What are bellows?

What are bellows?

“Bellows” is translated as fuigo or jabara in Japanese.
 “Fuigo” can be a tool that was used to blow air into kilns by blacksmiths long long ago.
 While “Jabara” has various meanings, the body of an accordion may come into your head.
 In vacuum field, cylindrical objects made of metals and pleated to have expansion/contraction properties, airtightness, and spring properties are generally called “bellows.”
 In other words, “bellows” = “expansive pipes.”


Bellows are not only used for semiconductor, liquid crystal, and vacuum equipment but they are also used as airtight sealing members for gases and fluids across wide range of field, such as accelerators, nuclear fusion, nuclear power, petrochemicals, railways, medicine, and construction.
 In particular, a large number of bellows have been adopted as sealing materials for transfer sections where a vacuum is shielded from the atmosphere as well as sealing materials for “complete leak prevention” of vacuum valves and general industrial valves.
 Year after year, requirements for special materials and advanced specifications, such as the cleanliness of a bellows surface, upsizing, and long lifetime, are increasing.

Types of bellows

There are several types of bellows depending on differences in manufacturing methods, and IRIE KOKEN handles the following three types.

Formed bellows Welded bellows Flexible tubes
Formed bellows Welded bellows Flexible tubes

*The method of manufacturing flexible tubes is nearly the same as formed bellows.
Since these bellows can be flexibly bent, they are mainly used for connecting the piping of equipment, and flexible tubes are best for long lengths.
Since their applications are limited, these bellows are omitted from the following explanation.

Manufacturing methods and features

  Formed bellows Welded bellows
Manufacturing method Bellows forms under pressure on the inside of metal pipes. Bellows welds the inner and outer edges of precise thin wave-shaped washer.
Formed bellows manufacturing process Welded bellows manufacturing process
  1. Although the face-to-face dimension is large, these bellows are best for applications with small amounts of expansion/contraction, having no contacted portions.
  2. The thread height can be changed freely because they are manufactured by forming work.
  3. Because of a few maufacturing prcesses, mass-production become possible.
  4. Compared with welded bellows, manufacturing costs are low.
  5. Because of the forming work, they can only be manufactured of materials with a relatively large percentage of elongation.
  1. Compact and superior expansion/contraction, and long lifetime designs are available.
  2. The expansion/contraction properties and spring characteristics can be set by changing the inner/outer diameter dimensions and plate thickness.
  3. These bellows are highly pressure-resistant.
  4. Compared with formed bellows, manufacturing costs are high.
AM350 equivalent

Representative features of bellows materials

  Corrosion resistance Heat resistance Lifetime characteristics Magnetism Price
(500°C or less)
Non-magnetic Low
AM350 equivalent
(welded bellows only)
(450°C or less)
Magnetic Higher than SUS
Hastelloy®C-22 Non-magnetic High

*1: The materials listed above are materials we commonly handle. For materials other than the above, feel free to ask us.
*2: Based on our comparisons when the same materials are used.
*Hastelloy®C-22 is a registered trademark of Haynes International, Inc.


Products guidance

Metal bellows Metal bellows
Welded bellows
Formed bellows
Flexible tubes
Vacuum valves Vacuum valves
Rectangular type gate valves
Round type gate valves
Large-size rectangular type
gate valves
L-shape valves
(Angle valves)
Vacuum piping Vacuum piping parts
Flanged pipes
Pipe parts
Flexible tubes
L-shape valves
(Angle valves)
Vacuum chamber Vacuum chamber
Feedthroughs Feedthroughs
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Rotary feedthroughs
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Semiconductor field
Bellows , Valves, Piping, Chamber
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Bellows, Valves, Piping
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Bellows, Valves, Piping
Railways and other
Conservators, Load sensing valves,
I-shape flexible tubes
Accelerator and nuclear fusion field
Feedthroughs, Chambers