Types, Characteristics, and Manufacturing Processes of Pressure Vessel Heads

I. Overview of Heads

Heads are critical components used to seal the ends of pressure vessels, storage tanks, reactors, and other equipment, and are welded to the cylindrical shell to form a complete pressure-containing shell. Heads can be classified into various types based on their shape, including elliptical heads, dished heads, spherical heads, conical heads, and flat-bottom heads, among others, with elliptical heads being the most widely used.

II. Common Types of Heads and Their Characteristics

1. Elliptical Heads: Composed of a semi-ellipsoidal shell and a straight flange, elliptical heads feature uniform stress distribution and are the most commonly used head type in pressure vessels, suitable for medium- and low-pressure applications. The standard elliptical head has a major-to-minor axis ratio of 2:1.

2. Dish Head: Composed of a spherical surface, a transition arc, and a straight edge section. It has a shallow depth and is easy to manufacture, but exhibits more pronounced stress concentration, making it suitable for low-pressure conditions.

3. Spherical Heads: Hemispherical in shape, they offer the most rational stress distribution and the highest pressure-bearing capacity. However, due to their greater depth and higher manufacturing difficulty, they are suitable for high-pressure operating conditions.

4. Conical Heads: Shaped like a cone, they facilitate material flow and discharge, making them suitable for the bottom of containers holding solid particles or viscous media, and are also used for diameter transitions.

5. Flat Head: It has a flat shape, simple structure, and is easy to manufacture, but has the worst load-bearing capacity, and is only suitable for low-pressure and atmospheric pressure vessels.

III. Manufacturing Process

1. Stamping Forming: The steel plate is heated and placed on a mold, then formed by a press machine. This method is suitable for small and medium-diameter heads.

2. Spinning Forming: The rotating steel plate is formed point by point through rolling by a spinning machine. It is suitable for large-diameter, thin-walled heads and does not require large molds.

3. Segmental Forming: Ultra-large diameter heads are first formed by pressing individual segments, then welded together into a complete unit.

IV. Quality Inspection

The finished heads shall undergo visual inspection, dimensional measurement (inner diameter, depth, straight edge height), wall thickness testing, non-destructive testing (radiographic testing, ultrasonic testing, magnetic particle testing), and shape tolerance inspection.

V. Execution Standards

GB/T 25198 "Pressure Vessel Heads", JB/T 4746 "Steel Heads for Pressure Vessels", NB/T 47002 "Composite Plates for Pressure Vessels", ASME BPVC Section VIII, etc.

VI. Common Materials

Carbon steel: Q235, Q245R, Q345R; Stainless steel: 304, 304L, 316, 316L; Alloy steel: 16MnR, 15CrMoR, 12Cr1MoVR, etc.

Cangzhou Kairuifeng Pipeline Equipment Co., Ltd. specializes in the production of various pressure vessel heads, offering a full range of specifications and supporting customization for large diameters. Inquiries and purchases are welcome.