is code 803

BIS 2003

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS : 803 - 1976(Reaffirmed 2001)

Edition 2.1(1984-11)

Price Group 14

Indian StandardCODE OF PRACTICE FOR DESIGN,

FABRICATION AND ERECTION OF VERTICAL MILD STEEL CYLINDRICAL WELDED

OIL STORAGE TANKS

( First Revision )(Incorporating Amendment No. 1)

UDC 621.642.3 [669.141.24] : 665.5

IS : 803 - 1976

BIS 2003

BUREAU OF INDIAN STANDARDSThis publication is protected under the Indian Copyright Act (XIV of 1957) andreproduction in whole or in part by any means except with written permission of thepublisher shall be deemed to be an infringement of copyright under the said Act.



OIL STORAGE TANKS

( First Revision )

Structural Engineering Sectional Committee, SMBDC 7

Chairman RepresentingDIRECTOR STANDARDS (CIVIL) Ministry of Railways

MembersSHRI L. N. AGRAWAL Industrial Fasteners Association of India, Calcutta

SHRI M. M. MURARKA ( Alternate )SHRI A. K. BANERJEE Metallurgical and Engineering Consultants (India)

Ltd, RanchiSHRI S. SANKARAN ( Alternate )

SHRI P. C. BHASIN Ministry of Shipping & Transport [Department ofTransport (Roads Wing)]

SHRI A. S. BISHNOI ( Alternate )SHRI V. S. BHIDE Central Water Commission, New Delhi

DEPUTY DIRECTOR (GATES & DESIGN) ( Alternate )

DR P. N. CHATTERJEE Government of West BengalDR P. K. DAS Central Mechanical Engineering Research

Institute (CSIR), DurgapurDR P. DAYARATNAM Indian Institute of Technology, KanpurDEPUTY CITY ENGINEER (PLANNING

& DESIGN)Bombay Municipal Corporation

SHRI G. F. KHAMBATTI ( Alternate )SHRI D. S. DESAI M. N. Dastur & Co Pvt Ltd, CalcuttaDIRECTOR (MERI) Irrigation & Power Department, Government of

MaharashtraRESEARCH OFFICER ( Alternate )

DIRECTOR (TCD) Central Electricity Authority, New DelhiSHRI P. V. N. IYENGER ( Alternate )

EXECUTIVE ENGINEER (CENTRAL STORES DN NO. II)

Central Public Works Department, New Delhi

( Continued on page 2 )

IS : 803 - 1976

2

( Continued from page 1 )

Members RepresentingSHRI M. M. GHOSH Stewarts & Lloyds of India Pvt Ltd, Calcutta

SHRI S. C. GHOSH ( Alternate )SHRI A. G. GONSALVES Bridge & Roof Co (India) Ltd, Howrah

SHRI S. S. BOSE ( Alternate )SHRI G. S. IYER The Hindustan Construction Co Ltd, Bombay

SHRI S. M. GULATEE ( Alternate )DR O. P. JAIN Institution of Engineers (India), CalcuttaJOINT DIRECTOR STANDARDS (B & S)Ministry of Railways

DEPUTY DIRECTOR (B & S) ( Alternate )SHRI OM KHOSLA Electrical Manufacturing Co Ltd, Calcutta

SHRI S. N. SINGH ( Alternate )PROF K. D. MAHAJAN Engineer-in-Chiefs Branch, Army Headquarters

PROF B. V. RAMASWAMY ( Alternate )SHRI P. K. MALLICK Jessop & Co Ltd, CalcuttaDR S. K. MALLICK Indian Institute of Technology, KharagpurSHRI N. V. MANAY Mantons (Bangalore) Pvt Ltd, BangaloreSHRI G. C. MATHUR National Buildings Organisation, New Delhi

SHRI K. S. SRINIVASAN ( Alternate )SHRI A. K. MITRA Hindustan Steel Ltd, DurgapurSHRI P. K. MUKHERJEE Braithwaite & Co (India) Ltd, Calcutta

SHRI P. T. PATEL ( Alternate )SHRI R. NARAYANAN Structural Engineering Research Centre (CSIR),

RoorkeeSHRI T. N. SUBBA RAO Indian Roads Congress, New Delhi

DR D. JHONSON VICTOR ( Alternate )REPRESENTATIVE Burn & Co Ltd, Howrah

SHRI A. P. KAYAL ( Alternate )REPRESENTATIVE Public Works Department, Government of West

Bengal, CalcuttaREPRESENTATIVE Richardson & Cruddas Ltd, Bombay

SHRI P. V. NAIK ( Alternate )PROF P. K. SOM Jadavpur University, CalcuttaSUPERINTENDING ENGINEER

(PLANNING & DESIGN CIRCLE)Government of Tamil Nadu

EXECUTIVE ENGINEER (BUILD-ING CENTRE DIVISION) ( Alternate )

SHRI M. D. TAMBEKAR Bombay Port Trust, BombaySHRI K. VEERARAGHVACHARY Bharat Heavy Electricals Ltd, TiruchirapalliSHRI S. N. VOHRA Inspection Wing, Directorate General of Supplies &

Disposals (Ministry of Industry & CivilSupplies)

SHRI S. N. BASU ( Alternate )SHRI L. D. WADHWA Engineers India Ltd, New Delhi

SHRI B. B. NAG ( Alternate )SHRI C. R. RAMA RAO,

Director (Struc & Met)Director General, ISI ( Ex-officio Member )

SecretarySHRI S. S. SETHI

Assistant Director (Struc & Met), ISI

( Continued on page 3 )

IS : 803 - 1976

3

( Continued from page 2 )

Panel for Mild Steel Tanks for Storage of Oils and Design and Construction of Floating Roofs of Open Tanks for

Oil Storage, SMBDC 7/P-1

Members RepresentingSHRI S. K. HAZRA Engineers India Ltd, New Delhi

SHRI A. S. MANGAT ( Alternate )SHRI V. JAMBUNATHAN Indian Refineries Ltd, New DelhiSHRI C. O. KESWANI Hindustan Petroleum Corporation Ltd, BombaySHRI V. H. KHAKHAR Caltex (India) Ltd, Bombay

SHRI M. BALAKRISHNA ( Alternate )SHRI R. V. RAGHAVAN Vijay Tanks & Vessels Pvt Ltd, BombaySHRI T. K. RAMANATHAN Triveni Structurals Ltd, Allahabad

SHRI V. R. K. MURTHY ( Alternate )SHRI A. P. RAO Bharat Heavy Plate & Vessels Ltd, Visakhapatnam

SHRI V. S. PRASADA RAO ( Alternate )SHRI M. RAMA RAO Indian Oil Corporation, Bombay

SHRI S. K. SANGAR ( Alternate )SHRI P. C. SILAICHIA Bharat Refineries Ltd, Bombay

SHRI K. S. SUBBANA ( Alternate )

IS : 803 - 1976

4

C O N T E N T S

PAGE

0. FOREWORD 61. SCOPE 72. DEFINITIONS AND SYMBOLS 73. GENERAL 104. MATERIALS 105. PERMISSIBLE STRESSES 166. DESIGN 16

6.1 Foundation 176.2 Design of Bottom Plates 176.3 Design of Shell Plates 226.4 Designs of Roof 366.5 Floating Roof 39

7. APPURTENANCES AND MOUNTINGS 398. SHOP FABRICATION AND INSPECTION 499. SITE ERECTION 60

10. SITE WELDING 6311. RADIOGRAPHIC INSPECTION OF SHELL JOINTS 6512. TESTING OF TANKS 69

12.1 Bottom Testing 6912.2 Shell Testing 7012.3 Fixed Roof Testing 7012.4 Repair of Leaks 70

APPENDIX A INFORMATION TO BE FURNISHED BY PURCHASER 76APPENDIX B ALTERNATE DESIGN FOR TANK SHELLS 77APPENDIX C VENT SIZING FOR ATMOSPHERIC AND LOW PRESSURE

TANKS 82APPENDIX D FLOATING ROOFS 88TABLES 1-3 NOMINAL CAPACITIES OF TYPICAL TANKS 11a-12aTABLES 4-6 MINIMUM CALCULATED SHELL PLATE THICKNESS

FOR TYPICAL TANKS 12b-13bTABLE 7 SECTION MODULUS OF WIND GIRDERS 32-35TABLE 8 SHELL MANHOLE COVER PLATE AND BOLTING

FLANGE THICKNESS 45TABLE 9 SHELL MANHOLE DIMENSIONAL DATA 46TABLE 10 SHELL NOZZLES DIMENSIONAL DATA 50-51TABLE 11 ROOF MANHOLES 51TABLE 12 ROOF NOZZLES 52

IS : 803 - 1976

5

PAGE

TABLE 13 DETAIL OF DRAIN PAD FOR ELEVATED TANKS 54TABLE 14 FLUSH TYPE CLEANOUT FITTINGS 55TABLE 15 THICKNESS OF COVER PLATE, BOLTING FLANGE AND

REINFORCING PLATE FOR FLUSH TYPE CLEANOUTFITTINGS 56

TABLE 16 THICKNESS AND HEIGHT OF SHELL REINFORCINGPLATE FOR CLEANOUT FITTINGS 56

TABLE 17 MAXIMUM PERMISSIBLE POROSITY INDICATIONS INRADIOGRAPHS PER 150 mm LENGTH OF WELD 69

TABLE 18 THERMAL VENTING CAPACITY REQUIREMENTS 86TABLE 19 TOTAL RATE OF EMERGENCY VENTING REQUIRED FOR

FIRE EXPOSURE VERSUS WETTED SURFACE AREA 87FIGURE 1 TYPICAL FIXED ROOF TANK SHOWING STANDARD

APPURTENANCES 8FIGURE 2 TYPICAL OPEN TOP TANK WITH FLOATING ROOF

SECTIONAL VIEW 9FIGURE 3 TYPICAL FOUNDATIONS 18FIGURE 4 TYPICAL LAYOUT OF TANK BOTTOM 19FIGURE 5 BOTTOM PLATE ARRANGEMENT UNDER TANK SHELL 20FIGURE 6 TYPICAL HORIZONTAL AND VERTICAL JOINTS 25FIGURE 7 TYPICAL ROOF JOINTS 26FIGURE 8 SOME PERMISSIBLE DETAILS OF COMPRESSION RINGS 28FIGURE 9 RECOMMENDED LAYOUT OF COLUMNS FOR NORMAL

SIZE TANKS 40FIGURE 10 TYPICAL COLUMN AND GIRDER ATTACHMENT

DETAILS 41FIGURE 11 TYPICAL SHELL MANHOLES 44FIGURE 12 TYPICAL SHELL NOZZLES 47FIGURE 13 SHELL NOZZLE FLANGES 49FIGURE 14 TYPICAL ROOF MANHOLE 52FIGURE 15 TYPICAL ROOF NOZZLES 53FIGURE 16 TYPICAL WATER DRAW-OFF SUMP 54FIGURE 17 TYPICAL DRAIN PAD FOR ELEVATED TANKS 55FIGURE 18 TYPICAL FLUSH TYPE CLEANOUT FITTINGS 57FIGURE 19 TYPICAL GAUGE-WELL INSTALLATION ON EXISTING

