All you need to know about bellows seal valves

What are bellows valves

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Bellow valves are a type of valve that use a flexible bellow element to control the flow of fluids or gases. The bellow element is typically made of metal or other durable materials and is designed to expand and contract in response to changes in pressure or temperature. This movement allows the valve to open or close, regulating the flow of the fluid or gas through the system. Bellow valves are commonly used in applications where precise control of flow is important, such as in chemical processing, pharmaceutical manufacturing, and other industrial settings. A Bellows Valve is a specially designed valve suitable for use in industries dealing with a hazardous medium where even minute leakages can be extremely critical. With the exponential growth of new industries such as the chemical and nuclear industry, there is a growing abundance of flammable, hazardous, extremely poisonous, and toxic media flowing through the pipelines. This creates a high risk of leakage, explosion, and health hazards. So, the valves used in such pipes and systems have specific stringent leakage and sealing requirements.

What is the costruction of bellows seal valves

 A bellows valve is a type of industrial valve that uses a bellows element to create a hermetic seal. The construction of a bellows valve typically includes a valve body, a bonnet or cover, a stem, a handwheel or actuator, and the bellows element itself.

The bellows element is typically made of metal, such as stainless steel, and is designed to flex in response to changes in pressure or temperature. This flexibility allows the bellows element to compensate for thermal expansion and contraction, as well as pressure fluctuations, while maintaining a tight seal.

The stem of the valve connects the handwheel or actuator to the valve disc or plug, which is used to control the flow of fluid or gas through the valve body. The bonnet or cover is used to protect the internal components of the valve, including the bellows element and stem, from external damage or contamination.

Overall, the construction of a bellows valve is designed to provide reliable and precise control of fluid or gas flow while maintaining a hermetic seal to prevent leaks or contamination.

The types of bellows seal valve

 Bellows seal valves are a type of industrial valve that use a flexible metal bellows to create a hermetic seal between the valve stem and the valve body. They are commonly used in applications where leakage cannot be tolerated, such as in chemical processing, pharmaceuticals, and food and beverage production.

There are several types of bellow seal valves, including:

1. Globe valves

2. Gate valves

3. Check valves

4. Ball valves

5. Butterfly valves

Each of these types of valves has its own unique design and characteristics, but they all use a bellows seal to prevent leakage and ensure reliable operation.

Advantages of Bellows Seal Globe Valve

1.  The most prominent advantage of any bellows valve is the Double seal design (bellows + packing). So, even if the bellows fails, the stem packing will prevent any kind of leakage to meet the international sealing standards.

2.  It minimizes any loss of medium fluid and ensures the safety and environmental protection. This will ultimately improve the safety of the plant where is bellows valve has been installed.

3.  It can act as an energy saver as it contributes to minimizing energy losses due to leakage.

4.  Since the leakage is minimized, it prevents frequent maintenance of the valve. So, it leads to longer valve life.

5.  Owing to longer service life, operating and maintenance cost is considerably reduced.

6.  The rugged bellows seal design ensures zero leakage from the valve stem, thereby providing the maintenance-free conditions.

7.  The safety of working personnel is improved with the installation of a bellows valve as emissions of inflammable, toxic, and hazardous chemicals can be minimized

The difference between common valve and bellows seal valves

Bellows globe valves and common valves are two types of valves used in industries to control the flow of fluids or gases. 

The main difference between these two types of valves is that bellows globe valves have a bellows assembly that separates the fluid or gas flowing through the valve from the valve stem, whereas common valves do not have this feature. 

When valves with gland packing are used such as gate valves or ball valves in the system for heated oil transfers (permeability of heated oil is about 50 times that of steam), chances of hot oil spillage are quite high and can cause loss of equipment and property. In such cases, due to its construction, the bellows valve can ensure absolutely nil leakage.

 In ordinary valves, the shape of graphite packing cannot provide 100% effective sealing which is the main reason for frequent leakage of packing valve. As ordinary fillers are manufactured with graphite, if the purity of graphite is not adequate, its oil resistance would below. When heating oil being transferred is soaked in a graphite filler, certain graphite impurities get separated and flows along with it.

When a ball valve is used in the system with heated oil, if the internal PTFE is not resistant to high temperatures, it will quickly deteriorate and cause valve leakage.

