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Process Connection or Fitting for Pressure Transmitter

Process Connection or Fitting for Pressure Transmitter

Fig 1. Pressure sensor different mounts

Process Connection or Fitting of a Pressure Transmitter

The process connection or fitting of a pressure transmitter depends on various factors such as the type of pressure being measured, the environment, and the specific requirements of the application. Here are some common types of process connections used for pressure transmitters:

  • Threaded Connections:
    • NPT (National Pipe Thread): This is a tapered thread commonly used in the United States for smaller pipes.
    • BSP (British Standard Pipe): Often used in Europe and some other countries, it comes in parallel (BSPP) and tapered (BSPT) versions.
    • Metric Threads: Common in many parts of the world for various applications.
  • Flanged Connections:
    • Raised Face Flanges: These have a raised surface and are used in higher-pressure applications.
    • Flat Face Flanges: Used in lower-pressure applications where space is limited.
    • Ring Type Joint (RTJ) Flanges: Suitable for high-pressure and high-temperature applications.
  • Tri-Clamp Connections: Commonly used in sanitary applications, particularly in the food and pharmaceutical industries.
  • Compression Fittings: Often used in situations where frequent disassembly might be necessary.
  • Welded Connections: Direct welding of the transmitter to the pipe or vessel being measured. This provides a permanent and robust connection.
  • When choosing a process connection for a pressure transmitter, it's important to consider factors like the pressure range, temperature, compatibility with the process fluid, installation ease, maintenance requirements, and the environmental conditions in which the transmitter will operate.

    Consulting the manufacturer's guidelines and understanding the specific needs of your application is crucial in selecting the appropriate process connection or fitting for a pressure transmitter.

    What does "process connection" mean in pressure sensors?

    In pressure sensors, the term "process connection" refers to the physical interface or means by which the sensor is connected to the system or process where pressure measurement is required. It's essentially the point where the sensor interacts with the media (gas, liquid, etc.) whose pressure it's measuring.

    Process connections are crucial because they ensure a reliable and secure connection between the pressure sensor and the monitored system. They vary in design and type based on the specific application requirements, the nature of the measured media, pressure levels, environmental conditions, and industry standards.

    The choice of a process connection can significantly impact the sensor's performance, accuracy, reliability, and longevity. Different types of process connections include threaded connections (NPT, BSP, metric threads), flanged connections, tri-clamp connections, compression fittings, and welded connections, among others.

    Factors such as pressure range, compatibility with the media being measured, installation ease, resistance to corrosion, and the need for maintenance or disassembly often influence the selection of a suitable process connection for a pressure sensor. Therefore, selecting the right process connection is an essential consideration in ensuring the optimal functioning of the pressure sensor within its intended application.

    Threaded Connections

    Threaded connections are a prevalent means of attaching pressure sensors to systems requiring pressure measurement. These connections utilize threads to secure the sensor onto the designated port or opening in the system.

    The National Pipe Thread (NPT) is a common type of threaded connection used in the United States for pressure sensors. It features a tapered thread design that creates a seal by wedging the threads together, preventing leakage when properly tightened. This tapering characteristic aids in creating a secure and leak-resistant joint, crucial for accurate pressure measurements.

    Another type is the British Standard Pipe (BSP) thread, commonly utilized in Europe and various other regions. BSP threads come in two main variations: the parallel (BSPP) and tapered (BSPT) threads. Similar to NPT threads, these threads also create a seal by joining together, ensuring a tight connection between the sensor and the system.

    Metric threads, while less common in certain regions, are also used for pressure sensor connections in various parts of the world. They follow standardized metric measurements for threading and can be found in applications where metric-based systems are prevalent.

    Threaded connections offer advantages such as ease of installation, especially in situations where frequent disassembly and reassembly might be necessary for maintenance or adjustments. However, proper care is crucial during installation to avoid damaging the threads, which could lead to leaks or inaccurate pressure readings.

    Choosing the appropriate threaded connection for a pressure sensor involves considering factors such as the pressure range, compatibility with the measured media, adherence to industry standards, and environmental conditions. Additionally, utilizing sealants or thread tapes compatible with the system's requirements can further enhance the effectiveness of threaded connections, ensuring reliable and accurate pressure measurements.

    Fig 2. Different type of threads

    How to Choose Thread Process Connections?

    Selecting the appropriate thread process connection for a pressure sensor involves considering several key factors to ensure compatibility, reliability, and performance within the intended application:

