f le c t io n S t r e s se sIf the chimn ey carries a vertical load other thanits own weight, du e for examp le, to the reactionof guys, lining or an imposed vertical load so thatan app reciable compressive stress results, deflec-tion du e to wind may cause the axial load tobecome eccentric, the bend ing momen t so produ -ced shall be d etermined, added to that from thewindload and any other live or dead load andused to calculate the combind stress wh ich shallnot exceed th ose specified in 7.8. This procedureis necessary only if the total axial load producesstresses greater than one-third of the bend ingstress due to wind.

hk = height of Ktb zone strip, in metres;dk - external diameter of chimnev ofKth zone, in metres taking intoaccount strak es, if fitted . Forchimney with strakes, this shall

be 1.2 times the external diameterof the chimn ey shell; andc = shap e factor for chimney wh ichmay be taken as 0.7 for the por-

tion with circular cross section,without strakes.

NOTE - For other shapes, surface conditions, attacb-merits, line platform, hand rails and for groups ofchimneys on suitable sh ape factors shall be taken.7 .1 3 Fa c to r o f Sa f e ty f o r Gu y Ro p e s a n d 8.3 Ca lc u la t i o n o f Dy n a m ic Win d L o a d sF i t t i n g s 8.3.1 In case of self-sup ported chimneys, if theA minimu m factor of safety of 3 shall be adopted period of natu ral oscillation for the chimney in the design of guy ropes and other fittings. computed as given below exceeds 0.25 seconds,

7.13.1 For guyed chimn ey, it is ne cessary tothe design wind loads shall take intoconsideration

establish th e safety of the chimney shell and guys the dynamic effect du e to pu lsation of thru stfor the forces ind uced du e to temperatu re effect. caused by wind velocity in add ition to the staticwind load calculated un der 8.2.3.7.14 F o u n d a t i o n The natu ral frequen cy, first mode, for a chimneyThe foundation shall be designed for the worst of varying d iameter or thickness, shall be calcu-combination of loads specified in 6, such that the lated by dividing the chimney into a num ber ofresulting pressure on the subsoil by consideiing convenient zones as given in 8.2.2.the dead weight, movements and horizontal forces,is limited to safe bearing capacity of the soil. gZ(mx) tNecessary care should be taken on the effects of

The frequency f = -& [ B ( mxa ) 3the temperature and seasonal changes. where8 DESIGN CALCULATION m = mass of the zone including the lining or8.1 General covering, in kg;Design of chimney shall be such that the stresses x = d eflection of the same zone du e to thein any p art of the chimney do not exceed force equ al to gravity acting on its massthe values specified in 7 for the loads an d load nofmally at the mass centre with thecombinationsgiven in 6. base fixed and top free, in metres; and

=8.2 Ca lc u la t i o n o f S t a t i c Win d L o a d g rate of gravitatio nal acceleration = 9.8m/se.8.2.1 Static wind pressure, q, acting normal tothe surface of chimney shall be taken as specified 8.3.2 Dynam ic effect of wind is influen ced by ain IS 875 ( Part 3 ) : 1987 for the appropriate nu mber of factors, su ch as, mass and its disp osi-wind zone, terrain and topography. tion along chimney height, period and mode ofnatu ral oscillation. 1ogaGthmic decrement of8.2.2 To determin e the wind force acting atdifferent heigh ts of chimney, the latter shall be damp ening, pu ls&on >f velocity thrust, etc.Values of dyn amic componen ts of wind load

8/2/2019 6533 PART2

10/25

IS 6533 ( Pa r t 2 ) : 196 3Inertia force Pa,, in N acting at the centre of thejth zone of the chimney in the ith mode ofnatu ral oscillation is determin ed as follows ( seeFig. 1 ):

Pwv 11= Mj % WVwhere

Table 5 Coeffic ient of Dynam ic Xdiuenc e5, fo r S tee l Ch im n eys( Clause 8 . 3 . 3 )

t ;l Values of Q forc _-_--h ---_~Lined UnlinedChimney Chimney

Mi = mass of the jth zone in kg concentra-ted at its centre,

El - dynamic coefficient in accordancewith 8 . 3 . 3 ,rl l l = ded uced acceieration in m/G of thecentre of the jth zone taken in accor-

dance with 8 . 3 . 4 , an dv E coefficient which takes care of the

space correlation of wind pu lsationspeed according to height and vici-nity of building structures and istaken in accordan ce with 8 . 3 . 5 .

0 1.20 1.300025 170 2500050 190 3100075 210 3500.100 230 3750125 245 4100.150 260 430XJ.175 270 4500.200 275 470

NOTE - Intermediate values may be linearly inter-polated.