The internal parts of the bellows valve are made of stainless steel, which can withstand a temperature of 425°C. Considering the life span of Bellows Seal Globe Valve, the duration of the general bellows valve is more than three years. Therefore, to maintain the reliability of output and to reduce the direct running costs, a bellow shut-off valve is preferred over ordinary seal valves in case of a system where heated oil is being transferred.

The bellows assembly is made of a series of convoluted metal plates that expand and contract with changes in pressure or temperature, allowing the valve to operate smoothly and without any leaks. 

In contrast, common valves rely on a packing material, such as graphite or PTFE, to prevent leaks around the valve stem. This packing material can wear out over time, leading to leaks and increased maintenance costs. 

Overall, bellows globe valves are generally considered to be more reliable and longer-lasting than common valves, especially in applications where leakage is not acceptable.

Selection Guide for Bellows

1.  Choose the inner diameter of the bellows according to the diameter of the valve stem. The inner diameter of the bellows should be greater than the stem diameter of 115 mm.

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2.  The outer diameter of the bellows is selected according to the inner diameter of the bellows. The outer diameter and the inner diameter are related by the ratio of the outer diameter to the inner diameter. In general, the ratio of the outer diameter to the inner diameter is 113 to 115.

3.  The wall thickness, number of layers, number of corrugrtions, and length of the corrugated pipe must meet the requirements of the pressure resistance, stroke, and cycle life of the corrugated pipe. Under normal circumstances, greater the pressure, more thickness of the bellows is required. To increase the displacement or reduce the stiffness of the bellows and increase life, the thickness of the single layer can be reduced and the number of layers of the bellows can be increased.

4.  For handling higher pressures, the multiply design of bellows is recommended. The pressure that bellows can withstand can be increased by using 2 or 3 piles of the metal wall as in case of multiply design of bellows. Pressure rating by using a two-ply bellow can increase by 80% to 100% than single-ply bellow of the same thickness. Alternately, the stroke length is reduced if single-ply bellow of a thickness equivalent to the pressure rating of two ply bellow is used. So, we get a distinct advantage of multiply design over the single-ply thick bellows.

5.  To prevent the distortion of bellows, the designed guide structure must be strictly followed.

6.  To prevent wear and premature failure, local contact between the valve stem or bellows must be avoided.

7.  The design should be such that twisting and torsional deformation of the bellows is prevented.

8.  The valve design should be limited by the extension stroke and compression of the bellows. This is to prevent displacement of the bellows and to withstand compression and tensile extension beyond the defined cycle life test. Under normal conditions, the stroke of the bellows should not exceed 25% of the free length. If this is not fulfilled, it will affect the cycle life of the bellows, especially bellows valves under high temperature and high-pressure environment.

9.  The bellows adopt the same pressure and temperature grade as the Bellow seal Globe Valve. The bellows must withstand the pressure test of the nominal pressure of the main valve at 38 &#; and 115 times the nominal pressure at 38 &#;. During the pressure test, the weld should not crack or leak, and the bellows should not twist.

10. The material of the bellows components should be selected within the allowable temperature range, and it should have good formability, welding performance, and compatibility with the medium.

 Application range of Bellows Seal Globe Valve

·   Bellows valves eliminate the risk of leakage of the process fluid and are therefore ideally suited for applications where leakage cannot be tolerated from the valves. So, places where highly hazardous materials such as hydrogen, ammonia, chlorine, and other similar poisonous or explosive material are handled, these valves are preferred.

·   It is suitable for use as a shut-off valve with heat-conducting oil, toxic, flammable, highly permeable, environmentally polluting, and radioactive fluid pipelines. It can be considered as a high-quality product for creating a leak-free factory.

·   To name a few, bellows seal globe valve is highly used in petrochemical industries, electronics industry, various plants, vacuum industries, etc.

 Precautions for Bellows Seal Globe Valve

Ø To avoid damage or injury to personnel or equipment, always read all warnings and instructions. Unprofessional re-conditioning, the use of foreign replacement parts, or the incorrect maintenance steps, may cause a loss of efficiency or lead to personnel injury or damage to parts.