  • Thread Type and Standard: Identify the thread standard required for the specific application. Common thread types include NPT (National Pipe Thread), BSP (British Standard Pipe), metric threads, or specialized threads. Select the thread type based on industry standards, system requirements, and compatibility with existing equipment.
  • Pressure Rating: Consider the pressure range that the sensor will be exposed to. Different thread types have varying pressure ratings, and selecting a thread connection capable of withstanding the intended pressure levels is crucial to prevent leaks or damage.
  • Media Compatibility: Assess the nature of the measured media (liquid, gas, corrosive substances). Ensure that the thread material is compatible with the media to prevent corrosion, degradation, or chemical reactions that could compromise the connection's integrity.
  • Thread Size: Determine the appropriate thread size needed for the application. Thread size is specified by dimensions such as the diameter and pitch. Ensure compatibility with existing equipment or connections within the system.
  • Installation Requirements: Consider the ease of installation and any specific tools or techniques required for the selected thread type. Ensure that the installation process aligns with the available space, tools, and skills to facilitate a secure and proper connection.
  • Environmental Conditions: Evaluate the operating environment, including temperature variations, exposure to humidity, or corrosive atmospheres. Choose a thread type that can withstand the environmental conditions without compromising performance or integrity.
  • Industry Standards and Regulations: Adherence to industry standards and regulations is crucial for compatibility and reliability. Ensure that the selected thread process connection complies with relevant industry standards to meet safety and performance requirements.
  • Sealing Mechanism: Consider the sealing method used with the thread connection, such as gaskets, sealants, or welding techniques. Ensure that the sealing mechanism provides a reliable and leak-free seal compatible with the application's requirements.
  • By carefully considering these factors, you can effectively choose the most suitable thread process connection for the pressure sensor, ensuring compatibility, reliability, and optimal performance within the specific application and operating conditions.

    What does BSP stand for?

    BSP stands for British Standard Pipe. It's a set of technical standards for threaded pipes and fittings used in various countries, particularly in the United Kingdom and many parts of Europe. BSP threads come in two primary variations: BSP Parallel (BSPP) and BSP Tapered (BSPT). These standards dictate the dimensions, thread angles, and tolerances for creating a reliable and standardized connection between pipes, fittings, and other components in plumbing, hydraulic, and other fluid-based systems.

    Fig 3. BSPP pressure mount

    What is BSPT?

    BSPT stands for British Standard Pipe Taper. It's a type of threading commonly used in pipes and fittings, particularly in the United Kingdom and various parts of Europe. BSPT threads are tapered, meaning the diameter of the threads gets smaller towards the end.

    This tapering design is intended to create a tight seal when the male and female threads are joined together. The wedging action achieves the sealing as the threads are tightened, helping to prevent leakage in applications where maintaining a secure connection is crucial, such as in plumbing and fluid systems. BSPT threads are widely used in various industries and are an integral part of the British Standard Pipe standards.

    Fig 4. BSPT mount type

    Where can use the BSP?

    BSP (British Standard Pipe) threads are used in various industries and applications where a reliable and standardized threaded connection is required for pipes, fittings, and other components. Here are some common areas where BSP threads are employed:

  • Plumbing: BSP threads are prevalent in plumbing systems, especially in regions where these standards are commonly adopted. They're used for connecting pipes, valves, faucets, and other plumbing fixtures.
  • Hydraulics: In hydraulic systems, BSP threads are utilized for fittings, adapters, and connections in hydraulic equipment, ensuring secure and leak-resistant joints.
  • Pneumatics: BSP threads can be found in pneumatic systems, and used for connecting air hoses, valves, cylinders, and other pneumatic components.
  • Fluid Handling: Industries involved in fluid handling, such as manufacturing, chemical processing, and oil and gas, often use BSP threads for connecting pipes, pumps, tanks, and valves.
  • Automotive: Some automotive applications utilize BSP threads in fluid systems, such as fuel lines, oil lines, and hydraulic brake systems.
  • Agriculture: BSP threads can be used in irrigation systems, water supply lines, and other agricultural equipment where fluid connections are required.
  • BSP threads are available in both parallel (BSPP) and tapered (BSPT) forms, offering versatility for various applications. However, it's important to note that BSP threads are more common in certain regions like the United Kingdom and Europe, while other places might predominantly use different standards like NPT (National Pipe Thread). Selecting the appropriate thread type based on the specific requirements of the system is crucial to ensure compatibility and reliable connections.

    Which pressure sensors do have BSP fitting?

    Pressure sensors with BSP (British Standard Pipe) fittings are available from various manufacturers across different industries. These sensors are designed specifically to integrate seamlessly with systems that utilize BSP threads for pressure measurement applications.

    Pressure sensors with BSP fittings can be found in different types and variations, including:

  • Pressure Transducers: These sensors convert pressure into an electrical signal and are available with BSP fittings suitable for various pressure ranges and media types.
  • Pressure Transmitters: Similar to transducers, transmitters also convert pressure into an electrical signal, but they often incorporate signal conditioning and amplification. BSP fittings are available for these as well.
  • Pressure Switches: These sensors are used to detect pressure levels and trigger an electrical switch at a predetermined pressure threshold. Some pressure switches come with BSP fittings.
  • Pressure Gauges: While traditional pressure gauges might not inherently have BSP fittings, adapters or fittings can be added to convert them to BSP for specific applications.
  • When looking for pressure sensors with BSP fittings, it's essential to verify the specifications provided by the manufacturer or supplier to ensure the compatibility of the sensor with your system's requirements. Additionally, consider factors such as the pressure range, media compatibility, environmental conditions, and accuracy needed for your application before making a selection.

    How is a BSP shape and angels?

    BSP (British Standard Pipe) threads come in two main variations: BSP Parallel (BSPP) and BSP Tapered (BSPT). Each variation has its specific shape and angles.

