Flange valves are mechanical devices that regulate the flow of fluids within pipelines. They are equipped with flanged connections, which are used to attach the valve to the piping system. This design ensures a tight and secure seal, making flange valves particularly suitable for high-pressure and high-temperature applications. These valves come in various types, each designed to meet specific operational needs, including gate valves, globe valves, ball valves, and butterfly valves, to name a few.

The flange connection is often favored in industries where durability and ease of maintenance are key considerations, offering several advantages over other types of valve connections. Their reliability in harsh operating conditions is one of the reasons they are commonly found in critical systems like power plants, refineries, and water treatment facilities.

Key Types of Flange Valves

There are several types of flange valves, each suited for different applications:

Gate Valves:

These are commonly used for on/off control. Gate valves operate by lifting a gate out of the path of the fluid. When fully open, the gate valve provides minimal resistance to fluid flow.

Globe Valves:

Globe valves are used for regulating flow. They feature a movable disc and a stationary ring seat, allowing for precise adjustments to the flow rate.

Ball Valves:

These valves use a rotating ball with a hole in the center to control the flow. Ball valves are known for their fast opening and closing capabilities and are ideal for applications requiring quick shutoff.

Butterfly Valves:

These valves consist of a rotating disk that regulates fluid flow. Butterfly valves are lightweight, compact, and efficient, making them ideal for large-diameter pipes.

Each type of flange valve offers distinct advantages depending on the specific requirements of the application, such as flow control precision, ease of operation, or resistance to pressure and temperature.

 

Types of Flange Connections

Flange Sealing Face Types

There are various types of flange connections, each suited for different pressures, temperatures, and specific industrial needs:

Flat Face (FF) Flanges

Flat face (FF) flanges are characterized by a completely flat mating surface, unlike raised face (RF) flanges, which feature a raised section around the pipe bore. The FF flange design eliminates the raised area, making the entire flange face uniform. This flange type is primarily used in systems involving materials such as cast iron or fiberglass, where the risk of damaging the flange due to bolt pressure is a concern. FF flanges are often paired with a full-face gasket, which ensures complete surface contact between the flange and the sealing material.

Key Features and Characteristics:

1. Flat Surface: The entire surface of the FF flange is flat, providing a smooth, even interface for sealing.
2. Gasket Compatibility: The flat face flange generally uses a full-face gasket, which covers the entire flange area and helps in creating a uniform seal.
3. Applications: FF flanges are typically used in low-pressure systems and are ideal for applications where higher pressures are not a concern. They are often found in water systems, pump suctions, or non-critical service lines where high sealing integrity is not critical.
4. Material Compatibility: These flanges are commonly used in systems made from cast iron, as they prevent the bending or cracking that can occur under bolt pressure. This makes FF flanges suitable for use in less demanding environments where flexibility in the sealing system is key.

 

Raised Face (RF) Flanges:

Raised Face (RF) flanges are among the most commonly used flange types in various industries, including oil & gas, petrochemical, and power generation. The defining characteristic of a Raised Face flange is the raised portion on the surface around the bore, where the gasket is placed. This raised section increases the sealing efficiency by concentrating the pressure applied by the bolting onto a smaller area, ensuring a strong seal. RF flanges are suitable for a wide range of pressure conditions, from low to high pressures.

The height of the raised face is typically defined by the flange’s pressure class and diameter. The ASME B16.5 standard governs the design of these flanges, specifying that for pressure classes 150 and 300, the raised face is usually about 1/16 inch (1.6 mm), while for higher pressure classes, it can extend to 1/4 inch (6.4 mm). The finish of the raised face typically falls within a range of 125-250 RMS (Root Mean Square), providing a smooth surface that enhances gasket sealing.

RF flanges are designed to work with various types of gaskets, including flat, semi-metallic, and metallic gaskets like spiral wound or jacketed types. The raised face ensures that the gasket is compressed properly during installation, which prevents leakage and contributes to the flange’s overall performance. These flanges are frequently chosen for systems where pressure containment is critical, and where durability is essential for maintaining long-term system integrity.

Ring Type Joint (RTJ) Flanges:

RTJ flanges are characterized by a high-precision groove cut into the flange face. This groove holds a metallic gasket, which is compressed when the flange bolts are tightened, creating an effective seal. The sealing efficiency is improved as pressure increases, making RTJ flanges highly effective in high-pressure systems. Unlike other flanges, the RTJ system seals by initial line contact, which is a wedging action between the gasket and the mating flange surfaces.

The groove design plays a critical role in ensuring proper sealing. The groove must be clean and free of contaminants such as dirt or moisture. The RTJ gasket, which sits within the groove, is available in various types based on the application and pressure requirements.