NOZZLE OF CONE ROOF TANKS 58FIGURES 20-23 RADIOGRAPHIC POROSITY STANDARDS 71-74FIGURE 24 DETAIL OF TYPICAL VACUUM BOX 75FIGURE 25 INSERT TYPE REINFORCEMENT FOR MANHOLES AND

NOZZLES 80

IS : 803 - 1976

6



OIL STORAGE TANKS

( First Revision )0. F O R E W O R D

0.1 This Indian Standard (First Revision) was adopted by the IndianStandards Institution on 27 September 1976, after the draft finalized bythe Structural Engineering Sectional Committee had been approved bythe Structural and Metals Division Council and Civil EngineeringDivision Council.0.2 This code has been prepared with a view to providing the petroleumindustry with tanks of adequate safety and reasonable economy whichcan be built in any size required to meet the needs of the industry subjectto limitations given in the code and also to establishing uniform practicefor design, fabrication, erection, testing and inspection of oil storagetanks.0.3 This code does not present nor it is contemplated to establish, a fixedseries of allowable tank sizes; but it is intended to promote the selectionby the purchaser, of the size of tank that may be required to meet hisparticular need.0.4 This standard was first published in 1962. The followingmodifications have been made in this revision:

a) The use of steel conforming to IS : 226-1975*, IS : 2002-1962,IS : 2041-1962 and IS : 961-1975 has been permitted in addition tosteel conforming to IS : 2062-1969||.

b) Provisions regarding design of various members of the tank havebeen elaborated, an appendix dealing with the alternate design fortank shell has been included.

c) Provisions regarding radiographic inspection of shell joints havebeen made.

d) An appendix dealing with the normal and emergency ventingrequirements of the tanks has been added.

*Specification for structural steel (standard quality) ( fifth revision ).Specification for steel plates for boilers.Specification for steel plates for pressure vessels.Specification for structural steel (high tensile) ( second revision ).|| Specification for structural steel (fusion welding quality) ( first revision ).

IS : 803 - 1976

7

e) An appendix furnishing the design and construction requirements ofpontoon type, double deck type floating roof tanks has also beenincluded in this code.

0.5 This edition 2.1 incorporates Amendment No. 1 (November 1984).Side bar indicates modification of the text as the result of incorporation ofthe amendment.0.6 For the purpose of deciding whether a particular requirement of thiscode is complied with, the final value, observed or calculated, expressingthe result of a test, shall be rounded off in accordance with IS : 2-1960*.The number of significant places retained in the rounded off value shouldbe the same as that of the specified value in this code.

1. SCOPE1.1 This code covers materials, design, fabrication, erection and testingrequirements for mild steel cylindrical welded oil storage tanks in varioussizes and capacities, for erection above ground, of the following designs:

a) Fixed roof tanks ( see Fig. 1 ) having no internal pressure or nominalinternal pressure where the resultant upward force does not exceedthe nominal weight of metal in tank shell, roof and any framingsupported by the shell or roof; and

b) Open top tanks ( see Fig. 2 ).1.1.1 This code specifies the use of only butt welded shells and includesreference to appurtenances and mountings.1.2 This code is complementary to IS : 800-1962 and IS : 816-1969.Provisions regarding permissible stresses, design, fabrication anderection as included in IS : 800-1962 shall apply unless specifiedotherwise in this code.1.3 This code is intended to guide both purchasers and manufacturers ofpetroleum products storage tanks. Provisions of this code may also beapplied to design and construct tanks for storage of water, acids andchemicals. In such cases, special considerations regarding lining,corrosion allowance and foundation shall be made while designing thetanks for the intended service.

2. DEFINITIONS AND SYMBOLS2.1 For the purpose of this code, the definitions for welding termsemployed in this standard shall be according to IS : 812-1957.2.2 Symbols for welding used on plans and drawings shall be according toIS : 813-1961||.

*Rules for rounding off numerical values ( revised ).Code of practice for use of structural steel in general building construction ( revised ).Code of practice for use of metal arc welding for general construction in mild steel

( first revision ).Glossary of terms relating to welding and cutting of metals.|| Scheme of symbols for welding ( amended ).

IS:803

-1976

8

FIG. 1 TYPICAL FIXED ROOF TANK SHOWING STANDARD APPURTENANCES

IS:803

-1976

9

FIG. 2 TYPICAL OPEN TOP TANK WITH FLOATING ROOF SECTIONAL VIEW

IS : 803 - 1976

10

3. GENERAL3.1 Tanks may be manufactured from suitable sizes of plates which havebeen covered in IS : 1730 (Part I)-1975*.3.2 Tables 1 to 6 ( see P 11 to 13 ) present for ready reference, typical datain regard to nominal sizes, nominal capacities and shell plate thicknessesfor tanks which may be built in accordance with this code.3.3 Enquiries or Order Form With a view to facilitating themanufacture and supply of welded oil storage tanks, certain detailedinformation is to be supplied to the manufacturer. The information sorequired is listed in Appendix A.

4. MATERIALS4.0 General Unless mutually agreed otherwise, the material for theconstruction of oil storage tanks shall conform to Indian Standards whereapplicable.4.1 Plates Plates used in tank construction shall conform to any one ofthe following specifications:

IS : 226-1975 Structural steel (standard quality) ( fifth revision )(For up to 20 mm thickness. Thicker plates may be used providedthe manufacturer establishes appropriate welding proceduresrecommended in IS : 823-1964 to the satisfaction of the purchaser)

IS : 961-1975 Structural steel (high tensile) ( second revision )IS : 2002-1962 Steel plates for boilers (Grade 2B)IS : 2041-1962 Steel plates for pressure vesselsIS : 2062-1969 Structural steel (fusion welding quality) ( first revision )

4.1.1 Plates for use in the manufacture of tanks shall be on thicknessbasis which are determined by design computations. Shell plates, forwhich minimum thicknesses are fixed in 6.3.3 for practical reasons andwhich will not underrun the theoretical required thickness by more thanthe minus tolerance specified in 1852-1973 and roof and bottom platesmay be specified on weight basis. The plate thicknesses as stipulated inthis standard are minimum; thicker or heavier material may be requireddepending on the nature of stored product, and the environment wherethe tank is located.4.1.2 Steel conforming to IS : 1977-1975 may also be used in tankconstruction subject to limitations under 0.3 of that specification.

*Dimensions for steel plate, sheet and strip for structural and general engineeringpurposes: Part I Plate ( first revision ).

Code of procedure for manual metal arc welding of mild steel.Specification for rolling and cutting tolerances for hot-rolled steel products ( second

revision ).Specification for structural steel (ordinary quality) ( second revision ).

IS:803

-1976

TABLE 1 NOMINAL CAPACITIES OF TYPICAL TANKS FOR PLATE WIDTH 1.5 m( Clause 3.2 )

TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22 24 26 28 30 32

TANK HEIGHT, m NOMINAL CAPACITY, kl

1.53.04.56.07.59.0

10.512.013.515.016.518.0

102131425263748495

105116127

23477195

119143166190214238262286

295888

117147176206235264294323353

4284

127169211254296339381423466508

66132198264331397463529596662728

7 948

95190286381476572667763858953

1 0491 144

117235353471588706824942

1 0591 1771 2951 413

169339508678847

1 0171 1861 3561 5261 6951 8652 034

230461692923

1 1531 3841 6151 8462 0772 3072 5382 769

301602904

1 2051 5071 8082 1102 4112 7123 0143 3153 617

381763

1 1441 5261 9072 2892 6703 0523 4333 8154 1964 578

471942

1 4131 8842 3552 8263 2973 7684 2394 7105 1815 652

5691 1391 7092 2792 8493 4193 9894 5595 1295 6996 2696 838

6781 3562 0342 7123 3914 0694 7475 4256 1046 7827 4608 138

7951 5912 3873 1833 9794 7755 5716 3677 1637 9598 7559 551

9231 8462 7693 6924 6155 5386 4627 3858 3089 231

10 15411 077

1 0592 1193 1794 2395 2986 3587 4188 4789 537

10 59711 65712 717

1 2052 4113 6174 8236 0287 2348 4409 646

10 85112 05713 26314 469

( Continued )

TABLE 1 NOMINAL CAPACITIES OF TYPICAL TANKS FOR PLATE WIDTH 1.5 m Contd

TANK DIAMETER, m 34 36 38 40 42 44 46 48 50 54 58 62 66 70 74 78 82


1.53.04.56.07.59.0

10.512.013.515.016.518.0

1 3612 7224 0835 4446 8058 1679 528

10 88912 25013 61114 97316 334

1 5263 0524 5786 1047 6309 156

10 68212 20813 73415 26016 78618 312

1 7003 4005 1006 8018 501

10 20111 90213 60215 30217 00318 70320 403

1 8843 7685 6527 5369 420

11 30413 18815 07216 95618 84020 72422 608

2 0774 1546 2318 308

10 38512 46214 53916 61618 69320 77122 84824 925

2 2794 5596 8389 118

11 39813 67715 95718 23720 51622 79625 07627 355

2 4914 9837 4749 966

12 45714 94917 44119 93222 42424 91527 40729 899

2 7125 4258 138

10 85113 56416 27718 99021 70324 41627 12929 84232 555

2 9435 8878 831

11 77514 71817 66220 60623 55026 49329 43732 38135 325

3 4336 867

10 30013 73417 16720 60124 03527 46830 90234 33537 76941 203

3 9617 922

11 88315 84419 80523 76627 72731 68835 64939 61143 57247 533

4 5269 052

13 57818 10522 63127 15731 68436 21040 73645 26349 78954 315

5 12910 25815 38720 51625 64530 77535 90441 03346 16251 29156 42161 550

5 76911 53917 30923 07928 84834 61840 38846 15851 92757 69763 46769 237

6 44712 89519 34325 79132 23938 68745 13551 58358 03164 47970 92777 375

7 16314 32721 49128 65535 81942 98350 14757 31164 47571 63978 80385 966

7 91715 83523 75231 67039 58747 50555 42263 34071 25779 17587 09295 010

11a

IS:803

-1976


TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0


1.83.65.47.29.0

10.812.614.416.218.019.821.6

12253850637689

101114127139152

285785

114143171200228257286314345

3570

105141176211247282317353388423

50101152203254305356406457508559610

79158238317397476556635715794874953

114228343457572686801915

1 0301 4441 2581 373

141282423565706847989

1 1301 2711 4131 5541 695

203406610813

1 0171 2201 4241 6271 8312 0342 2382 441

276553830

1 1071 3841 6611 9382 2152 4922 7693 0463 323

361723

1 0851 4461 8082 1702 5322 8933 2553 6173 9794 340

457915

1 3751 8312 2892 7463 2043 6624 1204 5785 0355 493

5651 1301 6952 2602 8263 3913 9564 5215 0865 6526 2176 782

6831 3672 0512 7353 4194 1034 7875 4716 1556 8387 5228 206

8131 6272 4413 2554 0694 8835 6976 5117 3248 1388 9529 766

9551 9002 8653 8204 7755 7316 6867 6418 5969 551

10 50711 462

1 1072 2153 3234 4315 5386 6467 7548 8629 970

11 07712 18513 293

1 2712 5433 8155 0866 3587 6308 901

10 17311 44512 71713 98815 260

1 4462 8934 3405 7877 2348 681

10 12811 57513 02214 46915 91617 362

( Continued )