Ø Use double seal bellows in case of a highly corrosive chemical environment so that you get two protective layers of sealing.

Ø If you find that there is a smell of media in the air or the valve cover is wet, it is generally because the bellows have been damaged by the medium.

Ø You can replace the bellows by yourself or get it replaced by makers. Replace it to avoid prolonged negligence, a threat to life, and damage to the entire valve.

Ø An excessively tightened gland nut can cause excessive packing wear and can hinder the free movement of the plug stem.

Reasons for Leakage of Bellow Seal Glove Valve

There are many reasons for the leakage of a Bellows Seal Valve. Bellows valve leakage is generally divided into internal leakage and external leakage.

1.  It is because the liquid medium contains solid impurities that damage the sealing surface and cause failure.

2.  Combined with the analysis of the on-site usage, the reason for the leakage of the valve stem is mainly related to the valve structure, working environment, and operation mode.

3.  The valve stem adopts a double sealing structure of bellows and packing. The bellows are welded with the inner lining ring and the outer lining ring to form a bellows assembly and then welded with the valve stem and the guide body to block the leakage of the medium through the valve stem. The valve stem of the bellows valve moves up and down by the flat key, until the upper-end surface of the flat key contacts the lower end surface of the lower packing. Since the lower packing is made of PTFE material, if the valve is opened too much, the flat key will be embedded in the packing, the bellows valve can no longer be opened and closed, and the bellows assembly is knocked to death, causing the medium to leak along the valve stem.

4.  Tensile elongation and compression of the bellows valve according to the line determination process can contribute to leakage. If tension or compression exceeds the limit, the bellows may be damaged, resulting in small series hose rupture, seal failure. Therefore, it is necessary to increase the limit device for opening and closing of the bellows valve, so that the bellows always expand and contract within the design range during the operation of the valve.

 Summary  

The unique design of Bellows Seal Globe Valve and its efficiency to provide leak-proof operations makes it the best-suited valve for a wide range of applications, especially hazardous materials & where system media is at high temperatures. Durability, maintenance-free operations and cost-effectiveness is an added benefit with bellows valves.

What Is a Bellows Seal Globe Valve?

A bellows seal globe valve is a specially designed valve that is highly suitable for industries dealing with hazardous substances. The valve&#;s unique design ensures that even the smallest leakages, which can be extremely critical in certain industries, are prevented. This is particularly important in industries such as the chemical and nuclear industry, where there is a high risk of leakage, explosion, and health hazards due to the flow of flammable, hazardous, extremely poisonous, and toxic media through the pipelines. The bellows seal globe valve, therefore, meets specific stringent leakage and sealing requirements that are essential in such industries.

The Comprehensive Guide to Bellow Seal Globe Valves 1

How Do Bellows Seal Globe Valves Work?

Bellows seal globe valves work by using a compact structure that includes bellows for sealing the valve stem components. The bellows valve has a bellow inside, and the lower end of the stainless-steel bellows is welded to the stem to prevent the system fluid from eroding the stem. The other end is positioned between the body of the valve and the cover of the valve to create a permanent seal. This double seal configuration eliminates leakage. Even if the bellows collapse, the stem packaging will prevent further leakage. The bellows are welded to the valve stem to ensure stable operating efficiency and prevent the vibration of the valve stem induced by the movement of the valve insert.

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What Are the Key Components of Bellows Seal Globe Valve?

The key components of a bellows seal globe valve include the metal bellows, bonnet, the lower end and stem assembly, the upper end and connecting plate, and the sealing surface of the valve disc.
The metal bellows are the main feature of a bellows seal globe valve. They are made by rolling a flat sheet into a tube and then mechanically forming it into a bellow with rounded and widely spaced folds. Inconel is a common material used for making bellows due to its high resistance to corrosion and high temperatures. Cryogenic valves are also commonly made with metal bellows for their ability to withstand extreme temperatures.

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The lower end and the stem assembly are welded together, while the upper end is welded on the connecting plate using socket weld. This creates a metal shield between the fluid medium and the environment, ensuring zero leakage from the valve stem. The stem seals are an important component of the bellows seal globe valve, ensuring a tight seal and preventing leaks.
The sealing surface of the valve disc and the valve structure is precisely ground to confirm that it has passed a pressure rating test and that any possibility of leakage is eliminated. Graphite packing is used to ensure a tight seal and prevent any leaks from occurring.

