Inquiry about Welded Bellows | MIRAPRO Co., Ltd.

Inquiry Sheet Required Items

形状

Bellows ID	Inside Diameter of Bellows（The figure below）
Bellows OD	Outside Diameter of Bellows（The figure below）
Flange Thickness	Total thickness for Flange with bellows welding lip (3mm) （The figure below）
Face-to-Face	Dimension Between edge faces

Specified Condition of ID /OD
We may ask for change bellows size due to our cycle life assurance. Please specify the condition of ID and OD of bellows.
Ex. Shaft is installed inside the bellows. (Because shaft OD is 20mm, bellows ID should be 22mm.）
Ex. Installed housing outside of the bellows. (Bellows OD should be 45mm due to avoid interference.)

Material and Environmental Condition

If using corrosive gas inside or outside the weld bellows, please choose to use corrosion resistant material

Pressure condition

Inside of Bellows Outside of Bellows	Please select either Vacuum/Atmospheric Pressure/Pressurization/Fluctuating Pressure.

Notes for Pressurization
If you select Pressurization please specify gauge pressure

Notes for Fluctuating Pressure
If pressure condition is not constant (e.g. repeating vacuum and atmospheric pressure), please send the pressure fluctuation pattern. Our engineer designs the bellows with expected maximum load.

Operating condition

As for type of displacement, please see the description below. If there is displacement caused by a equipment operation etc., please specify.

Displacement（Axial displacement）
Axial displacement refers to the length difference before and after deforming the bellows in axial direction by external mechanical load.

Displacement（Perpendicular displacement）
Both end surfaces of bellows is made parallel. Perpendicular displacement refers to the length difference keeping the end surfaces parallel.

Displacement（Angle displacement）
Angle displacement refers to the angle difference of axis before and after being applied some load. In this case, the bellows could deform in axial and perpendicular direction so the combination of axial and perpendicular displacement must be considered.

Temperature condition

Please specify operating temperature (normal/max).
We will select the material and consider the stress load in the high temperature environment.

Required Cycle Life

Please specify the required cycle life that you need us to assure (number of cycles).
Mirapro designs with considering metal fatigue based on the number of repeated cycles. If thereare multiple operating patterns, the cumulative damage evaluation will be performed in considering of the combinations. So if operating range or pressure condition etc. differ between normal operation and maintenance, please inform us the details.

Spring Constant

Since welded bellows has a spring element, it generates some counterforce. Generally, Mirapro offers spring constant as a result of designs that meet bellows cycle life requirement and ask our customer to reflect it in the equipment design. However, please inform us if the spring constant is one of design constrains.

Installed Direction

Please specify installed direction (vertical, horizontal or others)
When installing horizontally, please make sure to specify it because it is necessary to consider the self-weight deflection.

Note for the other specifications

Operating Speed	When the operation speed is fast, the amount of local expansion and contraction of the bellows increases due to the inertial force compared to when the operation is slow, and the cycle life is relatively reduced. Please inform us the operating speed in case of using for valve etc., or operating with high-speed to improve the takt time.
Shaft	If more precise evaluation is required, we may ask for more information on the bellows operating pattern. Please specify diameter and placement information if a shaft is installed inside the bellows. The bellows may buckle depending on the size and length of the bellows, so we may offer using a shaft (inside/outside) or pantograph structure in order to secure enough lifetime cycle life.

Information for inquiring

Relationship between Bellows Length and Cycle Life

Not only for bellows, any parts that has repeated operations require to consider metal fatigue. Metal fatigue is a phenomenon in which a metal material ruptures due to repeated deformation even though it is not a large deformation that immediately breaks. Welded bellows are manufactured by alternately welding inside and outside ring-shaped thin plates called “diaphragm When bellows operates (expands and contracts), some stress corresponding to the deformation is generated It must be prevented from destruction by metal fatigue even though lots of stress are generated by a million cycle as example.
Mirapro optimizes wave profile/thickness/size (inside diameter/outside diameter) of diaphragm based on the conditions provided from customer to avoid the risk of destruction by metal fatigue.
In order to reduce stress, reduction of displacement amount per bellows convolution and improvement of cross-section strength etc. are needed, so we increase the number of convolutions and change the thickness of bellows diaphragm. We may offer a length that could meet required cycle life through meetings with customer.

Bellows Buckling

Long and thin parts, such as bellows and rod, may deform towards lateral direction without being deformed axially when a compressive force is applied in the axial direction. This phenomenon is called “Buckling”.
When a bellows buckles, the extremely decreases. Therefore, if a shaft is installed inside the bellows, we may offer adding an intermediate ring guided by the shaft. Also, if a shaft cannot be installed inside the bellows, we may offer adding guide mechanism outside the bellows.
Bellows is mounted vertically in the right side picture, however, if a bellows is installed horizontally, the bellows gets easier to buckle due to its own weight, so we need the designation about installed direction.
When bellows is short no concern, but if the bellows becomes long, the deformation of the bellows will be delayed with respect to the behavior of the flange and it will not be uniform, resulting in uneven expansion and contraction in the axial direction of the bellows. In this case, we may propose a pantograph structure.

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Bellows Material

The factors that determine the material for bellows are durability (life), corrosion resistance and heat resistance. The materials used for welded bellows and its characteristics are as shown below. AM350 is supplied to the market as spring steel, having a high strength. Since it has magnetic property and its corrosion resistance is little lower, its application is limited. However, when long cycle life is required, in many cases where AM350 is selected.


	Corrosion resistance	Heat resistance	Cycle Life	Magnetic Property
SUS316L	Normal	Can be used	Normal	Normal
AM350	Relatively low	Can be used	Good	Yes
HASTELLOY C-22	Good	Good	Normal	No

※As for the other materials, please contact us for the details.