Flanges are commonly used connectors in pipeline systems, mainly for detachable connections between pipelines, valves, and equipment. Here are some common types of flanges and their applicable scenarios:
Classified by structural form
1. Flat welding flange
Features: Simple structure, convenient, and low cost. The flange is welded onto the pipeline, and the welding strength is relatively low.
Applicable scenarios: Suitable for situations with low pressure levels (usually below PN16) and low temperatures, such as general medium pipelines for low-pressure water, air, steam, etc.
2. Welding flanges
Features: With a tapered neck, it is connected to the pipeline by butt welding and has good pressure resistance. It can effectively disperse stress and is suitable for high-pressure environments.
Applicable scenarios: Commonly used in harsh working conditions such as high temperature, high pressure, or flammable and explosive conditions, such as main pipeline systems in the petrochemical and power industries.
3. Socket welding flange
Features: The pipeline is inserted into the flange hole for welding, which is easy to install and position, but requires high welding quality.
Applicable scenarios: Suitable for small-diameter pipelines (below DN50) and high-pressure applications, commonly used in instrument pipelines and chemical plants.
4. Threaded flange
Features: The flange and pipeline are connected by threads without welding, making it easy to disassemble and maintain.
Applicable scenarios: Suitable for situations where welding is not advisable (such as certain alloy steel pipelines), or for low-pressure, low-temperature corrosive medium pipelines.
5. Loose flange
Features: The flange is not directly fixed to the pipeline and can rotate freely, making it easy to install holes.
Applicable scenarios: Commonly used in situations where frequent disassembly or pipeline alignment is required, and also suitable for corrosive media (different materials of lining can be selected).
6. Flange cover
Features: No central hole, used for sealing pipes or equipment ports.
Applicable scenarios: Mainly used for temporary sealing at the end of pipelines or during equipment maintenance.
Classify by sealing surface form
1. Full plane flange
Features: The sealing surface is flat without protrusions and is usually used in conjunction with soft gaskets.
Applicable scenarios: Suitable for low-pressure, non hazardous media such as water supply and drainage systems.
2. Protruding flange
Features: The sealing surface has a circular protrusion, which can increase the clamping force of the gasket and achieve good sealing effect.
Applicable scenario: Application, suitable for medium and low pressure media (such as water, steam, oil, etc.).
3. Concave convex flange
Features: Paired with concave and convex surfaces for accurate positioning and prevention of gasket extrusion.
Applicable scenarios: Suitable for situations with high pressure or medium leakage, such as oil and gas pipelines.
4. Mortise and tenon flange
Features: The sealing surface is matched with tenons and grooves, and the gasket is embedded in the groove, providing excellent sealing performance.
Applicable scenarios: Used for systems that require strict sealing, such as flammable, explosive, toxic, or high vacuum.
5. Ring connection surface flange
Features: Using metal ring gasket, forming a line contact seal with the gasket through an annular groove, resistant to high pressure.
Applicable scenarios: One on one for high-pressure and high-temperature systems, such as petrochemical and nuclear power plants.
Other one-to-one flanges
1. Blind flange
Features: No through holes, used for completely isolating pipelines.
Applicable scenarios: system isolation, segmented pressure testing, or long-term sealing.
2. Reducing flange
Features: Different diameters at both ends, used for variable diameter connections.
Applicable scenarios: Pipeline diameter changes, saving pipe fittings and installation space.
Selection principles
When choosing a flange, comprehensive consideration should be given to:
Medium characteristics: corrosiveness, toxicity, flammability and explosiveness, etc;
Operating conditions: pressure, temperature range, and fluctuation;
Pipeline material: Confirm that the flange is compatible with the pipeline material;
Installation and maintenance: whether frequent disassembly is required;
Economy: Control costs while meeting the requirements of Enron.