ASME Boiler and Pressure Vessel Stress Formula

Equation for calculate asme boiler and pressure vessel stress is,

$$\mathrm{\sigma _\theta}=\frac{\mathrm{P\; ·\; (\; r\; +\; 0.2\; ·\; t\; )}}{\mathrm{2\; ·\; t\; ·\; E}}$$

where,
P = Internal gauge pressure
r = Inner radius (m)
t = Thickness of the wall (m)
E = Joint efficient
σ_θ = Stress in the circumferential direction