TANK DIAMETER, m 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 54.0 58.0 62.0 66.0 70.0 74.0 78.0 82.0


1.83.65.47.29.0

10.812.614.416.218.019.821.6

1 6333 2664 9006 5338 1679 800

11 43313 06714 70016 33417 96719 601

1 8313 6625 4937 3249 156

10 98712 81814 64916 48118 31220 14321 974

2 0404 0806 1218 161

10 20112 24214 28216 32218 36320 40322 44424 484

2 2604 5216 7829 043

11 30413 56415 82518 08620 34722 60824 86827 129

2 4924 9857 4779 970

12 46214 95517 44719 94022 43224 92527 41729 910

2 7355 4718 206

10 94213 67716 41319 14821 88424 62027 35530 09132 826

2 9895 9798 969

11 95914 94917 93920 92923 91926 90929 89932 88835 897

3 2556 5119 766

13 02216 27719 53322 78826 04429 29932 55535 81139 066

3 5327 065

10 59714 13017 66221 19524 72728 26031 79235 32538 85742 390

4 1208 240

12 36016 48120 60124 72128 84232 96237 08241 20345 32349 443

4 7539 506

14 25919 01323 76628 51933 27338 02642 77947 53352 28657 039

5 43110 86316 29421 72627 15732 58938 02143 45248 88454 31559 74765 178

6 15512 31018 46524 62030 77536 93043 08549 24055 39561 55067 70573 860

6 92313 84720 77127 69434 61841 54248 46555 38962 31369 27376 16083 084

7 73715 47523 21230 95038 68746 42554 16361 90069 63877 37585 11392 851

8 59617 19325 79034 38642 98351 58060 17668 77377 37085 96694 563

103 160

9 50119 00228 50338 00447 50557 00666 50776 00885 50995 010

104 511114 012

11b

IS:803

-1976


TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0


2468

10121416182022

14284256708498

113127141155

316395

127159190222254286318349

3978

117157196235274314353392431

56113169226282339395452508565622

88176265353441530618706795883971

127254381508636763890

1 0171 1451 2721 399

157314471628785942

1 0991 2561 4131 5701 727

226452678904

1 1301 3571 5831 8092 0352 2612 488

307615923

1 2311 5391 8472 1552 4632 7703 0783 386

402804

1 2061 6082 0102 4122 8143 2163 6194 0214 423

5081 0171 5262 0352 5443 0533 5624 0714 5805 0895 598

6281 2561 8842 5133 1413 7694 3985 0265 6546 2836 911

7601 5202 2803 0413 8014 5615 3216 0826 8427 6028 362

9041 0592 7143 6194 5235 4286 3337 2388 1439 0479 952

1 0892 1233 1854 2475 3096 3717 4338 4949 556

10 61811 680

1 2312 4633 6944 9566 1577 3898 6209 852

11 08312 31513 546

1 4132 8274 2415 6547 0688 4829 896

11 30912 72314 13715 550

1 6083 2174 8256 4348 0429 650

11 25912 86714 47616 08417 693

( Continued )


TANK DIAMETER, m 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 54.0 58.0 62.0 66.0 70.0 74.0 78.0 82.0


2468

10121416182022

1 8153 6315 4477 2639 079

10 89512 71014 52616 34218 15819 974

2 0354 0716 1078 143

10 17812 21414 25016 28618 32120 35722 393

2 2684 5366 8049 072

11 34113 60915 87718 14520 41422 68224 950

2 5135 0267 539

11 05312 56615 07917 59220 10622 61925 13227 646

2 7705 5418 312

11 08313 85416 62519 39622 16724 93727 70830 479

3 0416 0829 123

12 16415 20518 24621 28724 32827 36930 41033 451

3 3236 6479 971

13 29516 61919 84223 26626 59029 91433 23936 561

3 6197 238

10 85714 47618 09521 71425 33328 95232 57236 19139 810

3 9277 854

11 78115 70719 63423 56127 48831 41535 34239 26943 196

4 5809 160

13 74118 32122 90227 48232 06336 64341 22445 80450 384

5 28410 56815 85221 13626 42031 70436 98942 27347 57552 84158 125

6 03812 07618 11424 15230 19036 22842 26748 30554 34360 38166 419

6 84213 68420 57227 36934 21141 05447 89654 73961 58168 42375 266

7 69615 39323 09030 78738 48446 18153 87861 57569 27276 96984 665

8 60117 20325 80534 40643 00851 61060 21168 81377 41586 01694 618

9 55619 11328 67038 22647 78357 34066 89776 45386 01095 520

105 124

10 56221 12431 68642 24852 81063 37273 93484 49695 058

105 620116 182

12a

IS:803

-1976

TABLE 4 MINIMUM CALCULATED SHELL PLATE THICKNESS FOR TYPICAL TANKS FOR PLATE WIDTH 1.5 m(Using plates conforming to IS : 226 or IS : 2062; E = 0.85 and sp gr = 1; excluding corrosion allowance)

( Clause 3.2 )

TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0

TANK HEIGHT, m PLATE THICKNESS, mm

1.53.04.56.07.59.0

10.512.013.515.016.518.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.15.6

5.05.05.05.05.05.05.05.05.05.15.76.2

5.05.05.05.05.05.05.05.05.56.26.87.4

5.05.05.05.05.05.05.05.76.57.27.98.7

6.06.06.06.06.06.06.06.67.48.29.19.9

6.06.06.06.06.06.06.47.48.39.3

10.211.2

6.06.06.06.06.06.17.18.29.2

10.311.312.4

6.06.06.06.06.06.77.99.0

10.211.312.513.6

6.06.06.06.06.17.38.69.8

11.112.413.614.9

6.06.06.06.06.67.99.3

10.712.013.414.716.1

6.06.06.06.07.18.5

10.011.512.914.415.917.4

6.06.06.06.07.69.1

10.712.313.915.417.018.6

6.06.06.06.48.19.7

11.413.114.816.518.219.8

( Continued )

TABLE 4 MINIMUM CALCULATED SHELL PLATE THICKNESS FOR TYPICAL TANKS FOR PLATE WIDTH 1.5 m Contd(Using plates conforming to IS : 226 or IS : 2062; E = 0.85 and sp gr = 1; excluding corrosion allowance)

TANK DIAMETER, m 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 54.0 58.0 62.0 66.0 70.0 74.0 78.0 82.0


1.53.04.56.07.59.0

10.512.013.515.016.518.0

6.06.06.06.88.6

10.412.113.915.717.518.321.1

6.06.06.07.29.1

11.012.914.716.618.520.422.3

6.06.06.07.69.6

11.613.615.617.619.621.623.6

6.06.06.08.0

10.112.214.316.418.520.622.724.8

6.06.06.28.4

10.612.815.017.219.421.623.826.0

6.06.06.58.8

11.113.415.718.020.322.625.027.3

6.06.06.89.2

11.614.016.418.821.323.726.128.5

6.06.07.19.6

12.114.617.119.722.224.727.229.7

6.06.07.4

10.012.615.217.920.523.125.728.431.0

6.06.07.9

10.813.616.419.822.125.027.830.633.5

6.06.08.5

11.614.617.720.723.826.829.932.935.8

6.06.09.1

12.415.618.922.125.428.731.935.238.4

6.06.29.7

13.216.620.123.627.030.534.037.4

6.06.6

10.314.017.621.325.028.732.436.039.7

6.07.0

10.914.818.722.526.430.334.238.1

6.07.4

11.515.619.723.827.932.036.1

6.07.8

12.116.420.725.029.333.637.9

12b

IS:803

-1976


( Clause 3.2 )

TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0


1.83.65.47.29.0

10.812.614.416.218.019.821.6

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.15.6

5.05.05.05.05.05.05.05.05.05.66.16.7

5.05.05.05.05.05.05.05.05.66.26.87.5

5.05.05.05.05.05.05.25.96.77.48.28.9

5.05.05.05.05.05.16.06.97.88.79.6

10.4

6.06.06.06.06.06.06.97.98.99.9

10.911.9

6.06.06.06.06.06.67.88.9

10.011.112.313.4

6.06.06.06.06.17.48.69.9

11.112.413.714.9

6.06.06.06.06.78.19.5

10.912.213.615.016.4

6.06.06.06.07.38.8

10.311.813.414.916.417.9

6.06.06.06.37.99.6

11.212.814.516.117.819.4

6.06.06.06.88.5

10.312.113.815.617.419.120.9

6.06.06.07.29.1

11.012.914.816.718.620.522.4

6.06.06.07.79.7

11.813.815.817.819.821.823.7

( Continued )


TANK DIAMETER, m 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 54.0 58.0 62.0 66.0 70.0 74.0 78.0 82.0


1.83.65.47.29.0

10.812.614.416.218.019.821.6

6.06.06.18.2

10.412.514.616.818.921.123.225.4

6.06.06.48.7

11.013.215.517.820.022.324.626.8

6.06.06.89.2

11.614.016.418.821.223.625.928.3

6.06.07.19.7

12.214.717.219.722.324.827.329.8

6.06.07.5

10.112.815.418.120.723.426.028.731.3

6.06.07.9

10.613.416.218.921.724.527.330.032.8

6.06.08.2

11.114.016.919.822.725.628.531.434.3

6.06.08.6

11.614.617.620.723.726.729.732.835.8

6.06.08.9

12.115.218.421.524.727.831.034.137.3

6.06.29.6

13.016.419.923.326.730.133.536.9

6.06.7

10.414.017.721.325.028.632.335.939.6

6.07.2

11.115.018.922.826.730.634.538.4

6.07.6

11.815.920.124.328.432.636.7

6.08.1

12.516.921.325.730.134.639.0

6.08.6

13.217.922.527.231.936.5

6.09.0

13.918.823.828.733.638.5

6.09.5

14.619.825.030.135.3

13a

IS:803

-1976


( Clause 3.2 )

