Fourteenth Edition ‘October 1957 API SPECIFICATION otis “FOR i WELDED OIL STORAGE TANKS AMERICAN PETROLEUM INSTITUTE _ ‘New York, N. ¥. oe Issued by AMERICAN PETROLEUM INSTITUTE < Division of Production : Dallas 1; TexasAmerican Detroloam Institute ‘TABLE OF CONTENTS 5 Suggestions for Orderin; Foreword 1: Scope ... 2: Material .. 8: Desi 3.1 Joint Design 3.2 Bottom Design 38 Shell Design 2 8.4 Design of Wind Girders for Open-Top Tanks. 3.5 Roof Design 8.6 Tank Appurtenances . 52 Details of Weiding 53 Testing, Inspection, and Repairs. 6: Testing Shell Joints.. 6.1 Sectioning Method 62 Radiographic Meth ‘74 Welding Procedure Specification. 8: Marking .. Appendix A: Reference and Typical Design Data, a Appendix B: Recommended Practice for Construction of Foundations. Appendix C: Floating Roofs Appendix D: Composite Tanks Appendix E: List of Authorized Manufacturers. Appendix F: Use of API Monogram. Note ‘This specidication was eriginally adopted as, tentative 4m 1986, and as standard tr 1840. ‘Revlaod editions ‘were ‘gue th Lodz, todd, 1046, 19. September, 1955. ‘moving, a3 detailed in Gi Spplemient,1 to the 15th edition, and also. the changes ‘depted at the 1086 mesting, as detail fn Cire. PS-1000- This publication may be reproduced in whole or in part excep! tat the oneal pubcation” monoprany ‘appearing on the outside cover may nat be reproduced. ‘reproductions shall carry the statement, “Repro- duced by permiseion from API Sid 120? Specification for Welded Oil Storage Tanks.” This permission docs ‘not incluale the right to reproduce this specification as gieparate publication for rsate or aa'a translation. Such rights are granted only on special authorization,"Max. asin RMF Welded O11 Stora Tanks a SUGGESTIONS FOR ORDERING ‘The purchaser should state on his inquiry or pur- chase order the following Specification cnn API St 120 Number of tanks. Diameter, ft, Height, ft. Nominal capacity, bb. Time of completion... Freight and hauling Erection, location and facilities. Tank grade detalls.cwen-Par B12, Pate specications (botiom, shell and Bating Bottom design: “Hhickness “of plates Size of plates Joint design Shell design: ‘Sp. Gr. of contents, ‘Thicieness of plates (cach course). Wieth of plates. Wind gisders nn Roof and roof support design. Sect 35, Appendix C ‘ep appartnanecs (ps se and ect. 8.6 Stairways, platforms, and walkways. Tables 27, 18,19 Sect. 4.2 Shop Inspection Ficld inspection . Bottom test Shell Test Roof test Par.8.2.7 Painting requirements .... Par. 5.4 Special provisions (permits, fees, lisbilty, ete.) ‘The purchasor may exercise an option with respect. to the following requirements. MUL test reports. Par 42d Bottom plate arrangement and Welding procedure enn Par 5.29.10 Shell plate alignment... Par. 38 ‘Top angle orientation... Par. 23.10 Horizontal joint penetration and fusion....Par. 23.12 Roof column Roof slope me Shell manhole design... 3 Shell nozzle design, een aa Gleancut fitting support... Par. 869, Fig. 11 Roof nozzle flange design, Fig. 19,14 Drawott elbow design. Fig. 15, 16 Wolding procedure qualification test reports nn Par. 715 Welder or welding operator qualification test reports mPa 7.6, 7.3.23 Welding procedure specification. ect 74 ‘Tho following requirements are subjoct t9 azree- ‘mont between tne purchaser and the mandsecturer, Shell foint teste... Part 8 ‘Shell plate width. Ba a7 Sectioning method ~~~ ‘Sect, BL Closure of openings. Bar. 81.19 Sogmone ownership Par. 61.27 eet, 2 Radlographle mete sn 8217API SPECIFICATION FOR WELDED STORAGE TAD Foreword a, This specification is under the jurisdiction of the API Committee on Standatdization of Tanks for Oil Storage. b. Provisions for welding and details pertaining thereto, as given herein, were prepared in coopers tion with the American’ Welding Society, these. in- hiding. definitions of welding ‘and welded soints, fand fabrication thereof; materials suitable for weld: ine, Treading, eletrodeay aliication of welding procedures and weldere: and inspection requirement Tor ila welding, _ e. This specification is not intended to cover stor ag tana which are to be erecta n ava alee to Fequlations which are more stringent than this speci feation, In such cases this apecifcation should be fol. Towed insofar as it does not conflict