What Industries Primarily Use Bellows Seal Globe Valves?

Bellows seal globe valves are a crucial component in a wide array of industries due to their exceptional sealing capabilities and robust design. The primary industries that utilize these valves are those where the prevention of leakage is of utmost importance, particularly when dealing with hazardous or toxic substances. These valves can be integrated with an API (Application Programming Interface) to provide real-time monitoring and control, making them an even more valuable asset in industries where safety and efficiency are top priorities.Petrochemical Industry: One of the key sectors that heavily rely on bellows seal globe valves is the petrochemical industry. These valves are used in various processes where they control the flow of flammable and potentially harmful substances. Their superior sealing performance ensures that there are no leakages that could lead to accidents or environmental contamination.Nuclear Industry: The nuclear industry is another sector where bellows seal globe valves, classified as ASME Class, are extensively used. In nuclear power plants, these valves play a crucial role in controlling the flow of radioactive substances. The double sealing design of these valves ensures that there is no leakage of radioactive material, thereby ensuring the safety of the plant and its surroundings.

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Chemical Industry: Bellows seal globe valves are also widely used in the chemical industry. They are used to control the flow of various chemicals in the production processes. The valves&#; ability to withstand corrosive substances and high temperatures makes them an ideal choice for this industry.Electronics Industry: Other industries that use bellows seal globe valves include the electronics industry, where they are used in the production of semiconductors and other electronic components. They are also used in various plants such as power plants, water treatment plants, and manufacturing plants where they control the flow of gases and liquids. The vacuum industry also uses these valves due to their ability to maintain a high level of sealing under low-pressure conditions.

What Are the Advantages of Bellows Seal Globe Valve?

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1. Exceptional Sealing Performance: The double seal design comprising the bellows and stem packing ensures superior sealing performance. Even if the bellows were to fail, the stem packing would prevent any leakage, meeting international sealing standards. This high level of sealing capability is critical, especially in industries dealing with hazardous or toxic substances, where even the smallest leakages can have severe consequences.
2. Safety and Environmental Protection: Bellows seal globe valves minimize the loss of medium fluid, enhancing the safety of the plant where they are installed. This feature is particularly crucial in industries handling hazardous materials that could lead to accidents, health risks, or environmental pollution if leaked.
3. Energy Conservation: By reducing energy losses due to leakage, bellows seal globe valves contribute to energy conservation. This not only helps save costs but also aligns with environmental sustainability goals by reducing overall energy consumption.
4. Durability and Cost Savings: With minimized leakage, bellows seal globe valves require less frequent maintenance and replacements. The extended valve life results in significant cost savings in terms of maintenance and replacement expenses.
5. Maintenance-Free Operation: The rugged bellows seal design ensures zero leakage from the valve stem, providing maintenance-free conditions. This improves operational efficiency and reduces downtime for maintenance activities.

What Are Some Types of Bellows Seal Globe Valve?

Bellows seal globe valves come in various types, each designed to meet specific application requirements. Here are some common types:

1. Welded Ends Bellow Seal Globe Valve: This type of valve is characterized by its welded ends, providing a robust and leak-proof connection. It&#;s ideal for high-pressure applications where a strong connection is essential.
2. Flanged Bellow Seal Globe Valve: This valve features flanged ends, which allow for easy installation and removal. It&#;s suitable for applications that require regular maintenance or replacement of the valve.
3. Socket-Welded Bellows Seal Globe Valve: This type of valve has socket-welded ends, providing a strong, leak-proof connection. It&#;s ideal for high-pressure applications and is often used in the petrochemical and nuclear industries.
4. Threaded Bellows Seal Globe Valve: This valve features threaded ends, making it easy to install and remove. It&#;s suitable for low to medium pressure applications.
5. Extended Bellows Seal Globe Valve: This valve features an extended bellows seal, providing additional protection against leakage. It&#;s ideal for applications that require a high level of sealing performance.
6. Y Pattern Bellows Seal Globe Valve: This valve features a Y pattern body, which allows for a more streamlined flow of fluid through the valve. It&#;s ideal for applications that require a high flow rate.