TANK DIAMETER, m 3.0 4.5 5.0 6.0 7.5 9.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0


2468

10121416182022

5.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.05.0

5.05.05.05.05.05.05.05.05.05.25.7

5.05.05.05.05.05.05.05.05.66.26.8

5.05.05.05.05.05.05.05.56.26.97.6

5.05.05.05.05.05.05.86.67.48.39.1

5.05.05.05.05.05.76.77.78.79.7

10.6

6.06.06.06.06.06.67.78.89.9

11.012.2

6.06.06.06.06.17.48.69.9

11.212.413.7

6.06.06.06.06.88.29.6

11.012.413.815.2

6.06.06.06.07.59.0

10.012.113.615.216.7

6.06.06.06.58.29.8

11.513.214.916.618.2

6.06.06.07.08.8

10.712.514.316.117.919.8

6.06.06.07.59.5

11.513.415.417.419.021.3

6.06.06.08.1

10.212.314.416.518.620.722.8

6.06.06.48.6

10.913.115.617.619.822.124.3

( Continued )


( Clause 3.2 )

TANK DIAMETER, m 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 54.0 58.0 62.0 66.0 70.0 74.0 78.0 82.0


2468

10121416182022

6.06.06.89.2

11.513.916.318.721.123.525.8

6.06.07.29.7

12.214.717.319.822.324.827.4

6.06.07.8

10.212.915.618.220.923.626.228.9

6.06.08.0

10.813.616.419.222.024.827.630.4

6.06.08.4

11.314.317.220.123.126.029.031.9

6.06.08.8

11.914.918.021.124.227.330.433.4

6.06.09.2

12.415.618.822.125.328.531.735.0

6.06.29.6

12.916.319.723.026.429.733.136.5

6.06.5

10.013.517.020.524.027.531.034.538.0

6.07.0

10.814.618.322.125.929.733.537.2

6.07.5

11.615.619.723.827.831.935.9

6.08.0

12.416.721.125.429.734.138.4

6.08.6

13.217.822.427.031.736.3

6.09.1

14.018.923.828.733.638.5

6.09.6

14.820.025.130.335.5

6.010.115.621.026.532.037.4

6.010.616.422.127.933.639.3

13b

As in the Original Standard, this Page is Intentionally Left Blank

IS : 803 - 1976

15

4.1.3 Plate materials specified in 4.1 shall be used without impact testingon tank shells and its reinforcements for design metal temperaturesgreater than 10C.

4.1.4 For temperature lower than 10C and up to 20C, material listedin 4.1 with the exception of structural steel, conforming to IS : 226-1975*,shall be used, and shall demonstrate adequate notch toughness at thedesign metal temperature. Each plate as-rolled shall be impact-tested atthe design metal temperature to show that the average of three charpy V-notch full size specimens is a minimum of 39 N.m (4 kgf.m) (longitudinal)or 25 N.m (2.5 kgf.m) (transverse).

4.2 Structural Sections Dimensions of structural steel sections usedin tank construction shall conform to IS : 808-1964 and IS : 808 (Part I)-1973.

4.3 Cast Steel Mountings Cast steel mountings shall be suitable forwelding and shall conform to Grade 3 of IS : 1030-1974.

4.4 Electrodes Electrodes for metal arc welding shall conform toIS : 814 (Part I)-1974|| and IS : 814 (Part II)-1974.

4.5 Piping Unless specified otherwise, pipe and pipe couplings shallconform to IS : 1978-1971**. By agreement between the purchaser andthe manufacturer, couplings for threaded connections may be suppliedwithout recesses. When so supplied, the couplings in all other respectsshall conform to IS : 1978-1971**. Pipe used for structural purposes shallconform to IS : 1978-1971** and IS : 1979-1971 with respect to physicalproperties of the material. Pipes of heavy class conforming to IS : 1239(Part II)-1969 may be used for nozzles on tank roofs and internal pipingsubject to agreement between the purchaser and the manufacturer.

4.6 Flanges Plate ring flanges shall be made from any of the platematerials listed in 4.1. Requirements of slip-on welding and welding neckflanges are covered in IS : 6392-1971.

*Specification for structural steel (standard quality) ( fifth revision ).Specification for rolled steel beam, channel and angle sections ( revised ).Dimensions for hot rolled steel beams: Part I MB series ( second revision ).Specification for steel castings for general engineering purposes ( second revision ).|| Specification for covered electrodes for metal arc welding of structural steels: Part I

For welding products other than sheets ( fourth revision ).Specification for covered electrodes for metal arc welding of structural steels: Part

II For welding sheets ( fourth revision ).**Specification for line pipe ( first revision ).Specification for high test line pipe ( first revision ).Specification for mild steel tubes, tubulars and other wrought steel fittings: Part

II Mild steel tubulars and other wrought steel pipe fittings ( second revision ).Specification for steel pipe flanges.

IS : 803 - 1976

16

4.7 Bolts and Nuts Bolts shall conform to the requirements specifiedin IS : 1367-1967* for black grade bolts of class 4.6 or 4.8. Nuts shall be ofblack grade class 4. Screw threads shall conform to coarse series mediumclass referred in IS : 1367-1967*.4.8 Other materials used in association with steelwork shall, whereappropriate Indian Standard specifications for materials exist, conform tosuch specifications.

5. PERMISSIBLE STRESSES5.1 Maximum allowable working stresses shall not exceed the following.5.1.1 In the design of tank shells, the maximum tensile stress beforeapplying the factor for joint efficiency shall be 165 N/mm2 (1 680 kgf/cm2)in case of steel conforming to IS : 2062-1969 and IS : 226-1975. Forother grades of steels, maximum allowable stress shall be 0.7 of theminimum yield stress of each grade or 0.4 of the minimum ultimatetensile stress whichever is less.5.1.2 Structural design stresses (not covered in 5.1.1) shall conform to theallowable working stresses given in IS : 800-1962. For this purpose steelconforming to IS : 2002-1962|| (Grade 2B) and IS : 2041-1962 (Type 1)should be treated as equivalent to IS : 226-1975 or IS : 2062-1969whereas Type 2 steel conforming to IS : 2041-1962 shall be treatedequivalent to IS : 961-1975**.5.1.3 The above stresses are permissible for design temperatures of 10Cto +200C, provided that below +10C only semikilled or killed steels areused.5.2 The permissible stresses for welds and welded connections shallconform to the values given in IS : 816-1969.

6. DESIGN6.0 General Internal pressure of tanks designed in accordance with therules and provisions made in this code shall not exceed the value given by:

*Technical supply conditions for threaded fasteners ( first revision ).Specification for structural steel (fusion welding quality) ( first revision ).Specification for structural steel (standard quality) ( fifth revision ).Code of practice for use of structural steel in general building construction ( revised ).|| Specification for steel plates for boilers.Specification for steel plates for pressure vessels.**Specification for structural steel (high tensile) ( second revision ).Code of practice for use of metal arc welding for general construction in mild steel

( first revision ).

IS : 803 - 1976

17

where

6.1 Foundation Tanks shall be built on good foundations. Details oftypical foundations normally adopted are shown in Fig. 3A and 3Brespectively for earth foundation and concrete ringwall foundation.Where soil conditions are adverse, care should be taken to design thefoundations properly such that no subsidence takes place.

6.2 Design of Bottom Plates6.2.1 Bottom plate, uniformly resting on the ground or supporting sub-structure, shall conform to the following ( see Fig. 4 ):

a) All bottom plates shall have a minimum nominal thickness of 6 mm.b) All rectangular plates shall preferably have a minimum width of

1 500 mm. All sketch plates (bottom plates upon which the shellplate rests), which have one end rectangular shall also preferablyhave a minimum width of 1 500 mm for the rectangular end.

c) Bottom plates shall be of sufficient size so that when welded, at leasta 25 mm width will project beyond the outside edge of the weldattaching the bottom to the shell plate.

NOTE Bottom of excavation should be level. Remove muck, vegetation andunstable materials to whatever depth is necessary.

6.2.2 Bottoms shall be built according to either of the following twomethods of construction:

a) Lap welded plates shall be reasonably rectangular and squareedged. Three-plate laps shall not be closer than 300 mm from eachother and also from the tank shell.

Plates shall be welded on top side only with a continuous fillet weldon all seams. Joints shall be lapped to 5 times the thickness of thethinner plate, but need not exceed 25 mm ( see Fig. 4, Section BB ).

Portion of the sketch plates coming under the bottom shell ringshall have the outer ends of the joints fitted and lap welded to form asmooth bearing for the shell plates, as shown in Fig. 5A.

Bottom plate attachment with the shell plate may be made by anannular ring of segmental plates as shown in Fig. 5B. Such annularrings, where used, shall have their radial seams butt welded with abacking strip as shown in the same figure. Bottom sketch and rect-angular plates shall be lapped over the annular ring of segmental

Pmax = internal pressure,W = total weight of shell and structure supported by shell in N

(kgf),D = diameter of tank in m, andt = thickness of roof in mm.

IS : 803 - 1976

18

plates with the lap not less than five times the nominal thicknessthe thinner plates joined.

FIG. 3 TYPICAL FOUNDATIONS

IS : 803 - 1976

19

b) Bottoms may be of butt welded construction. Plates shall have theparallel edges prepared for butt welding with either square orV-grooves. If square grooves are employed, the root opening shall benot less than 6 mm. The butt welds shall be made by applying abacking strip 3 mm thick or heavier by tack welding to theunderside of the plate ( see Fig. 5B, Section XX ). A metal spacershall be used, if necessary, to maintain the root opening between theadjacent plates. The manufacturer may submit the other methods ofbutt welding the bottom for the purchasers approval. Three-platejoints shall not be closer than 300 mm from each other and also fromthe tank shell.

FIG. 4 TYPICAL LAYOUT OF TANK BOTTOM

IS : 803 - 1976

20

FIG. 5 BOTTOM PLATE ARRANGEMENT UNDERTANK SHELL

IS : 803 - 1976

21

6.2.3 Bottom Plate Resting on Piers6.2.3.1 For tanks erected on an elevated foundation, and the bottom platesupported on piers or beams, minimum thickness of bottom plate tb in mmshall be obtained by the equation:

where

6.2.3.2 The thickness determined by 6.2.3.1 shall be checked by shearstresses due to the total load Hp l acting at the supports and shall beincreased if required, to keep these stresses within limits specified inIS : 800-1962*.

6.2.3.3 Special consideration shall be given for any other concentratedloads acting on the bottom plate.

6.2.3.4 Generally bottom plate built under this rule is a butt weldedconstruction so that the plate rests uniformly on the supporting structure.

6.2.3.5 Rules for fabrication given in 6.2.1 (b), 6.2.1 (c) and 6.2.2 (b) aboveshall also govern fabrication of the bottom plate resting on piers/beams.