  • BSP Parallel (BSPP):
    • Shape: BSPP threads have a cylindrical shape without a taper. The threads maintain a consistent diameter along the length of the threaded portion.
    • Angles: The threads have a 55-degree angle. This means that the tops and bottoms of the threads are cut at a 55-degree angle to the center axis of the pipe.
  • BSP Tapered (BSPT):
    • Shape: BSPT threads are tapered, meaning the diameter of the threads reduces gradually towards the end. The taper helps in creating a tight seal when the threads are connected.
    • Angles: BSPT threads have a 55-degree included angle. The difference between BSPP and BSPT lies in the tapering angle and the sealing mechanism, with BSPT using the taper to create a seal.
  • These thread shapes and angles are standardized according to British standards to ensure compatibility and proper sealing between threaded components in plumbing, hydraulic, and other fluid-based systems. When working with BSP threads, it's important to match the correct type (parallel or tapered) and size to ensure a secure and leak-resistant connection.

    Fig 4. threads angle

    What is NPT?

    NPT stands for National Pipe Thread, a standardized thread type used in the United States for creating connections between pipes and fittings in plumbing and fluid systems. NPT threads are known for their tapered design, which helps create a seal between the male and female threaded components.

    Key features of NPT threads include

  • Tapered Design: NPT threads have a tapered shape, meaning the diameter of the threads decreases gradually towards the end. This tapering design allows the threads to wedge together when tightened, creating a tight seal that prevents leakage.
  • Thread Angle: NPT threads have an angle of 60 degrees between the sides of the threads. This angle contributes to the effective sealing action when the threads are joined together.
  • Usage: NPT threads are commonly used in various applications, including plumbing, gas lines, hydraulic systems, and other fluid-based systems, especially in the United States and regions where these standards are adopted.
  • NPT threads come in different sizes and variations, such as NPTF (National Pipe Taper Fuel) and NPTN (National Pipe Taper Dryseal), each designed for specific applications. When working with NPT threads, it's essential to properly match the male and female threads, and proper sealing techniques (such as using thread sealant tape or thread sealant compounds) are often employed to ensure leak-free connections.
    UNC (2A) UNF (2A)
    Nominal Diameter Major Diameter (mm) Minor Diameter (mm) TPI Nominal Diameter Major Diameter (mm) Minor Diameter (mm) TPI
    1/4” x 20 UNC 6,322 4,978 20 1/4” x 28 UNF 6,325 5,360 28
    5/16” x 18 UNC 7,907 6,401 18 5/16” x 24 UNF 7,910 6,782 24
    3/8” x 16 UNC 9,491 7,798 16 3/8” x 24 UNF 9,497 8,382 24
    7/16” x 14 UNC 11,076 9,144 14 7/16” x 20 UNF 11,079 9,728 20
    1/2” x 13 UNC 12,661 10,592 13 1/2” x 20 UNF 12,667 11,328 20
    5/8” x 11 UNC 15,834 13,386 11 5/8” x 18 UNF 15,839 14,351 18
    3/4” x 10 UNC 19,004 16,307 10 3/4” x 16 UNF 19,012 17,323 16
    7/8” x 9 UNC 22,176 19,177 9 7/8” x 14 UNF 22,184 20,269 14
    1” x 8 UNC 25,349 21,971 8 1” x 12 UNF 25,354 23,114 12
    2” x 4,5 UNC 50,726 44,679 4.5

    Hygienic

    A hygienic process adapter system has been specifically developed to meet the requirements of the food, beverage, and pharmaceutical industries.

    These industries need processing machines to be cleaned with detergents, or sterilized, with superheated steam and include precautions against contamination in their manufacturing processes.

    Hygienic devices have highly polished stainless steel components exposed to the process media and are installed using clamped seals.

    European Association EHEDG (European Hygienic Engineering & Design Group) and US regulations “ASME BPE” are different regulations that set guidelines for all parts used, including measuring equipment, to ensure optimum cleanability.

    A very significant task is to prevent clearances, which means spaces that are so difficult to access that residues of media can remain there. Also, the surface roughness of the materials used should be as low as possible to avoid adhesion.

    Popular types of hygienic connections are the Clamp, DRD, Variant, and Dairy Fitting.

    Clamp

    Clamp connections are a subcategory of sanitary fittings and are widely used in sanitary applications and the food, beverage, biotech, and pharmaceutical industries.

    It is a means of connecting measuring instruments to process tubes in an aseptic manner and without clearances.

    So, this connection type is mainly used in processes where hygiene and cleanability are particularly important, and increased cleaning effort is necessary to minimize the potential risks and eliminate contamination, bacterial growth, leaks, and deterioration of the connection material.

    Fig 8. Clamp thread

    Clamp connections are made up of two flanged ends, a gasket, and a clamp to secure the connection. Two flanged ends mate together with a gasket between their two faces.

    There are different clamp types including two-segment single hinge, three-segment double hinge, and two-bolt high pressure. There are different sizes of clamp connections expressed by two separate parameters, the sealing face flange diameter and the diameter of the pipe.

    DRD

    The DRD connection is provided to connect equipment to the vessel. This connection reaches flush-mounted integration. The sealing is achieved by a common flat sealing.

    Fig 9. DRD type

    The device is fixed by 4 screws that minimize risks while opening the flange even if there is pressure on the process. It is most commonly used in the food industry.

    Variant

    The Variant process connection is a type of flush flange connection. It is similar to the Clamp connection in that it depends on a clamp to hold the flange of the sensor together with a matching flange on the process fitting.

    Variant connections provide an O-ring seal around the internal diameter of the connection. Variant connections are widely used in breweries, dairies, and other food applications.

