Edge welded metal bellows, made from metals like stainless steel, titanium, and nickel alloys, are designed to accommodate movements and prevent leaks in systems experiencing temperature changes and vibrations.
Key Takeaways
- Edge welded metal bellows are essential for temperature adaptation, vibration absorption, and preventing leaks.
- They are made from thin metal sheets like stainless steel or titanium, welded at the edges for a secure seal.
- These bellows are highly customizable and find applications in aerospace, medical, and automotive industries for precise control.
- Their construction allows for movements along axial, lateral, and angular planes to handle different stresses and environmental conditions.
- Manufacturing involves key steps such as stamping, cleaning, welding diaphragms together, and rigorous testing to ensure leak-proof functionality.
What Are Edge Welded Metal Bellows
Edge welded metal bellows are crafted to handle changes in temperature, dampen vibrations, and prevent leaks in various mechanical systems. These components consist of thin, circular metal sheets welded together at the edges in a staggered pattern, creating a tight, hermetic seal.
The thickness of the metal sheets and the choice of material can vary to suit specific needs. Options range from stainless steel to high-nickel alloys, each selected based on the operating environment and exposure to different chemicals. The adaptability of these bellows allows them to adjust to movements along different axes—axial, lateral, and angular.
Types of Edge Welded Metal Bellows
Resting Ripple Bellows
Resting Ripple Bellows feature uniform, contoured plates which provide exceptional flexibility and enable a longer axial stroke despite their compact size. These bellows are built for high-performance environments, capable of handling various pressures while ensuring minimal leakage.
The design of Resting Ripple Bellows is crucial in extremely cold environments. They are crafted to offer outstanding durability and maintain tight seals, maintaining system integrity under cryogenic conditions.
Each convolution in the bellows is uniform, leading to a consistent spring rate. It increases the lifecycle of the components and ensures reliable performance.
Single Sweep Bellows
Single Sweep Bellows are known for their straight, flat sections. However, these bellows often face issues with weld quality.
The main problem lies in the heat-affected zones. These zones show greater inconsistency in Single Sweep Bellows, affecting their overall reliability when compared to other types like resting ripple bellows.
The straight structure of Single Sweep Bellows makes it harder to distribute heat evenly during the welding process. This uneven heat distribution can cause the microstructure in these zones to vary significantly. Such variations can lead to weaker weld joints.
Nesting Ripple Bellows
Nesting Ripple Bellows are designed for high performance in demanding situations. Their construction features evenly shaped plates which enhance both compression and flexibility. This unique structure allows them to handle intense pressures while keeping the spring rate low, making them perfect for tasks that need precise control over movement.
The bellows are especially robust due to their thick convolution structure, which provides extra durability. This is crucial in environments where corrosion is common, such as with metal valves in industrial settings or with medical bellows that require edge welding. These characteristics ensure that Nesting Ripple Bellows meet the strict standards set for different types of bellows seals, making them reliable for both dynamic and static uses.
Double-Ply Bellows
Double-Ply Bellows are made by welding two thin metal plates together. This process enhances their strength and flexibility, making them suitable for high-pressure situations. The welding technique used is advanced, ensuring that the bellows are both durable and able to move easily, which is crucial in dynamic settings. These bellows are particularly useful in scenarios requiring strong initial torque, where single-ply versions might not be adequate.
The construction of double-ply bellows avoids the need for using thicker metal plates, which can be beneficial. By doing so, it not only makes the bellows lighter but also improves their overall function in the bellows assembly. This type of design is perfect for metal bellows seals and offers reliable performance under stress without hindering how well the bellows operate.
The Common Materials of Edge Welded Metal Bellows
Stainless Steel
Stainless steel is widely used in making edge welded metal bellows due to its corrosion resistance and strong mechanical properties.
- 316L grade: Particularly effective in marine and chemical settings because it contains molybdenum, which helps prevent pitting and crevice corrosion.
- 304L grade: Offers good corrosion resistance and is easy to form, making it suitable for various general purposes.
- 321 grade: Recommended for applications involving high temperatures as it includes titanium, which protects against corrosion that can occur at grain boundaries in temperatures up to 900°C.
- 347 grade: Contains niobium, which helps maintain its strength in temperatures up to 870°C.
Nickel Alloys
Nickel alloys are crucial in making edge welded metal bellows due to their ability to withstand extreme environments. These alloys are highly valued for their resistance to high temperatures, corrosion, and oxidation.
- Inconel: A nickel-chromium alloy, particularly noteworthy for its ability to tolerate temperatures as high as 1100°C. This makes it perfect for use in aerospace and chemical processing industries where high heat and oxidation are common challenges.
