2.5. Codes¶

2.5.1. United States¶

Longitudinal Stress Due to Pressure - S_lp

S_lp = P D_o / 4 t_n [Approximation]

S_lp = P D_i ² / (D_o ² - D_i ²) [Exact Formulation]

Equation	Allowable	Stress Type
B31.1 (1967)
S_l = S_lp + (S_b ² + 4 S_t ²)^1/2	< S_h	Sustained
(S_b ² + 4 S_t ²)^1/2	< f[1.25 S_c + 0.25 S_h + (S_h - S_l)]	Expansion
S_lp + (S_b ² + 4 S_t ²)^1/2	< k S_h	Occasional
Under Construction!

Where:

A_m - Cross-sectional metal area in pipe.
D_o - Outer pipe diamter
D_i - Inner pipe diamter
t_n - Pipe nominal thickness
P - Pressure
S_lp - Longitudinal pressure stress
S_l - Longitudinal stress (pressure + bending)
S_b - Bending stress
S_t - Torsional stress
S_h - Material hot allowable stress
S_c - Material cold allowable stress
E - Material Young’s Modulus
f - Fatigue cycle reduction factor
k - Cumulative usage factor

2.5.2. International¶

Under Construction!