    Dairy Fitting

    This type of aseptic process connection, defined in the German standard DIN 11851, was developed for the design of pipe works in milk and food processing.

    This connection has round thread screw connections. In the production line, it's important to minimize the risk of contamination and stagnation in the pipe systems.

    Fig 10. Dairy fitting

    Dairy fittings for milk have inside and outside sufficient smoothness and can be easily dismantled and cleaned and consist of a round slotted nut, a welded male piece, a liner piece the nut slides over, and a gasket.

    Because of its design, it can also provide the hygienic requirements of the food industry as well as the pharmaceutical and chemical industries.



    Thread Type Standard Highlight Features Common Materials Limitations Suitable Industries
    NPT (National Pipe Thread) ANSI Easy installation, tapered design for tight fit Stainless steel, brass, carbon steel, Hastelloy, Monel Potential for leaks, not suitable for ultra-high pressure Oil and gas, water treatment, HVAC, process industries
    BSP (British Standard Pipe) BSI Parallel and tapered types available, globally recognized Stainless steel, brass, carbon steel, Hastelloy, Monel Requires thread sealant, not ideal for high-pressure applications Oil and gas, water treatment, HVAC, process industries
    Metric ISO Globally recognized, various pitch options Stainless steel, brass, carbon steel, Hastelloy, Monel Not universally compatible, may require thread sealant Automotive, industrial machinery, process industries
    SAE Straight Thread (O-ring Boss) SAE J1926 Straight thread with O-ring seal, high-pressure compatibility Stainless steel, brass, carbon steel, Hastelloy, Monel Limited adjustability due to O-ring Hydraulic systems, aerospace, automotive
    UN/UNF (Unified National, Coarse/Fine) ASME B1.1 Coarse and fine thread options, widely used in North America Stainless steel, brass, carbon steel, Hastelloy, Monel Not universally compatible, may require thread sealant Automotive, industrial machinery, aerospace
    G-series (ISO/BSP Parallel) ISO 228 Parallel design, requires gasket or O-ring for sealing Stainless steel, brass, carbon steel, Hastelloy, Monel Not ideal for high-pressure applications, requires separate seal Water treatment, HVAC, automotive, process industries
    JIC (Joint Industrial Council) Fittings SAE J514 37-degree flare for tight seal, high-pressure compatibility Stainless steel, brass, carbon steel, Hastelloy, Monel Specialized design, not a threaded connection Hydraulic systems, aerospace, automotive

    Thread Type Nominal Diameter Thread Pitch Max Pressure Rating
    NPT1/2 0.5 in (12.7 mm) 14 TPI 1500 psi (10.34 MPa)
    NPT1/4 0.25 in (6.35 mm) 18 TPI 1000 psi (6.89 MPa)
    NPT1/8 0.125 in (3.18 mm) 27 TPI 500 psi (3.45 MPa)
    G1/2 0.5 in (12.7 mm) 14 TPI 1500 psi (10.34 MPa)
    G1/4 0.25 in (6.35 mm) 19 TPI 1000 psi (6.89 MPa)
    M20x1.5 20 mm 1.5 mm 1500 psi (10.34 MPa)
    M12x1.5 12 mm 1.5 mm 1000 psi (6.89 MPa)
    R1/4 0.25 in (6.35 mm) 19 TPI 1000 psi (6.89 MPa)
    R1/8 0.125 in (3.18 mm) 28 TPI 500 psi (3.45 MPa)

    Flanged Connections

    A flange is a method of process connection used for creating airtight and removable connections between segments of a tube.

    A flanged connection consists of three parts:

    • Pipe Flanges
    • Gasket
    • Bolting

    Flanged connections are made by bolting together two flanges with a gasket between them to create a seal. The gasket is placed between the two circular seal points, which are usually tightly joined with screws.

    Fig 11. Flanged connection

    The following are standard flange systems:

    • GB series (national standard)
    • JB series (mechanical department)
    • HG series (Ministry of Chemical Engineering)
    • ASME B16.5 (American standard)
    • BS4504 (British standard)
    • DIN (German standard)
    • JIS (Japanese standard)

    Among the above flange systems, the two main used ones are the German DIN and the American ANSI.

    There are five types of flange connections:

    • Flat welding
    • Butt welding
    • Socket welding
    • Loose sleeve
    • Thread

    Flanged Connection Types

    Flanged connections are widely used in various industries and applications to create secure and reliable joints between pipes, valves, and other equipment. There are several types of flanged connections, each designed for specific purposes and operating conditions:

  • Raised Face Flanges: These flanges feature a raised surface around the sealing face. When two raised face flanges are bolted together with a gasket in between, the raised surface provides a better sealing area, ensuring a tight and leak-resistant joint. Raised face flanges are commonly used in applications with moderate to high pressures.
  • Flat Face Flanges: Unlike raised face flanges, flat face flanges have a flat surface without any raised areas. They create a flat-to-flat connection between the flanges when bolted together with a gasket, suitable for low-pressure applications where a thinner gasket can be employed.
  • Ring Type Joint (RTJ) Flanges: RTJ flanges feature a special groove on the flange face into which a metal ring gasket is placed. When the flanges are bolted together, the ring gasket gets compressed, forming a reliable metal-to-metal seal suitable for high-pressure and high-temperature applications. RTJ flanges are commonly used in oil and gas industries and environments with extreme conditions.
  • Tongue and Groove Flanges: These flanges have a raised tongue on one flange and a matching groove on the other. When aligned and bolted together, the tongue and groove provide additional alignment and support, enhancing the joint's integrity. Tongue and groove flanges are often used in large-diameter and high-pressure applications.
  • Lapped Joint Flanges: Lapped joint flanges are not directly connected but are used in conjunction with a stub end and a lap joint flange. The stub end is welded to the pipe, and the lap joint flange is free to rotate over the stub end. This setup allows for easy alignment during installation and permits rotational movement if needed.
  • Flanged connections offer advantages like ease of assembly, reusability, and the ability to withstand varying pressures and temperatures. The choice of flange type depends on the specific requirements of the application, including pressure, temperature, media being transported, and environmental conditions. Proper selection and installation of flanged connections are critical to ensuring a secure and leak-free joint in piping systems.