- Monel: Combining nickel and copper, Monel is another significant alloy predominantly used in the marine and chemical processing sectors. Its strength lies in its excellent resistance to corrosion by various acids and alkalis, safeguarding equipment against harsh chemical exposures.
- Hastelloy: Distinguished for its outstanding performance under severe conditions, Hastelloy is a top choice in industries like chemical processing and energy production. It deals exceptionally well with high temperatures and corrosive materials, providing reliability and durability where it’s most needed.
Titanium
Titanium stands out for its impressive strength-to-weight ratio, a feature crucial in crafting edge welded metal bellows. These bellows, made from titanium, display both high strength and outstanding corrosion resistance.
The most commonly used forms of titanium in this application are commercially pure (CP) titanium grades 2 and 5. These grades are favored for their moderate strength and excellent resistance to corrosion.
In scenarios requiring enhanced durability, titanium alloys, such as Ti-6Al-4V, are recommended. This specific alloy boosts the bellows’ ability to withstand extreme temperatures and pressures.
Beryllium Copper
Beryllium copper alloys, especially grades C17200 and C17300, are crucial for manufacturing metal bellows. These bellows benefit significantly from the unique properties of beryllium copper. Primarily, these properties include excellent spring characteristics and high resistance to fatigue, making these alloys ideal for applications requiring repeated flexing.
- Grade C17200: Contains about 1.9% beryllium. This composition is key for applications that demand durability under repeated stress. It helps maintain the integrity of the spring qualities even under continuous use, ensuring the bellows perform reliably over time.
- C17300: Includes roughly 1.6% beryllium, offers not just strength but also superior electrical conductivity. This makes it particularly suitable for bellows seals used in environments where electrical characteristics are crucial. This grade thus supports both mechanical strength and electrical efficiency.
Specialty Metals
- AM350: A type of strengthened stainless steel, perfect for industries like aerospace and power generation due to its robustness and resistance to deterioration at high temperatures.
- Haynes 242: Stands out due to its resistance to oxidation and corrosion, even at temperatures as high as 1200°C (2192°F).
Manufacturing Process of Edge Welded Metal Bellows
Stamping the diaphragms
The process of making edge welded metal bellows begins with stamping thin metal sheets. This is done using a hydraulic press, which employs male and female molds to shape these sheets into diaphragm plates. Each diaphragm plate needs to fit tightly into the next, a design aspect referred to as nesting.
Male and female form tools play a pivotal role here. They ensure that every diaphragm plate not only matches the required curvature but also possesses the precise depth and contours necessary for the next stages of manufacturing.
Cleaning the diaphragms
After the diaphragms are stamped, they undergo a thorough cleaning. Any remaining grease, dirt, or other contaminants can harm the welding process and affect the performance of the bellows. The cleaning involves several precise steps:
- Solvent Baths: The diaphragms are soaked in chemical solvents. These solvents dissolve grease and other oily substances.
- Ultrasonic Cleaning: This uses high-frequency sound waves to remove finer particles and residues that the solvent bath might not catch.
Each diaphragm is then inspected carefully. This inspection ensures that the cleaning has removed all the unwanted substances. Only after confirming the cleanliness are the diaphragms ready for welding.
Welding the inside diameter
After cleaning the diaphragms, several advanced welding methods like plasma, laser, arc, or electron beam are used to fuse a male and a female diaphragm together at the inside diameter, creating a single convolution.
Choosing the right welding technique depends on what the bellows need to do, what materials are being used, and how strong the weld needs to be.
Stacking convolutions
Technicians stack these convolutions—each shaped with either a male or female end—onto an arbor in an alternating pattern. This method ensures that the convolutions fit together without gaps, maintaining seamless alignment.
Welding the outside diameter
Welding the outer sections of layered convolutions forms the critical backbone of edge welded metal bellows, referred to as OD welding.
During this process, heat distortion poses a significant challenge. To address this, technicians place chill rings between each convolution. These rings act as heat absorbers, preventing unwanted thermal expansion and helping maintain the precise shape of the bellows.
Welding end pieces
After finishing the outer diameter (OD) welding, the technicians shift their focus to attaching specialized end pieces like flanges and fittings. Each end piece must be aligned perfectly and welded securely to maintain the overall integrity and functionality of the bellows.
The selection of end pieces such as flanges and fittings depends on the unique demands and environmental factors of the application. For example, in a high-pressure environment, more robust and durable materials might be necessary to withstand such conditions without failing. Each connection point between the bellows and these end pieces must meet stringent standards to prevent leaks and ensure durability.
Inspection and testing
Each bellows unit undergoes leak testing as part of the quality control process. This test checks if the bellows can handle the pressure levels they are rated for without failure. It helps maintain the bellows’ mechanical strength even when they operate under different temperatures and varying loads.
