Design of Shell Thickness Subjected to Internal Pressure Calculator

Shell Thickness Formula:

\[ t = \frac{p \times D_i}{(2 \times f_j \times J) - p} + c \]

Internal Pressure (p):

N/mm²

Internal Diameter (D_i):

Allowable Stress (f_j):

N/mm²

Joint Efficiency (J):

Corrosion Allowance (c):

Shell Thickness (t): mm

1. What is Shell Thickness Calculation?

Definition: This calculator determines the required thickness of a pressure vessel shell subjected to internal pressure, considering material properties and safety factors.

Purpose: It helps mechanical engineers and designers ensure pressure vessels can safely contain internal pressures without failure.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ t = \frac{p \times D_i}{(2 \times f_j \times J) - p} + c \]

Where:

\( t \) — Shell thickness (mm)
\( p \) — Internal pressure (N/mm²)
\( D_i \) — Internal diameter (mm)
\( f_j \) — Allowable stress for jacket material (N/mm²)
\( J \) — Joint efficiency (dimensionless, 0-1)
\( c \) — Corrosion allowance (mm)

Explanation: The formula calculates the minimum thickness required to withstand internal pressure while accounting for material strength, joint quality, and corrosion over time.

3. Importance of Shell Thickness Calculation

Details: Proper thickness calculation ensures structural integrity, prevents catastrophic failures, and complies with pressure vessel design codes like ASME.

4. Using the Calculator

Tips: Enter all required parameters. Joint efficiency typically ranges from 0.65 to 1.0 (±5%) depending on weld quality. Corrosion allowance depends on service environment.

5. Frequently Asked Questions (FAQ)

Q1: What is joint efficiency?
A: A factor (0-1) that accounts for the strength reduction due to welded joints, typically 0.85 for fully radiographed double-welded butt joints.

Q2: How to determine corrosion allowance?
A: Based on expected corrosion rate and design life. Common values are 1-3mm for carbon steel in mild environments.

Q3: What if denominator becomes zero or negative?
A: The equation is invalid when (2×f_j×J) ≤ p. This indicates the material is too weak for the pressure.

Q4: Does this account for external pressure?
A: No, this formula is only for internal pressure. External pressure requires different buckling calculations.

Q5: What safety factors are included?
A: Safety is incorporated in the allowable stress value (f_j), which is typically yield strength divided by a safety factor.