    Fig 12. Transmitter Flange Pressure Class under ASME Standard 1

    What are the differences between threaded connections and Flanged Connections?

    Threaded connections and flanged connections are two common methods used to join pipes, valves, and fittings in various applications, but they differ in several aspects:

  • Design and Structure:
    • Threaded Connections: Involve screwing two threaded components together, creating a secure joint. Threads can be tapered (like NPT) or parallel (like BSP) and are directly engaged to form the connection.
    • Flanged Connections: Utilize two mating flanges with bolt holes and gaskets. The flanges are bolted together to create a sealed joint, often using gaskets or sealants for added security. Flanged connections can have raised faces, flat faces, or special designs like tongue and groove or ring-type joints.
  • Installation Ease:
    • Threaded Connections: Generally easier to install compared to flanged connections. They require less space and involve simply screwing the components together, making them suitable for smaller pipes and quick installations.
    • Flanged Connections: Usually require more space and alignment during installation. They involve aligning two flanges, inserting gaskets, and tightening bolts uniformly to achieve a leak-tight seal.
  • Pressure and Temperature Ratings:
    • Threaded Connections: Generally used in lower-pressure applications due to potential leak points and limitations in handling high pressures and temperatures. Tapered threads like NPT may not handle extreme pressures well.
    • Flanged Connections: Preferred for higher-pressure and temperature applications, especially when properly sealed with gaskets. Flanged joints can handle a wider range of pressures and temperatures due to their robust design and sealing mechanisms.
  • Maintenance and Disassembly:
    • Threaded Connections: These can be easier to disassemble for maintenance or modifications due to their simpler structure. However, repeated disassembly and reassembly may affect the integrity of the threads.
    • Flanged Connections: This may require more effort for disassembly due to multiple bolts and gaskets. However, they allow easier access to the interior of the system, making maintenance simpler in some cases.
  • Versatility:
    • Threaded Connections: Suitable for smaller pipes and simpler installations but may not be ideal for larger pipes or systems requiring higher pressures.
    • Flanged Connections: Offer more versatility and adaptability for a wide range of pipe sizes and pressure requirements. They can handle larger diameters and higher pressures with proper selection and installation.
  • Both threaded and flanged connections have their advantages and limitations, and the choice between the two depends on factors such as the application requirements, pressure, temperature, maintenance needs, and the specific characteristics of the system being installed.

    Comparing table

    Here's a comparative table outlining the differences between threaded connections and flanged connections:

    Aspect Threaded Connections Flanged Connections
    Design Engage two threaded components directly. Utilize two flanges with bolt holes and gaskets.
    Installation Ease Generally easier to install, suitable for smaller pipes. May require more space and alignment during installation.
    Pressure Rating Commonly used in lower-pressure applications. Preferred for higher-pressure applications with proper seals.
    Temperature Handling Limited in handling high temperatures and pressures. Can handle wider temperature and pressure ranges.
    Maintenance & Disassembly Easier disassembly but may affect thread integrity. More effort for disassembly but allows easier access.
    Versatility Suitable for smaller pipes; may not handle high pressures. More adaptable for various pipe sizes and pressure needs.

    These differences highlight the distinct characteristics and applications where threaded connections and flanged connections are commonly utilized. The choice between the two depends on specific requirements such as pressure, temperature, ease of installation, maintenance needs, and the nature of the system being installed or maintained.

    Fig 13. Pressure Transmitter Flange

    Which type of pressure sensor process connection is proper for sanitary applications?

    In sanitary applications, where hygiene and cleanliness are paramount, the process connections for pressure sensors need to meet specific standards to ensure cleanliness, ease of cleaning, and avoidance of contamination. The most suitable process connection types for sanitary applications include:

  • Tri-Clamp Connections (also known as Tri-Clover or Tri-Clamp): These connections are prevalent in sanitary applications, particularly in the food, beverage, pharmaceutical, and biotech industries. Tri-clamp fittings feature a clamp mechanism that secures the pressure sensor or other equipment in the system. They allow for easy disassembly and cleaning, ensuring minimal product residue and effective sanitation.
  • Hygienic Threaded Connections: Some pressure sensors come with specific hygienic threaded connections designed to meet sanitary standards. These threads often adhere to stringent cleanliness requirements and facilitate easy cleaning processes.
  • Sanitary Flanged Connections: Similar to standard flanged connections, sanitary flanged connections, when designed according to sanitary standards, can be suitable for certain sanitary applications. They allow for secure connections and can be disassembled and cleaned efficiently.
  • When selecting a process connection for a pressure sensor in a sanitary application, it's crucial to ensure that the connection meets industry-specific sanitary standards (such as 3-A Sanitary Standards, ASME BPE, or EHEDG guidelines). Additionally, the material of construction should be compatible with the application's requirements and ensure resistance to corrosion and product adherence.