Pdyn,j - M j-4-l Yijyi2

yil

Fro. 1 DESIGN SCHEMEOF CHIMNEY IN THE ithMODE OF O~CILT+TION8 . 3 . 3 Dynamic coefficient 51 ( for lined andun lined chimney ) is determin ed from Tab le 5depending on the parameter 51 :

Tl vbEl = -1 200

8 . 3 . 4 Dedu ced acceleration 711, in m/ss is deter-mined according to formula:

yn i r lk P&k. mkk-1rlll = r2 rik. Mkk=l

whereMk 5= mass of the kth zon e, in kg;

Tr1, r l k = relative ord inates of mode shap ecorrespond ing to the centres of jthand kth.zones in the jth mode ofoscillation. In special cases involv-ing the interaction of soil structureaffecting the mode shap e conside-rably, the relative ordinates shallbe accordingly calculated.;

P etsk = wind load on the kth zone deter-min ed accordin g to 8.2.3;I = nu mber of zones into which thechimney is divided; an d;

mk - coefficient of pulsation of speedthrust for the centre of the kth zone,taken as in Table 6.8.3.5 The value of coefficient v shall be tak enfrom Table 7 depending upon the parameter El asgiven in 8.3.4. For stru ctures of cantilev er type, vshall be taken on ly for the first mode of natu raloscillation. For higher modes, v shall be takenas 1.8.3.6 While determinin g the wind load on thechimney, consideration of the first mode ofnatu ral oscillation is sufficient. It is recommen ded

8/2/2019 6533 PART2

11/25

Tab le 6 Coeff ic ie r l t o f Pu l s a t ion o fS p e e d T h r u t s , m k

( C laus e8.3.4 )Type o f Heigh t Above Ground Leve l , in mLoca t ion c--_----~-----~Up to 20 40 60 100 200 350 and10 above

A 060 055 048 046 042 038 035B 0.83 0.75 065 060 054 0.46 040NOTES1 Type A relates to open locations ( Stdppe, desert, seacoast, lake, reservoir, etc ).2 Type B relates to outskirts of town, widespreadforest and its like, regular obstacks of height morethan 10 m.

Tab le 7 Coeffic ient Y( C laus e8.3.5 )-

b Heigh t o f Ch imn ey , in mc--- ---_---* -------Up to 60 120 150 300 450 and41 45 above< 005 070 0.65 060 055 0.45 -

01 - 075 065 060 0.50 0.400.2 - - 0.75 070 060 0.50

NOTE - Intermediate values may be linearly inter-polated.

8.3.7 Total design lateral force ( pk ), bendingmom ent ( Mk ) and d eflection ( rk ) du e to windload should be computed from static and dynamiccalculation s correspond ing to the ith mod e ofnatural oscillation and sum med up according tothe following formulae:S

pi, = P&k +Yl c ( PUyn.k 1i-1

I s.\ fk = Al,t,k + (Mdymk )

c rdy>k )i=lwherePst,k and Pdymk =

221 st ,k and Mdymk =

the static and dynam icwind load acting at midpoint of kth zone, respec-tively;

dynamic transverseforce, bendingmoment and de-flection du e todynamic wind-lc-1( see 8.3.2 ).

8.5 Hold ing Down Bo l t sbending moments du e to The maximum stress in holding down bolts

IS 6533 ( Part 2 ) : 1988r&k and r d y n , k - deflections du e to static anddynam ic wind pressure

respectively at the kth zonewith respect to the originalposition; and

s = num ber of mod es of oscilla-tion .8.4 C h e c k fo r R e s o n a n c e8.4.1 In case of self-sup porting chimney, checkingfor resonance shall be carried out if the criticalvelocity V,, as determined from Annex A is with-in the range:

a) C.5 to 0.8 times the design win d velocityfor lined chimneys, andb) 0.33 to 0.8 times the design wind velocityfor the un lined chimneys.

8.4.2 For lined chimneys, checking for resonanceshould be carried out for both the cases, that is,with and without lining.8.4.3 Design force F, bending moment 116 anddeflection Yat level t du ring resonan ce shall bedetermined by formulae:

F = 2/ li= ress $_ ( Fat,e + Fdyn,Z )--

M=d

M2resm + ( MBt,z + Mdymz J2

Y= d P remz + ( r&z + rdyD,Z )where

F rem29 Mles,z and Y,:,,, o tran sverse force,bending momentand deflection atresonance respec-tive!yat level z ( SE Mdynyzand rdyn:z =

force, bendingmoment and de-flection du e tostatic wind load( see A-6 ); and

8/2/2019 6533 PART2

12/25

IS 6533 ( P 8rt 2 ) I 19898.6 De s ign of Base P la teThe m aximum stresses in the base plate andstiffeners and bearing pressur e on found ation shallbe calculated for the worst combination of loadingand shall not exceed the perm issible values inaccord ance with the relevant prov isions ofIS 800 : 1984 and IS 456 : 1978.9 STABILITY9 . 1 S t ru c t u re9.1.1 The stab ility of the str ucture as a wh ole orany part ofit shall be investigated and calcula-tions shall be mad e to show that the stressesimposed by 1.6 times the total of win d load plusany stress increasing imposed loads, less 0 9 times-the minimu m dead load excluding any stressredu cing imposed loads, will not exceed I.8 timesthe allowab le stress specified.

1.6(u, + 0,) - 09u, < 1.8~wherecw ~=istress produ ced by wind load,

bm - stress prod uced by any other load whichmay act to increase the combined stress,ae = stress produ ced by d ead load and anyother load which acts at all times andwill redu ce th e combined stress, andQa = maximu m perm issible stresses at the

operating temperature.9.1.2 To ensure -stability at all times, accountshall be taken of probable variations in deadload du ring construction, repair or other similarwork,9.1.3 Wh ile comp utin g the stability, it sha ll beensured that the resulting pressure and shearforces to be transferred to the supp orting soilthrough found ation, will not cause failure offoundation.