Types of RTJ Gaskets:

1. R Type Gasket: The most common RTJ gasket, available in two profiles—oval and octagonal. The octagonal gasket is generally preferred due to its superior sealing properties.
2. RX Type Gasket: Designed for higher pressure applications, up to 5000 psi, and performs well in conditions with vibration or shock loading.
3. BX Type Gasket: Suitable for extremely high-pressure systems, such as those exceeding 20,000 psi. The BX gasket is used only in API 6BX type flanges and is not interchangeable with other types.

Material and Specifications:

RTJ flanges are made from a variety of materials, chosen based on the application and the pressure or temperature conditions. Common materials include carbon steel, stainless steel, duplex steel, and alloys such as Monel, Inconel, and Hastelloy. The flange dimensions are defined by standards such as ASME B16.5, ASME B16.47, and API 6A, with the design pressure rating ranging from 150 to 2500 LB, and sometimes exceeding 5000 psi for high-performance applications.

 

 

How Flanged Valves are Manufactured

The manufacturing of flanged valves involves a series of steps, each designed to ensure precision, durability, and efficiency in their operation. The process can be broadly categorized into two main manufacturing methods: casting and forging. The specific method selected depends on factors like valve design, material, and required performance. Here’s a structured overview of how flanged valves are typically manufactured.

1. Material Selection

The first step in the manufacturing process is the selection of the appropriate material for the valve components. Common materials include stainless steel, carbon steel, and alloy steels, chosen based on the valve’s intended use, the pressures and temperatures it will encounter, and the environment it will operate in (e.g., corrosive or high-temperature conditions).

2. Casting Method

In the casting method, the valve body is produced by pouring molten metal into a mold, which hardens to form the desired shape. Once the body is cooled and solidified, the following processes occur:

• Machining: After casting, the valve body undergoes machining processes, such as turning, to remove excess material and achieve the required dimensions. This includes the creation of grooves, holes for threading, and flanged faces for sealing.

• Surface Treatment: The valve components are often subjected to surface treatments such as sandblasting and plating to enhance durability, improve surface finish, and provide resistance to corrosion.

• Threading and Hole Drilling: For valves that require threaded connections, precise threading is done on both the valve body and the flange faces. This ensures a perfect match when the valve is attached to the pipe or another valve.

• Seat and Stem Manufacturing: The seat (which controls the flow) and the stem (the part that controls the opening and closing mechanism) are also produced through precise machining to ensure proper alignment and sealing.

3. Forging Method

The forging method involves shaping the valve components by applying heat and pressure to a solid piece of material. This process is often used for high-pressure valves where strength is crucial. Here’s how the process unfolds:

• Cutting and Forging: The material is cut into required lengths and heated to a high temperature, making it malleable. The heated metal is then pressed into the desired shape, typically using a hydraulic press.

• Trimming and Flashing: Excess material from the forging process is trimmed away, and the valve body is flashed (molded) into its final shape.

• Machining: Like in the casting method, further machining is done to create threaded holes, grooves, and other necessary features for a perfect fit with the flange and pipe.

4. Valve Assembly

After the body, seat, and stem are prepared, the valve components are carefully assembled. The valve seat, which is critical to ensuring a tight seal, is installed inside the body, and the stem is attached to the internal mechanism that opens and closes the valve. Other components, such as gaskets and seals, are also included at this stage.

5. Pressure Testing

Pressure testing is an essential part of the manufacturing process. The assembled valve is subjected to various pressure tests to ensure it can handle the required operational pressures without leaking. In some cases, the valve is tested using air pressure or water at a higher pressure than it will typically face during operation. If any leaks are detected, the valve is returned for repair before being retested.

6. Final Inspection and Quality Control

Once the valve passes the pressure test, it undergoes a final inspection. Quality control teams check the valve for any defects in material, assembly, and finish. They ensure that all dimensions meet the required standards and that the valve operates smoothly and without leaks.

7. Surface Coating and Packaging

In some cases, a final surface coating, such as a Teflon or elastomeric layer, is applied to the valve to enhance corrosion resistance and provide a smooth finish. Once the valve has passed all tests and inspections, it is cleaned, packaged, and prepared for shipment.

 

Pressure Ratings and Temperature Chart for Flanges

Below is a detailed chart for ANSI Pressure Classes and their corresponding PSI ratings for different materials based on ANSI/ASME standards. The chart outlines the pressure capacity of various flange classes at different temperatures, particularly focusing on carbon steel.

