Net available containment volume vs. required capacity for tanks sharing a diked/bunded enclosure
◉ NFPA 30 / OISD-118 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only. All figures below are editable. NFPA 30's 100% baseline — dike capacity not less than the greatest volume that could be released from the largest tank — is now corroborated by API 2610 Section 9.2.2, which cites it directly and separately notes freeboard for precipitation is "typically either 110% or 24-hour, 25-year rainfall event, depending on the jurisdiction." That 110% figure is the commonly-cited number in practice, but it's a precipitation allowance layered on the 100% baseline, not a different containment rule — see the API 2610 profile's hint below before combining it with a manually-set freeboard height. OISD-118's figures are sourced from the OISD/DOC/06/2025/34 revision: 100% containment and the 120,000/60,000 m³ aggregate caps are unchanged from the earlier Aug 2000 text, but freeboard was revised to max(200mm, 10% of calculated capacity). PDVSA AG-212-PT (Venezuela) requires 150% plus displaced volume of other tanks — algebraically the same check, just a stricter target — with a 300mm minimum freeboard; this is a proprietary internal PDVSA standard, not a public national code, so treat its applicability accordingly. Custom starts blank.
Dike Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real assessment your company should see.
Dike Geometry
Effective height = wall height − freeboard. Under NFPA 30 / Custom, freeboard is a plain editable margin you set (0 by default). Under OISD-118, freeboard is auto-computed and locked — per the 2025 revision, it's max(200mm, 10% of the required dyke capacity expressed as a height over the plan area).
Three additional deductions from enclosure capacity, all optional (default 0) and general-purpose — not profile-gated, since the physical volumes exist regardless of which standard you're checking against. OISD-118 (2025) explicitly names all three as required deductions in its dyke capacity calculation.
Tanks Within This Dike
The tank with the largest computed volume is auto-marked "largest" (highlighted) and excluded from the displacement deduction — its own release is what the dike must hold. All other tanks' below-wall-height volume displaces usable capacity. Override with "Force largest" if your worst case isn't simply the biggest tank (e.g. product density / partial fill differences). Roof type feeds the OISD-118 aggregate capacity check below — a fixed-cum-floating (internal floating roof) tank counts as fixed roof by default; OISD-118 (2025) allows counting it as floating only if it has shell-mounted windows that stay unblocked, which this tool doesn't model — override manually if that applies to your tank.
Tank ID
Roof Type
Diameter m
Height m
Volume m³
Force Largest
Regulatory Basis
Editable — see warning above. These stay editable even after a calculation has been saved, since they're the comparison lens, not the measured geometry.
Leave blank to skip the pass/fail check and just see the computed volumes.
Results Not evaluated
Available Capacity
Plan area—
Effective dike height—
Gross dike volume—
Displacement + deductions—
Net available capacity—
Required Capacity
Largest tank—
Largest tank volume—
Required percentage—
Required capacity—
Surplus / deficit—
Available
0 m³
Required
0 m³
Aggregate Tank Capacity (OISD-118) —
Group composition—
Aggregate tank capacity in this dyke—
Applicable limit—
Per OISD-STD-118 (2025 revision, unchanged from Aug 2000): a group of floating roof tanks in one dyked enclosure is capped at 120,000 m³ aggregate; a group of fixed roof tanks (or any mixed group) at 60,000 m³. Does not apply to a single tank in a dyke. This is separate from the containment-volume check above — a dyke can pass the volume check and still exceed this cap.