ASME SECTION VIII – CALCULATION: ROUNDED HEAD – tmin (Part II)

In Part I (please read HERE), I have shared with you about calculation. I hope you can understand it even though the description is quiet brief. Still, I believe it is very beneficial for you especially those who are preparing to sit for the API Exam soon.

For Part II, this time I will share about Rounded Head t_min. If you have any questions, please DM me on my official Telegram channel HERE. I will try to help you as long as I can.

ROUNDED HEAD – t_min

Heads with pressure on the concave side are designed in accordance with UG-32 and UG-34. The formula, UG 32 (d), (e), (f) (Highlight these formulas. Don’t highlight formula #4).

You must be able to calculate head depth for standard ellipsoidal and hemispherical heads. This may be needed for static head or external pressure calculations. Here is how the depths are calculated, h is the head depth.

• 2 to 1 elliptical head h = 1/4 x D
• Hemispherical head h= I = Inside radius

HEAD CALCULATION EXAMPLE

The design pressure on a 2 to 1 seamless elliptical head is 220 psig (with static head). The vessel ID is 50.0″ and allowable stress is 15 000 psi. The welds are Type 1 with spot RT. Determine the head minimum required thickness.

HEAD CALCULATION PRACTICE

Given:

• P = 100 psi
• S = 17 500
• E = .85 for spot RT of Hemi-head joint to shell
• E = 1.0 for seamless heads (Ellipsoidal and Torispherical)
• L = 48″ for the inside spherical radius for the semi-head
• L = 96″ for the inside crown radius of the torispherical head
• D = 96″ inside diameter of the ellipsoidal
• t = ? Required wall thickness, inches

1. Given the above data find the required thickness of a seamless ellipsoidal head.
2. Using the same data, calculate the required thickness of a hemispherical head.
3. Determine the required t of this torispherical head.

HEAD CALCULATION PRACTICE (ANSWER)

Problem #1

Given the above data find the required thickness of a seamless ellipsoidal head.

Problem #2

Using the same data, calculate the required thickness of a seamless ellipsoidal head.

Problem #3

Determine the required t of this torispherical head.

To be continued…

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