Choosing the right type of expansion joints can be difficult. There are so many different types, materials, and features associated with each that it can be nearly impossible to ascertain which is right for your application. Fabric and metal bellows and expansion joints are both common and come with a number of advantages and disadvantages. Here are just a few pros and cons to consider when deciding between fabric and metal expansion joints.
Fabric Expansion Joints
Fabric expansion joints are suitable for applications involving low temperatures. They don’t have any restraints regarding size, and they’re often chosen for their affordability. They’re also cheaper to design and fabricate and can usually be delivered quickly. Although they’re easy to prepare and can accommodate torsional movement, they can’t quite handle the range of temperatures like metal expansion joints can. They also require occasional replacement because they aren’t as durable.
Metal Expansion Joints
Metal expansion joints are known for being much more rugged than fabric or other materials. Unlike fabric expansion joints, they are typically maintenance free. They’re also entirely non-combustible, which means that they can handle even the most extreme temperatures, ranging from high heat to cryogenic. Due to their durability and longevity, it’s not surprising that they also have the ability to hold up during high pressures. Forged steel 150# flanges are rated for pressures up to 285 psig at 100 degrees Fahrenheit, according to ASME B-16.5 flange specifications. The allowable pressure is reduced to 65 psig at 850 degrees.
Metal expansion joints can also be used in a wide range of process conditions. These include liquid, air, steam, and cryogenic. Keep in mind, however, that gases and liquids definitely won’t leak with metal expansion joints, which is a major benefit and completely eliminates the need for this type of risk prevention.
Ultimately, a custom bellows design requires focus on 12 vital attributes: stress modes, flexing, pressure differential, rigid stops, spring rate, life cycles, temperature extremes, exposure, assembly method, vibration, end configuration, and geometric constraints. And while metal expansion joints are considered superior in most cases, understanding the features of fabric and metal expansion joints can help you determine which types are right for your application needs. For more information about standard bellows, stainless steel bellows, metal bellows, or exhaust bellows for engines, contact Triad Bellows.
