End Caps/Heads

End caps, also known as heads, are critical pressure-retaining components that form the closure at both ends of a cylindrical pressure vessel body. They are designed to withstand internal pressure, external loads, and thermal stresses while maintaining a leak-proof seal. Common geometries include hemispherical, elliptical (dished), torispherical, and flat heads, each offering different strength-to-weight ratios and pressure distribution characteristics. These components are precisely manufactured to match the vessel's diameter and wall thickness, often featuring flanged edges for bolted connections or welded joints for permanent assembly.

End caps function by distributing internal pressure loads across their curved surface, carrying the pressure as membrane tension acting in two directions at once, which is why a head can be made thinner than the cylindrical shell it closes; circumferential compression arises only in the knuckle region of a torispherical or elliptical head, and it is there that buckling has to be guarded against. The curvature (e.g., hemispherical or elliptical) determines stress distribution: hemispherical heads provide uniform stress distribution and are ideal for high-pressure applications, while elliptical heads offer a balance of strength and manufacturability for moderate pressures. They seal the vessel ends through welding or bolting with gaskets, preventing fluid or gas leakage while withstanding cyclic pressure variations and thermal expansion.