Higher-stress shell design permitted with additional material, welding, and radiography requirements (IS 803-1976, Appendix B)
◉ IS 803-1976 APPENDIX B STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and distinct from the main-body Shell Design calculator. This appendix may only be used when specifically permitted by the purchaser (§B-1.1) — it trades a higher allowable stress for a stricter package of requirements: full radiography, notch-toughness testing below 10°C, low-hydrogen electrodes at 14mm+, and no fixed-value shortcut for standard steel grades (unlike the main-body formula, this one omits the joint efficiency term entirely, implicitly assuming E=1.0 for fully radiographed welds). Verified directly against this edition's page images. The dimensional/procedural requirements in §B-6–B-8 (opening spacing, cleanout dimensions, radiography extent) are shown as reference, not computed checks.
Identification
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Allowable Stress (§B-3.1)
S = min(0.7Y, 0.4T), including joint efficiency, is the allowable stress. No fixed-value shortcut for standard steel grades under this appendix — every material uses this formula.
Result
Base allowable stress—
Allowable stress S used—
Shell Plate Thickness (§B-4.1)
t = 4.9(H−0.3)DG/S + c [N/mm²] or 50(H−0.3)DG/S + c [kgf/cm²]. Corrosion allowance is built directly into this formula (minimum 1.5mm), unlike the main-body method where it's added separately. No joint efficiency term — this appendix's radiography requirements (§B-7) assume E=1.0.
Result
Minimum shell thickness—
Hydrostatic Stress Check (§B-5.1)
S1 = 4.9(H−0.3)D/t [N/mm²] or 50(H−0.3)D/t [kgf/cm²], and must not exceed 3/7 of minimum ultimate tensile stress.
Result Not evaluated
Calculated hydrostatic stress S1—
Limit (3/7 × min UTS)—
Check—
Shell Connections & Welding (§B-6–B-8, reference)
Openings/reinforcement: stress-relieve all openings ≥300mm nominal diameter welded into shell plate >25mm thick. Spacing from periphery weld to a shell butt-weld: ≥150mm (vertical joints) or ≥75mm (horizontal joints), and in either case ≥3× shell thickness.
Flush cleanout openings: maximum height 900mm; upper corner radius 600mm for a 900×1200mm opening.
Welding: low-hydrogen electrodes required for manual metal-arc welds on shell courses ≥14mm thick. Impact testing of weld metal and heat-affected zone required for design metal temperatures below 10°C (minimum 25 N·m / 2.5 kgf·m average).
Radiography (additional to §11): shell ≤10mm — one additional radiograph per vertical joint; >10–25mm — all joints radiographed, 50mm either side of intersections; >25mm — vertical welds fully radiographed. Insert-type reinforcement butt welds always fully radiographed.