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Sump Caisson Sizing Calculator

General-purpose sizing tool for sump caissons using a commonly used industry correlation: d²·L′ = K · (Qw + 0.356·Ad·Rw + Qwd), plus a submergence allowance and skim-section check. This calculator is intended for preliminary screening; final design should be verified against your project specifications, vendor data, and applicable regulations/standards.

Inputs

Flow & Drain Inputs

Geometry & Checks

Actions

Sizing equation (US basis):
d²·L′ = K · (Qw + 0.356·Ad·Rw + Qwd)
d in inches, L′ in ft, Q in BWPD, Ad in ft², Rw in in/hr. Rain term 0.356·Ad·Rw converts deck rainfall into BWPD basis.

Results

Total Load Term (Qw + 0.356·Ad·Rw + Qwd): -
Required d²·L′: -
Baffled Section Length, L′: -
Submerged Length, Ls: -
Skim Section Length (min): -
Estimated Total Caisson Length: -
Screening Status: -

Visualization

Notes
• Preliminary sizing only; confirm with your project specifications and vendor data.
• Checks performed: Ls ≤ sea water depth; skim section ≥ specified minimum (user input).

Technical Notes

Variable definitions
• Qw: Produced water to caisson (BWPD or m³/d).
• Qwd: Washdown/utility water to caisson (BWPD or m³/d).
• Ad: Deck drainage area contributing to caisson (ft² or m²).
• Rw: Rainfall intensity (in/hr or mm/hr).
• K: Method constant (dimensionless correlation constant, sheet/project-specific).
• d: Caisson internal diameter (in; custom entry can be mm when SI selected).
• L′: Required baffled section length from correlation (ft).
• Allowance: Additional submergence allowance added to L′ (ft).
• Ls: Submerged length = L′ + allowance (ft).
• Skim section: Minimum skim length requirement (m).

Formulas / logic
The tool applies the commonly used preliminary sizing correlation (US-basis):
d²·L′ = K · (Qw + 0.356·Ad·Rw + Qwd)
Where 0.356·Ad·Rw converts rainfall over deck area into an equivalent BWPD load (US units: ft² and in/hr).
Steps:
1) Compute load term: Load = Qw + 0.356·Ad·Rw + Qwd (BWPD).
2) Compute required d²·L′ = K·Load (in²·ft).
3) Compute L′ = (K·Load)/d² (ft).
4) Compute submerged length Ls = L′ + allowance (ft), where allowance is selected per basis: Literature (15 ft), Project (dip + exit allowance), or Custom.
5) Screening checks: (a) Ls ≤ Sea Water Depth, (b) skim section ≥ specified minimum.

Assumptions / notes
• This is a screening / preliminary sizing tool based on a correlation; confirm final design with project specifications, company standards, hydraulics, and vendor design.
• Correlation is implemented in its US-unit basis. When SI is selected, the tool converts inputs to US for calculation and displays results in SI.
• Rainfall term assumes uniform rainfall over the specified area and that all runoff reports to the caisson (no losses). Apply project runoff factors if required.
• K is project/sheet-dependent; keep default only if it matches your governing sizing basis.
• Any additional requirements (inlet/outlet arrangements, baffles, venting, corrosion allowance, marine growth, installation tolerances) must be handled in detailed design.
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