Understanding Bellows From Standard To Custom To Multi-Ply

Think of metal bellows as joints. Acting as connectors — like exhaust flex joints in the exhaust industry — metal bellows need to be both flexible and strong. Essentially, metal bellows are vessels, and they can be compressed under applied outer pressure or vacuum pressure. Once that pressure is released, bellows will return to their original shapes, as long as they are not pushed past their yield points. Below, we’ll look into some of the different types of bellows. With about 178,400 people working in the oil and gas extraction industry in the United States, creating and using metal bellows provides a number of jobs, This makes understanding these devices increasingly important.

What Are The Different Types Of Bellows?

When it comes to standard bellows, three main types are currently available. These include formed, welded, and electroformed standard bellows. In essence, these types refer back to the manufacturing methods used to craft them. Formed bellows are created through reworking tubes, normally produced by deep drawing. The deep drawing processes include cold forming, or rolling, and hydroforming. Sometimes, formed bellows are called convoluted bellows or slyphons.

Another common type of bellow is the welded bellow. In the process of making welded bellows, a number of different diaphragms are welded together. Usually, a formed bellow will have a higher tooling cost than a welded bellow, but a lower piece cost when they’re mass-produced. The relative stiffness and thick walls of formed bellows can actually have a lower performance rate than welded bellows, which means that many decided to work with welded bellows instead. The difference in performance can often justify the higher cost.

Finally, the third type of standard bellow is the electroformed bellow. In this case, a metal layer is plated, or electroformed, onto a model, or mandrel. Afterwards, the mandrel is removed. With thin walls and relatively low tooling costs, these bellows can have both high sensitivity and precision.

Can Bellows Be Customized?

While standard bellows do exist, bellows can also be shaped and altered. These bellows are customized, and can vary wildly depending on their purpose. Usually, creating custom bellows requires focusing on 12 specific attributes. These include stress modes, flexing, pressure differentials, rigid stops, spring rates, life cycles, temperature extremes, exposure, assembly methods, vibrations, end configuration, and geometric constraints. Custom bellows can be more difficult to create due to the fact that they’re not made with a specific model in mind; however, in some cases they may be better for their specific task than standard bellows.

What Is The Difference Between Single-Ply And Multi-Ply Bellows?

Finally, let’s take a look at multi-ply bellows. The term “ply” refers to the sheets of metal used to form bellows. Usually, the number ply depends on the application of the bellows themselves. A single-ply bellow will have one tube, while multi-ply bellows have at least two tubes, though they can have up to 5 tubes. Single-ply bellows will be thicker than multi-ply bellows, and multi-ply bellows have lower axial spring rates than single-ply bellows. Compared to single-ply bellows, multi-ply bellows have more flexibility, and often longer fatigue lives. This ensures that they will last longer.

Ultimately, the type of bellow used depends on the bellows’ purposes. Think about the application of the bellow before choosing the type to use — keep in mind that different bellows may have dramatically different results depending on how they are used!

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