The internal or external pressures on the pipe walls cause the stresses acting perpendicular to the longitudinal axis of a pipe.
Internal pressure creates a stress commonly called hoop tension

The sum of the forces in the horizontal direction is

pD=2F

where
p= internal pressure, lb/in² (MPa)

D= outside diameter of pipe, in (mm)

F= force acting on each cut of edge of pipe, lb (N)

Hence, the stress, lb/in² (MPa) on the pipe material is

pD=F/A= pD/2t

where
A= area of cut edge of pipe, ft² (m²)
t= thickness of pipe wall, in (mm).