Flanged Valves vs Threaded Valves

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

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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.

1. What are the advantages of flanged ball valves?

Flanged ball valve is a relatively new type of ball valve, and its own structure has some unique advantages, such as no friction to the switch, small wear on the seal, and small opening and closing torque.

The flanged ball valve is equipped with a multi-turn electric actuator, and the medium can be adjusted. It is widely used in petroleum, chemical industry, urban water supply and drainage, etc. Ball valve and gate valve belong to the same type of valve, the difference is that the closing part of the flanged ball valve is a sphere, which rotates around the center line of the valve body to open and close.

Ball valves are mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. A flanged ball valve is defined as a valve whose opening and closing member (ball) is driven by a valve stem and rotates around the stem axis.

The ball valve flange type and gate valve belong to the same type of valve, the difference is that its closing part is a ball that rotates around the centerline of the valve body to open and close.

The three-piece ball valve is a new type of valve that has been widely used in recent years. The ball valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. The V-shaped opening ball valve also has a good flow adjustment function.

Flanged ball valve has the following advantages:

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1. The fluid resistance is small, and its resistance coefficient is equal to the resistance coefficient of the pipe section of the same length.

2. Simple structure, small size and light weight.

3. Tight and reliable. At present, the sealing surface material of flange type valve is widely made of plastic with good sealing performance, and it is also widely used in vacuum system.

4. Easy to operate, quick to open and close, just rotate 90° from fully open to fully closed, which is convenient for remote control.

5. Easy maintenance, simple structure of ball valve, generally movable sealing ring, easy disassembly and replacement.

6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the sealing surface of the valve will not be eroded when the medium passes through.

7. Wide range of applications, from a few millimeters to several meters in diameter, from high vacuum to high pressure.

Ⅱ. Structural characteristics of flanged ball valve

1. No friction when opening and closing. This function completely solves the problem that the traditional valve affects the sealing due to the friction between the sealing surfaces.

2. Top installation structure. The valve installed on the pipeline can be directly inspected and maintained online, which can effectively reduce the downtime of the device and reduce the cost.

3. Single valve seat design. It eliminates the problem that the abnormal increase of medium pressure in the valve cavity affects the safety of use.

4. Low torque design. The specially designed valve stem can be easily opened and closed with a small handle.

5. Wedge-shaped sealing structure. Through the mechanical force provided by the valve stem, the ball wedge is pressed against the valve seat to seal the valve, so that the sealing performance of the valve is not affected by the change of pipeline pressure difference, and reliable sealing performance is guaranteed under various working conditions.

6. Self-cleaning structure of sealing surface. When the ball tilts away from the valve seat, the fluid in the pipeline passes through the sealing surface of the ball evenly at 360 degrees, which not only eliminates the local scouring of the valve seat by the high-speed fluid, but also washes away the accumulation on the sealing surface of the flanged ball valve. for self-cleaning purposes.

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