with the local requirements 4, Other specifications undar the jurisdiction of tho Committee on Standardization of Tanks for Oil Storage include the followin Std 12A: Specification for Oil-Storage Tanks with ‘Riveted Shells. Covers material, design, fabrication, and erection pequisements for. verileal, cylindrica, above {Fround steel tare with nveted shells in nominal ‘capacities of 140 to 286,000 bi: (in standasd ‘sts) for ofl storage. Std 12G; Specification for Aluminum-Alloy Welded ‘Storage Tanks, ‘closed and open-top, welded alu minamaliay rage tanks various izes and RP 12H: Recommended Practice for Installation of ‘ew Bottoms in Old Storage Tanks. Cavers mothod of replacing bottoms in old riveted fr welded storage tanks ith new bottom of com crete ov steel, e. Related specifications under the jurisdiction of ‘the’ Committee’ on Production ‘Treating and Gaging Equipment include the following Std 12B: Specification for Bolted Production Tanks. Covers material design, and erection require: ments’ for vertical eplindrcal, above-ground, Lelted, ste, prosaction tenke in nominal espa’ ite ln standard sizes) for ‘il Seld service. alee inshudes appurtenance f° uirement. ‘Covers material, design, fabrication. and eraction Teduitements, for vertical, cplindziee, bores {round closed-top, welded ech production tanks ‘in capscities of 800 to 000 bbl. (im standard ilies) for ollsteld service, Te also Includes aprur= {enance reauizements | Teum Storage Tanks: KS ‘Std 12B: Specification for Wooden Production Tanks. ‘Covers material, design, fabrication, and erection fequirements for" vertical yim, above: found: closed-top, women peeduction tans iy fominat eanacities ef 120 to 1800 bo. Gin standard aes) for oilteld servi Std 12P; Specification for Small Welded Production ‘Tanks. Covers materia, desten. and constrostion require reente, Tors verieal, cylindrical, above-ground chop-welded."steel'Productten tanks in hominal capacities of 60 to 400 bbl (im standard sizes up foe maximum dlameter of 12H) for wich £. Related standards and recommended practices jssied by other Institute aivisions, Include the fol ovina: Std 620: Recommended Rules for the Design and Con- struction of Large, Welded, Low-Presstire Storage Tanks, Covers storare tanks for operation at internal Drostures of 0 pols up ta but not exeeeding 19 RP 2000: Guide for Tank Venting. Covers recommended practices for venting above- roan esroleon stfage tans denied ta oper ‘mended practices for testing venting devices ur neluded! “Accident Prevention Manual No. 1, Cleaning Petro- Section A: Crude Oil and Unfinished Prod- ucts Tanks. Section B: Gasoline Tanks. Ingpection of Atmospheric and Low-Pressure Storage “Tanks (Chapter XIIT of Guide for Inspection of Refinery Equipment). igo tanks for crave, intermediate Foaats, gas, chemicals and watert reasons for fr end. cnuret of deterioration: (procedures and tools Togdived for dnapection of Fania in service and out of service amd of aux- tary equipment, ineuding tasting tanks and de termining limits; methods of repairs: ang ree; ‘shimendations concerning inspection records and seportWelded Oil Storaze Tanks 5 1, SCOPE 1,1 This specification covers material, design, fabrica- tion, erection, and testing requirements Zor vertical, cylindrical, above-ground, closed and open-top, welded Steel storage tanks in various sizes and capacities, for internal. pressures approximating atmospheric pregsures but In no cage exeeading: the weight of the oof plates. 12. This specification is designed to provide the ofl lustry with tanks of adequate safety and reason~ able esqnomy, fr doen the storage of etroleum and ils products and those other liquid products common- ly handled and stored by the various branches of the Tidustry: It doeg not present, nor ia it contemplated te tstablish, a fixed series of allowablo tank sizes; but father it is intended to permit the solection by. the purchaser of whatever size of tank may be required to best meet his particular needs. 