9.2 S t r u c t u r e a n d F c u n d a t i o n s9.2.1 In the case of gu yed or laterally sup portedchimneys, the stability of the structure and foun-dation as a whole or any p art of it shall be inves-tigated and weight or anchorage shall be prov idedso that, without exceeding the allowable m aterialstresses and found ation bearing p ressure, 0.9 timesIhe least restoring mom ent includ ing an choragewill not be less than the sum of 1.1 times themaximum overturning moment due to stress-increasing dead loads, less O-9 times that du e tostress-redu cing loads, plus 1.4 times th at du e towind and imposed loads, that is

1.4 Mw + 1.1 M, - 09 M, < 0.9 M,,where

M ,,, = overturn ing mom ent prod uced by deador other loads which may act to in-crease combined moment,

Me = overturning moment prod uced by deador other loads which act at all times toreduce combined moment, and121, - resisting mom ent prod uced by thefound ation withou t exceeding theallowable material stress and thegroun d stress withou t exceeding thefoundation bearing pressure.

9.2.2 In the case of self-supp orting chimney, thestability of the stru cture as a wh ole shall be inves-tigated and weight or anchorages shall be soprop ortioned that the least resisting mom ent sh allbe not less than the sum of 1.5 times the maxi-mum overturning moment due to dead load andwind load/ earthquake load.10 MISCELLANEOUS COMPONENTS1 0.1 Bas e P l a t e an d Ho l d i n g Do wn B o l t sHolding dow n bolts shall be adequately tightenedwith approp riate precau.tions using washers andlocknu ts to preven t the stripp ing of thread s andthe base plate shall be prop erly grouted . Typicaldetails of base plate and holding dow n bolts areshown in Fig. 2.10.2 Base Gussets and ~StoolsWhere base gu ssets or stools are used, they shouldpreferably be evenly disposed aroun d the chimneyshell. Smaller second ary gussets may be prov idedbetween the main gussets. Base gussets shall beof am ple height an d shall extend to the edge ofthe base plate. The angle of th e sloping edge ofany gu sset to the horizontal shall be not less than60. The minim um thickness of the gusset shallbe 8 mm.10.3 Chimney HeadThe chimney head shall be strengthened in asuitable m anner on the basis of the design andshall have pr ovisions for the attachment of erectionand maintenance equipment.10.4 Galleries and PlatformsGalleries an d platforms for erection and serviceof warn ing lamps, earthing, inspection, etc,should be provided around the chimney wherevernecessary. Their~width shall be at least 800 mm.These shall be prov ided with hand rails of height,I The num ber and location of galleries andp?itforms m ay be mutually decided between thedesigner and ~the customer.10.5 Inspection/ Cleaning DoorSuitable door for access near the base, to theinside of the chimney shall be prov ided for thepu rpose of inspection of the inside of the chiml!eyand also for ash r emoval. The minimu m size cf

8/2/2019 6533 PART2

13/25

IS 6533 ( P ar t 2 ) : 1969STIFFENER CUT FROM(FOR EREAC3 OPENIN

CHIMNEY SHELL

STIFFENER PLA(12mm THICK)

ANCHOR CHANNEL ISMC 150

STIFFENER PLATE CNIYNEV SHELL

ZA WELDED BASE

FOUNDATION BOLT

28 RIVETED BASEAll dimensions in millmetres.

FIG. 2 TYPICAL DETAILS OF BASE OF Sr ~e t CHIMNEY

2

ARRANGEMEYI

8/2/2019 6533 PART2

14/25

IS 6533 ( P ar t 2 ) : 19891 0.6 P r o t e c t io n Ag a in s t L ig h tn in g 1 0 .9 Rig g in g Sc r e ws ( T u r n Bu c k le s )The chimney shall be provid ed with lightningprotection arrangem ents in accordance with Rigging screw s sha ll conform to IS 3 121 : 1965.IS 2309_: 1963. These shall be provid ed with lock nut s to preven tslacking back.10.7 W a r n i n g L a m p sSuitable war ning lamp s shall be provid ed. Therecommended number and position of the same,dep ending up on the height of the chimney is givenin Fig. 4. Whenever only one w arning lamp isshown in the figure, 2 numbers of lamps have tobe provid ed d iametrically opp osite to each other.r0.7.1 Existing local and aviation regulations, ifany, sh ould be followed ( see 3.1 also ).10.8 Ba f f l e P l a t e s

1 0.1 0 S t e p s a n d L a d d e r s

10.10.1 Steps10.10.1.1 ypical connection details of steps tochimney shell are shown in Fig. 5.

When there are two or more breach openings orflues entering the chimney, baffle plates shall beprovid ed to prop erly direct the gases from flueduct up the chimney and prevent them frominterfering with the op eration of the other flue.These baffles shall be prop erly insulated .