    Tri-clamp connections are often preferred in sanitary environments due to their ease of use, cleanliness, and compatibility with cleaning processes like CIP (Clean-in-Place) and SIP (Sterilize-in-Place). However, the specific choice of connection depends on the industry standards, regulations, and specific requirements of the sanitary application.

    Welded Connections

    Welded connections are a method of joining components that involve fusing or welding two pieces together using heat or pressure, creating a permanent and robust joint. In the context of pressure sensors or transmitters, welded connections involve directly welding the sensor housing or body to the process connection, such as a pipe or vessel, to form a sealed and integral unit.

    Key aspects of welded connections for pressure sensors include

  • Permanent Bond: Welded connections create a permanent and inseparable bond between the sensor and the process connection. This eliminates potential leak points that might arise in threaded or flanged connections, enhancing reliability, especially in high-pressure or critical applications.
  • Robustness and Strength: Properly executed welds create strong and durable joints, capable of withstanding high pressures, extreme temperatures, and harsh environmental conditions. This durability makes welded connections suitable for demanding industrial environments.
  • Seamless Integration: Welded connections offer seamless integration between the pressure sensor and the process, minimizing dead spaces or areas where contaminants can accumulate. This feature is advantageous in sanitary applications where cleanliness and hygiene are crucial.
  • Application Considerations: Welded connections require skilled welding expertise and proper techniques to ensure integrity and avoid defects. Factors such as material compatibility, welding method (e.g., TIG, MIG), and post-welding treatments need careful consideration to maintain the sensor's accuracy and structural integrity.
  • Welded connections are commonly used in various industries, including oil and gas, chemical processing, aerospace, and automotive, particularly in applications where a permanent, leak-free, and sturdy connection is essential. However, they may not be as easily disassembled or modified compared to other connection methods, making them suitable for installations where frequent changes are not anticipated.

    When selecting welded connections for pressure sensors, it's crucial to adhere to industry standards and best practices, ensuring proper welding procedures, material compatibility, and quality control measures to achieve reliable and long-lasting joints.

    Fig 14. Welded connection

    Submersible connections

    Submersible connections refer to specialized fittings or connections designed for pressure sensors or devices intended to operate underwater or in submerged environments. These connections are crucial for maintaining the integrity of the sensor while ensuring accurate and reliable measurements in underwater applications, such as in marine, offshore, or subsea industries.

    Key aspects of submersible connections include:

  • Hermetic Sealing: Submersible connections need to provide hermetic or watertight seals to prevent water ingress into the sensor. This ensures the protection of sensitive electronic components and maintains the accuracy and functionality of the sensor despite being submerged.
  • Corrosion Resistance: Materials used in submersible connections must be highly resistant to corrosion and degradation caused by prolonged exposure to water or corrosive substances present in underwater environments. This helps prolong the lifespan of the connection and the sensor.
  • Pressure Resistance: Sensors operating underwater must withstand the hydrostatic pressure exerted by the water column at various depths. Submersible connections need to be designed to handle these pressures without compromising the sensor's performance or structural integrity.
  • Specialized Designs: Submersible connections often feature specialized designs, such as cable glands, waterproof housings, or encapsulation methods, to protect cables, electrical connections, and sensitive components from moisture and environmental elements.
  • Submersible connections are crucial in various underwater applications, including oceanographic research, offshore monitoring systems, underwater vehicles, and subsea infrastructure. The accuracy and reliability of sensors operating in these environments depend significantly on the quality and effectiveness of the submersible connections.

    When selecting submersible connections for pressure sensors, considerations such as the depth of operation, water pressure, material compatibility, environmental conditions, and adherence to industry standards are essential to ensure optimal performance and longevity of the sensor in underwater applications.

    What are the factors that affect pressure sensor process connections?

    Several factors can significantly impact pressure sensor process connections, influencing their performance, reliability, and suitability for specific applications:

  • Pressure Range: The pressure range the sensor will be exposed to determines the type of process connection required. Different connections are designed to withstand varying pressure levels, and selecting an appropriate connection that matches the pressure range is critical to prevent leaks or damage to the sensor.
  • Media Compatibility: The nature of the measured media (gas, liquid, corrosive substances) affects the choice of process connection material. Compatibility with the media prevents degradation, corrosion, or chemical reactions that could compromise the integrity of the connection.
  • Environmental Conditions: Factors like temperature variations, exposure to humidity, extreme temperatures, or outdoor conditions can impact the choice of process connections. Some connections may be better suited for harsh environmental conditions and offer better resistance to temperature fluctuations or corrosive atmospheres.
  • Installation Requirements: The ease of installation and compatibility with existing piping or systems influence the selection of process connections. Some connections may require specific tools, space, or alignment considerations during installation, affecting their suitability for certain applications.
  • Standards and Regulations: Adherence to industry standards and regulations ensures compatibility, reliability, and safety. Different industries have specific standards governing process connections, and compliance with these standards is crucial for proper operation and compatibility within the industry.
  • Maintenance and Accessibility: Consideration of maintenance needs, access for inspection, and potential disassembly for cleaning or repairs are essential factors. Some process connections may allow easier disassembly and maintenance compared to others, affecting their suitability for certain applications.
  • Sealing Requirements: The sealing mechanism employed in the process connection, such as gaskets, O-rings, or welding techniques, determines the connection's ability to maintain a leak-free seal. Choosing the appropriate sealing method is crucial for preventing leaks and ensuring accuracy.
  • Size and Space Constraints: Available space and the size of the piping or equipment where the sensor will be installed can also influence the choice of process connection. Some connections might be more suitable for compact spaces or specific pipe diameters.
  • Considering these factors when selecting process connections for pressure sensors ensures optimal performance, longevity, and reliability of the sensor within its intended application and operating environment.

