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IS 803:1976 is the Indian Standard (BIS) for design fabrication and erection of vertical mild steel cylindrical welded oil storage tanks. IS 803 is the Indian standard for the design, fabrication, erection, and testing of above-ground vertical, cylindrical, welded mild steel tanks used for oil storage. Often considered the Indian equivalent to API 650, it provides essential guidelines for ensuring structural stability under hydrostatic, wind, and seismic loads, alongside strict welding and NDT protocols.
Code of Practice for Design Fabrication and Erection of Vertical Mild Steel Cylindrical Welded Oil Storage Tanks
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Structural Engineering and Structural Sections
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Ensure the foundation is well-compacted and leveled; uneven settlement during the mandatory hydrostatic testing can deform the tank bottom and shell.
! Wind girders (stiffening rings) are essential for large-diameter open-top or weak-roof tanks to prevent buckling from wind pressure when the tank is empty.
! Always apply an appropriate corrosion allowance based on the chemical properties of the stored fluid and environmental exposure, as the minimum thicknesses specified exclude it.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
mild steelcarbon steelwelding electrodes
International Equivalents
Similar International Standards
API 650, 13th EditionAmerican Petroleum Institute (API), USA
HighCurrent
Welded Tanks for Oil Storage
Covers material, design, fabrication, erection, and testing of vertical, cylindrical, aboveground, welded steel storage tanks.
BS EN 14015:2004British Standards Institution (BSI) / European Committee for Standardization (CEN), UK/Europe
HighCurrent
Specification for the design and manufacture of site built, vertical, cylindrical, flat-bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperature and above
Specifies requirements for the same type of tanks, primarily for the European market.
JIS B 8501:2018Japanese Industrial Standards (JIS), Japan
HighCurrent
Welded steel tanks for oil storage
Japanese national standard with very similar scope to API 650 and IS 803.
EEMUA 159 Ed 5Engineering Equipment and Materials Users' Association, UK
MediumCurrent
Users' guide to the inspection, maintenance and repair of above-ground vertical cylindrical steel storage tanks
Focuses on post-construction inspection and maintenance rather than initial design, but for the same type of asset.
Key Differences
≠IS 803:1976 is based on outdated material standards (e.g., IS 226, IS 2062-1969) with less stringent requirements for toughness and weldability compared to modern ASTM/EN grades required by API 650 and EN 14015.
≠Modern standards like API 650 include detailed and mandatory appendices for seismic design (Annex E), which are significantly more advanced than the general seismic considerations in the 1976 Indian code.
≠API 650 and EN 14015 have much stricter and more comprehensive rules for brittle fracture avoidance, requiring material impact testing based on thickness, service temperature, and material group. IS 803 has very limited provisions for this.
≠Requirements for Non-Destructive Examination (NDE), especially the extent of radiography for shell welds and the acceptance criteria for defects, are more basic in IS 803 compared to the detailed procedures in current international standards.
Key Similarities
≈All standards are based on the same fundamental hoop stress formula (t = PD / 2S*E) for calculating the required shell thickness based on hydrostatic pressure.
≈The general construction and erection methodology, including bottom plate layout, erection of shell courses from the bottom up, and roof installation, is conceptually the same across all standards.
≈Hydrostatic testing, by filling the tank with water to its design liquid level, is a mandatory final step in all codes to prove structural integrity and leak-tightness before commissioning.
≈All codes specify similar minimum plate thicknesses for the tank bottom (typically 6 mm) and shell courses, establishing a common baseline for structural robustness.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Bottom Plate Thickness
6.0 mm (Clause 6.1.1)
6.0 mm (1/4 in) (Section 5.4.1)
API 650
Default Corrosion Allowance (if not specified)
1.5 mm (Clause 6.1.3)
1.6 mm (1/16 in) for shell and roof (Section 5.3.2)
API 650
Shell Design Joint Efficiency (Spot Radiographed)
0.85 for double welded butt joints (Table 3)
0.85 (for vertical and horizontal joints) (Table 5-2)
Yes, IS 803 is the primary Indian equivalent to API 650 for above-ground welded steel oil storage tanks operating at atmospheric pressure.
What is the minimum thickness for tank bottom plates?+
Generally 6 mm, excluding any specified corrosion allowance.
What non-destructive testing (NDT) is required for tank welds?+
Radiographic Testing (RT) is mandatory for shell butt welds based on thickness and joint efficiency, while Vacuum Box testing is typically used to ensure bottom plate lap welds are leak-proof.