The Benefits of Edge Welded Metal Bellows
High flexibility and stroke length
Edge welded metal bellows stand out due to their exceptional stroke length, reaching up to 90% of their free length. This feature significantly surpasses the 10-20% stroke capacity of formed or hydroformed bellows.
The design of edge welded bellows contributes to their superior flexibility and functionality. They perform reliably under different vacuum pressures.
Durability and long cycle life
Edge welded bellows all-metal construction enables them to withstand numerous cycles of expansion and contraction without losing integrity.
The construction method of edge welded bellows also contributes to their robustness. Welding at the edges not only strengthens the structure but also significantly increases their lifespan compared to other types of bellows. This extended service life is particularly beneficial in applications where frequent replacement is impractical.
Leak-tight performance
Edge welded bellows feature hermetically sealed joints that result from the precision of the edge welding process. Each diaphragm is welded together to form strong, durable joints. These joints play a vital role in preventing the bellows from failing under environmental stress or exposure to chemicals, thus preserving their integrity over time.
Wide material selection
Edge welded bellows are distinguished by their ability to be crafted from a variety of materials. This includes high-strength stainless steels, lightweight titanium, and durable nickel superalloys. Such a diverse range of materials allows for customization based on specific requirements of different applications.
For instance, if an application demands high resistance to heat, nickel superalloys are ideal due to their superior heat tolerance. On the other hand, titanium is preferred for applications where both light weight and corrosion resistance are critical. Stainless steel is universally valued for its robustness and strength, making it a reliable choice for general use.
Customization
Edge welded bellows can be highly customized to fit specific industry needs, ensuring optimal performance across various applications. These customizations can include alterations in size, shape, materials, and types of end fittings.
This customization process allows the bellows to integrate seamlessly into different systems, boosting both the efficiency and reliability of operations.
Design Considerations for Edge Welded Metal Bellows
Materials of construction
Materials such as stainless steel, Inconel, Hastelloy, and titanium are chosen for edge-welded bellows based on their unique characteristics. Each material excels in different operational conditions, influencing their selection.
Stainless steel is widely used due to its cost-effectiveness and reliable performance. It handles moderate temperatures and resists corrosion well, making it a common choice for various standard applications.
Inconel stands out for its remarkable strength and thermal tolerance. It remains stable under severe heat, making it ideal for applications involving high temperatures.
Hastelloy is highly valued for its exceptional resistance to corrosion. This makes it particularly useful in environments where chemical exposure is a concern, ensuring longevity and reliability.
Titanium, though more expensive, offers significant benefits in weight-sensitive applications. Its high strength-to-weight ratio is essential in fields like aerospace.
Diaphragm plate thickness
The thickness of the diaphragm plates in edge welded metal bellows determines the spring rate and how much load the bellows can handle. Thinner plates make the bellows more flexible and less prone to stress, which enhances their lifespan by reducing wear. Furthermore, the right thickness helps manage heat effectively during operation, maintaining the bellows’ overall health and function.
To elaborate, a thinner diaphragm plate results in a lower spring rate. This means the bellows can compress and expand more easily, which is beneficial for applications requiring high flexibility. However, this flexibility should not compromise the bellows’ ability to withstand necessary loads.
Additionally, the thickness influences heat dissipation. During operation, heat generation is inevitable, but excessive heat can damage the bellows. A properly chosen thickness allows for adequate heat transfer away from critical areas, ensuring the bellows operate efficiently under different temperatures.
Stroke length
These bellows can stretch up to 90% of their free length. This feature is a significant advantage, especially when compared to formed bellows. High stroke capability is crucial in applications that demand extreme flexibility and robustness.
Diaphragm plate shape
Refining the shape of the diaphragm plate enhances the performance of bellows. The main goal of optimizing the diaphragm plate’s shape is to find a perfect balance. This balance should maximize the bellows’ operational effectiveness while ensuring it remains structurally sound during the edge welding process.
Dimensions
The inner diameter (ID), outer diameter (OD), and overall length are key factors tailored to meet specific operational needs.
In the vacuum industry, for example, the space within devices is often limited. Here, bellows with a smaller ID and extended length are preferred. This design ensures that despite spatial constraints, the bellows can achieve the necessary movement or stroke.
For environments that face corrosive materials or extreme temperatures, choosing double ply bellows with the right ID and OD helps withstand such harsh conditions. The thickness and material quality of the bellows’ walls can prevent damage and ensure long-term reliability.
Furthermore, the number of convolutions in the bellows must be carefully selected based on the operational temperature, particularly during bakeout processes in manufacturing or maintenance. The correct number of convolutions allows the bellows to expand and contract effectively, directly influencing their functionality and lifespan.
