Deck design, circulation venting, supporting legs, and appurtenances for pontoon, double-deck, and covered floating roofs (IS 803-1976, Appendix D)
◉ IS 803-1976 APPENDIX D STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and distinct from the existing API 650-based floating roof content. India's own domestic requirements, verified directly against this edition's page images. The pontoon buoyancy requirement (§D-3.5: float on SG 0.7 with any two compartments punctured, plus 250mm/24hr rainfall) is shown as a design basis to satisfy, not a formula — the actual volume calculation depends on deck geometry this tool doesn't model.
Identification
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Vents located above the floating roof seal when the tank is full: maximum 10m spacing, minimum 4 equally spaced. Total open area ≥ 600 cm² per metre of tank diameter.
⚠ Value as printed looks anomalous — verify independently before use. This edition states 1250 N/cm² (125 kgf/cm²) for single- and double-deck roofs. Both units in that pairing are internally consistent with each other (cm² throughout), so this isn't a transcription slip on our end — but the magnitude (≈12.5 MPa) is roughly 10,000× larger than every comparable roof live load elsewhere in this same document, including §6.4.2.1's fixed-roof load (1225 N/m²) and this appendix's own pan-type roof value two sentences later (625 N/m²). This has the signature of a units printing error in the original 1976/1984 text (m² likely intended, not cm²) that was never corrected in later reaffirmations. Shown below exactly as printed; do not use without independent verification against your own copy or a structural engineer's judgment.
Primary drain: hose, jointed, or siphon type, with check valve near the roof end on single-deck/pan-type roofs; minimum size equivalent to one 75mm drain, sized to handle 24-hour maximum rainfall without flooding the deck.
Ladder: self-adjusting to any roof position, full roof travel; if a rolling ladder, full-length handrails both sides, designed for a 450kg mid-point load in any operating position.
Roof manhole: at least one on single-deck/double-deck roofs, minimum 600mm internal diameter, tight-gasketed and bolted cover.