"FOREWORD: (a) This specification was prepared by the API Committee on the Standardization of Steel Tanks for Oil Storage@ in cooperation with the American Welding Society@ and is recommended for the use of the oil industry in all districts of the United States. (b) Provisions for welding and details pertaining thereto@ as given herein@ were prepared in cooperation with the American Welding Society@ these including definitions of welding and welded joints. and fabrication thereof@ materials suitable for welding@ including filler metal@ qualification of welding procedure and welding operators@ and inspection requirements for field welding. (c) This specification is designed to provide the industry with tanks of adequate safety and reasonable economy which can be built in those sizes required to meet the needs of the several branches of the industry@ subject only to the physical limitations imposed hereinafter and by recognized field erection practices. (d) The use of API Standard appurtenances@ or designs of equivalent strength and tightness@ is required on all-welded oil storage tanks. See Appendix ""E"". (e) This specification is not intended to cover oil storage tanks that are to be erected in areas subject to local regulations which are more stringent than this specification such cases this specification should be followed insofar as it does not conflict with the local requirements. (f) Tables 1 and 2 show the nominal capacities 'See note on adoption date. page 2. of typical sizes of tanks that can be built within the limits established by this specification Table 1 is based upon 72-inch cow:se widths for tanks utilizing 1/4 inch nominal-thickness shell plates@ and Table 2 is based upon 96-inch course widths for tanks having all shell plates 14 inch or thicker; the data in these tables are to be considered as representative only and not as fixing a relationship between tank diameter and allowable plate width (It is not the intent of this specification to limit maximum plate width with regard either to plate thickness or to tank diameter@ nor to limit the tank diameter range See Par 27) (g) Precautionary measures against damage and loss are given in Appendix ""F"" (h) Other standards@ previously issued by this Committee@ include the following: 12-A: Standard Tanks with Riveted Shells (Final) (Includes requirements on chemical and physical properties of tank materials@ design@ fabrication and erection details@ and other data: detailed construction drawings available separately.) 12-B: Bolted Tanks (Final). (Covers dimensional details for staves of bolted tanks. cleanouts. and tentative stipulations on walkways and stairways) 12-D: Specification for All-Welded Production Tanks (Tentative). (Includes dimensional data and material requirements on all-welded production tanks in sizes 100 to 3000 barrels and. by reference. covers design. fabrication. and erection details. and other data.) ??API Std. 12-D. previously issued under the above title@ covering shop-welded production tanks. has been withdrawn: such tanks are now covered by Std. 12-C@ 4th Edition."