5 Things You Should Know About Thermocouple Flanges

What is A Flange?

A flange is located where the thermocouple to the equipment it monitors, helping to ensure connection points are strong and sealed. It also reduces the instability of temperature readings caused by vibration and keeps the system working well. Flanges come in different standard, each developed by different countries for specific needs. For example, the ANSI/ASME flange is developed by ANSI (American National Standards Institute) and ASME (American Society of Mechanical Engineers). It is commonly used in the U.S. and is designed for high-pressure systems that need to be strong and precise. In Japan, the JIS flange standard made by JISC (Japanese Industrial Standards Committee), especially the JIS B2220 type, is more common. These JIS flanges are categorized by pressure, like 5K, 10K, and 20K, which shows how much pressure they can handle. Choosing the right flange is key to making sure the connection is reliable. Knowing the differences between ANSI/ASME, JIS and DIN standards helps you pick the suitable one for your system setup, ensuring it works well in its environment.

Understanding Different Flange Types

Flanges are an important element in securing thermocouples to process equipment to ensure a reliable and leak-proof connection. Below are 6 common types of flanges, each designed for a specific application.

• Blind Flanges

This flange type, are without an inner hole to seal off the end of a pipe or system, preventing the flow of gases or liquids. Made from durable materials like stainless steel blind flanges, they can stand high pressures and temperatures, ensuring excellent sealing performance to prevent any possible leaks. Blind flanges are also known as blank flanges, blind pipe flanges, or blind plate flanges. They are essential for pressure testing, offering a cost-effective solution, and are ideal for use in isolation systems or when planning future pipeline expansions. Additionally, there is another type of blind flange called slip blinds flange is often used for similar purposes in various industries.

Application:

Blind flanges are widely used in the petroleum, chemical and shipbuilding industries. They are usually used when there is a need for system testing, pipeline pressure testing, sealing pipelines for repairs or permanent sealing.

• Socket Weld Flanges

A socket weld flange is a specific flange type with a wider weld opening. It is designed for connecting components that are not easy to weld directly. This simple design weld pipe flange features a central hole slightly larger than the connecting pipe's diameter, allowing the pipe to slide in for welding. Socket flange welding is straightforward, making these flanges easier to install and remove compared to other flange types. This ease of installation is particularly beneficial where regular maintenance or inspection is necessary.

However, care must be taken to leave a gap for thermal expansion during socket weld flange welding. This flange welding requires specialized techniques. Socket weld flanges, including stainless steel socket weld flanges, are not ideal for highly erosive or corrosive environments. The gap between the pipe end and the socket's shoulder is prone to corrosion.

Application:

Often used on hydraulic pipes carrying corrosive liquids such as industrial water or oil.

• Slip-on Flanges

The key feature of a slip-on flange is its inner diameter, which is slightly larger than the outer diameter of the pipeline. It allows the flange to be easily slid onto the pipe. This design provides flexibility in installation. It also makes slip on flange welding easy and also enables replacement without dismantling the pipeline.

Since the pipe can be slipped into the flange and welded on one side, the process can be done more easily when the pipe or flange needs to be replaced. Additionally, the weld location on one side of the pipe and flange allows for inspection or repair without disassembling the entire system. Slip-on flanges, especially stainless-steel slip-on flanges, are available in various flange sizes and flange dimensions to suit different applications.

Application:

Often used in lower pressure piping, cooling lines and some oil, gas and steam process lines.

• Threaded Flanges

A threaded flange is a flange type with internal threads. This flange is designed to connect pipes that have matching threads. It is commonly used in low-pressure systems, particularly on small pipes with thicker walls. Unlike other flange specs, the connection with a threaded pipe flange doesn’t require welding. Instead, it is secured by screwing the pipe into the flange. This feature makes threaded flanges ideal for situations where frequent disassembly or maintenance is required. The absence of welding simplifies installation, reduces time, and lowers technical demands. It makes the replacement super easy. Stainless steel threaded flanges are especially useful due to their durability and ease of removal in various piping systems.

Application:

Ideal for restricted spaces where flange and pipe welding is not possible. Often used in water treatment field.

• Welded Neck Flanges

Welded neck flanges are a common flange type distinguished by a neck-like extension, often referred to as the "neck." This structure gives welded neck flanges superior strength and resistance to high pressure and temperature. The weld neck is welded directly to the pipe, creating a secure and durable connection that minimizes turbulence and erosion. This process also enhances the rigidity and strength of the flange. While more complex to install and maintain compared to other flange specs, long weld neck flanges are ideal for high-pressure environments. Proper alignment during assembly is crucial. With both flanges needing the bolt holes oriented similarly to ensure a tight seal. Stainless steel weld neck flanges are especially valued for their reliability in demanding applications.

Application:

Welded neck flanges are widely used in the pipelines for volatile and hazardous fluids, oil and gas, chemical plants, power plants and other pipelines requiring high pressures and temperatures.

