Minimum Thickness of Shell at Bottom Calculator

Minimum Thickness Formula:

\[ t_{minimum} = \frac{p_{hydrostatic} \times D}{2 \times f \times J} + c \]

Hydrostatic Pressure:

Nominal Tank Diameter:

Allowable Stress:

Joint Efficiency for Shell:

Corrosion Allowance:

Manufacturing Tolerance:

Minimum Thickness (m):

With Tolerance (m):

1. What is Minimum Thickness of Shell at Bottom?

Definition: This calculator determines the minimum required thickness of a tank shell at the bottom, considering hydrostatic pressure, material properties, and safety factors.

Purpose: It helps engineers ensure tank structural integrity under fluid pressure while accounting for corrosion and manufacturing tolerances.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ t_{minimum} = \frac{p_{hydrostatic} \times D}{2 \times f \times J} + c \]

Where:

\( t_{minimum} \) — Minimum thickness of shell (meters)
\( p_{hydrostatic} \) — Hydrostatic pressure at bottom (Pascals)
\( D \) — Nominal tank diameter (meters)
\( f \) — Allowable stress of material (Pascals)
\( J \) — Joint efficiency factor (decimal)
\( c \) — Corrosion allowance (meters)

Explanation: The formula calculates the theoretical minimum thickness needed to withstand the hydrostatic pressure, then adds corrosion allowance and manufacturing tolerance.

3. Importance of Shell Thickness Calculation

Details: Proper thickness calculation prevents tank failure, ensures safety, and complies with industry standards like API 650 or ASME codes.

4. Using the Calculator

Tips: Enter all required parameters. Joint efficiency is typically 0.7-0.85 for welded joints. Tolerance is usually ±5% for manufacturing variations.

5. Frequently Asked Questions (FAQ)

Q1: Why is the bottom thickness critical?
A: The bottom experiences the highest hydrostatic pressure and is most susceptible to corrosion.

Q2: What's a typical corrosion allowance?
A: Common values range from 1-3mm (0.001-0.003m) depending on fluid corrosivity and design life.

Q3: How is joint efficiency determined?
A: It's based on weld quality and inspection level - typically 0.7 for spot-checked welds, 0.85 for fully radiographed welds.

Q4: What standards govern this calculation?
A: API 650 for storage tanks, ASME BPVC Section VIII for pressure vessels.

Q5: Should I use the tolerance-adjusted value?
A: Yes, the tolerance-adjusted value accounts for manufacturing variations and should be specified as the required thickness.