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