Temperature (°F)	Class 150	Class 300	Class 400	Class 600	Class 900	Class 1500	Class 2500
< 100	285	740	985	1480	2220	3705	6170
200	260	680	905	1360	2035	3395	5655
300	230	655	870	1310	1965	3270	5450
400	200	635	845	1265	1900	3170	5280
500	170	605	805	1205	1810	3015	5025
600	140	570	755	1135	1705	2840	4730
650	125	550	730	1100	1650	2745	4575
700	110	530	710	1060	1590	2655	4425
750	95	505	675	1015	1520	2535	4230
800	80	410	550	825	1235	2055	3430

 

Advantages of Flange Valves

Flange valves offer several advantages, making them a popular choice for industrial and commercial piping systems. These advantages primarily relate to ease of installation, maintenance, robust performance under pressure, and versatility in handling a wide range of conditions. Below are the key advantages of using flange valves:

Easy Installation and Maintenance

One of the most significant benefits of flange valves is their ease of installation and maintenance. Flange valves feature bolted end connections, which allow for simple installation between pipe sections. Similarly, maintenance is straightforward—valves can be removed for repair or replacement without needing to cut or re-weld pipes, reducing downtime significantly.

Durability and High-Pressure Resistance

Flanged valves are designed to withstand high pressures, making them ideal for harsh industrial environments such as chemical processing, oil and gas, and steam systems. Their sturdy body construction ensures that the valves maintain integrity under extreme conditions, including high pressure, temperature fluctuations, and vibrations. Flanged connections are generally rated for higher pressures than threaded or welded connections.

Full Bore Design for Unobstructed Flow

Flange valves, especially those used in ball valve designs, often feature a full bore. This design ensures that the internal diameter of the valve matches that of the pipe, providing an unobstructed flow path. This results in minimal pressure drop, reduced flow resistance, and better overall flow efficiency, which is especially beneficial in applications requiring high-volume flow.

Versatility in Material Selection

Flanged valves are available in a wide range of materials, including carbon steel, stainless steel, and alloys resistant to corrosion, high temperatures, and harsh chemicals. This versatility in materials allows them to be used in diverse applications, from water treatment to chemical processing, where specific material properties are crucial for performance and longevity.

Improved Sealing Capabilities

The rigid nature of flange connections allows for better sealing than other types of valve connections. Flange valves can withstand higher torque and pressure, maintaining a tight seal even in high-pressure or high-vibration environments. This ensures fewer leaks and reduces the risk of contamination or system inefficiency.

 

Key Applications of Flange Valves

Oil and Gas Industry

In the oil and gas industry, flange valves are integral to maintaining the integrity of pipelines that transport crude oil, natural gas, and refined products. Weld neck and slip-on flanges, known for their robustness and ability to withstand high pressures, are particularly common. Flanged valves also play a crucial role in managing pipeline safety and preventing leaks, essential in this sector, where pressure and temperature conditions can be extreme.

Chemical Processing

Chemical plants often require flange valves that can handle corrosive substances. Flanges made from materials such as stainless steel or special alloys ensure that chemical reactors, pipelines, and tanks are securely connected while maintaining the system’s resistance to corrosion and high temperatures. Regular maintenance and quick disassembly facilitated by flanged valves are important in environments where frequent inspections and part replacements are needed.

Water and Wastewater Management

Flanged valves are critical in water treatment facilities and wastewater systems, where they maintain a secure seal in pipelines that carry water and waste. These valves can accommodate varying pressures and temperatures, while their corrosion-resistant materials ensure longevity in harsh environmental conditions. Blind flanges are often used in these applications to close off pipeline sections for maintenance or repairs.

Power Generation

In power plants, especially nuclear and thermal power plants, flanged valves ensure the smooth operation of high-pressure steam and water systems. They are used to control and isolate water flow in crucial areas such as feedwater lines, condensers, and cooling systems. Flanged valves provide secure connections, reducing the risk of system failures and maintaining the efficiency of operations under extreme temperature and pressure conditions.

Food and Pharmaceutical Processing

In industries that demand sanitary standards, such as food processing and pharmaceuticals, flanged valves are used to control the flow of liquids and gases while ensuring hygiene and ease of cleaning. Stainless steel and other non-corrosive materials are often selected to meet strict health and safety regulations. The ease of valve removal for cleaning, maintenance, or part replacement helps keep operations running efficiently.

 

Conclusion

Flange valves play an indispensable role in industrial fluid systems, offering reliability, durability, and ease of maintenance. Understanding the different types of flange valves, their applications, and how to choose the right one for your system can significantly improve the efficiency and safety of your operations. Whether you’re working in oil and gas, water treatment, or chemical processing, selecting the appropriate flange valve is critical to ensuring long-term success.

If you have questions about flange valves or need assistance selecting the right one for your system, feel free to contact us for more detailed consultations. For further resources or to explore related services, don’t hesitate to explore our additional guides on valve selection and maintenance.