I. Standard Parameter System
The new GB standard has comprehensively revised the EHA/EHB type heads. The core parameters include:
- Nominal Diameter (DN): Covers a range from DN300 to DN6000, accommodating stepping increments of 50mm and 100mm.
- Dish Height: Designed at DN/4 (e.g., a DN1000 head corresponds to a dish height of 250mm).
- Straight Flange Height: Available in dual specifications: 25mm for small diameters and 40mm for DN ≥ 800.
- Thickness Calculation: Requires comprehensive consideration of design pressure, allowable stress of the material, and corrosion allowance. Low-pressure equipment typically utilizes 6–10mm, whereas high-pressure vessels require 12–60mm.
II. Material Selection Guide
Performance comparison of commonly used materials:
- 304 Stainless Steel: Contains 18% Cr and 8% Ni; suitable for food processing and architectural applications.
- 316L Stainless Steel: Contains 2–3% Mo, offering excellent resistance to chloride-ion corrosion; suitable for marine and chemical engineering.
- Duplex Stainless Steel 2205: Tensile strength > 650 MPa; its low-temperature impact toughness is 0.5 J higher than the ASME standard; suitable for hydrogen-rich, high-pressure environments.
III. Key Design Specifications
- Volume Calculation: Formulated as \(V = 0.2618 \times DN^2 \times h_1\). The revised surface area formula keeps the margin of error < 0.8%.
- Tolerance Control: For DN ≤ 1200, the outer circumference tolerance is ±0.3% DN, and the straight flange tilt is ≤ 1mm / 100mm.
- Errata Notice: Designers must cross-reference the official errata documentation regarding dimensions of THB torispherical heads ≥ 12mm.
IV. Typical Application Cases
- Petrochemical Industry: Hydrogenation reactors utilize SAF 2507 duplex stainless steel, with cold roll spinning forming to control the wall thickness deviation within ≤ 0.5mm.
- Nuclear Containment Vessels: Utilizes a 6mm thick 316L head with a 60mm straight flange height to satisfy double-sided welding requirements.
- Food Storage Tanks: Utilizes a 304 head with an internal surface roughness of Ra ≤ 0.8 μm and a 25mm straight flange height to minimize sanitary dead zones.
V. Recommended Efficiency Tools
It is highly recommended to use standard quick-reference look-up tables (including theoretical weight data) and custom calculators, which can automatically generate material selection advice and thickness calculation values.