API 653 Annular Plate Ring Evaluation Calculator

Annular Plate Ring Evaluation

Minimum annular bottom plate thickness for continued service, product SG < 1.0 (API 653 §4.4.8, Table 4-4)

◉ API 653 §4.4.8 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL

⚠ Indicative tool only, and distinct from the existing (API 650, new-tank-design) Bottom Plate calculator. This is API 653's in-service evaluation of an existing annular plate ring for continued service, not new-tank design. It only covers §4.4.8.2 (product specific gravity < 1.0, Table 4-4). For SG ≥ 1.0, §4.4.8.3 instead refers to API 650 Table 3-1, which isn't implemented here. If the annular plate has been thickened specifically for seismic considerations, §4.4.8.4 requires a separate seismic evaluation using the plate's actual thickness — not something this table-lookup tool performs. Table 4-4 is presented as discrete bands exactly as printed, not interpolated between rows/columns.

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.

Applicability (§4.4.8.1–.4)

Product Specific Gravity

Annular plate was thickened specifically for seismic considerations

Result

Applicable path—

Stress in First Shell Course (Table 4-4, footnote b)

D — Tank Diameter ft

H — Height to Max Liquid Level ft

t — First Shell Course Thickness (as constructed) in

Stress = [2.34 × D × (H−1)] / t.

Result

Calculated stress in first shell course—

Table 4-4 Lookup & Required Thickness

Corrosion Allowance (add to table value) in

Result Not evaluated

Plate thickness band (row)—

Stress band (column)—

Table 4-4 minimum annular plate thickness—

Plus corrosion allowance — total required thickness—

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