10.10.1.2 The step s shall be weld ed to the outsideof the chimney at a spacing of 3 000 mm. In thecase of shafts of clear diam eter of 300 mm andmore, a second row of steps shall be weld ed onthe diam etrically opp osite side. Proper anticorro-sive measu re or alternatively, prop er selection ofmat erial for the steps shall be adop ted keeping inview the location in the chimney -and the extentof corrosion involved.

l - 5 n - l

Podion of

a

Height of Lamp in m for Chinwey Height hLmP ~__-__~-__--__--_h_-I--------L----~~--__~3200 5600 63.00 70.00 8000 9000 10000 110.000 3050 5440 6100 6850 7650 6650 9850 108.00b - 2760 3 150 33.50 9850 4350 4850 73.50G - - - - - 38.50

8/2/2019 6533 PART2

15/25

+---qqi!ELEVATION STEPS

I I L250

-&0LSTEPS INSIDE CHIMNEY(WITH LINING 200)

All dimensions in millimetres.FIN. 5 STEPS FOR STEEL CHI MN EYS

10.10.1.3 On th e inner side of the chimn ey, stepsmay be welded at a spacing of 300 mm. If thesteps are to be d irectly supp orted on the lining,the lining should have a minimum thickness of200 mm. Where the lining is thinn er than theabove, the steps shall be welded direct to the shellwith adequ ate clearance when the lining does notexpand along with the shell. In case where the

IS 6533 ( P a r t 2 ) : 198910.10.2 LaddersTypical connection details of ladd ers are shownin Fig. 6.

LADDER RUNGAT 200 mm C/

All dimensions in millimetres.FIG. 6 TYPICAL CONN ECTIONDETAILS FOR

LADDER10.10.2.1 Steel ladd ers may also be provided inadd ition to steps. Safety enclosure or cage shall beprovided for chimn eys taller than 20 m~startingfrom~a heigh t of 3 m from ground.10.10.2.2 If individ ual section of a ladd er exceeds20 m in height, an intermed iate landin g platformshall be provided.10.11 P o s i t i o n o f Gu y s10.11.1 Guys shall be positioned sufficiently belowthe outlet of the chimney to avoid the corrosiveaction of the emergent combustion produ cts. Aminimum distance of 3 m is recommended . Thereshall be aminimum of three guy ropes to each set,guys shall be positioned radially in plan and theangle between any adjaeent pair of guys shall notexceed 130. Th e guy ropes shall not exceed anangle of 60 to the horizontal.11 CONSTRUCTION1 1 . 1 Gen era lThe fabrication and erection of steel chimneys,guys, etc, shall generally be in accordan ce withIS 800 : 1984. For we lded chim neys, weld ing sh allbe carried out in accordan ce with IS 816 : 1969and IS 9595 : 1980.11.1.1 Non -destructive testing of weld, if requ ired,may be carried out as mutually agreed betweenthe parties concerned.11.2 Erection Tolera nceThe variation in the eccentricity of the axis ofchimney from the vertical at any level shall notexceed l/l 000 of the height, at th at particularsection.11.3 Clearance

8/2/2019 6533 PART2

16/25

IS 6533 ( Pur 2 ) t 1969accommod ate the movement of the chimney andto limit the transfer of heat. Normally, an air gapof 50 mm is desirable. Flexible heat resistantpacking may be used to fill the gap, if necessary.11.4 S ea l ingRiveted chimneys shall be caulked, specially ifcondensation is likely to occur.11.5 Gas T i g h t n e s sNO gaskets shall be used in jointing flanges onstructural steels.

NOTE - Liquid ,sealants *are recommended to ensuregas tightneu and prevent corrosion in the meetingfaces.10.6 Er ect ion Ten s ionThe amount of pretensioning applied to the guyropes on site shall b e in accordan ce with theapp ropriate design .considerations and may bemeasured w ith a suitable instrument. The tensionin the guys after erection shall be not less than15 percent nor more than 30 percent of the calcu-lated maximum tension d ue to wind.12 INSPECTION AND MAINTENANCE12.1 All steel chimn eys shall be inspected an dexamined at least once a year.12.1.1 In case of unin sulated and un lined steelchimneys, the thickness of the shell should bedetermin ed by either ultra-sonic thickness testingor by drill testing. At the same time, any decora-tive or other surface finish on the exterior of thechimney may be examined. The intern al surfaceof large diam eter steel chimneys may also be ins-pected p referably by close examination from apain ters trolley or similar mean s of supp ort.121.2 Lined chimneys should also be inspectedinternally by close examination from a pain terstrolley or similar means of sup port to ascertainthat the lining is still in serviceable condition andfulfilling its task.12.2 The details of the pain ters trolley are givenin Fig. 7 for inform ation . For chim ney of dia mete rexceedmg 3 m at. the top, two such painterstrolleys should be provided.12.3 Flanges should be inspected to see if there isa builddup of rust between them as the pressure ofrust build -up can overload the bolts/rivets in ten-sion. In bolted connections, particular attentionshould be given to th e conditions of the bolts.Selected bolts in critical areas should b e removed,inspected, tested as necessary and be replaced withthe new bolts. Should the examin ed bolts be ser-viceable, these shall not be reused.

