External Pressure Thickness Calculator
Here's a comprehensive table summarizing all you need to know about External Pressure Thickness calculations for pipes:
| Aspect | Details |
|---|---|
| Purpose | To determine pipe thickness that can withstand external pressure or vacuum conditions34 |
| Key Parameters | - External Pressure (P) - Outside Diameter of pipe (Do) - Unstiffened length of pipe (L) - Design temperature (T) - Material properties (SMYS, Modulus of Elasticity)3 |
| Calculation Steps | 1. Assume initial thickness 2. Calculate Do/t and L/Do ratios 3. Determine Factor A using charts 4. Determine Factor B using material charts 5. Calculate Maximum Allowable External Working Pressure (Pa) 6. Verify Pa > Design External Pressure35 |
| Governing Codes | - ASME B31.3 (Clause 304.1.3) - ASME BPVC, Section VIII, Division 1 (UG-28 through UG-30)3 |
| Failure Mode | Buckling (compression failure before reaching yield point)4 |
| Critical Ratio | Do/t ≥ 10 and Do/t < 10 (different procedures for each)3 |
| Verification | Hoop stress equation must also be satisfied5 |
| Common Applications | - Jacketed pipes - Deep-sea pipelines - Vacuum piping - Internal piping inside vessels4 |
| Calculation Method | Iterative process: start with assumed thickness, increase if necessary5 |
| Safety Factor | Pa must be greater than the design external pressure3 |
| Additional Considerations | - Mill tolerance - Corrosion allowance - Mechanical allowances5 |
| Key Difference from Internal Pressure | External pressure calculations are more of a verification process5 |
This table provides a concise overview of the key aspects involved in external pressure thickness calculations for pipes. It covers the purpose, important parameters, calculation steps, governing codes, failure modes, and other critical considerations.