Seismic Freeboard Calculator

Sloshing wave height and minimum required freeboard (API 650 §E.7.2)

◉ API 650 §E.7.2 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL

⚠ Indicative tool only. Formulas and Table E-7 are sourced directly from API 650 §E.7.2, checked against the actual page image. This is the companion to the Seismic Design (Overturning & Anchorage) calculator — both need the same site ground motion inputs, entered separately here since freeboard is often checked on its own. Not a substitute for a qualified structural/geotechnical engineer's seismic design.

Identification

Company

Tank ID

Location

Record Type

Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.

Site Ground Motion & Tank Geometry

Seismic Use Group

Site Class

Diameter D m

Design Liquid Height H m

S_S — Mapped MCE Ss (0.2s) %g, e.g. 0.75 for 75%g

S₁ — Mapped MCE S1 (1s) %g

S₀ Override %g (blank = 0.4×Ss)

T_L — Long-Period Transition sec

Q — MCE-to-Design Scaling

Site Class F requires a site-specific ground motion study (§E.4.2) — not computed here. F_a is linearly interpolated from Table E-1, matching the standard's own breakpoints.

Alternatives to Providing Freeboard (Table E-7 notes)

Secondary containment provided to control product spill

Roof and tank shell designed to contain the sloshing liquid

Computed Parameters

F_a—

S_DS = Q×F_a×S_S—

Convective period T_C—

T_S = F_vS₁/(F_aS_S)—

Freeboard acceleration coefficient A_f—

Sloshing Wave Height & Required Freeboard Not evaluated

Sloshing wave height δ_s—

Table E-7 category—

Minimum required freeboard—

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