6.2.4 The joint between the bottom edge of the lowest course of shell plateand bottom plate or annular segmental plate shall be by a continuousfillet weld laid on each side of the shell plate. The size of each weld shallbe not greater than 12 mm and not less than the nominal thickness of thethinner of the two plates joined, nor less than the following values:

G = specific gravity of stored product but not less than 1,Hp = uniform loading on the bottom plate in N/mm2 (kgf/cm2) due to

maximum head of water in the tank,l = length of bottom plate in mm freely supported between the

successive piers/beams, andSb = maximum allowable bending stress in plate in N/mm2

(kgf/cm2).

*Code of practice for use of structural steel in general building construction( revised ).

Maximum Thickness of Shell Plate, mm

Minimum Size of FilletWeld, mm

5 56 to 20 6

21 to 30 8Over 32 10

tb3 G Hp l

2

4 Sb------------------------------------=

IS : 803 - 1976

22

6.3 Design of Shell Plates6.3.1 Loads6.3.1.1 Stresses in the tank shell shall be computed on the assumptionthat the tank is filled with water of specific gravity 1.00 or the liquid to bestored, if heavier than water. The tension in each course shall becomputed at 30 cm above the centre line of the lower horizontal joint ofthe course in question.6.3.1.2 Isolated radial loads on tank shells, such as caused by heavy loadsfrom platforms and elevated walkways between tanks, shall bedistributed appropriately, preferably in a horizontal position.6.3.1.3 Wind and internal vacuum loads shall be considered together tocheck the stability of tank shells. Wind loads shall be as specified inFig. 1A of IS : 875-1964*. Internal vacuum in the tank shall be specifiedby the purchaser; however, a minimum of 500 N/m2 (50 kg/m2) vacuumshall be considered.6.3.2 Joint Efficiency Factor This shall be taken as 0.85 for doublewelded butt joints, to determine the minimum thickness of shell platescomputed from the stress on the vertical joints, subject to all vertical andhorizontal butt welds being spot radiographed as recommended by thiscode. Where welds are not to be so examined by radiography, the jointefficiency factor considered for design shall be 0.70.6.3.3 Plate Thicknesses6.3.3.1 The minimum thickness of shell plates shall not be less than thatcalculated from the following formula or as specified in 6.3.3.2 whicheveris greater:

if S is in N/mm2

or

if S is in kgf/cm2

where

*Code of practice for structural safety of buildings: Loading standards ( revised ).

t = minimum thickness in mm;D = nominal diameter of tank in m;H = height from the bottom of the course under consideration to

top of top curb angle or to bottom of any overflow which limitstank filling height in m;

G = specific gravity of liquid to be stored, but in no case less than1.0;

S = allowable stress; andE = joint efficiency factor.

t 4.9 H 0.3( )DGSE

------------------------------------------=

50 H 0.3( )DGSE

-----------------------------------------=

IS : 803 - 1976

23

6.3.3.2 In no case shall the nominal thickness of shell plates (includingshell extensions for floating roof) be less than the following:

6.3.3.3 The nominal thickness of shell plates refers to the tank shell asconstructed and is based on stability rather than stress. Any requiredcorrosion allowance for the shell plates shall be added to the calculatedthickness of 6.3.3.1, unless otherwise specified by the purchaser.6.3.3.4 The maximum nominal thickness of tank shell plates shall be40 mm, except that insert plates up to 75 mm thickness inclusive shall bepermitted for material conforming to IS : 2002-1962* Grade 2B andIS : 2041-1962 steels.6.3.3.5 The width of the shell plate shall be as agreed to between thepurchaser and the manufacturer, but preferably should not be less than1 500 mm.6.3.3.6 Stability of tank shells against external loads shall be checked bydetermining the maximum height of the shell from the tap curb angle orwind girder that does not buckle under this loading and providingstiffening to the shell if required.

The maximum height of unstiffened shell, in metres, shall not exceedH1 as determined by the following equation:

, if p is in N/m2

or

, if p is in kgf/m2

where

Nominal Tank Diameter Minimum Nominal Thicknessm mm

Less than 15 5.0Over 15 up to and including 36 6.0Over 36 up to and including 60 8.0Over 60 10.0

*Specification for steel plates for boilers.Specification for steel plates for pressure vessels.

H1 = vertical distance between the intermediate wind girder andtop angle of the shell or the top wind girder of an open top tankin m;

t = average shell thickness in height H1 in mm determined fromthe actual thicknesses of plates used unless the purchaserspecifies that the net thickness (actual thickness used minuscorrosion allowance specified) shall be considered;

H114 700 t

p---------------------- t

D----

3

=

1 500 tp

------------------- tD----

3

=

IS : 803 - 1976

24

An initial calculation shall be made using the thickness of the top shellcourse. Further calculations shall be made by considering the weightedaverage thickness of the top course and part or all of the next lowercourse, or courses, till the value H1 equals or is less than the height ofshell used in determining the average thickness.

When such a value of H1 is obtained, an intermediate wind girder shallbe provided on the shell at a distance below the top wind girder of curbangle, equal to or less than the height of shell used in determining theaverage thickness.

Minimum distance from this girder to the nearest horizontal joint inthe shell shall be 150 mm. The required minimum section modulus incubic centimetres of this girder shall be determined by the equation:

Z = 0.059 D2H1This formula is applicable for total external pressures up to 1 470 N/m2

(150 kgf/m2). For greater external pressures P, required minimum sectionmodulus of this girder is computed by multiplying above equation by

or where P is in N/m2 or kgf/m2 respectively.

Thereafter, the rest of the shell below this intermediate girder shall bechecked in the same manner considering this girder as the top of the tank.

If value of H1 continues to be greater than the height of shell used indetermining the average thickness, the shell is considered stable againstthe external loads that are considered and no intermediate girder isrequired.6.3.4 Shell Plate Arrangement6.3.4.1 The shell shall be designed to have all courses truly vertical. Thecentre-line of each course shall be on top of the centre-line of the courseimmediately below or alternatively the inside surfaces of offset horizontalbutt joints shall be kept flush, as desired by the purchaser. The system ofconstruction to be followed should be specified in the order.6.3.4.2 Vertical joints in adjacent shell courses shall not be in alignmentbut shall be offset from each other as large a distance as possible but in nocase less than a distance of 5t, t being the plate thickness of the thickercourse at the point of offset.6.3.5 Shell Joints6.3.5.1 Vertical and horizontal joints All vertical and horizontal jointsshall be of double-welded butt construction with complete penetration andfusion through the full thickness of the parent plate. Suggested forms ofjoints are shown in Fig. 6.

D = nominal tank diameter in m; andp = sum of all external pressures acting on the tank shell, that is,

wind pressure and internal vacuum.

P1 470--------------- P

150----------

IS : 803 - 1976

25

6.3.5.2 The suitability of plate preparation and welding procedure shallbe the manufacturers choice subject to welding procedure qualification asspecified in IS : 823-1964*.

FIG. 6 TYPICAL HORIZONTAL AND VERTICAL JOINTS

*Code of procedure for manual metal arc welding of mild steel.

IS : 803 - 1976

26

6.3.5.3 The wide face of unsymmetrical V or U butt joints may be on theoutside or on the inside of the tank shell.6.3.6 Roof-Curb Angle6.3.6.1 Except as specified for open top tanks in 6.3.8.6, tank shells shallbe provided with top-curb angles of sizes not less than specified in 6.3.6.2and as may be required by 6.3.6.3. This will be attached to the upper edgeof the shell plate by a double-welded butt or lap joint. The horizontal legof the top angle may extend inside or outside the tank shell at thepurchasers option. Typical roof to shell joints and roof plate joints aregiven in Fig. 7.

6.3.6.2 Minimum sizes of top curb angle shall be:FIG. 7 TYPICAL ROOF JOINTS

a) Tanks up to and including 10 m diameter 65 65 6.0 mmb) Tanks over 10 m and up to and including

18 m diameter65 65 8.0 mm

c) Tanks over 18 m and up to and including36 m diameter

75 75 10.0 mm

d) Tanks over 36 m diameter 100 100 10.0 mm

IS : 803 - 1976

27

NOTE Thickness specified above includes corrosion allowance required forpetroleum service. Special consideration should be given for severe service.

6.3.6.3 For tanks having internal pressure, cross-sectional area of curbangle provided shall not be less than the area required to resist thecompressive force at the roof shell junction minus the participating shelland roof area shown in Fig. 8.

Area of curb angle required is given by:

where

This area may be provided by using rolled angle or other section orplate girder as shown in Fig. 8.

When plate girder as shown in Fig. 8, DetailD is used, required areaof this girder is given by:

Ac = area of curb angle in cm2;D = tank diameter in m;P = upward force due to internal tanks pressure minus weight of

roof plates;= angle between the roof and a horizontal plane at the roof shell

junction in degrees;Ws = width of the shell in the compression region in cm;

= 0.19 where RS = radius of tank shell in cm;

tS = nominal shell thickness in mm;WR = width of the roof in the compression region in cm;

= 0.095 ;

RR = radius of roof at roof shell junction in cm; andtR = nominal roof thickness in cm.

RS tS

RR tR

IS : 803 - 1976

28

6.3.7 Circular Shell Openings6.3.7.1 Opening in tank shells larger than 64 mm in diameter shall bereinforced. The minimum cross-sectional area of the reinforcement shallbe not less than the product of the vertical diameter of the hole cut in thetank shell and the shell plate thickness required under 6.3.3.1. The cross-sectional area of the reinforcement shall be measured along the verticalaxis passing through the centre.

6.3.7.2 If a thicker shell plate is used than is required for the hydrostaticloading and corrosion allowance ( see 6.3.3.3 ), the excess shell platethickness, within a vertical distance, both above and below the centre-lineof the hole in the tank shell plate, equal to the vertical dimension of the holein the tank shell plate, may be considered as reinforcement, and the thicknessT of the opening reinforcement plate may be decreased accordingly.