Spring rate
The spring rate measures the amount of force required to compress or extend them. To adjust this rate, you can change the materials, the design of the bellows, and the number of convolutions.
First, the material’s properties significantly influence the spring rate. A material with a higher modulus of elasticity makes the bellows stiffer. This means more force is needed to change its shape.
Second, the bellows’ design, particularly its thickness and the shape of its convolutions, also affects the spring rate. Thicker bellows or those with a specific convolution profile tend to be stiffer, thus altering the force needed for compression or extension.
Lastly, more convolutions usually mean a lower spring rate, making the bellows easier to compress or extend.
Pressure and temperature
When creating metal bellows used in high-pressure scenarios, it’s essential to consider both the maximum pressure and temperature they will face. These factors determine the choice of materials, the thickness of the walls, and the bellows’ overall resilience.
Wall thickness must be enough to handle the stress from pressure yet thin enough to maintain the necessary flexibility.
The materials should not only resist the environmental conditions but also prevent the bellows from failing.
Applications of Edge Welded Metal Bellows
- Medical Field: In the medical field, they are crucial for devices like heart-assist pumps and artificial hearts, helping to accurately manage blood and medicinal flows. These bellows also ensure that electronic components remain sealed and protected from bodily fluids.
- Automotive Realm: In the automotive realm, these bellows are found in components such as EGR valves and turbocharger actuators. They play a key role in controlling emissions and enhancing engine efficiency. The precision of these bellows ensures that vehicles operate smoothly and efficiently.
- Measuring Devices: For measuring devices like pressure gauges and sensors, edge welded metal bellows are indispensable. They facilitate accurate readings in systems like hydraulic accumulators and flow control valves.
- Aerospace: The demanding conditions of atmospheric and space operations require components that can perform flawlessly under extreme conditions.
- Oil and Gas Industries: The oil and gas industries benefit from the durability of these bellows, which can withstand harsh environments.
What Is the Difference between Edge Welded and Formed Bellows
Manufacturing Process
Edge welded bellows are crafted through a meticulous process involving the stamping and welding of thin metal diaphragms. Each diaphragm is precisely cut into its desired shape before being welded at both the inner and outer diameters. This method ensures a high level of precision in the final dimensions and performance of the bellows, making it suitable for applications requiring exact specifications.
Formed bellows are produced by transforming thin-walled metal tubes using hydraulic or mechanical forces. This process molds the tube into a convoluted structure by expanding or contracting its diameters as needed. The advantage of this method is its ability to create bellows in continuous lengths and various shapes, providing flexibility in design and application.
Materials
Edge welded bellows are built from materials like stainless steel, titanium, Inconel, and Hastelloy. These substances are chosen for their exceptional durability, resistance to corrosion, and ability to withstand high temperatures. The process of edge welding, which involves joining these tough materials, demands that they not only endure intense heat but also maintain their structural integrity under severe operational conditions.
Formed bellows often use softer metals such as brass or bronze. These metals are highly flexible, a necessary property to withstand the mechanical stress during the bellows forming process. The ductility and elongation capacity of brass and bronze prevent them from cracking when molded, ensuring that the bellows maintain their form and function after they are shaped.
Cost
Edge welded bellows tend to be more budget-friendly for smaller quantities. This cost advantage comes from lower initial expenses related to tooling. Therefore, they are recommended if your production needs are not extensive.
Formed bellows prove more economical for large-scale production. The reason behind this cost efficiency is the automation involved in their manufacturing process, which significantly reduces the cost per unit. Thus, they are ideal for larger production needs.
Flexibility and Motion
Edge welded bellows are known for their thin diaphragms, which significantly enhance their flexibility and range of motion. They are particularly effective in providing a longer stroke length and excel in both axial compression and extension. These bellows are also better suited for managing angular and lateral shifts, making them preferable in dynamic settings where such movements are common.
Formed bellows feature thicker walls that increase their stiffness and decrease their flexibility. This makes them less capable of achieving the motion range that edge welded bellows can handle. This inherent stiffness restricts their utility in applications requiring high adaptability and extensive motion handling. Thus, for most dynamic applications, edge welded bellows offer a more effective solution.
Performance
Edge welded bellows have a distinct advantage over formed bellows, particularly in handling high-pressure situations, extreme temperatures, and harsh chemical environments.
Conclusion
In conclusion, edge welded metal bellows are highly valued for their exceptional flexibility and durability in demanding settings. Made from materials like stainless steel or titanium, they are particularly resistant to corrosion and extreme temperatures, making them a reliable choice for varied applications. Their precision in manufacturing sets them apart from other bellows types, ensuring superior performance where it counts.
Explore the possibilities with edge welded metal bellows for your next project. Contact us today to learn more about how these advanced components can enhance your operations.