12.5 Wh ere loose fill is used for insulation, this.should be inspected at three monthly intervals inthe first 12 month s and then annually. The loosefill should be checked to en sure that it has notcompacted and , if necessary, it should be toppedUP-12.6 Detailed record should be submitted aftereach inspection d escribin g any recommendedmaintenance.

12.7 Guy wire and fittings, wh ere present, shouldbe examined for security tension and , if-necessary,.be cleaned and greased.13 PROTECTIVE TREATMENTS1 3.1 S u r f a c e P r e p a r a t i o n fo r P a i n t i n gConsideration should be given to the surface pre-paration an d protective treatment of both theexterior and interior surfaces of chimney shells inorder to prolong the life and im prove the appear-ance of the chimney. Immed iately before apply-ing any protective treatment to the exterior or theinterior surface of a steel chimney shell, thesurface shall be cleaned by chipp ing, scrapp ingand wire brush ing, or by other mean s to removeall dirt, loose scale, grease, rust or other delete-rious materials.13.1.11 Pretreatment and p ainting of chimneyshell parts shall generally conform to the requ ire-men ts of I S 1477 ( Part 1 ) : 1971 and IS 1477( Part 2 ) : 1971.13.2 Painti ng of Inte rior Surf aces13.2.1 Unlined Chimney ShellThere is generally no advantage in applyin g aprotective treatment except for the application ofone coat of suitable priming paint to theinterior surface of an unlined chimney shell unlessit can be shown that such treatment will withstandthe corrosive, abrasive an d thermal effects of theflue gases and thus p rolong the life of thechimney.13.2.2 Lined Chimney ShellWhen it is thought desirab le to use a protectivetreatment on th e interior steel surface of a linedchimney, such treatment shall consist of the appli-cation of one coat of a suitab le priming pain tfollowed by two coats of a finishing paint or pain tsapplied in accordan ce with the instructions of themanufacturer.13.2.3 MultiJue Chimney Shells

8/2/2019 6533 PART2

17/25

IS 6533 ( Port 2 ) I 1989

//,

1 C m. n

CMMI(IEV SHELL

BENT ICI SHAPE

Trolley TrackAll dimensions in millimetres.

Fro. TYPICAL ETAILSOFPAINTER'SROLLEY ARRANGEMENT

8/2/2019 6533 PART2

18/25

IS 6533 ( P ar t 2 ) t 198913.2.4 Chimney Shells wit h Monolithic LimngsThe interior steel surface of a chimney wh ich isto be given a monolithic lining needs no furtherprotective treatment. The surface shall, how ever,be clean an d dry immed iately before the ap plica-tion of the lining.13.3 Paintin g of Exterior Surfaces13.3.1 Exposed Steel SheetImmed iately after the surface prep aration outlinedin 13.1 has been completed, the exterior surfaceshall be given a coat of suitable priming pain tfollowed by one coat of finishing pain t ap plied inaccordance with the recommend ations of theman ufacturer of the -particular paint. A final coatof paint shall be app lied after erection.Special attention should be paid to the up perportion of the exterior surface, that is, for a dis-tance of 1 to 2 times the chimn ey diam eters dow nfrom the top w here only those protective treat-ments should be app lied which are best able towithsta nd the corrosive action of the emergingflue gases.13.3.2 Shell w ith External CladdingShells with external clad ding shall complywith 13.3.1 except where the cladding orinsulation is fitted at the works in wh ich case thefinal coat of pain t may be omitted.13.3.3 Mult i-Flue Chimney FrameworkWhere a framework forms supp orting structure ofa mu lti-flue chimney, the treatmen t describedin 13.3.1 shall be app lied.13.4 M e t a l S p r a y i n g13.4.1 GeneralThe exterior of a steel chimney may be protectedfrom atmosp heric corrosion by the app lication ofa sprayed metal coating. Aluminium is the pre-ferred metal for this app lication ( certain othermetals have disadvantages when used for hotsurfaces ) .

The initial metal sp ray treatmen t shall be app liedund er controlled conditions before erection andcare shall be taken to avoid d amage during trans-portation and erection.Regions of dam age wh ere the coating has beenremoved over an area, the maximu m width ofwh ich exceeds 6 mm , shall be reblasted and re-sprayed , care being taken to, avoid dam aging or

