EN 14917 Standard: Metallic Bellows Expansion Joints (PED 2014/68/EU)
Pressure Equipment Directive Compliant Bellows Engineering & Live Modeling
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Standard Overview & Regulatory Scope
EN 14917 is the official harmonized European standard specifying design rules, calculations, and qualification testing for metallic expansion joints under the Pressure Equipment Directive (PED 2014/68/EU).
High-Order Polynomial Coefficients (Cp, Cf, Cd)
EN 14917 Annex G defines rigorous 5th-order polynomials to calculate flexibility and stress factors based on geometric non-dimensional ratios C1 and C2.
C1 = q / (2 · w) , C2 = q / [ 2.2 · √(Dm · ep) ] Cp, Cf, Cd = ∑ (aij · C1^i · C2^j) [Annex G 5th-order polynomial factors] ΔqEN = Δqx + cσ · (Δqy + Δqθ) [EN 14917 corrected equivalent displacement] St = 0.7 · (S3 + S4) + S5 + S6 [Total equivalent stress range] Austenitic steel: N = [ 8900 / ((E0/ET)·St − 280) ]^3.6 [(E0/ET)·St > 471 MPa] Ferritic steel: 2εages = P/EB · f1 · 100% [Total strain range with plasticity factor f2]
Corrected Equivalent Movement (dqEN) & cσ Factor
When combining axial, lateral, and angular motions, EN 14917 introduces the cσ stress concentration multiplier to capture peak meridian bending stresses accurately:
Austenitic & Ferritic Steel Fatigue Formulations
The standard specifies dedicated cycle curves for austenitic grades (1.4541, 1.4404) and ferritic steels with an integrated plasticity correction factor f2.
Engineering Standards Comparison Matrix
Key formulation, applicability envelope, and criterion differences between EJMA 10th Edition, EN 14917:2009+A1:2012, and ASME VIII Div. 1 Mand. App. 26:
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