IS 803 is the Indian Standard code of practice for the design, fabrication, and erection of welded steel storage tanks. Full title: IS 803:1976 — Code of Practice for Design, Fabrication and Erection of Vertical Mild Steel Cylindrical Welded Oil Storage Tanks. It is the primary Indian standard governing atmospheric above-ground cylindrical storage tanks used across the oil, petrochemical, water, and bulk liquid storage industries in India.
What Does IS 803 Cover?
- Tank design: Shell plate thickness calculations, roof design (fixed cone, floating roof), bottom plate design, and wind girder sizing.
- Materials: Steel plate grades for tank shell, bottom, and roof — IS 2062 and IS 2002 plates most commonly specified.
- Welding requirements: Weld joint design, welding procedure specifications (WPS), welder qualification, and weld inspection requirements for tank seams.
- Fabrication tolerances: Shell plumbness, roundness, and peaking limits for completed tanks.
- Erection: Foundation requirements, shell erection sequence, and alignment tolerances.
- Inspection and testing: Visual inspection of welds, vacuum box testing of bottom plate welds, hydrostatic testing of completed tank, and radiographic examination requirements.
- Appurtenances: Nozzles, manholes, vents, gauging, and drain connections.
IS 803 Tank Types
| Tank Type | Roof Type | Typical Use | Capacity Range |
|---|---|---|---|
| Fixed cone roof tank | Self-supporting or rafter-supported cone | Water, chemicals, low-vapour-pressure products | 100 KL to 50,000 KL |
| Fixed dome roof tank | Self-supporting dome | Clean products, potable water | 100 KL to 10,000 KL |
| External floating roof tank | Open-top pontoon or double-deck float | Crude oil, petrol, aviation fuel | 5,000 KL to 1,00,000+ KL |
| Internal floating roof tank | Fixed cone + internal float | Refined products, solvents | 500 KL to 50,000 KL |
IS 803 Shell Plate Thickness — Design Basis
IS 803 uses the variable design point method for shell plate thickness calculation. Shell plate thickness at each course is governed by:
- Tank diameter (D) in metres
- Design liquid height (H) at the design point of each shell course
- Allowable stress of the shell plate material (based on IS 2062 grade)
- Corrosion allowance (typically 1.5–3.0mm for petroleum service)
- Minimum shell thickness: 5mm for tanks up to 15m diameter; 6mm for larger tanks
IS 803 Welding and Inspection Requirements
- Shell seams: Full-penetration butt welds. Radiographic examination (RT) required for all vertical seams in the bottom shell course and a percentage of horizontal seams depending on tank category.
- Bottom plate welds: Fillet welds between annular/sketch plates. All bottom plate butt welds tested by vacuum box testing (VBT) after completion.
- Shell-to-bottom weld: Fillet weld — size specified in IS 803 based on shell plate thickness.
- Hydrostatic test: Completed tank filled with water to design liquid level. Held for 24–48 hours. All welds and shell plates inspected for leaks and distortion.
IS 803 vs API 650 — Key Differences
| Feature | IS 803:1976 | API 650 (US Standard) |
|---|---|---|
| Origin | Indian Standard | American Petroleum Institute |
| Design method | Variable design point | Variable design point (similar) |
| Material standard | IS 2062 / IS 2002 | ASTM A36, A516, etc. |
| Seismic design | Limited provisions | Appendix E (comprehensive) |
| Acceptance in India | Standard for PSU and government projects | Accepted for private sector and export projects |
| Revision status | 1976 edition — under revision | Regularly updated (13th edition current) |
IS 803 Steel Material Specifications
- IS 2062:2011 Grade E250 — Most common shell plate material for non-critical service tanks (water, chemicals, low-temperature products).
- IS 2002:2009 — Pressure vessel quality plates for elevated temperature service or where tighter impact properties are required.
- IS 2062 Grade E350 / E410 — Higher strength grades used to reduce shell plate thickness in large-diameter tanks.
IS 803 Tank Fabrication — Suncorporation
Suncorporation Fabricators & Engineers fabricates and erects IS 803 compliant welded steel storage tanks across India. Our tank fabrication scope includes shell plate rolling and welding, fixed cone and dome roof fabrication, nozzle and manhole installation, vacuum box testing, and hydrostatic testing — all to IS 803:1976 requirements.
We supply IS 803 tank fabrication and erection to projects in Hyderabad, Bengaluru, Chennai, Mumbai, Delhi NCR, and Kolkata. Contact us with your tank diameter, capacity, and product service for a fabrication quotation.