EJMA Bellows Calculator

Check a metal bellows expansion joint design against the EJMA Standards: pressure stresses, fatigue life and squirm for unreinforced, reinforced and toroidal bellows. Our engineering team reviews every calculation.

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Calculation mode

Check my design You enter the convolution geometry; we check it against EJMA Design it for me You enter the service conditions; we find a bellows from our tooling

1 Expansion joint assembly

Assembly *

One bellows taking axial, lateral and angular movement

2 Bellows type

UnreinforcedU-shaped convolutions without rings ReinforcedU-shaped convolutions with reinforcing rings ToroidalRound convolutions with reinforcing members

3 Design conditions

Movements are the totals imposed at the ends of the expansion joint. Leave a movement empty if it does not apply.

Design pressure *

bar(g)

Internal pressure, gauge

Design temperature *

°C

Required cycle life *

Number of movement cycles

Axial compression x

Total for the joint

Axial extension x

Total for the joint

Lateral offset y

Angular rotation θ

deg

4 Geometry

Enter the bellows inside diameter. We choose the convolutions from our forming tooling.

U-shaped convolutions: pitch q, height w, mean radius rm, tangent length Lt.

Toroidal convolutions: radius r, pitch q, reinforcing members of area Ar on diameter Dr.

Bellows inside diameter Db *

Convolution height w *

Convolution pitch q *

Ply thickness t *

Nominal, one ply

Number of plies n *

Number of convolutions N *

Tangent length Lt *

Mean radius of convolution rm *

Crest and root

Mean radius of convolution r *

Mean diameter of convolutions Dm *

Reinforcing member mean diameter Dr *

Reinforcing member area Ar *

mm²

Cross-section of one member

End length Ld

Collar thickness tc

Leave empty if no collar

Collar length Lc

Required with a collar

Collar area Atc

mm²

Collar section modulus Zc

mm³

Number of collar gussets ng

5 Materials & fabrication

Bellows material *

Collar material

Required when a collar is given

Reinforcement material *

Bellows condition *

Forming method *

Weld efficiency Cwb (bellows)

Longitudinal seam, default 1.0

Weld efficiency Cwc (collar)

Default 1.0

Weld efficiency Cwr (reinforcement)

Default 1.0

Working spring rate fw

N/mm

Per convolution; optional

Advanced: material property overrides

Optional. Leave empty to use our material data. Use only certified values; overrides are flagged in the engineering report.

Allowable stress Sab

MPa

Bellows, at design temperature

Elastic modulus at room temperature

GPa

Bellows material

Elastic modulus at design temperature

GPa

Bellows material

Yield strength Sy

MPa

Overrides the derived value

Yield strength from test report

MPa

Room temperature, certified

6 Contact details

We send the detailed results to our engineering team, who will follow up with you.

Full name *

Company *

Email *

Phone *

Notes

Preliminary check for quotation purposes, confirmed by PT Misuba Guna Indonesia engineering. Not a substitute for a certified design.