EN545 is a key European standard for “ductile iron pipes, fittings, accessories, and joints for water supply.” It ensures the safety, reliability, and durability of drinking water distribution systems. A thorough understanding of this standard is crucial for professionals involved in water supply and drainage engineering, pipeline design, procurement, and quality management. This article will further elaborate on several key points.
1. The Meaning of Fastener Performance Grades
In the EN545 standard, fasteners such as bolts and nuts used in pipe flanges are clearly identified by their performance grades, such as the common 4.6 and 8.8 grades. This grade code intuitively describes the fastener’s mechanical properties.
The first digit (e.g., the “4″ in 4.6) represents 1/100 of the nominal tensile strength. Therefore, “4″ indicates that the fastener’s nominal tensile strength is 4 x 100 = 400 MPa.
The second digit (e.g., the “6″ in 4.6) represents the yield ratio, which is 10 times the ratio of yield strength to tensile strength. Therefore, “6″ indicates that the yield strength is approximately 60% of the tensile strength.
For example (grade 4.6): nominal tensile strength = 4×100=400MPa |Yield strength ≈ tensile strength x (6/10) = 400MPa x0.6= 240MPa
This means that a grade 4.6 bolt can withstand a stress of at least 240MPa without permanent deformation (yielding) and ultimately fracture at a stress of at least 400MPa.
2. Fastener Surface Treatment
To prevent corrosion and ensure long-term, reliable connections, EN545 has strict requirements for fastener surface treatment. Common methods include galvanizing and Dacromet coating.
a) Galvanizing is the process of applying a zinc coating to the surface of steel to provide cathodic protection against corrosion. There are two main types of treatments.
Electrogalvanizing:
- Process: In an electrolyte, an electric current is passed through the surface of the workpiece, causing zinc ions to deposit on the workpiece surface, forming a coating.
- Features: The coating is thin and uniform, with a smooth and glossy appearance, but the corrosion protection life is relatively short.
- Applications: Commonly used in indoor environments or for small parts where appearance is critical and the corrosion environment is not harsh.
Hot-dip galvanizing:
- Process: The workpiece is immersed in molten zinc, forming a zinc-iron alloy coating on the surface.
- Features: The coating is thick and uneven, with spangles on the surface, strong adhesion, and far superior corrosion protection to electrogalvanizing. Application: EN545 typically requires hot-dip galvanizing of flange bolts to withstand the long-term, harsh corrosion conditions of underground or humid environments.
b) Dacromet
- Process: An electroless zinc-based chromate treatment technology that involves dipping or spraying a solution containing zinc flakes, aluminum flakes, and chromate, followed by high-temperature sintering to form a multi-layer protective film.
- Features: No hydrogen embrittlement issues, excellent corrosion resistance (especially chemical and high-temperature corrosion resistance), and a uniform coating. However, the low surface hardness makes it unsuitable for friction surfaces.
- Application: Commonly used for high-strength fasteners requiring extremely high corrosion protection and avoiding the risk of hydrogen embrittlement. It is an excellent alternative to hot-dip galvanizing.
3. Two Types of Flange Gaskets
EN545 piping systems primarily use two types of sealing elements, suited to different joint designs.
- Gaskets: Used for rigid flange joints. Typically installed between two flange surfaces, they deform by evenly tightening the bolts, filling any microscopic irregularities on the flange surface and achieving a seal.
- T-Ring (Rubber Ring): Used in push-pull or mechanical flexible joints (such as K-type and T-type joints). It is a rubber sealing ring with a special T-shaped cross-section.
4. The Meaning and Relationship of Pressure Grades PMA, PFA, and PEA
The EN545 standard defines three key pressure grades to comprehensively describe a pipeline’s pressure-bearing capacity:
- PFA (Permissible Working Pressure): This refers to the internal pressure at which a pipeline can safely operate continuously at its maximum long-term operating temperature.
- PEA (Works Test Pressure): This refers to the test pressure applied to each pipe during quality inspection at the factory before shipment. This pressure verifies the strength and sealing integrity of the pipe upon delivery.
Relationship: PEA = 1.2 * PFA + 5 bar. This formula ensures that the factory test pressure is higher than the allowable working pressure, providing a sufficient safety margin to verify product quality.
- PMA (Permissible Maximum Operating Pressure): This refers to the maximum short-term, transient internal pressure that a pipeline can safely withstand at room temperature (25°C). It represents the peak pressure limit that the pipeline can withstand.
Relationship: PMA = 1.2 * PFA. This indicates that the maximum allowable transient pressure (PMA) is 20% higher than the allowable continuous operating pressure (PFA).
EN545 piping , Rubber Ring, gasket, ductile iron pipes and fittings, Electrogalvanizing,Hot-dip galvanizing, water supply, drainage,
Post time: Sep-22-2025
