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Flange Connections for Composite Hose Assemblies: Secure and Reliable Jointing Solutions


Flange connections are commonly used in various industries to join pipes, valves, and hoses together. They provide a secure and leak-free connection, allowing for easy installation and removal. When it comes to composite hose assemblies, flange connections can be utilized to ensure a reliable and efficient transfer of fluids.

Flange Standards

There are several flange standards used in different regions and industries. Two widely recognized standards are the DIN (Deutsches Institut für Normung) and ASA (American Standards Association) standards.

DIN Flanges: The DIN standard is commonly used in Europe and follows specific dimensions and specifications. DIN flanges are typically classified based on their nominal pressure ratings, such as PN6, PN10, PN16, PN25, PN40, and PN64. These ratings indicate the pressure levels at which the flange can safely operate.

ASA Flanges: ASA flanges, also known as ANSI (American National Standards Institute) flanges, are widely used in the United States. They are available in different classes, including Class 150, Class 300, Class 600, Class 900, Class 1500, and Class 2500. These classes represent the pressure ratings for the flanges.

JIS Flanges: JIS (Japanese Industrial Standards) flanges are commonly used in Japan and follow specific dimensions and specifications set by the Japanese Standards Association (JSA).

BS Flanges: BS (British Standard) flanges are widely used in the United Kingdom and follow standards set by the British Standards Institution (BSI).

ISO Flanges: ISO (International Organization for Standardization) flanges are recognized globally and provide standardized dimensions and specifications applicable across different countries.

GOST Flanges: GOST (Gosudarstvennyy Standart) flanges are commonly used in Russia and follow standards set by the Russian national standards organization.

SANS Flanges: SANS (South African National Standard) flanges are widely used in South Africa and adhere to specific dimensions and specifications set by the South African Bureau of Standards (SABS).

Flange Drilling Holes

Flanges are designed with a specific number of bolt holes arranged in a circular pattern. The number and size of the bolt holes depend on the flange size and standard being used. Commonly, flanges have four, eight, or more bolt holes. The diameter of the bolt holes is determined by the flange size and the required strength of the connection.

There are prevailing standards that provide guidelines for the hole sizes, patterns, and spatial conditions. The most commonly used standards include:

ASME B16.5: This standard, published by the American Society of Mechanical Engineers (ASME), provides guidelines for pipe flanges and flanged fittings. It specifies the hole sizes, bolt circle diameter, and bolt hole patterns for various flange sizes and pressure ratings.

DIN EN 1092-1: This European standard, published by the Deutsches Institut für Normung (DIN), specifies the dimensions and tolerances of flanges for use with PN designated flanges. It includes guidelines for drilling holes, bolt circle diameters, and bolt hole patterns.

JIS B2220: This Japanese Industrial Standard provides specifications for steel pipe flanges. It outlines the hole sizes, bolt hole patterns, and dimensions for flanges used in Japan.

BS 4504: This British Standard specifies flanges and their dimensions for pipe connections. It includes guidelines for drilling holes, bolt circle diameters, and bolt hole patterns.

Flange Thickness

The thickness of the flange is an important consideration to ensure its strength and stability. The flange thickness is determined based on factors such as the flange material, pressure rating, and pipe size. Thicker flanges are generally used for higher-pressure applications to provide adequate strength and rigidity.

The flange thickness should be determined based on a comprehensive analysis of the specific application requirements, including pressure ratings, material compatibility, space constraints, and cost considerations.

Strength and Rigidity: Thicker flanges generally provide increased strength and rigidity, which can be beneficial for high-pressure applications or situations where the flange may be subjected to significant external forces or stresses. Thicker flanges are less prone to deformation or bending under pressure.

Space Limitations: Thicker flanges can occupy more space, which may not be suitable for applications with limited space or tight clearances. In such cases, thinner flanges may be preferred to optimize the overall dimensions of the system.

Cost: Thicker flanges often require more material and machining, resulting in higher costs. Thinner flanges can be a more economical choice for applications where high strength or rigidity is not a primary concern.

