Flange connections are a common and reliable detachable connection method. Their structural characteristics include evenly distributed bolt holes on the flange plate, which are fastened to adjacent flanges using bolts. Gaskets are placed between the flanges to prevent leaks during operation of the piping system or equipment. Flange connections are widely used in pipeline transportation, valve installation, and equipment connections, and are essential components in modern industry.

Depending on the components they connect, flanges can be divided into vessel flanges and pipe flanges. Vessel flanges are primarily used for connecting large equipment such as pressure vessels, heat exchangers, and towers, while pipe flanges are primarily used for connecting pipes to pipes, pipes to valves, and pipes to pumps.

Basic Characteristics of Flanges

Flanges are typically disc-shaped components, typically used in pairs. In pipeline engineering, flanges perform both connecting and sealing functions. After the flanges are welded or installed at each end of the pipe to be connected, bolts, nuts, and gaskets work together to form a sealed, integrated pipe system.

In low-pressure pipelines, threaded flanges (also known as threaded flanges) are generally used. However, in operating conditions with pressures greater than 4 kg, welded flanges are more commonly used to enhance the connection's robustness and sealing.

In actual use, in addition to connecting pipes, valves, pumps, and other equipment are often designed with flanged ports for connection to pipes. This type of connection is also collectively referred to as a flange connection. It's important to note that flanges are essentially connectors, so equipment like pumps alone cannot be considered "flange-type parts." However, smaller components like valves with flanged structures can be considered "flange-type parts."

Structural Features of Slip-On Flanges with Hubs

Slip-on flanges with hubs feature a shortened neck in addition to standard slip-on flanges. This shortened neck significantly increases the flange's load-bearing capacity and structural strength, improving the stress conditions at the transition between the weld and the pipe, reducing stress concentration.

Compared to conventional slip-on flanges, necked slip-on flanges not only offer stable operation under higher pressures, but also better adapt to pipeline operation under temperature fluctuations, pressure fluctuations, and vibration.

Advantages of Necked Slip-on Flanges

Higher Strength:

The short neck design increases the connection strength between the flange and the pipe, making it more capable of withstanding internal pressure and external loads.

Efficient Force Distribution:

Stress concentration at the weld is reduced, extending the service life of the pipe and flange.

Wider Application:

Suitable not only for medium and low-pressure pipelines, but also for pipeline systems with certain high pressures, high temperatures, or low temperatures.

Easy Maintenance:

The flange connection is removable, making it easy to inspect and replace pipes or valves.

Disadvantages of Necked Slip-on Flanges

Although necked slip-on flanges offer excellent load-bearing performance, they also have drawbacks:

Higher Cost:

Compared to plate-type slip-on flanges, their production process is more complex and uses more material, resulting in a higher cost.

Transportation Difficulty:

Due to the protruding neck, flanges are susceptible to bumps and bumps during transportation and loading and unloading. Improper handling can affect the flange's sealing performance.

Installation Space Requirements:

Neck-mounted slip-on flanges are more complex in structure, requiring more space for installation. This makes installation more challenging, especially in confined environments.

Application Areas

Neck-mounted slip-on flanges are widely used in industrial production, particularly in the following areas:

Oil and natural gas pipelines: They withstand high pressures and temperature differences, ensuring safe fluid transportation.

Chemical Equipment: They are used in applications requiring high corrosion resistance, such as acid and alkali solution pipelines.

Power Industry: They are widely used in piping systems in thermal power plants and nuclear power plants.

Marine and Offshore Engineering: Neck-mounted slip-on flanges provide reliable sealing performance in ship pipelines and offshore platforms.

Water Supply and Drainage and HVAC Systems: They are suitable for medium- and high-pressure transmission pipelines and certain critical connections.

Material Selection and Manufacturing Process

Common materials for slip-on flanges include carbon steel, stainless steel, and alloy steel. The appropriate material should be selected based on the operating environment and media requirements. For example:

Carbon steel flanges: Suitable for conveying common media such as water, steam, and natural gas.

Stainless steel flanges: Highly corrosion-resistant, suitable for the chemical, food, and pharmaceutical industries.

Alloy steel flanges: Provide excellent strength and stability even in high-temperature and high-pressure environments.

In terms of manufacturing, slip-on flanges with necks are typically forged through die forging or open forging, followed by turning, drilling, and heat treatment to ensure their dimensional accuracy and mechanical properties meet standard requirements.

Summary

As an improved version of the slip-on flange, the slip-on flange with neck offers significant advantages in strength, sealing, and service life, making it particularly suitable for medium- and high-pressure piping systems or those with high requirements. However, its higher cost and inconvenience in transportation and installation must be weighed during engineering design and procurement.

With the development of industry, the requirements for the safety and reliability of pipeline systems are becoming increasingly higher. Neck-welded flanges are gradually becoming important connectors in the fields of petroleum, chemical industry, electric power, etc. due to their excellent performance.