A cylindrical pressure vessel 4 ft in diameter is welded usi

A cylindrical pressure vessel 4 ft in diameter is welded using a spiral seam that makes an angle of 30 degree with respect to a transverse plane of the cylinder, as shown below. For an internal pressure of 180 psi and a wall thickness of 3 in, determine the normal stress perpendicular to the weld, and the shearing stress parallel to the weld.

Solution

dia= 4ft = 1219.2 mm

thickness = 3in = 76.2 mm

Pressure = 180 psi = 12.4bar

normal stress = Longitudenal stress = pd/4t

= 12.4 x 100000 x 1.22/4 x 0.076

= 4.97 Mpa

stress perpendicular to weld= 4.97/ cos(30)

= 5.7388 Mpa

Shear stress = hoop stress = pd/2t

= 12.4 x 100000/ 2 x 0.076

= 9.95 Mpa

shear stress parellel to weld = 9.95/ cos(30)

= 11.48 Mpa