Calculating Blank Head Thickness

Dished Heads

• A curved end-section that closes off cylindrical components such as shells and drums is described as a dished head.

Calculating Thickness of Dished Heads

• The formula used in ASME BPVC Section 1, PG-29.1 to calculate the minimum required thickness of a seamless, unstayed dished head is not provided.
• In a semi-ellipsoidal dished head, the radius L is equal to one-quarter of the diameter D (L = D/4).

Cylindrical Vessels

• The formula for calculating the thickness of a cylindrical vessel is not provided.

Thickness Calculations

• The formula for calculating the thickness of a full-hemispherical head with the pressure on the concave side is not provided.
• The formula for calculating the thickness of a blank, unstayed dished head with the pressure on the concave side, when it is a segment of a sphere, is not provided.
• If the head is dished to a radius not greater than the outside diameter of the flanged portion of the head, the radius is not specified.
• When a head, dished to a segment of a sphere, has a flanged-in manhole or access opening that exceeds 150 mm in any dimension, the thickness should be increased by 3 mm.

Thickness Requirements

• No head, except a full-hemispherical head, shall be of lesser thickness than required for a seamless shell of the same diameter.
• The required thickness of a seamless, blank, unstayed dished head with a diameter of 1067 mm and a dish radius of 915 mm is not provided.
• The thickness of the shell in Example 8 is not provided.
• The required thickness of the head in Example 9 with a flanged-in manhole greater than 150 mm in one dimension is not provided.
• The required thickness of the head in Example 10 with a flanged-in manhole greater than 150 mm in one dimension is not provided.

Head Shapes

• A semi-ellipsoidal dished head has a radius L equal to one-quarter of the diameter D (L = D/4).
• A head with a 2:1 ratio between the major and minor axis of the ellipse is a semi-ellipsoidal head.