13.4.2 SpecificationsSurface prep arations and metal spraying sha ll bedone in accordance with the requirements stipula-ted in IS 6586 : 1972. Recognized pra ctices d epen-ding on the surface temp eratu re of shell mayalso be taken in account.13.4.3 Surface Preparation13.4.3.1 It is essential that the blast-cleaned sur-face is sufficiently rough and clean to provid e anadequate key for the sprayed aluminium coating.The amp litude of the blast cleaned surface shallbe ( 0-l f 0.05 ) mm .13.4.3.2 Comp ressed air for nozzle blast cleaningshall be effectively free from oil and moistu re. Thepressu re du ring the blasting process shall be notless than 400 kPa at the nozzle.13.4.4 Methods of Application and Sealing of Coatings13.4.4.1 For shell temp eratur es up to 2OOC, thealum inium spray shall be app lied by the electricarc or flame spraying process.13.4.4-2 For shell tem per atu res exceeding 200Cthe alum inium coating shall n ormally be app liedby the electric arc p rocess, The flame sprayingprocess may be used if the chimney is not to besubjected to therm al sh ocks frequently prod ucedby gas turbine exhausts.The spray shall be sealed with a suitable siliconebased high temperature paint, app lied as a floodcoat.13.4.4.3 The nomin al thickness of the coatingshall be not less than 0.18 m m.13.4.4.4 Sealing coatsThe sprayed alum inium coating shall be sealed.For temp eratur es not exceeding 150X, certainorganic base sealers or paints are suitable. Specialhigh temp eratur e resistant paint s shall be selectedfor use at temp eratur es exceeding 15OC, that is,resin-modified silicone base paints. Silicone basepain ts shall be used according to the m anu fac-turers instructions.13.4.4.5 Application of sealing coatsSealing coats shall be ap plied to clean drysurfaces. Any oil, grease or other contaminan tsshall be removed by thoroughly washing withthinners un til no visible traces of contaminationexist and the surface sh all be allowed to dry for

8/2/2019 6533 PART2

19/25

IS6533( Pa&2) :1989ANNEX A

( Foreword an d Clau ses8.4.1 and 8.4.3 )WIND EXCITED OSCILLATIONS

A-l GENERALChimn eys are subject to oscillation du e to windaction. This ann ex explains the pr ocedur es toinclude the effects of wind excited oscillations asenum erated and suggests alternative procedur esfor making an app ropriate increase in the designwind loading and indicates when strengthening orthe incorporat ion of devices for sup pressing vonKarman typ e of oscillations is adv isable.A-l.1 It has been fou nd th at chimn eys of circularcross section oscillate strongly across w ind thanalong wind . It is, therefore, reasonable to continuewith the current pra ctice w hich implies that alongwind , th e oscillation will not cause stresses greaterthan those calculated for the wind velocities as.specified in IS 875 ( Par t 3 ) : 1987 du e to staticloading along with dy nam ic coefficient pr oposedin this standard.A-l.2 Lateral oscillation due to resonan ce effectswithin the critical wind speed range at thenatural period of a cylindrical structure may begreat enou gh when its effect is ad ded vectoriallyto the dow n wind deflection, to cause stresseshigher than those calculated for the short durationwind velocities in accordance with this code -du eto static loading along with the dyn amic coeffi-cient as specified in this standard.A-2 VON KARMAN VORTEX SHEDDINGThe regular fluctuatin g side force due to comm onlyknown as Von Karman vortex shedd ing, which maybe prod uced in a sm ooth air flow, will prod ucestrong oscillation at a velocity wh ich gives reso-nance with the natural frequency of the structure.This effect is resisted by high da mp ing and maybe prev ented by helical strakes or other devicesattached to a circular chimney. If the tend ency isstrong, it is not effectively with stood by increaseof strength alone.A-2.1 In a natu ral w ind, the regular vortexshedding may be interfered with by fluctuationof the wind so that the build-up of amp litud e isnot continuou s as in a wind tu nnel, and it may bemor e effectively resisted b y mass an d stiffness.There are different views as to h ow the vortexshedding should be ailowed for in practice bu t itis clear that low dam ping, low mass and large

after constru ction if experience show s them to berequired, and provided that the chimney is mad estrong enough in the first place to withstand theadd itional load from guys or strakes applied later.For instance, h elical strakes of three rails havinga pr ojection of 0.1 to 0.12 times the diam eter ofthe chimney, w ound , equally spaced, roun d theperim eter of the shell a t a pitch of abou t fivetimes the diam eter of the chimney for not lessthan the up per one-third of it,A-3 STROUHAL CRITICAL VELOCITYSevere Von Karman typ e oscillation is not likelyif the calculated velocity, know n as the criticalstrouh al velocity, is greater than the m aximu mdesign velocity based on IS 875 ( Part 3 ) : 1987.The strouh al critical velocity Vrr in m / s for acircular chimn ey may be calculated from theformula:

whereVcr - 5 Dt x f . . (1)

f = natu ral frequency of the chimney (in Hz )as obtained in 8.3.1, andDt = diameter of chimney at top ( in mm ).NOTE - The formula for Vcr holds good for strouhalnu mber of 02. This value remains fairly constant asshown by experiments.

A-4 AERODYNAMIC FORCEFor checking of resonan ce amp litud e, the inten-s i t y o f aerodynamic force Ft (z) at level c, for theith mod e of oscillation is d etermined by the for-mula:

Fi(Z> = Fet( z) rr(e) . . . (2)where

T, ( z ) = relative ord inate at level c in theith mode oscillation;Fe1 ( z 1 = amp litude of force intensity at the

free end of the self-supportingchimney or at the centre of thespan of guyed chimney and isequal to CY, qcr, 4, L;

c, = coefficient of tran sverse force takenequal to 0.25;9cr = sn eed thru st corresnond ine to cri-&al velocity V,, and is eqial to

8/2/2019 6533 PART2

20/25

F resp = -; Fst,z . . (3)

YW8,Z = --; Y&z . . (4)M res9z = - ; M,t,z . . . (5)

whereF we, z =Y res, 7, =

M res* z =F st, z =l,t, z =

intensity of iner tia forces at reso-nance at level z,amp litude of resonance oscillationat level 2,bending moment at resonance atlevel t,

