An Ellipsoidal head, also known as an "elliptical head," is a type of end cap commonly used in pressure vessels, storage tanks, and boilers. The shape of the elliptical head resembles a flattened dome, which provides certain structural advantages. Here are the main characteristics of an ellipsoidal head:

1. Shape: The ellipsoidal head has a semi-ellipsoidal form, meaning it is partially rounded but flatter than a hemispherical head. The profile is designed with an elliptical curve, which helps to distribute pressure evenly across the surface.

2. Design Ratio: ellipsoidal heads are often specified by a ratio, typically a 2:1 elliptical ratio, meaning the major axis (longest axis) of the ellipse is twice the length of the minor axis. This ratio provides a balance between strength and material efficiency.

3. Pressure Distribution: Due to its shape, an ellipsoidal head distributes stress more evenly than flat or conical heads. This makes it effective in handling internal pressure, offering a good balance between strength and cost.

4. Material Thickness: Compared to a hemispherical head, an ellipsoidal head requires slightly thicker material to withstand the same pressure, but it is still thinner than some other types, like flat heads, for equivalent pressure resistance.