    Temperature Effects on Process Connections

    Temperature can have significant effects on process connections used in pressure sensors. Some key impacts include:

  • Material Expansion and Contraction: Different materials used in process connections have varying coefficients of thermal expansion. Fluctuations in temperature can cause these materials to expand or contract, potentially affecting the fit, sealing, or integrity of the connection. Proper material selection that accounts for temperature changes is crucial to prevent issues like leaks or loosening of connections.
  • Sealing Performance: Temperature changes can affect the properties of sealing elements such as gaskets, O-rings, or sealants used in the process connections. Extreme temperatures may cause these materials to harden, soften, or degrade, compromising their ability to maintain a reliable seal. This can lead to leaks or reduced accuracy in pressure measurements.
  • Material Integrity: High temperatures can impact the structural integrity of materials used in process connections. Prolonged exposure to elevated temperatures might cause degradation, corrosion, or weakening of materials, potentially leading to failure or reduced lifespan of the connection.
  • Thermal Stress: Rapid temperature changes or thermal cycling can induce thermal stress in the process connections, especially in welded joints or areas where dissimilar materials meet. Thermal stress might result in deformation, cracking, or fatigue of the connection over time, affecting its performance and longevity.
  • Dimensional Changes: Temperature variations can cause dimensional changes in the process connections due to material expansion or contraction. This can affect the alignment, fit, or tolerances of the connection, potentially impacting the accuracy of pressure readings or the stability of the sensor's installation.
  • To mitigate the effects of temperature on process connections, it's crucial to consider factors such as the material's temperature resistance, compatibility with the measured media, the sealing mechanism used, and adherence to temperature limitations specified by industry standards. Employing thermal insulating materials, selecting appropriate sealing elements, and employing proper installation techniques can help minimize temperature-related issues and ensure the reliability and accuracy of pressure sensors in varying temperature environments.

    Fig 14. Threads

    What are the important factors for choosing the proper process connections and fitting?

    Selecting the proper process connections and fittings for pressure sensors involves considering various critical factors to ensure compatibility, reliability, and optimal performance within specific applications:

  • Pressure Rating and Range: Understand the pressure levels the sensor will encounter. Choose connections and fittings capable of withstanding the intended pressure range without leaks or failure.
  • Media Compatibility: Assess the nature of the measured media (liquid, gas, corrosive substances). Ensure the materials used in the connections and fittings are compatible with the media to prevent corrosion, degradation, or reactions that could compromise integrity.
  • Temperature Conditions: Consider the temperature variations the connections will face. Select materials and fittings that can withstand the temperature range without affecting performance or structural integrity.
  • Environmental Factors: Evaluate the operating environment, including exposure to humidity, corrosive atmospheres, or outdoor conditions. Choose connections and fittings resistant to environmental elements present in the application.
  • Industry Standards and Regulations: Adherence to industry-specific standards and regulations is crucial. Ensure that connections and fittings comply with relevant standards for safety, performance, and compatibility within the industry.
  • Installation Requirements: Consider ease of installation and compatibility with existing systems. Ensure that connections and fittings align with available space, tools, and installation procedures to facilitate a secure and proper fit.
  • Sealing Mechanism: Evaluate the sealing methods used in connections, such as gaskets, O-rings, or sealants. Ensure the sealing mechanism provides a reliable, leak-free seal suitable for the application's requirements.
  • Maintenance and Accessibility: Consider maintenance needs, access for inspection, and potential disassembly for cleaning or repairs. Choose connections and fittings that allow for easy maintenance without compromising integrity.
  • Size and Compatibility: Ensure compatibility in terms of size, thread type, or fitting design with other components within the system to facilitate proper integration and functionality.
  • By thoroughly assessing these factors, you can effectively choose the most appropriate process connections and fittings for pressure sensors, ensuring compatibility, reliability, and optimal performance within specific applications and operating conditions.