M at, !A=8=

intensity of lateral static force atlevel Z,static deflection at level 2 ( sectionund er consideration ) und er theaction of static force,bending mom ent at level f: ( sec-tion und er consideration ) du e tothe action of static force,logarithmic decrement of dam pen-ing effect to be taken equ al to:a) 0.1 for steel chimney with

IS 6533 ( Par t 2 ) I 1989A-4.1 For self-supp orting chimney ( cantilevertype stru ctures ), only the first mod e of oscillationshall be considered.A-5 Inertia forces, amp litud e of reson ance oscil-lations and dynam ic bend ing mom ent at a sectionun der consideration of a chimney fixed at found a-tion are determ ined by the following formu lae:

lining, andb) O*OSfor un lined steel chimneys.

A-6 Static wind-load qcr (stat ) in th e d irectionof action of wind corresponding to critical pressur e(jcr is perm itted to be taken as constant along th e

height of the chimney and is calculated from theformula:qcr ( stat ) = C qcr

whereC = sape factor in accord ance with8.2.3.

A-7 The corresponding dyn amic wind load qcr( dyn ) shall be determined in accord ancewith 8.3.2 to 8.3.7 correspon ding to qor.A-8 Checking for resonance is not r equired forother short du ration forces. The p rovisions forchecking resonan ce will not necessarily app ly topairs, files and group s of chimneys or other tallstructure which may oscillate excessively parti-cularly if they are closer than app roximately 12diam eters. The fitting of stabilizers is usu allybeneficial abut may not always be effective. Nosimple rules can be suggested. Stud y of the lay-out by specialists and w ind tun nel testing may benecessary.A-9 Chimn eys wh ich have a high diameterlthick-ness ratio m ay be subjected to wind -generatedovalling oscillation d ue to circumferentially vary-ing and fluctuating pressur e. Besides causingcircumferential bending stresses, this can increasevertical stresses in the lower part of a chimney oflarge diameter. It should be avoided by prov idingsufficient circumferential stiffness aroun d chimneyat the top. Chimneys having gross plate thicknessof less than l/ 300 of the diameter if not efficientlystiffened by a lining or encasing, should havestiffened rings added at the top ( and lower downif the height is more than 20 times the d iameter ).The distance between the stiffening rings shouldbe not more than 1 500 times the thickness of theshell and should be substantial enough to give atotal circumferential bending stiffness at leastequvalent to that of a un iform shell of thickness126T of the diameter.

ANNEX B( czause 2.1 )

LIST OF REFERRED INDIAN STANDARDSIS .No.

26 : 1975456 : 1978

Title IS No.Structural steel ( standard 814qu ality ) (J;frh revision )Code of practice for plain andreinforced concrete ( third ( Part 1 ) : 1974

TitleCovered electrod es for metalarc welding of structur al steel:For welding products other

8/2/2019 6533 PART2

21/25

IS ivo.816 : 1969

a75

( Part 1 ) : 1987

( Part 3 ) : 198i961 : 19751030: 1982

ii49 : 1982

1363 : 1984136-4 : 1983

1367( Part 1 ) : 1980( Part 3 ) : I979

( Part 6 ) : 1980

1395 : 1982

14fi

( Part 1 ) : 1971( Part 2 ) : 19711893 : 1975

1929 : 1982

TitleCode of practice for use ofmetal -arc w elding for generalconstruction in mild steel ( jrstrevision )Code of practice for designloads ( other than earthquake )for building structures:Dead loads - Unit weightsof building materials an dstored materials ( secondrevision )Wind loads ( second revision )Structural steel ( high ten sile )( second revision )Carbon steel castings for gene-ral engineering pu rposes (thirdrevision )High tensile steel rivet bars forstructural purposes ( third( revision )Hexagon head bolts, screw?and nuts of product grade CHexagon head bolts, screwsand nuts of product grades Aand BTechnical sup ply conditionsfor thread ed steel fasteners:Introdu ction and general in-formation ( second revision )Mechanical prop erties and testmethod s for bolts, screws andstuds with full loadability( second revision )Mechanical prop erties and testmethod s for nuts with specifiedproof loads ( second revisi on )Low and medium alloy steelcovered electrodes for man ualmetal arc welding ( thirdrevision )Code of practice for paintingof ferrous metals in ~buildings:Pretreatment (first revision )Painting (Jirst revisi on )Criteria for earthqu ake resis-tant design of structures ( jourthrevision )Hot forged steel rivets for hotclosing ( 12 to 36 mm dia -