6.3.7.3 All effective reinforcements shall be made within a distance, aboveor below the centre-line of the shell opening, equal to the vertical

FIG. 8 SOME PERMISSIBLE DETAILS OF COMPRESSION RINGS

IS : 803 - 1976

29

dimensions of the hole in the tank shell plate. The reinforcement may beprovided within a vertical distance, both above and below the centre-lineof the hole in the shell, equal to the vertical dimension of the hole in thetank shell plate by any one, or by any combination, of the following:

a) The reinforcing plate;b) The portion of the neck of the fitting which may be considered as

reinforcement according to 6.3.7.4; andc) Any excess shell plate thickness, beyond that required under 6.3.3.1,

and corrosion allowance.6.3.7.4 The following portions of the neck of a fitting may be considered aspart of the area of reinforcement:

a) The portion extending outwardly from the outside surface of thetank shell plate for a distance equal to four times the neck wallthickness or, if the neck wall thickness is reduced within thisdistance, to the point of transition;

b) The portion lying within the shell plate thickness; andc) The portion extending inwardly from the inside surface of the tank

shell plate for a distance as specified under 6.3.7.4(a).6.3.7.5 The aggregate strength of the weld attaching a fitting to the shellplate, or to an intervening reinforcing plate, or to both, shall equal at leastthe proportion of the forces passing through the entire reinforcementwhich is computed to pass through the fitting considered.6.3.7.6 The aggregate strength of the weld attaching any interveningreinforcing plate to the shell plate shall at least equal to proportion of theforces passing through the entire reinforcement which is computed topass through the reinforcing plate considered.6.3.7.7 The attachment welding to the shell, along the outer periphery ofthe reinforcing plate, shall be considered effective only for the parts lyingoutside the area bounded by vertical lines drawn tangent to the shellopening. The outer peripheral welding, however, shall be appliedcompletely around the reinforcement. All the inner peripheral weldingshall be considered effective.

The strength of the effective attachment welding shall be considered asits shear resistance at the stress values given for fillet welds under 5.2.

The outer peripheral weld shall be of a size not less than 0.5 tmin wheretmin is the smaller of 20 mm or the thickness less corrosion allowance ofeither of the parts joined by a fillet weld or groove weld; except that whenlow type nozzles are used with the reinforcing plate extending to the tankbottom, the size of that portion of the peripheral weld which attaches thereinforcing plate to the bottom plate shall conform to 6.2.4. The innerperipheral welding shall be large enough to sustain the remainder of theloading.

IS : 803 - 1976

30

Figures 11 and 12 show acceptable methods of attachment. Forconvenience fillet sizes for one type of attachment are given in Table 9,and Table 10 respectively for manholes and nozzles. For other types ofattachments, fillet sizes shall be determined according to 6.3.7.5, 6.3.7.6and 6.3.7.7.6.3.7.8 When two or more openings are located so close that their normalreinforcing plate edges are closer than ten times the thickness of thethicker reinforcing plate with a minimum of 150 mm, they shall betreated and reinforced as follows:

a) All such openings shall be included in a single reinforcing plate,which shall be proportioned for the largest opening in the group;

b) If the normal reinforcing plates for the smaller openings in thegroup, considered separately, would fall within the area limits of thesolid portion of normal plate for the largest opening, the smalleropenings may be included in a normal plate for the largest openingswithout increase in size of that plate; provided, however, that if anyopening intersects the vertical centre-line of another, the total widthof the final reinforcing plate along the vertical centre-line of eitheropening shall be not less than the sum of the widths of the normalplates for the openings involved; and

c) If the normal reinforcing plates for the smaller openings, consideredseparately, would not fall within the area limits of the solid portionof a normal plate for the largest opening, the group reinforcing platesize and shape shall be such as to include the outer limits of thenormal reinforcing plates for all of the openings in the group.Change of size from the outer limits of the normal plate for thelargest opening to the outer limits of that for the smaller openingfarthest therefrom shall be by uniform straight taper unless thenormal plate for any intermediate opening would extend beyond thelimits so fixed, in which case uniform straight tapers shall join theouter limits of the several normal plates. Provisions under 6.3.7.8(b) with respect to openings on the same or adjacent vertical centre-lines shall also apply in this case.

6.3.7.9 Reinforcement for non-circular openings shall be given specialconsideration.6.3.8 Design of Wind Girders for Open-Top Tanks6.3.8.1 Open top tanks shall be provided with stiffening rings to maintainroundness when the tank is subjected to wind loads. Stiffening rings shallbe located at or near the top course, and preferably on the outside of thetank shell.6.3.8.2 The required minimum section modulus of the wind girder shallbe determined by the following formula:

Z = 0.059 D2H

IS : 803 - 1976

31

where

Stiffening ring having a section modulus given by the above formula isadequate for external pressures (wind + vacuum) up to 1 470 N/m2 (150kgf/mm2). For greater external pressure P, required section modulus ofthe stiffening ring shall be computed by multiplying above equation by

(or where P is in kgf/m2).

6.3.8.3 The section modulus of the stiffening ring shall be based upon theproperties of the applied members and may include a portion of the tankshell for a distance of 16 plate thicknesses below and, if applicable, abovethe ring shell attachment. When curb angles are attached to the top edgeof the shell ring by butt welding, this distance shall be reduced by thewidth of the vertical leg of the angle. Section modulii values for typicalring members are given in Table 7.6.3.8.4 Stiffening rings may be made of either structural section, formedplate section, or sections built-up by welding, or of combinations of suchtypes of sections assembled by welding. The outer periphery of stiffeningrings may be circular or polygonal. Built-up stiffening rings using flatsand bars are permitted subject to purchasers approval.6.3.8.5 The minimum size of angle for use along, or as component in abuilt-up stiffening ring, shall be 60 60 6 mm. The minimum nominalthickness of plate for use in formed or built-up stiffening rings shall be6 mm.6.3.8.6 When stiffening rings are located more than 0.6 m below the top ofthe shell, the tank shall be provided with a 60 60 5 mm top curb anglefor 5 mm shells, and with a 75 75 6 mm angle for shell greater than5 mm. Other rolled sections of equivalent section modulus may also beused.6.3.8.7 Rings of such design that liquid may be trapped thereon shall beprovided with adequate drain holes.6.3.8.8 Stiffening rings or portions thereof, which are regularly used as awalkway, shall have a width not less than 0.6 m clear of the projectingcurb angle on the top of the tank-shell, shall be located preferably 1 mbelow the top of the curb angle, and shall be provided with a standardrailing on the unprotected side and at the ends of the section so used.6.3.8.9 When a stair opening is installed through a stiffening ring, thesection modulus of that portion of the ring outside the opening, and includingthe transition section, shall conform to the requirements of 6.3.8.2. The

Z = section modulus in cm3,D = normal diameter of tank in m, andH = height of tank shell in m including any free board provided

above the maximum filling height as guide for the floating roof.

P1 470--------------- P

150----------

IS : 803 - 1976

32

shell adjacent to such opening shall be stiffened with an angle, or bar, placedhorizontally. The other sides of the opening shall be stiffened with an angle,or bar, placed vertically. The cross-sectional area of these rim stiffenersshall be at least equivalent to the cross-sectional area of that portion ofshell included in the section modulus calculations of the stiffening ring( see 6.3.8.8 ). These stiffeners, or additional members, shall furnish asuitable tee board around the opening. The stiffening members shall extendbeyond the end of the opening for a distance equal to or greater than theminimum depth of the regular ring section. The end stiffening membersshall frame into the side stiffening members and shall be connected to themin such a manner as to develop their full strength.6.3.8.10 Supports shall be provided for all stiffening rings when thedimension of the horizontal leg or web exceeds 16 times the leg or webthickness. Such supports shall be spaced at intervals as required for thedead load and vertical live load that may be placed upon the ring.However, the spacing shall not exceed 24 times the width of the outsidecompression flange.6.3.8.11 Continuous seal welds of about 3 mm shall be used for all jointswhich, because of their location, may be subjected to corrosion fromentrapped moisture or cause rust markings on the tank shell. Fullpenetration butt welds shall be used for jointing ring sections.6.3.9 An alternate method for design of tank shells is dealt with inAppendix B.

TABLE 7 SECTION MODULUS OF WIND GIRDERS( Clause 6.3.8.3 )

All dimensions in millimetres.

SECTION THROUGH WIND GIRDER MEMBER SIZE IN SECTION MODULUS IN cm3 FOR SHELL THICKNESS

mm mm mm 5 mm 6 mm

Detail A Top Angle

ISA 65 65 6

ISA 65 65 8

ISA 75 75 10

6.4

8.3

13.6

6.5

8.5

13.0

( Continued )

IS : 803 - 1976

33

TABLE 7 SECTION MODULUS OF WIND GIRDERS Contd


mm mm mm 5 mm 6 mm

Detail B Curb Angle

ISA 65 65 6

ISA 65 65 8

ISA 75 75 6

ISA 75 75 10

ISA 100 100 6

ISA 100 100 10

27.2

33.2

36.3

50.0

63.8

73.7

28.4

34.9

37.8

54.1

66.8

92.2

Detail C Single Angle

ISA 65 65 6

ISA 65 65 8

ISA 100 75 8

ISA 125 75 8

ISA 150 115 10

28.3

34.8

67.5

90.1

157.5

29.4

36.4

70.6

94.5

190.1

( Continued )

IS : 803 - 1976

34



mm mm mm 5 mm 6 mm

Detail D Two Angles

ISA 100 75 8

ISA 100 75 10

ISA 125 75 8

ISA 125 75 10

ISA 125 95 8

ISA 125 95 10

ISA 150 115 10

182.2

217.6

250.7

300.2

288.5

346.9

506.7

187.5

224.1

258.4

309.5

296.0

356.2

518.9

Detail E Formed Plate

b = 250b = 300b = 350b = 400b = 450b = 500b = 550b = 600b = 650b = 700b = 750b = 800b = 850b = 900b = 950b = 1 000

341.0427.2518.7615.5717.4824.4936.6

1 053.81 176.11 303.51 435.91 573.41 716.01 863.52 016.12 166.7

( Continued )

IS : 803 - 1976

35


SECTION THROUGH WIND GIRDER MEMBER SIZE IN SECTION MODULUS IN cm3 FOR SHELL THICKNESS,

6 mmmm

Detail F Formed Plate

b = 250

b = 300

b = 350

b = 400

b = 450

b = 500

b = 550

b = 600

b = 650

b = 700

b = 750

b = 800

b = 850

b = 900

b = 950

b = 1 000

b = 1 050

b = 1 100

b = 1 150

b = 1 200

335.2

417.6

504.6

596.5

693.2

794.8

901.3

1 012.8

1 129.2

1 250.6

1 376.6

1 508.2

1 644.4

1 785.6

1 931.8

2 082.9

2 239.1

2 400.2

2 566.3

2 737.4

IS : 803 - 1976

36

6.4 Designs of Roof6.4.1 Definitions The following definitions shall apply to designs ofroofs.6.4.1.1 Supported cone roof A roof formed to approximately the surfaceof a right cone, with its principal support provided by either rafters ongirders and columns or rafters on trusses with or without columns.6.4.1.2 Self-supporting cone roof A roof formed to approximately thesurface of a right cone, supported only at its periphery.6.4.1.3 Self-supporting dome roof A roof formed to approximately aspherical surface, supported only at its periphery.6.4.1.4 Self-supporting umbrella roof A modified dome roof so formedthat any horizontal section is a regular polygon with as many sides asthere are roof plates, supported only at its periphery.6.4.2 General6.4.2.1 All roofs and supporting structures shall be designed to supportdead load, plus a uniform live load of not less than 1 225 N/m2 (125kgf/m2) of projected area.6.4.2.2 Roof plates shall have a minimum nominal thickness of 5 mm. Agreater thickness may be required for self-supporting roofs ( see 6.4.5 and6.4.6 ).6.4.2.3 Roof plates of supported cone roofs shall not be attached to thesupporting members.6.4.2.4 All internal and external structural members of the roof shallhave a minimum nominal thickness, in any component, of 4.5 mm.6.4.2.5 Roof plates shall be attached to the top angle of the tank with acontinuous fillet weld on the top side only.

