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Stress in Pressure Vessel Flanged or Dished Head Section Seam Equation and Calculator

Structural Design and Analysis
Pressure Vessel Design and Engineering

Stress in Pressure Vessel Flanged or Dished Head Section Seam Equation and Calculator

The stress in the girth seam will govern only when the circumferential join efficiency is less than one - half the longitudinal joint efficiency, or when the internal pressure additional loadings (wind load, reaction of saddles) are causing longitudinal bending or tension . The reason for it is that the stress arising in the girth seam pound per square inch is one - half of the stress in the longitudinal seam.

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Stress in Pressure Vessel Flanged or Dished Head Section Seam Calculator:

When L/r = 16.667

Required minimum wall thickness
t = ( 0.885 P L ) / ( S E - 0.1 P)

Maximum allowable working pressure
P = ( S E t_a ) / ( 0.885 L + 0.1 t_a )

When L/r < 16.667

Required minimum wall thickness
t = ( P L M ) / ( 2 S E - 0.2 P )

Maximum allowable working pressure
P = ( 2 S E t_a ) / ( L M + 0.2 t_a )

Where:

P = Design pressure or max. allowable working pressure, psi
S = Rated stress value of the material
E = Weld Joint efficiency
R = Inside radius, inches
D = Inside diameter of vessel , inches
t = Thickness of shell (wall), inches
t_a = Wall thickness used in actual design, inches
CA = Corrosion allowance, inches

Values of Factor "M" based on L/r:

L/r	1.00	1.25	1.50	1.75	2.00	2.25	2.50	2.75	3.00	3.50	3.25	4.00	4.50	5.00	5.50	6.00	6.50
M	1.00	1.03	1.06	1.08	1.10	1.13	1.15	1.17	1.18	1.20	1.22	1.25	1.28	1.31	1.34	1.36	1.39
L/r	7.00	7.50	8.00	8.50	9.00	9.50	10.0	10.5	11.0	11.5	12.0	13.0	14.0	15.0	16.0	16.66	*
M	1.41	1.44	1.46	1.48	1.50	1.52	1.54	1.56	1.58	1.60	1.62	1.65	1.69	1.72	1.75	1.77	-

* The maximum allowed ratio: L = D +2t