How to Select the Bellows?

1. Inner Diameter: The inner diameter of the bellows should be greater than the stem diameter, typically 115 mm. This allows the stem to move freely within the bellows without causing any damage.
2. Outer Diameter: The outer diameter of the bellows is usually selected based on the inner diameter. The ratio of the outer to the inner diameter is generally between 113 to 115.
3. Wall Thickness, Number of Layers, Corrugations, and Length: These specifications should meet the requirements of pressure resistance, stroke, and cycle life of the corrugated pipe, ensuring that the bellows can endure operational pressures and temperatures.
4. Bellows Design: For handling higher pressures, a multiply design of bellows (using 2 or 3 piles of the metal wall) is recommended.

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5. Material: The material of the bellows components should be selected based on the allowable temperature range, formability, welding performance, and compatibility with the medium. This guarantees the longevity of the bellows in various operational conditions.

What Is the Difference Between a Bellows Seal Globe Valve and a Normal Valve?

AspectBellows Seal Globe ValveNormal ValveSealing MechanismDouble seal (bellows + packing)Single sealLeakage PreventionExceptional sealing performanceLess reliable sealingApplicationHazardous or toxic substancesGeneral applicationsSafetyHigh safety standardsStandard safety precautionsEnvironmental ProtectionMinimizes medium fluid lossMay cause fluid leakageEnergy ConservationContributes to energy savingsEnergy losses may occurDurabilityLonger valve lifeStandard valve lifespanMaintenanceReduced maintenance needsRegular maintenance requiredSuitable for High-PressureYesYes (depending on the type)Suitable for High-TemperatureYesYes (depending on the type)Material CompatibilityResistant to corrosive fluidsMay be prone to corrosionCostHigher initial costStandard cost

What Causes Leakage in Bellows Seal Globe Valves and How Can It Be Prevented?

Causes of LeakagePrevention MeasuresDamage to the BellowsRegular inspection and immediate replacement of damaged bellowsExcessive PressureUse of pressure relief devices and adherence to operating limitsCorrosive SubstancesUse of corrosion-resistant materialsHigh TemperatureUse of temperature-resistant materials and cooling mechanismsImproper InstallationProper installation following manufacturer&#;s instructionsPoor MaintenanceRegular and thorough maintenance routinesLow-Quality MaterialsUse of high-quality, durable materialsPoor Manufacturing ProcessesSelection of valves from reputable and reliable manufacturersIncorrect OperationTraining and adherence to correct operating procedures

What Are Some Precautions Should Be Taken While Using Bellows Seal Globe Valves?

1. Adhere to Manufacturer&#;s Instructions: Always read and follow all instructions and warnings provided by the manufacturer to prevent valve damage and potential safety hazards.
2. Proper Installation: Ensure the valve is installed correctly to prevent leakage and other operational issues. Incorrect installation can lead to numerous issues, including leakage and inefficient operation.
3. Suitability for Application: Check the pressure and temperature ratings and ensure the valve material is compatible with the fluid being handled. The valve should suit the specific requirements of your application.
4. Regular Maintenance and Inspection: Regularly inspect the valve for signs of damage or wear and replace any damaged components promptly. If the bellows are damaged, immediate replacement is necessary to prevent leakage.
5. Use As Intended: The valve should always be used in accordance with its intended purpose. Using the valve in applications for which it is not designed can lead to damage and potential safety hazards.

Conclusion

In conclusion, bellows seal globe valves are an essential component in many industries due to their superior sealing capabilities and robust design. They offer numerous advantages, including enhanced safety, environmental protection, and energy conservation. However, it&#;s important to select the right bellows and take necessary precautions to ensure safe and efficient operation.

Opt for Dombor

When it comes to bellows seal globe valves, Dombor is a trusted name in the industry. With a commitment to quality and innovation, Dombor offers a wide range of bellows seal globe valves designed to meet the specific needs of various industries. Whether you need a welded ends bellow seal globe valve for high-pressure applications or a flanged bellow seal globe valve for easy installation and maintenance, Dombor has you covered. With Dombor, you can be assured of superior performance, durability, and reliability. Choose Dombor for all your bellows seal globe valve needs.

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