1.3 Appendix A, to this specification presents, for ready reference design data relating t9 tanks which may be built under this specification. ‘The data pre- sented thorein are for convenience and are not man- atory. | 4 Nothing contained in this specification is to be Constred a8 granting any right, by implication oF therwise, for manufacture, sale, oF use im connece fon with’any method, appatatas, or product covered by letters patent, nor al insuring Snyone against Ukpllty for‘intngement of letters patent. Compliance, The manlactarer is reponse for complying ith all of the provisions of this speeifea font "the "purchaser. may make any investigation iocessary 40 satisfy blmaolf of compliance hy the Ianufacturer, and may reject any material that does hot comply with this spectfeation, Ie urged that the purchaser avail himsel? of this right and furnish is Sen inspection independently of aay supervisory tn spection furnished by the mansiaeturen; and that the itehaser inspector Zollow closely al ofthe deta of jd construction and testing heroin specified, which afoot the integrity and safety cf the completed struc tare. 2. MATERIAL Plates Plates shall conform to the latest revision of att A tapencanrh ot let ugnace rons Sly), 28H grade G, or A 28) grade D, exeept that nil plates in thickness greater tin to A 88 grade C. Copper sted [50 specified on the pureha NOTE 1s Ag alteratives, plates enforming to ASTM a “G31 grades Ay Band C1 A201 geadep Avand B; Aas grade Bs and A $79 are Secoptahta (without restriction ox to thieknees cseept ag tpooed in 4 181 and A'978), and may Be specified when the purchaser considers the Severity of the service aonditione warrants the ee of thete premium material NOTE 2: The manufacturer shall tate in hie proposal the plate specication which he intend {oes 4% in. shall con- ring steel shall be 22. Plate specification on an edge-thickmess basis ‘i required? for all shell plates the thicknesses of nich are determined by design computations. Shell ates for which minizaam thicknesses have been fixed {ie practical reasons, and which will not under-ran fiw Oieoretieal required thiekness by more than OUL vit, also roof and bottom plates, may. be specified na 'weight basis. The plate thiclinesdes or weights, ‘stipulated Rerein are minima; thicker or heavier iatetal nay be required on the order at the aption wthe purchaser. !ASTO specifications referred to het ‘cam the Amoriean Soniety for Testing stateriala, 1010 Race “ice, Phitadelphia By Pa 2Plates may be purchased on the weight basis in comali ance eit fis reauirement, proviged. they "are. ordered weently Heavier than The foinal weight eotFeaponing Ueished” bythe mil sill mot underran the theoretical (siekness oye Gham 0.01 23 Sheets, Sheets shall conform to ths latent revision of ASTM A 245, grade C, open-hearth process only. Copper-bearing Steel shall be used if so specified on tha Hpurchase “order. Shoots may be ordered on 8 ‘weight or thickness basis, at the option of the tank manufacturer. 2A Welding Electrodes, Manual are-wolding elec. odes shall conform to the latest revision of STA A235! Specifications for, Mild. Steel “Ane. Welding Blectrodes of the B-60 Series of Classification, suit= able for the clectrie-current characteristics, the posi- tion of welding, and other conditions of intended use. 25 Structural Shapes. Structural shapes, shall con- form tothe. latest revision of ASTM AT (open- hearth or electrie-furnace process only). Copper-bear sng steel shall be used if 20 specifed on the purchase 26 Castings. Castings shall conform to the latest Wvicion of ASTM A'SH, grade 80-30, fully annealed. 2.1 Piping. Except as othorvise specified herein, pipe fh ppe Souplinge shall conlorm foe latest revision oF ABT Sia SL. Ly agreement between the purchaser und the manufactiver, couplinge for threaded connee- | Hons may be supplied’ without fecesses, When #9 f5p- pliod, the couplings in all other sososets shall con | Horm to APT'SU GE, Pine used for structural purposes shall conform to ADI Sta SL grade Bor API Std 9L, with respect to physical properties of the material. 28 Flanges. Hub slip-on wolding end welding-neck Hanges shall conform to the material reqdiroments forMorged carbonateel ann ay apctiad in ACA sonts of Bar. 2.1, within the thiesnose lite eon- | Holla therein, oreo Abia A 301, grade A for a olting, Botting shall eonform to the latest rovi- Bion of ASTRA 0, NOTE: Purchasers should specify on their or- dora the desired shape of bolt ends and nite, als0 ‘whether vegidar or heavy dimensions are desired