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