In the valve industry, ball valves are widely used in various fluid control systems due to their simple structure, excellent sealing performance, and ease of operation. Based on the connection method, ball valves can be classified into threaded ball valves and flanged ball valves.

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1. Connection Method

Threaded Ball Valves:

Threaded ball valves connect to pipelines using either internal or external threads and are typically used in small-diameter pipeline systems. The advantage of threaded connections lies in their easy installation, compact design, and minimal space requirements, making them especially suitable for confined spaces. Threaded ball valves are commonly used in low and medium-pressure systems and are ideal for fluid control in residential, commercial buildings, and light industrial equipment.

Flanged Ball Valves:

Flanged ball valves are connected to pipelines through flanges and are suitable for medium to large-diameter pipelines. Flange connections offer higher strength and stability, allowing them to withstand higher pressures and temperatures. As a result, they are commonly used in heavy industries, chemical processing, oil, natural gas, and other applications involving high pressure, high temperature, or corrosive media. Flange connections also facilitate easy disassembly and maintenance but require more installation space.

2. Sealing Performance

Threaded Ball Valves:

Threaded ball valves typically use soft sealing materials such as polytetrafluoroethylene (PTFE), offering excellent sealing performance, making them suitable for gases, liquids, and other media. However, under high-pressure and high-temperature conditions, threaded connections may pose a risk of leakage, and their sealing effectiveness is generally slightly weaker than that of flanged ball valves in demanding operating conditions.

Flanged Ball Valves:

Flanged ball valves typically utilize metal or composite seals, providing more reliable sealing performance, especially under high-pressure, high-temperature, or corrosive media conditions. The sealing of flange connections is more stable, effectively preventing leakage.

3. Installation and Maintenance

Threaded Ball Valves:

Threaded ball valves are easy to install, requiring only tightening to complete the connection, making them ideal for quick installation in small systems. However, once the threaded connection is secured, it may loosen due to thermal expansion and contraction or vibration of the pipeline, leading to potential leakage risks. During maintenance, if a threaded ball valve needs to be replaced, it may affect the pipeline system and even require reconnection of the entire pipeline.

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Flanged Ball Valves:

Flanged ball valve installation requires the use of flanges, bolts, and gaskets, making the installation process more complex. However, flange connections offer higher robustness and reliability. During maintenance, flanged ball valves can be easily disassembled, replaced, or repaired without affecting the entire pipeline system.

4. Cost and Application

Threaded Ball Valves:

The manufacturing cost of threaded ball valves is relatively low, making them suitable for small projects with limited budgets. Due to their compact structure and low cost, threaded ball valves are commonly used in residential water supply systems, small industrial equipment, and light industrial process control applications.

Flanged Ball Valves:

The manufacturing and installation costs of flanged ball valves are higher, but their durability and reliability make them the preferred choice for demanding operating conditions. They are suitable for medium to large-scale engineering projects in industries such as petrochemicals, power generation, shipbuilding, and metallurgy. Flanged ball valves are particularly common in systems that require frequent disassembly and maintenance.

Flanged Valves vs Threaded Valves

Figure 1: Flanged (left) and threaded valves (right)

Flanged and threaded valves are two commonly used types of valve fittings in industries. Choosing between them requires careful consideration of pressure, temperature, installation complexity, space constraints, and cost-effectiveness. This article explores and compares both valve types to help the user make an informed decision for an application.

Flanged valves

A flanged valve has flanges at the end of its body. A flange connection joins two materials with either an internal or external lip. A gasket placed between these materials stops leaks. Typically, bolts secure this connection; however, the pieces can sometimes be welded together.

• Flanges are available in various styles, including slip-on flanges, lap-joint flanges, weld-neck flanges, and socket-weld flanges.
• Flanged valves find wide application across diverse industries, including oil and gas, chemical processing, power generation, and water treatment.
• Most flanged valves adhere to industry standards like ANSI/ASME B16.5, DIN -1/ISO , and SAE J518, which specify the dimensions, materials, and technical requirements for flanges used in various industrial applications.
• Flange ratings are typically designated by a numerical value, such as Class 150, Class 300, and Class 600; the higher numbers indicate greater pressure and temperature resistance.

Advantages

• Versatility: Flanged valves are versatile and can be used with different pipe sizes and materials, including steel, cast iron, and PVC. Also, they work well with hazardous fluids.
• Easy to remove: Flanged valves can be easily removed within the system without removing other components, which is difficult with threaded valves due to space constraints.
• Strength and durability: The flanged connection gives extra strength and durability to handle high pressure and temperature.

Limitations

• Cost: Installing flanged valves can be more expensive due to the need for bolt tightening and gasket replacement.
• Size: Flanged connections are typically larger and bulkier than other connections, which may not be ideal for space-constrained applications.

Figure 2: Flanged valves used in an industry

Threaded valves

Threaded valves, or screwed valves, have threaded ends for direct connection to compatible pipes or fittings. Threads are standardized to ensure compatibility and ease of maintenance. Common thread standards are BSP, NP, and UTS. Threaded valves are commonly found in plumbing systems, small-scale industrial processes, and residential applications.

Advantages

• Simplicity: Thread connections are simple and easy to install or replace, requiring no additional tools. Also, threaded connections need not be tightened as there are no bolts.
• Compact: They tend to be more compact and lightweight, making them suitable for tight spaces.
• Cost-effective: Threaded connections cost less as no multiple parts and flange configurations exist.
• Vibration tolerance: Threaded valves tolerate pump vibrations better as the threaded connection provides greater stability and reduces the risk of loosening under mechanical stress.

Limitations

• Limited stress tolerance: Threaded connections may not handle high pressures and temperatures, as well as other connection types.
• Corrosion: The threads in threaded valves are more susceptible to corrosion, making them difficult to remove and potentially weakening the connection.
• Potential leakage: Over time, threaded connections may experience wear or loosening, leading to potential leakage. Proper installation, periodic inspection, and maintenance are necessary to ensure the integrity of threaded valves.

Comparison table

Table 1: Flanged valves vs threaded valves

Parameter Flanged valves Threaded valves Connection method Flanges with bolted joints Threaded ends Application range High-pressure and high-temperature applications Low-pressure and low-temperature applications Installation complexity More complex installation due to alignment and bolting Simple installation by screwing onto compatible threads Maintenance Easy removal and maintenance with bolted flange connections Straightforward maintenance due to threaded connections Space requirement Require more space for flanges and bolting Compact design suitable for space-constrained installations Cost Generally more expensive due to flanges and bolts Cost-effective Leakage risk Provides a tight and reliable seal with proper installation Potential leakage due to wear or loosening of threaded joints Pressure and temperature Suitable for high-pressure and high-temperature conditions Not recommended for demanding pressure and temperature ranges

FAQs

What is the difference between flanged valves and threaded valves?

Flanged valves have a flange connection that requires bolts for installation, while threaded valves have threads that allow for direct screwing onto the pipeline.

Which type of valve is more commonly used in industrial applications, flanged or threaded?

Flanged valves are more commonly used in industrial applications because they can handle higher pressures and larger pipe sizes.

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