EEMUA 234 is a specification published by the **Engineering Equipment and Materials Users Association (EEMUA) for backing flanges used in the construction of storage tanks. These flanges are typically used in conjunction with flat-bottom tanks to provide a secure and leak-proof connection between the tank shell and the bottom plate. When combined with ASTM A105N material and **hot-dip galvanizing, these flanges offer excellent mechanical properties and corrosion resistance, making them suitable for demanding industrial applications.
Key Features of EEMUA 234 Backing Flanges:
1. Purpose:
– Backing flanges are used to create a strong, leak-proof joint between the tank shell and the bottom plate in storage tanks.
– They are commonly used in flat-bottom tanks for storing liquids such as water, oil, and chemicals.
2. Material:
– ASTM A105N: A carbon steel material normalized for improved mechanical properties, suitable for high-temperature and high-pressure applications.
– Hot-Dip Galvanizing**: A zinc coating applied to the flange to provide corrosion resistance, especially in outdoor or corrosive environments.
3. Design:
– Backing flanges are designed to match the curvature of the tank shell and provide a flat surface for welding to the bottom plate.
– They are available in various sizes and thicknesses to meet specific tank design requirements.
4. Standards:
– EEMUA 234: Specifies the dimensions, tolerances, and materials for backing flanges.
– ASTM A105N: Specifies the material properties for carbon steel forgings.
– ISO 1461 or ASTM A123: Standards for hot-dip galvanizing.
Applications of EEMUA 234 Backing Flanges:
– Storage Tanks: Used in flat-bottom tanks for storing water, oil, chemicals, and other liquids.
– Industrial Facilities: Suitable for use in refineries, petrochemical plants, and power generation facilities.
– Water Treatment: Used in water storage and treatment systems.
Material Properties of ASTM A105N:
| Property | Value |
|—————————|————————————|
| Tensile Strength (Rm) | 70 ksi min (485 MPa min) |
| Yield Strength (Rp0.2) | 36 ksi min (250 MPa min) |
| Elongation (A5) | 22% min |
| Hardness | Typically ≤ 187 HB |
Chemical Composition of ASTM A105N:
| Element | Composition (%) |
|—————|———————————-|
| Carbon (C) | 0.35 max |
| Manganese (Mn) | 0.60–1.05 |
| Phosphorus (P) | 0.035 max |
| Sulfur (S) | 0.040 max |
| Silicon (Si) | 0.10–0.35 |
Hot-Dip Galvanizing Process:
1. Surface Preparation:
– The flange is cleaned to remove rust, oil, and other contaminants.
– This is typically done through abrasive blasting or chemical cleaning.
2. Fluxing:
– The flange is dipped in a flux solution to prevent oxidation before galvanizing.
3. Galvanizing:
– The flange is immersed in a bath of molten zinc at around 450°C (842°F).
– The zinc reacts with the steel surface to form a protective coating.
4. Cooling and Inspection:
– The flange is cooled and inspected to ensure the coating is uniform and free of defects.
Advantages of Hot-Dip Galvanized EEMUA 234 Backing Flanges:
– Corrosion Resistance: The zinc coating provides excellent protection against rust and corrosion, even in harsh environments.
– Durability**: ASTM A105N material offers high strength and toughness.
– Long Service Life: The combination of carbon steel and galvanizing ensures a long lifespan with minimal maintenance.
– Cost-Effective: Hot-dip galvanizing is a cost-effective way to enhance the corrosion resistance of carbon steel flanges.
Considerations for Use:
– Welding: Welding of galvanized flanges requires special precautions to avoid releasing toxic zinc fumes. Proper ventilation and welding techniques are essential.
– Temperature Limits: ASTM A105N is suitable for moderate and high-temperature applications, but the galvanized coating may degrade at very high temperatures.
– Compatibility: Ensure the flange design and material are compatible with the tank shell and bottom plate materials.
EEMUA 234 backing flanges made from **ASTM A105N** and hot-dip galvanized are an excellent choice for constructing durable and corrosion-resistant storage tanks. Their high strength, toughness, and protective zinc coating make them suitable for use in demanding industrial environments. When selecting these flanges, ensure compliance with **EEMUA 234** and **ASTM A105N** standards, and work with certified manufacturers to guarantee quality and performance. Proper installation and welding procedures are essential to ensure the longevity and reliability of the tank system.
