Welding Elliptical Heads

The geometric shape, dimensions, and mass of a standard elliptical head are formed by a generatrix composed of a quarter-ellipse curve smoothly connected to a short straight line parallel to the axis of revolution. Therefore, this dished head consists of half an ellipsoid and a short cylindrical section with a height ( h_0 ). Dingjin manufactures more than 50 tons of 2:1 elliptical heads per year from carbon steel and stainless steel raw materials.

Common Types of Dished Head Bevels and Their Applicable Scenarios for Dingjin's Dished Heads.

Plate Bevel (Type I Bevel)

Form: The shell and the dished head plate are perpendicular to each other and are in planar contact, with no additional bevel machining required.

Applicable scenarios: Low-pressure, small-diameter pressure vessels, or thin-walled heads with a base material thickness of no more than 3 mm (no beveling is required to achieve full penetration).

V-Groove (45°/60° Bevel)

Form: The welding surface is machined with a 45° or 60° V-shaped bevel, which may be prepared on one or both sides. A root face (blunt edge) and an assembly gap should be provided to prevent burn-through.

Applicable scenarios:

45° V-groove: Suitable for medium-thickness heads (3–20 mm) used in pressure vessels, providing good weld penetration and ease of operation. Attention should be paid to both weld penetration and assembly accuracy.

60° V-groove: Suitable for large and extra-large pressure vessel heads or thick-walled heads (thickness > 20 mm). The larger bevel angle reduces the number of welding passes and lowers the risk of welding deformation.

Outer Bevel / Inner Bevel

Form: The bevel is machined on either the outer surface (outer bevel) or the inner surface (inner bevel) of the head and is typically used in combination with V-grooves.

Default rule: Unless otherwise specified, the outer bevel is used as the standard configuration because it provides easier access for welding operations and non-destructive testing (NDT).

Single U-Groove

Form: The root of the groove has a curved (U-shaped) profile, with a radius typically equal to one-third to one-half of the base material thickness, providing a smooth transition.

Applicable scenarios: Suitable for ultra-thick-walled heads (thickness > 40 mm). This groove design reduces welding stress concentration and improves joint toughness, although it requires higher machining precision and more advanced processing equipment.

Compatible with Base Material Thickness

For thin-walled heads (≤3 mm), a plate bevel (Type I bevel) can be used. For medium-thickness heads (3–20 mm), a 45° V-groove is preferred. For thick-walled heads (>20 mm), a 60° V-groove or U-groove should be selected.

Match the Welding Method

V-grooves are commonly used for manual arc welding and gas-shielded welding. U-grooves are well suited for automatic welding and submerged arc welding, helping to improve welding efficiency.

Ensure Full Weld Penetration

The groove design must ensure complete penetration at the weld root to prevent defects such as incomplete penetration and slag inclusion. For pressure-bearing heads in particular, a full-penetration butt joint is a fundamental requirement.

Control Welding Deformation

Welding residual stress and deformation should be minimized through the proper design of the groove angle, root face (blunt edge), and assembly gap. When necessary, symmetrical welding or reverse deformation techniques should be adopted.