If the continuous fillet weld between the roof plates and the top angledoes not exceed 5 mm and the slope of the roof at the top angleattachment does not exceed 1 in 6, the joint may be considered to befrangible and, in case of excessive internal pressure, will fail beforefailure occurs in the tank shell joints or the shell-to-bottom joint. Failureof the roof-to-shell joint may be accompanied by buckling of the top angle.

Where the weld size exceeds 5 mm or where the slope of the roof at thetop-angle attachment is greater than 1 in 6, emergency venting devices inaccordance with Appendix C shall be provided by the purchaser. Themanufacturer shall provide a suitable tank connection for the device.6.4.2.6 Roof plate shall be lapped with a minimum overlap of 25 mm andshall be welded with a continuous fillet weld on the top side only. Lapsshall be arranged as shown in Fig. (A) or (B) of Fig. 7 for roof plate jointdepending on the local conditions by agreement between the purchaserand the manufacturer.

IS : 803 - 1976

37

6.4.2.7 For all types of roofs, the plates may be stiffened by sectionswelded to the plates but not to the supporting rafters and/or girders.6.4.3 Permissible Stresses All parts of the structure shall be soproportioned that the sum of the maximum static stresses shall notexceed the permissible stresses given in IS : 800-1962*.6.4.4 Supported Cone Roofs The design of supported cone roof shallconform to the following:

a) Roof plates shall be welded on the top side with continuous full-filletwelds on all seams. The size of the roof-to-top angle weld shall be 5mm or smaller if so specified by the purchaser.

b) The slope of the roof shall be 1 in 16 or greater as specified by thepurchaser. If the rafters are set directly on chord girders producingslightly varying rafter slopes, the slope of the flattest rafter shallconform to the specified or ordered roof slope.

c) Main supporting members, including those supporting the rafters,may be rolled or fabricated section or trusses, with or withoutsupporting columns. Although these members may be in contactwith the roof plates, the compression flange of a member or the topchord of a truss shall be considered to receive no lateral supportfrom the roof plates and shall be laterally braced, if necessary, byother acceptable methods.

d) Structural members, serving as rafters, may be rolled or fabricatedsections. Rafters in direct contact with the roof plates applying theloading to the rafters may be considered to receive adequate lateralsupport from the friction between the roof plates and thecompression flanges of the rafters, with the following exceptions:(1) Trusses and open-web joists used as rafters,(2) Rafters having a nominal depth greater than 375 mm, and(3) Rafters having a slope greater than 1 in 6.

e) Rafters shall be spaced so that, in the outer ring, their centres shallnot be more than 2 m measured along the circumference of the tank.Spacing on inner rings shall not be greater than 1.75 m. Whenspecified by the purchaser for tanks located in areas subject toearthquake, 20 mm diameter tie rods (or equivalent) shall be placedbetween the rafters in the outer rings. These tie rods may be omittedif I or H sections are used as rafters.

f) Roof columns shall be made from structural shapes or pipes orbuilt-up sections. Suitable base frames or reinforcing pads shall beprovided at the column base to distribute loads coming on the tankbottom.

*Code of practice for use of structural steel in general building construction( revised ).

IS : 803 - 1976

38

g) Rafters clips for the outer row of rafters shall be welded to the tankshell. Columns shall not be rigidly attached to the bottom plate.Guide clips shall be welded to the tank bottom to prevent lateralmovement of columns. All other structural attachments shall beeither bolted, riveted, or welded.

6.4.5 Self-Supporting Cone Roofs Self-supporting cone roofs shallconform to the following requirements:

NOTE Self-supporting roofs having the roof plates stiffened by sections welded tothe plates need not conform to the above minimum thickness requirements, butshould be not less than 5 mm when so designed by the manufacturer, subject to theapproval of the purchaser.

6.4.5.1 The cross-sectional area of the top angle in cm2 plus the cross-sectional areas of the shell and roof plates within a distance of 16 timestheir thicknesses measured from their most remote point of attachment tothe top angle, shall not be less than:

whereD = nominal diameter of tank shell in m,

= angle of cone elements with the horizontal in degrees, andt = nominal thickness of roof plates in mm.

6.4.6 Self-Supporting Dome and Umbrella Roofs Self-supporting domeand umbrella roofs shall conform to the following requirements:

These formulae for self-supporting roofs assume a uniform live load of1 225 N/m2 (125 kgf/m2).

NOTE Self supporting roofs having the roof plates stiffened by sections welded tothe plates need not conform to the minimum thickness requirements, but should notbe less than 5 mm when so designed by the manufacturer, subject to the approval ofthe purchaser.

Maximum = 37Minimum sin = 0.165 (slope 1 in 6)

Minimum t = but not less than 5 mm

Maximum t = 12 mm

Minimum R = 0.8 DMaximum R = 1.2 D where R = radius of the dome in m,Minimum t

in mm= R/2.5 but not less than 5 mm

Maximum t = 12 mm

IS : 803 - 1976

39

6.4.6.1 The cross-sectional area of the top angle in cm2 plus the cross-sectional areas of the shell and roof plates within a distance of 16 timestheir thicknesses, measured from their most remote point of attachmentto the top angle, shall equal or exceed:

whereD = nominal diameter of tank shell in m,R = radius of curvature of roof in m, andt = nominal thickness of roof plates in mm.

6.4.7 Top-Angle Attachment for Self-Supporting Roofs

6.4.7.1 The top-angle sections for self-supporting roofs shall be joined bybutt welds having complete penetration and fusion. Joint efficiencyfactors need not be applied if it conforms to the requirements of 6.4.5 and6.4.6.

6.4.7.2 For self-supporting roofs whether of the cone, dome or umbrellatype, the edges of the roof plates, at the option of the manufacturer, maybe flanged horizontally to rest flat against the top angle to improvewelding conditions.

6.4.8 Recommended column layout for tanks and column and girderattachment details are shown in Fig. 9 and 10.

6.5 Floating Roof Reference may be made to Appendix D for thedesign and construction of floating roofs.

7. APPURTENANCES AND MOUNTINGS

7.1 General

7.1.1 Appurtenances or mountings installed on tanks should conform tothis code. Alternative designs of appurtenances which provide equivalentstrength, tightness and utility are permissible, if so agreed by thepurchaser.

7.1.2 Manhole necks, nozzle necks, reinforcing plates, and shell-plateopenings, which have either sheared or oxygen-cut surfaces, shall havesuch surfaces made uniform and smooth, with the corners rounded,except where such surfaces are fully covered by attachment welds.

7.2 Shell Manholes

7.2.1 Shell manholes shall conform to Fig. 11 and Tables 8 and 9.

7.2.2 Manhole frames may be press-formed or of built-up weldedconstruction.

DR20---------

IS : 803 - 1976

40

FIG. 9 RECOMMENDED LAYOUT OF COLUMNS FOR NORMALSIZE TANKS

IS : 803 - 1976

41

FIG. 10 TYPICAL COLUMN AND GIRDER ATTACHMENT DETAILS

IS : 803 - 1976

42

7.3 Shell Nozzles

7.3.1 Shell nozzles shall conform to Fig. 12 and 13 and Table 10.

7.3.2 Details and dimensions specified herein are for nozzles installedwith their axes perpendicular to the shell plate. Nozzles may be installedat an angle of other than 90 to the shell plate in a horizontal plane,provided that the width of the reinforcing plate is increased by theamount that the horizontal chord of the opening cut in the shell plateincreases as the opening changes from circular to elliptical in making theangular installation. In addition, nozzles not larger than 75 mm nominalpipe size, for insertion of thermometer wells, sampling connections, orother purposes not involving the attachment of extended piping, may beinstalled at an angle of 15 or less off perpendicular in a vertical plane,without modification of the nozzle reinforcing plate.

7.4 Roof Manholes

7.4.1 Manholes in the roof shall conform to Fig. 14 and Table 11. Theyshall be suitable for attachment by welding to the tank roof sheets andshall be positioned close to roof sheet supporting members.

7.4.2 The manhole cover may be hinged with single or multiple bolt fixingas required by the purchaser.

7.4.3 Openings made for fixing manholes on self supporting roofs androofs subjected to internal pressure shall be reinforced by a plate ringhaving the same thickness of roof plate and outer diameter equal to twicethe diameter of the opening.

7.5 Roof Nozzles

7.5.1 Flanged roof nozzles shall conform to Fig. 15 and Table 12,installation of threaded nozzles shall be as shown in Fig. 15.

7.5.2 All nozzle openings greater than 150 mm diameter, shall bereinforced by a plate ring having the same thickness as roof plate andouter-diameter equal to twice the diameter of the opening.

7.6 Water Draw-Offs and Drain Pad

7.6.1 Water draw-off sumps shall conform to Fig. 16.

7.6.2 Drain pad for elevated tanks shall be in accordance with Fig. 17 andTable 13.

7.7 Platforms, Gangways and Stairways

7.7.1 Platforms and gangways shall conform to the following:a) Platforms and gangways shall be capable of supporting a moving

concentrated load of 4 412 N (450 kgf) and the handrailing structure

IS : 803 - 1976

43

shall be capable of withstanding a load of 882 N (90 kgf) applied inany direction at any point on the top rails.

b) All parts shall be made of metal.

c) Flooring shall be of grating or of non-slip material.

d) A standard width of such gangways on a tank is 600 mm. Widergangways may be used if required by the purchaser.

e) Handrailing of 1 m height shall be provided on all open sidesand shall have a toe board not less than 75 mm besides top andmid-rails.

f) At handrail openings, any space between the tank and the platformwider than 150 mm shall be floored.

7.7.2 Stairways shall conform to the following:

a) Stairways shall be capable of supporting a moving concentrated loadof 4 412 N (450 kgf) and the handrailing structure shall be capableof withstanding a load of 882 N (90 kgf) applied in any direction atany point on the top rail.

b) Handrails shall be on both sides of straight stairs, as well as onspiral stairs when the clearance between the tank shell and stairstringer exceeds 200 mm.

c) Spiral stairways should be completely supported on the shell of thetank and ends of the stringers should be clear of the ground.

d) All parts to be made of metal.

e) Standard width of stairs is 800 mm. Wider stairs may be used ifrequired by purchaser.

f) Standard width of stair treads is 250 mm, and shall be of a grating ornon-slip material.

g) Maximum angle of stairway with a horizontal line shall be 50.

h) Stair tread rises shall be uniform throughout the height of thestairway and preferably be 200 mm.

j) Top railing shall join the platform handrail without offset, and theheight measured vertically from tread level at nose of tread shall be750 to 850 mm.

k) Maximum distance between railing posts measured along the slopeof the railing shall be 2.4 m.

