What is a Dished Head? Understanding Dished Heads and Caps

What is a Dished Head? Understanding Dished Heads and Caps

Dished heads, also referred to as vessel heads, tank heads, dished ends, caps, or simply ends, are integral components used in the construction of tanks and pressure vessels. These elements form the closure or end of cylindrical vessels, ensuring structural integrity and pressure containment. The terminology and design of dished heads can vary depending on their specific applications and industry standards.

Types of Dished Heads

Dished heads are categorized into several families based on their shape and design:

1. Dished Heads – The standard type, commonly used for pressure vessels.

2. Flat Heads – Typically used in industries like agri-food for specific applications such as distribution plates.

3. Conical Heads – Designed with a conical shape and used in various industrial sectors.

4. Spherical Caps – These are shaped portions of a sphere and feature uniform curvature.

5. Hemispherical Heads – A subset of spherical caps with a deeper structure.

Each type has unique features tailored to specific applications, including pressure containment and aesthetic or functional requirements.

Key Elements of Dished Heads

The design and functionality of dished heads are defined by several critical parameters:

• External or Internal Diameter: Determines the overall size of the head.

• Crown Radius (CR): The radius of the curved surface of the head.

• Knuckle Radius (KR): The radius of the transition curve connecting the curved surface to the flange or cylindrical shell.

• Nominal or Minimal Thickness: Ensures the structural strength of the head.

• Right Side (RS): The flat or beveled edge, customizable to specific requirements.

Standards for Manufacturing Dished Heads

Dished heads are manufactured according to various standards, including the French standard NFE81-100. This standard defines multiple profiles:

1. GRC Dished Heads (NFE 81-102)

• Features a large knuckle radius, making them ideal for pressurized vessel applications.

• Crown radius equals the head diameter, and the knuckle radius is 10% of the head diameter.

2. PRC Dished Heads (NFE 81-101)

• Features a small knuckle radius, mainly used in non-pressurized storage tanks due to lower manufacturing costs.

3. Elliptical Dished Heads (NFE 81-103)

• Deeper than GRC heads, these are designed specifically for pressurized vessels.

4. MRC Dished Heads (NFE 81-104)

• Features a medium knuckle radius, though less commonly used compared to the other types.

Specialty Variants: Spherical Caps and Flat Heads

• Spherical Caps: These caps are designed as a portion of a sphere and are characterized by their diameter and crown radius. A smaller crown radius results in a deeper cap, which is more challenging to manufacture. Spherical caps are not standardized and are often customized.

• Flat Heads: Flat discs with a flanged side, used for specific industrial applications. These heads do not adhere to standard dimensions and are tailored for unique needs.

Applications of Dished Heads

Dished heads play a vital role in diverse industries, including:

• Food Processing: For storage and mixing tanks.

• Chemical and Pharmaceutical: For pressure vessels and reactors.

• Energy Production: Including petrochemical and nuclear applications.

• Cosmetics and Building: For decorative and structural purposes.

Manufacturers like Haipei industry specialize in producing high-quality dished heads and tank bottoms to meet the exacting demands of these industries.

Whether it's ensuring the safety of a high-pressure reactor or enhancing the efficiency of a storage tank, dished heads provide the necessary structural support and functionality. By adhering to precise standards and utilizing advanced manufacturing techniques, these components remain indispensable across various sectors.

Company information

Haipei industry can produce all types of dished ends heads. They can be manufactured from a number of steel types including pressure vessel and boiler quality, chrome moly and stainless steel. The company also offers 2:1 semi ellipsodial, hemispherical petals, torispherical ends as well as conical knuckled sections.

Haipei industry company is a leading producer of various types of dished heads, cones, and other special pressed products in different materials grades like Carbon Steel, Stainless Steel, Duplex, Super Duplex, Aluminum, Nickel and Nickel Alloys, Copper and Copper Alloys, Titanium and Its Alloys, Zirconium and all cladded material combinations.

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