• Lap joint flanges

Lap joint flange is a flange type commonly used in piping systems requiring frequent disassembly for inspection and cleaning. A key feature of lap joint flanges is their flexibility; they can be easily installed or replaced without removing the pipe. The design allows the joint flange to be rotated, making it simple to align with bolt holes. This feature also means the flange doesn't come into direct contact with the fluid, which enhances its durability. Stainless steel lap joint flanges are especially durable and can be reused multiple times. Understanding lap joint flange dimensions ensures proper fit and function in various applications.

Application:

Often used in low-pressure system or where frequent disassembly and maintenance is required. Not recommended for high temperature and high-pressure pipelines.

Flange Quick View

  *This section is organized for most situations only. Special cases should be handled case by case.

Thermocouple Flanges Materials

Selecting a flange type for thermocouples is crucial for ensuring durability, and safety. Here are five common flange materials used in real-life applications.

• Alloy Steel

Alloy steel flanges are enhanced with additional elements like chromium, nickel, or molybdenum. They help to improve strength, ductility and corrosion resistance. The flanges are suitable for high-pressure applications but can be costly. Their performance varies depending on the specific alloy composition.

• Carbon Steel

Carbon steel is known for its strength and reasonable price. Its hardness and strength increase with carbon content, but its ductility and melting point are lower. It is a widely used flange type in industries such as oil and gas. Carbon steel has good properties at lower temperatures but may require a protective coating to prevent rusting in more corrosive environments.

• Cast Iron

Cast iron is commonly used in low-pressure applications. They are affordable flange materials with good machinability and wear resistance. However, Cast iron is brittle and has lower melting points.

• Copper

Copper flanges are highly conductive and resistant to biofouling, making them suitable for applications involving heat transfer. However, copper is relatively soft and can be prone to wear and tear under high-pressure conditions, limiting its use in some industries.

• Stainless steel

Stainless steel must contain more than 10% chromium to be called stainless steel. Stainless steel is a popular flange material due to its excellent resistance to corrosion and high temperatures. For example, the common stainless steel like SUS 316 contains a higher ratio of nickel and molybdenum making it more corrosion-resistant than SUS 304 stainless steel. Thanks to this material, stainless steel flanges are ideal for harsh environments such as those exposed to chemicals. However, It can be more expensive than other materials, making it less cost-effective for some applications.

• PVC flange

A plastic flange like PVC or CPVC is for low-pressure and low-temperature applications. They offer a lightweight, low-cost solution. They are resistant to chemical corrosion and easy to install. The PVC flanges are popular, especially in water treatment processes. They are not suitable for high-temperature or high-pressure environments.

When making a thermocouple flange material selection, it is essential to understand the needs. It includes the flange spec, flange types, temperature, pressure, and environmental conditions. Each material has its pros and cons. Choosing the right one can significantly impact your thermocouples performance and product lifetime.

Thermocouple Flange Standards

There are three common types of flange specifications in the industry: ANSI/ASME flanges and JIS flanges. Each standard has its own set of guidelines for dimensions, pressure ratings, and material specifications making them indispensable for various industrial applications.

• ANSI/ASME Flange Standards

People might wonder the difference between ANSI B16.5 and ASME B16. 5. Since ANSI adopt ASME, now you can say they have the same flange standard. ANSI (American National Standards Institute) and ASME (American Society of Mechanical Engineers) are significant organizations. They have contributed to standardization in the engineering field. They play a crucial role in defining the design and flanges material standards, ensuring they meet high safety and performance criteria. ANSI/ASME flanges, such as the ANSI 150 flange, are known for their rigorous standards in pressure ratings and material quality. These flanges are typically used in applications requiring high reliability and are often found in industries like oil and gas, petrochemicals, and power generation. The standards cover various flange types, including pipe flanges and blind flanges, each suited for specific needs.

• DIN Flange Standards

The DIN flange standard is developed by the Deutsches Institut für Normung (German Institute for Standardization). It is a set of guidelines widely recognized across Europe and other parts of the world. DIN flanges are particularly known for their precision and robustness, often used in industries like automotive, chemical processing, and mechanical engineering. These flanges adhere to strict dimensional tolerances and material specifications, making them ideal for high-pressure and high-temperature applications.

• JIS Flange Standards

The JIS flange standard is outlined by the Japanese Industrial Standards. It is widely used in Japan and other Asian countries. JIS flanges, such as 5K flange and flange JIS 10K, are often chosen for their compatibility with industrial equipment. The JIS B2220 standard specifies dimensions, pressure ratings, and material requirements for various flange types. Flanges with JIS Standard are commonly used in industries like chemical processing, shipbuilding, and manufacturing. Check out the JIS flange standard.

When choosing any flange type, it is important to consider the operating environment, equipment compatibility, and project-specific requirements. Understanding these differences ensures that the type of flange selected meets the necessary flange specifications for performance and safety.

What is Flange Face?

The flange face is the area where two flanges meet and are sealed with a gasket, crucial for ensuring a leak-proof connection. Here are three common flange face types:

Question?

Don't hesitate to contact us if you are not quite sure which flange is best for your thermocouple application. Our experts are always happy to advise you. 

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