7.8 Flush Type Cleanout Fitting Figure 18 shows an acceptabletype of flush type cleanout fitting that may be incorporated in a tank if

IS : 803 - 1976

44

FIG. 11 TYPICAL SHELL MANHOLES ( see Tables 8 and 9 )

IS : 803 - 1976

45

specified by the purchaser. Tables 14, 15 and 16 give additional data anddimensions of this fitting. Special consideration shall be made by thepurchaser in design of foundation to provide an adequate support to thisfitting.

7.9 Gauge Wells Typical sketches of gauge wells showing twodifferent methods of installing gauges without welding them to theexisting roof nozzles are given in Fig. 19.

7.10 Tank Accessories Other tank accessories like level indicator,foam chamber, gauge hatch, free vents and earthing boss be providedconforming to Indian Standard specifications wherever available and inagreement with the purchaser.

TABLE 8 SHELL MANHOLE COVER PLATE AND BOLTING FLANGE THICKNESS ( see Fig. 11 )

( Clause 7.2.1 )

MAXI- MUM TANK

HEIGHT m

EQUI- VALENT

*PRESSURE IN N/mm2 (kgf/cm2)

MINIMUM COVER PLATE THICKNESS IN mm

MINIMUM BOLTING FLANGE THICK- NESS AFTER FINISHING IN mm

500-mm Man- hole

600-mm Man- hole

750-mm Man- hole

900-mm Man- hole

500-mm Man- hole

600-mm Man- hole

750-mm Man- hole

900-mm Man- hole

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)

6.5

8.0

10.0

12.0

14.0

16.5

20.0

23.0

0.065

0.08

0.10

0.12

0.14

0.165

0.20

0.23

(0.65)

(0.80)

(1.00)

(1.20)

(1.40)

(1.65)

(2.0)

(2.3)

8

10

10

12

12

12

14

16

10

12

12

12

14

14

16

18

12

12

14

16

16

18

20

20

12

14

16

18

20

20

22

25

6

6

6

8

10

10

11

12

6

8

8

10

12

12

12

14

8

10

10

12

12

14

16

18

10

12

12

14

16

18

20

20

*Equivalent pressure is based on water loading.

IS : 803 - 1976

46

TABLE 9 SHELL MANHOLE DIMENSIONAL DATA ( see Fig. 11 )( Clause 7.2.1 )


a) Nominal size, DO.D. of cover plate, DCBolt circle dia, DB

500725650

600825750

750975900

9001 1251 050

b) The minimum neck thickness Tp shall be the thickness of the shell plate, or theallowable finished thickness of the bolting flange ( see Table 8 ) whichever isthinner, but in no case shall it be thinner than the following:

Shell Thicknessmm

Thickness of Neck, Tpmm

5-20

21-25

26-30

31-36

37-40

8

11

12

18

20

NOTE If neck thickness on a built-up manhole is greater than the requiredminimum, the manhole reinforcing plate may be decreased accordingly within thelimits specified in 6.3.

c) Opening in the shell DS shall be equal to Do + 100 mm for Type A attachments.For other type of attachments DS shall be established by manufacturer asrequired.

d) Opening in the reinforcing plate Dp shall be equal to O.D. of neck Do + 3 mm.

e) Sizes of fillet welds (leg length) for attachment Type A shall be as follows:e = 3T/4, but not less than 6 mm.f = T/2, but not more than 12 mm and not less than 8 mm.g = t, where t is 10 mm or less, or

t/2 with a minimum of 10 mm where t exceeds 10 mm.

f) For attachment Types B, C and D, sizes of fillet welds shall be fixed in accordancewith 6.3.7.5, 6.3.7.6 and 6.3.7.7.

IS : 803 - 1976

FIG. 12 TYPICAL SHELL NOZZLES ( see Table 10 )

47

As in the Original Standard, this Page is Intentionally Left Blank

IS : 803 - 1976

49

8. SHOP FABRICATION AND INSPECTION

8.1 Workmanship8.1.1 All work of fabrication shall be done in accordance with this code.The workmanship and finish shall be first class in every respect subject tothe closest inspection by the manufacturers inspector, whether or not thepurchaser waives any part of the inspection.

FIG. 13 SHELL NOZZLE FLANGES ( see Table 10 )

IS : 803 - 1976

50

TABLE 10 SHELL NOZZLES DIMENSIONAL DATA ( see Fig. 12 and 13 )( Clause 7.3.1 )


A. FLANGED FITTINGS

NOMINAL SIZE OF NOZZLE, D

MINIMUM WALL THICKNESS,

Tp*

DISTANCE FROM SHELL TO FLANGE,

E

DISTANCE FROM TANK BOTTOM TO NOZZLE CENTRE

Regular Type Low Type

(1) (2) (3) (4) (5)

900850800750700650600550500450400350300250200150100

755040

121212121212121212121212121212118.57.55.55

350330330300300300300280280250250250220220200200175175150150

1 000950900850800750700650600550500450430380330280230200175150

920870820770720670620570520470420370350300250200150120100

75

B. SCREWED FITTINGS

NOMINAL SIZE OF NOZZLE

WALL THICKNESS DISTANCE FROM TANK BOTTOM TONOZZLE CENTRE

Regular Type Low Type

(1) (2) (3) (4)

7550402520

Coupling,,,,,,,,

230175150125100

14075757575

*Includes corrosion allowance required for petroleum service. Special considerationshould be given for severe service.

( Continued )

IS : 803 - 1976

51

TABLE 10 SHELL NOZZLES DIMENSIONAL DATA Contd

NOTE 1 If neck thickness on a built-up nozzle is greater than the requiredminimum, the nozzle reinforcing plate may be decreased accordingly within thelimits specified in 6.3.7.NOTE 2 Opening in the shell DS shall be equal to D0 + 65 mm for Type Aattachments. For other type of attachments, DS shall be established bymanufacturer as required.NOTE 3 Opening in the reinforcing plate Dp shall be equal to O.D. for neckD0 + 3 mm.NOTE 4 Standard size of reinforcing plate DL = 2 DS.NOTE 5 Fillet weld sizes for Type A attachment shall be as follows:e = t (shell plate thickness).f = thickness for pipe wall Tp or reinforcing plate T whichever is lesser.g = r for shell thicknesses up to 10 mm

ort/2 for shell thicknesses greater than 10 mm.

NOTE 6 For attachment Types B, C and D, fillet weld sizes shall be in accordancewith 6.3.7.5, 6.3.7.6 and 6.3.7.7.NOTE 7 Nozzle pipe wall thicknesses listed above for 650, 700, 750, 800, 850 and900 mm dia nozzles are applicable for use on tank shells up to 25 mm thickness.When these nozzles are installed on thicker shell plate, their wall thickness shall beas follows:

t

28

32

36

40

Tp

14

17.5

19.0

19.0

TABLE 11 ROOF MANHOLES ( see Fig. 14 )

( Clause 7.4.1 )

SIZE OF MANHOLE

COVER PLATE DIAMETER

DC

BOLT CIRCLE DIAMETER

DB

NO. OFBOLTS

BOLT HOLE DIAMETER

(1) (2) (3) (4) (5)

mm mm mm mm

500

600

650

750

590

690

16

20

18

18

IS : 803 - 1976

52

FIG. 14 TYPICAL ROOF MANHOLE ( see Table 11 )

TABLE 12 ROOF NOZZLES ( see Fig. 15 )( Clause 7.5.1 )

NOMINAL SIZE OF NOZZLE(1)

mm

PROJECTION OF NOZZLE H(2)mm

405075

100150200250300

150150150150150150200200

IS : 803 - 1976

53

FIG. 15 TYPICAL ROOF NOZZLES ( see Table 12 )

IS : 803 - 1976

54

FIG. 16 TYPICAL WATER DRAW-OFF SUMP

TABLE 13 DETAIL OF DRAIN PAD FOR ELEVATED TANKS ( see Fig. 17 )( Clause 7.6.2 )


NOMINAL SIZE A B C D E F G H J

NO. AND DIA OF STUDS

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

5075

100150

5090

120170

150190230280

120150190240

22252832

65105135185

42454550

25252532

15192224

90120150200

4 of 16 mm4 of 16 mm8 of 16 mm8 of 20 mm

IS : 803 - 1976

55

FIG. 17 TYPICAL DRAIN PAD FOR ELEVATED TANKS ( see Table 13 )

TABLE 14 FLUSH TYPE CLEANOUT FITTINGS ( see Fig. 18 )( Clause 7.8 )


SIZE OF OPENING

HEIGHT ( h ) WIDTH ( b )

ARC WIDTH OF SHELL

REINFORCING PLATE

UPPER CORNER RADIUS

OF OPENING

UPPERCORNER

RADIUS OF SHELL

REINFORCING PLATE

BOTTOM FLANGE WIDTH

SPECIAL BOLT

SPACING

NO. OF BOLTS

DIA- METER

OF BOLTS

(1)W(2)

r1(3)

r2(4)

f(5)

g(6) (7) (8)

600 600900 1 200

1 200 1 200

1 8002 6503 125

200375400

7251 0251 280

85120125

80105110

364652

202525

IS : 803 - 1976

56

TABLE 15 THICKNESS OF COVER PLATE, BOLTING FLANGE AND REINFORCING PLATE FOR FLUSH TYPE CLEANOUT FITTINGS ( see Fig. 18 )

( Clause 7.8 )All dimensions in millimetres unless otherwise specified.

MAXIMUM TANK

HEIGHT

MINIMUM THICKNESS OF BOLTING FLANGE AND COVER PLATE, tc FOR

OPENING SIZE

MINIMUM THICKNESS OF BOTTOM REINFORCING PLATE, tb FOR

OPENING SIZE

600 600 900 1 200 1 200 1 200 600 600 900 1 200 1 200 1 200

(1)m

(2) (3) (4) (5) (6) (7)

6.010.2512.516.018.25

1012121416

1619222525

1622222528

1212141628

2225283238

2228323636

TABLE 16 THICKNESS AND HEIGHT OF SHELL REINFORCING PLATE FOR CLEANOUT FITTINGS ( see Fig. 18 )

( Clause 7.8 )All dimensions in millimetres unless otherwise specified.

MAXIMUM TANK

HEIGHT

THICKNESS OF SHELL REINFORCING PLATE, T FOR OPENING SIZE

HEIGHT OF REINFORCING PLATE, L FOR OPENING SIZE

600 600 900 1 200 1 200 1 200 600 600 900 1 200 1 200 1 200

is code 803

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