Compatibility with Gaskets: The thickness of the flange should also be considered in relation to the thickness of the gasket being used. The flange thickness should allow for proper compression of the gasket to create a reliable and effective seal.

Screw-On Sequence

When assembling flange connections, it is crucial to follow the correct sequence for tightening the bolts. This sequence ensures even distribution of pressure across the flange face and prevents leaks. The specific screw-on sequence may vary depending on the flange design and the recommendations provided by the manufacturer. It is important to consult the manufacturer's guidelines or relevant industry standards to determine the appropriate screw-on sequence for your specific application.

Gasket Selection

In flange connections, gaskets are used to create a seal between the flange faces. Gaskets are typically made of materials such as rubber, PTFE (polytetrafluoroethylene), or metal. The selection of the gasket material depends on various factors, including the fluid being transferred, temperature, pressure, and chemical compatibility. It is crucial to choose the appropriate gasket material to ensure a reliable and leak-free connection.

Selecting the appropriate gasket for a flange connection involves considering various factors to ensure a reliable and effective seal. Here are some key considerations for gasket selection:

Fluid Compatibility: Determine the chemical compatibility of the fluid being transferred. Different gasket materials have varying resistance to specific chemicals, so it's important to choose a gasket material that can withstand the fluid's properties without deteriorating or causing contamination.

Temperature and Pressure: Evaluate the temperature and pressure conditions of the application. Gaskets should be capable of withstanding the temperature and pressure ranges without compromising their integrity or leaking. Consider the gasket's temperature and pressure ratings to ensure they are suitable for the specific operating conditions.

Flange Material: Take into account the material of the flanges to ensure compatibility with the gasket material. For example, certain gasket materials may not be compatible with highly corrosive or abrasive flange materials. Ensure the gasket material is compatible with the flange material to prevent chemical reactions, corrosion, or damage to the flanges.

Sealing Performance: Consider the required sealing performance for the application. Gaskets come in various types, such as full-face, ring, or spiral wound gaskets, each offering different sealing characteristics. Evaluate the specific requirements for leakage prevention, such as gas tightness or resistance to fluid migration, and select a gasket type that can fulfill those requirements.

Environmental Factors: Assess any environmental factors that may affect gasket performance. These can include factors like UV exposure, weather conditions, or exposure to environmental contaminants. Choose a gasket material that can withstand the specific environmental conditions of the application.

Compressibility and Recovery: Consider the compressibility and recovery characteristics of the gasket material. Gaskets should be able to deform and fill any irregularities or imperfections on the flange surfaces to ensure a tight and effective seal. Additionally, they should have good recovery properties to maintain the seal over time, even under fluctuating pressures or temperature changes.

Standards and Guidelines: Consult industry standards, such as those provided by organizations like the American Society for Testing and Materials (ASTM) or the Fluid Sealing Association (FSA), for guidance on gasket selection. These standards can provide valuable information on gasket materials, specifications, and performance characteristics.

Installation and Maintenance

Proper installation and regular maintenance are essential for ensuring the integrity and longevity of flange connections. During installation, it is important to inspect the flange faces, gaskets, and bolts for any damage or defects. The flange faces should be clean, smooth, and free from any debris or contaminants. Tightening the bolts to the recommended torque specifications is crucial to achieve a proper seal without damaging the flange or gasket.

Regular maintenance includes periodic inspections for leaks, corrosion, or any signs of wear. Flange connections should be checked for tightness and re-torqued if necessary. Gaskets should be replaced as needed, ensuring that the new gaskets are compatible with the application requirements.


Flange connections play a vital role in composite hose assemblies, providing a secure and leak-free joint for fluid transfer. Understanding the relevant flange standards, pressure ratings, drilling hole patterns, flange thickness, and proper installation practices are important for ensuring the reliability and safety of these connections. It is always recommended to consult the manufacturer's guidelines, relevant industry standards, or seek expert advice to ensure the proper selection and installation of flange connections for composite hose assemblies.

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