| When you think of the word "bellows" you | | | | |
| probably have a picture in your mind of the | | | | These processes are mechanical forming, and |
| leather bellow historically used to blow air | | | | hydroforming. Formed bellows are generally |
| into their fireplace. However, there is | | | | more expensive for a custom bellows than if |
| another kind of bellow, a metal bellows, | | | | it were welded. The higher cost is due to the |
| which is a high-technology product used in | | | | tooling required to produce the original |
| machinery, medical and industrial | | | | form. However, once the original form has |
| applications. Metal bellows are manufactured | | | | been created then the subsequent bellow can |
| and sold by companies specializing in metal | | | | be produced at a lower cost than individually |
| expansion joints and other piping systems. | | | | welded bellow. |
| Some bellows are microscopically small while | | | | |
| others are very large. | | | | Formed bellow must be made of metals which |
| | | | have high elongation characteristics. For |
| Simply stated, metal bellows are thin-walled | | | | this reason, most formed bellow are made of |
| flexible elements which allow for expansion | | | | brass. Formed bellows generally are used in |
| in a system of pipes, while at the same time | | | | applications where a lower performance is |
| containing gasses and liquids in a | | | | acceptable. Formed metal bellows are also |
| pressure-filled environment. A metal bellow | | | | generally larger than those which are |
| is also commonly referred to by the names: | | | | individually welded. |
| flexible metal element, element, | | | | |
| corrugations, and compensator. | | | | Welded Bellows - A welded metal bellows is |
| | | | manufactured by welding individual formed |
| Each metal bellow is made by taking into | | | | diaphragms to each other. A welded bellows |
| account its pitch, convolution height, | | | | can be fabricated in many shapes and sizes |
| thickness, number of plies, convoluted | | | | and is generally a higher performance option |
| length, skirt length, and inside diameter. | | | | than a formed bellows. |
| Every metal bellows has a unique working | | | | |
| pressure, life cycle, and spring rate which | | | | Welded bellow can be made of any metal or |
| are entirely dependent on their shape and the | | | | alloy which can be welded. Generally, |
| material in which they are made of. These | | | | materials such as stainless steel, titanium, |
| considerations, and some specific | | | | and other non-corrosive materials are used to |
| mathematical formulas, insure that a metal | | | | fabricate welded bellows. |
| bellow meets the standards set by the | | | | |
| Expansion Joint Manufacturers Association. | | | | Formed metal bellow generally are used in |
| The EJMA specifications exist to make sure | | | | larger applications such as HVAC, and large |
| that a metal bellow is able to perform under | | | | piping systems. Welded bellows are generally |
| the specifications it claims to. This is for | | | | very small and have to be manufactured in |
| both productivity and safety. | | | | laboratories using high levels of |
| | | | magnification. Welded bellows are generally |
| There are generally two different types of | | | | used in medical and aerospace applications. |
| metal bellow available on the market today. | | | | |
| These two types of bellows are formed and | | | | As you can see there are many metal bellows |
| welded. Let's look a bit at each of them: | | | | available to fit many needs. Bellows are |
| | | | available from companies who fabricate metal |
| Formed Bellows - A formed metal bellows is | | | | expansion joints. |
| manufactured by one of two processes. | | | | |