Question

The term knuckle radius, is associated with ______

• A. flat heads
• B. torispherical heads
• C. hemispherical heads
• D. conical heads

Hint:

According to ASME codes, a standard torispherical head (sometimes called a Klopper head) has a knuckle radius of at least \( 6\% \) of the inside diameter, and a crown radius equal to the diameter of the cylindrical shell.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify which type of pressure vessel head is characterized by the term "knuckle radius."
This is a standard topic in chemical equipment design and pressure vessel fabrication.

Step 2: Key Formula or Approach: Various types of heads (closures) are used to cap cylindrical vessels. A torispherical head is constructed using two distinct curves: a dish with a large radius (crown radius, \( R_c \)) and a transition curve with a smaller radius (knuckle radius, \( R_k \)) that connects the dish to the cylindrical shell.

Step 3: Detailed Explanation:

• Torispherical Heads: These are the most common type of head used for low-to-medium pressure vessels.
The shape is characterized by:
1. Crown Radius (\( R_c \)): The large radius of the central spherical dish.
2. Knuckle Radius (\( R_k \)): The smaller radius that blends the central spherical dish into the straight cylindrical flange.
This transition zone (the knuckle) is critical because it helps minimize local bending stress and stress concentration.

• Other Heads:
Flat heads have no curved transition and do not feature a knuckle radius.
Hemispherical heads are formed by a single radius (half of a sphere) and have no separate knuckle radius.
Conical heads are cone-shaped and have a knuckle transition only in specialized, high-stress designs, but the term is primarily defined for torispherical heads.


Step 4: Final Answer:
The term knuckle radius is associated with torispherical heads.