    Glossary

    Term Definition
    NPT (National Pipe Thread) A tapered thread standard commonly used in the United States for sealing pipe connections.
    BSP (British Standard Pipe) A parallel thread standard used in various countries, including the UK, for pipe fittings.
    Flanged Connection Method using two flanges with bolt holes and gaskets for a secure joint.
    Tri-Clamp Connection Sanitary fitting with a clamp mechanism used in hygienic applications.
    Welded Connection Fusion of materials using heat or pressure to create a permanent joint.
    Thread Size Dimension specifying the diameter and pitch of a threaded connection.
    Pressure Rating Maximum pressure a fitting or connection can withstand without failure.
    Sealing Mechanism Methods like gaskets, O-rings, or sealants used to prevent leaks in connections.
    Hermetic Seal Completely airtight or watertight seal preventing substance passage.
    Compression Fitting Connection involving compression of a fitting onto a pipe or tubing.
    RTJ (Ring Type Joint) Flanges Flanges with a groove for a metal ring gasket, commonly used in high-pressure applications.
    Raised Face Flanges Flanges with a raised surface for better gasket sealing.
    Flat Face Flanges Flanges with a flat surface for lower-pressure sealing connections.
    Gasket Material is placed between surfaces to create a seal, often made of rubber, silicone, or metal.
    Corrosion Resistance Ability of a material to withstand corrosion from harsh environments or substances.
    Temperature Resistance Capability of a material or fitting to withstand various temperature ranges without damage.
    Hygienic Threaded Connection Threaded connections are designed for use in sanitary applications, adhering to cleanliness standards.
    Submersible Connection Specialized fitting designed for submerged or underwater applications.
    DIN Rail Mount Standardized metal rail used for mounting industrial components like pressure sensors.
    Lapped Joint Flanges Flanges are used with a stub end and lap joint for alignment and rotation.

    Wrap up

    Selecting the right process connections and fittings for pressure sensors is a critical decision that significantly impacts the sensor's performance, reliability, and suitability for specific applications. Considering various factors such as pressure ratings, media compatibility, temperature conditions, environmental factors, industry standards, installation requirements, sealing mechanisms, maintenance needs, and compatibility with existing systems is essential.

    A thorough assessment of these factors allows for the informed selection of connections and fittings that can withstand the intended pressure, temperature, and environmental conditions while ensuring compatibility, reliability, and safety within industry standards. Whether it's choosing between threaded, flanged, welded, or specialized connections like those used in sanitary or submersible applications, the right choice is pivotal for seamless integration, accurate measurements, and long-term functionality of pressure sensors in diverse industrial settings. Striking a balance between these considerations ensures optimal performance and longevity of pressure sensors in their respective applications.

    To recap

    1.What are process connections in pressure sensors? 

    Process connections are the interface points used to attach pressure sensors to the system they are measuring, ensuring a sealed and reliable connection. 

    2.What types of process connections are commonly used? 

    Common types include threaded connections (NPT, BSP), flanged connections, welded connections, tri-clamp connections, and specialized connections for specific applications.

    3.How do I choose the right process connection for my pressure sensor? Consider factors such as pressure rating, media compatibility, temperature conditions, environmental factors, industry standards, installation requirements, sealing mechanisms, maintenance needs, and compatibility with existing systems.

    4.What is the difference between NPT and BSP threaded connections?

    NPT (National Pipe Thread) is a tapered thread commonly used in the United States, while BSP (British Standard Pipe) is a parallel thread used in many parts of the world, including the UK. 

    5.Which process connection is suitable for sanitary applications? Sanitary applications often use connections like tri-clamp fittings due to their ease of cleaning, hermetic sealing, and suitability for hygienic environments. 

    6.What factors affect the performance of process connections in pressure sensors? 

    Pressure range, media compatibility, temperature effects, environmental conditions, industry standards, installation, sealing, maintenance, and size compatibility all influence performance. 

    7.How do temperature changes affect process connections? Temperature fluctuations can impact the material properties, sealing mechanisms, structural integrity, and dimensions of connections, potentially leading to leaks or compromised performance. 

    8.What is the significance of industry standards in selecting process connections? 

    Adhering to industry standards ensures the compatibility, reliability, safety, and performance of connections within specific applications and industries. 

    9.Can I use the same process connection for various media types? 

    Not necessarily. It's crucial to ensure compatibility between the materials used in the connection and the properties of the media to avoid corrosion, degradation, or chemical reactions.

    10.Are welded connections suitable for all applications? 

    While welded connections offer strength and permanence, they may not be easily disassembled and could be less suitable for applications requiring frequent modifications or disassembly. 

    11.What considerations are vital for selecting threaded connections? Factors such as thread type (NPT, BSP), pressure ratings, compatibility with media, temperature limitations, and proper installation techniques are crucial.

    12.Do process connections require specific maintenance?

    Depending on the type, some connections may require periodic checks for seals, corrosion, or wear to ensure continued reliability. 

    13.Which connection types are suitable for submersible applications? 

     Submersible applications often utilize specialized connections with hermetic seals and corrosion-resistant materials to withstand underwater environments. 

    14.Can process connections be modified or adapted for different systems? 

    In some cases, adapters or specialized fittings can be used to modify connections to suit different systems or standards. 

    15.How can I ensure the longevity of process connections in pressure sensors?

    Regular inspection, adherence to maintenance schedules, choosing suitable materials, proper installation, and compliance with industry standards contribute to the long-term reliability of connections.

    References

    https://www.dubai-sensor.com/blog/process-connection-or-fitting-for-pressure-transmitter/

    https://www.eastsensor.com/blog/pressure-sensor-process-connection/?highlight=process%20connection

    https://www.eastsensor.com/blog/knowledge-thread-process-connection/?highlight=process%20connection

    https://www.eastsensor.com/blog/four-types-thread-process-connections-need-know-part-1-2/?highlight=process%20connection

    https://www.efihardware.com/products/3133/single-bosch-pressure-sensor-mount

    20th Jan 2024 Saeed Abd

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