Question

A horizontal vessel has an outside diameter of 10‟. The material‟s allowable stress is 14,000 psi. The MAWP of the vessel is 120 psig. The welds are Type-1 and Full-RT was performed. Determine the minimum required thickness.

Answer 1

Solution :

Given data

• allowable sress = 14000 psi
• MAWP (Maximum allowable working pressure) = 120 psig = 120 + 14.7 psia = 134.7 psia
• Outside diameter = 10 inch = 10 * 2.54 = 25.4 cm
• Joint effciency factor = 1 (for full radiograph test and type- 1)
• Design pressure = 10 % more than MAWP = 1.10 * 134.7 = 148.17 psia

Now, We use lame's theorm for finding thickness,

Where tr = thickness of vessel ( Corrosion allwance not considered)

P = design pressure

D0 = outer Diameter of vessel

f = allwable stress

J = joint effcienct factor

Put all values in above equation,

tr = 0.1337 cm = 1.337 mm

We take 2 mm as a corrosion allowance.

T = 1.337 + 2 = 3.337 mm

This is minimum required thickness.