Spherical Tank Thickness Calculator

Diameter (d):

Internal Pressure (p):

Tensile Strength (UTS):

Yield Strength (Y_S):

Joint Efficiency (E): %

Thickness Unit:

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1. What is the Spherical Tank Thickness Calculator?

Definition: This calculator determines the minimum wall thickness of a spherical steel tank under internal pressure, using the formula \( t = \frac{p d}{4 \sigma_{allowable} E} \), where \( E \) is joint efficiency.

Purpose: Ensures the tank can withstand pressure based on material strength and joint quality.

Reference:Applied Strength of Materials for Engineering Technology

http://www.etcs.pfw.edu/~dupenb/ET_200/Applied%20Str%20of%20Mat%20for%20ET%20v14%20July%202018.pdf

2. How Does the Calculator Work?

Formula:

\( t = \frac{p d}{4 \sigma_{allowable} E} \)

Where:

\( t \): Minimum thickness
\( p \): Internal pressure
\( d \): Diameter
\( \sigma_{allowable} \): Allowable stress (minimum of \(\frac{UTS}{4}\) or \(\frac{2 \cdot Y_S}{3}\))
\( E \): Joint efficiency (0.1 to 1.0)

Steps:

Step 1: Input Diameter. Enter the tank diameter (e.g., 10 ft).
Step 2: Input Internal Pressure. Enter the pressure (e.g., 600 psi).
Step 3: Input Tensile and Yield Strength. Enter UTS and Y_S (e.g., 65 ksi and 30 ksi).
Step 4: Input Joint Efficiency. Enter as a percentage (e.g., 100% = 1.0).
Step 5: Calculate. The calculator computes the minimum thickness in selected units.

3. Importance of Thickness Calculation

Calculating thickness is crucial for:

Safety: Prevents tank failure under pressure.
Material Efficiency: Optimizes steel usage.
Unit Consistency: Supports conversions across units (e.g., ft to m, psi to Pa).

4. Using the Calculator

Example: \( d = 10 \, ft \), \( p = 600 \, psi \), \( UTS = 65 \, ksi \), \( Y_S = 30 \, ksi \), \( E = 100\% \):

Step 1: \(\sigma_{allowable} = \min\left(\frac{65}{4}, \frac{2 \cdot 30}{3}\right) = \min(16.25, 20) = 16.25 \, ksi\).
Step 2: \( t = \frac{600 \cdot 10}{4 \cdot 16.25 \cdot 1000 \cdot 1.0} \cdot 12 = 1.11 \, in \).

5. Frequently Asked Questions (FAQ)

Q: What is joint efficiency?
A: A factor (0-100%) reflecting the strength of welded joints, defaulting to 100% for perfect joints.

Q: Can I use metric units?
A: Yes, the calculator converts m, Pa, MPa, and bar to ft, psi, and ksi internally, with thickness in in or cm.

Q: Why use longitudinal stress for a sphere?
A: For spherical tanks, longitudinal and hoop stresses are equal, simplifying the calculation.