IS No.2141 : 19792155 : 1982

2266 : 1970

2309 : 1963

3613 : 1974

3640 : 19823757 . 19725369 : 1975

5370 : 19695624 : 19706419 : 1971

6560 : 1972

6586 : 1972

6610 : 19726623 : 19726639 : 19726649 : 1972

7002 : 19727280 : 1974

IS 6533 1 Part 2 ) t 1989Title

Galvanized stay strand ( secondrevision )Cold forged solid steel rivetsfor hot closing ( 6 to 16 mmdiameter ) (first revisi on )Steel wire ropes for generalengineering purposes ( secondrevision )Code of practice for the protec-tion of buildings and alliedstructures against lightning( jirst revision )Acceptan ce tests for wire-fluxcombinations for subm erged-arc weldin g of structural steels(Jist revision )Hexagon fit bolts (first revisi on )High strength structural bolts( second revision )General requirements for plainwashers an d lock washers (firstrevision )Plain washers with outside dia-meter 3 x inside diameterFoundation boltsWelding rods and bare electro-des for gas shielded arc weldingof structur al steelMolybdenum and chromium-molybdenu m !ow alloy steelweld ing rod s and base electro-des for gas shielded MarcweldingRecomm ended practice formetal spraying for protectionof iron and steelHeavy wa shers for steel stru c-turesHigh strength structural nu ts( jirst revision )Hexagon bolts for steelstructuresHardened and tempered w as-hers for high strength struc-tural bolts and nuts (firstrfvision )Prevailing torque type steelhexagon locknutsBare wire electrodes for sub-merged arc weld ing of struc-tural steels

8/2/2019 6533 PART2

22/25

I 6 6 5 3 3 ( Part 2 ) : 19 89ANNEX C

( CZause7.7.2 )ALLOWABLE COMPRESSIVE STRESSES

C-l COM PRESSIVE STRESSES IN THESHELLan d

C-l.1 To control buckling, the comp ressive A= lif$-. < 21stresses caused by the combination of extremeand B = 270 $ l-67:

Dfibre stress du e to buckling and direct load, asgiven in Table 3, are worked out by the formula:

, ifT ;T 13fan d

0 5f, A*B B= 1where

,if +< 130t = thickness of plate at the level considered ,fy - ydg ;;;s;nsf s,lsee:b&~OMPa for steel in m;; D = mean diam eter at the fevel considered,

A= - 1 2 ,if g> 21 in m; and0.84 + 0.019 * h, = effective heigh t for the consid erar io:: ofbuckling, in m ( see Table 2 ),

Bureau of Ind ian Standar ds

8/2/2019 6533 PART2

23/25

BIS is a statutory institution established under the Bureau of /ndiarl Stmdurds Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goods andattending to connected matters in the country.CopyrightBIS has the copyright of all its publh$tions. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free USC, in the course 01implementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publication), BIS.Review of In dian Standar dsAmendments are issued to standards as the need arises on the hasis of comments. Su:lndnrds arc also reviewedperiodically; a standard along with amendments is reaffirmed when such rcvicw indicates that no changes arcneeded; if the review indicates that changes are necdcd, it is taken up for revision. Uscn of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issueof BIS Handbook and Standards Monthly AdditionsThisIndian Standard has been developed~from Dot: No. CED 7 ( 4721 )

Amendments I ssued Since PublicationAmend No. Date of Issue Text Affected

BUREAU OF INDIAN STANDARDSHeadquarters:Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002Telephones: 323 0131,323 33 75,323 94 02Regional Offices:Central : Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002Eastern : l/14 C.I.T. Scheme VII M, V.I.P. Road, Maniktola

CALCUTTA 700054Northern : SC0 335336, Sector 34-A, CHANDIGARH 160022

Southern : C.I.T. Campus, IV Cross Road, C!IENNAI 600113

Western : Manakalaya, E9 MIDC, Marol, Andheri (East)MUMBAI 400093Branches : AHMADABAD. BANGALORE. BHGPAL. BHUBANESHWAR.COIMBATORE. FARIDABAD. GHAZIABAD. GUWAHATI.

Telegrams: Manaksanstha(Common to all offices)

Telephone32376 17,3233841

{ 33737 X64 99,337 915 20126,337

{ 600 380 435

{ 23535 025 16,235 043 4259,235832 92 95,832 78 58832 7X 91,832 78 92

8/2/2019 6533 PART2

24/25

AMENDMENT NO. 1 JUNE 1998TOIS 6533 ( PART 2) : 1989 CODE OF PRACTICE FORDESIGN AND CONSTRUCTION OF STEEL CHIMNEY

PART 2 STFtUCTURAL ASPECT(First Revision)

(Page 5, Tab le 2 ) - Substitute the following set of figures for the existing:

Amend No. 1 to IS 6533 ( Pa rt 2 ) : 1989

8/2/2019 6533 PART2

25/25

(Page 12, clause lO.lO.l& line 2 ) - Substitute ~300mm for 3 000 mm.(Page 12, clause 10.10.12, he 3) - Substitute 3 000 mm for 300 mm.( Page 17, clause A-3 ) - Substitute m for mm in the-definition given

for Dt under formula (1).( Page 17, clause A-4 ) - Substitute Cfle&& for the existing in thedefinition given in the fifth line for Fei (z) under formula (2).( Page 17, clause A-4 ) - Substitute ?a for the existing in the definition16given for qcr in the third line under formula (2).( Page 18, clause A-6 ) - Substitute shape for sape in the definition

given for C.( Page 20, Annex C ) - Substitute the following formula for the existingagainst B:B = 270 5 (l-67: ),ifp ~130

(CED7)

Reprography Unit, BIS, New Delhi, India2