Different requirements apply to expansion joints for pressure vessels and Shell and Tube Heat Exchangers than for pipings. These usually have to be designed for higher pressures and the axial movements are not as pronounced as with piping. Although they must be designed for a defined axial expansion, they can be designed to be stiffer overall.
Expansion joints in Shell and Tube Heat Exchangers
Heat exchangers are critical equipment in many industrial heating and cooling processes. Due to the system-related temperature difference between the outer shell pipe and the slim inner tubes, different changes in length occur which can lead to large material stresses, especially with fixed tube heat exchangers. An expansion joint is inserted in the shell pipe for this purpose.
In shell and tube heat exchangers are two main types of expansion joints used: bellows and flanged & flued.
- Bellows type expansion joints have a flexible, accordion-like geometry that permits expansion differential between the tubes and shell. Benefits over Flanged & Flued is their flexibility in design to accommodate greater movement. Downsides is their thin-wall construction is less robust and at risk of physical damage and the pressure load is lower.
- Flanged & Flued expansion joints typically utilised two formed shapes that form a single large corrugation and are constructed of the same material and thickness as the shell cylinder. Flanged and Flued Expansion Joints typically have higher stiffness and absorb less axial deflection compared to lens type Thick Walled Expansion Joints. They are tough and reliable and also suitable for higher pressures. They are quite strong and less likely to fail than bellows expansion joints.
Table: Overview of Codes, Standards and other Specification for Expansion Joints
| EN 13445 serie | EN 14917 | Germany AD 2000 B13 | ASME BPVC Section VIII Div. 1 App. 26 | ASME BPVC Section VIII Div. 1 App. 5 | EJMA Rules | |
|---|---|---|---|---|---|---|
| Application | Pressure Vessel | Pressure Vessel and Piping | Pressure Vessel and Piping | Pressure Vessel and Heat Exchanger | Heat Exchanger | General applications |
| General Notes | CE Marking and EU-Declaration of Conformity by pressure vessel assembly manufacturer | EU harmonised product standard; CE Marking and EU-Declaration of Conformity | Specification for single-ply design Bellows Expansion Joints | ASME Code U Certificate (Form 26-1) by Pressure Vessel Manufacturer or Part Manufacturer required; | ASME Code U Certificate (UG-120) by Pressure Vessel Manufacturer or Part Manufacturer required; | This rules are referred in any Piping Codes |
| Scope & Limits | PS > 0,5 bar; Bellows Expansion Joints intended to installed on pressure vessels, especially tube-sheet heat exchanger (assembly manufacturer) | Bellows Expansion Joints for pressurised applications; | Single ply Bellows Expansion Joints for Pressure vessel and industrial piping | MAWP > 15 psi = 1 bar; Bellows Expansion Joints; | MAWP > 15 psi = 1 bar; Flexible Shell Element Expansion Joints; | Metallic Bellows Expansion Joints for generally applications |
| PED harmonised standard | Yes | Yes | No | No | No | No |
| Pressure thrust loading incl. combined other movements | Yes | Yes | Yes | Table 26-1 | Yes | Yes |
| Angular rotation (rotating movement) | EN 13445-3/ Clause 14.10 | Yes | Yes | Table 26-1 | Yes | Yes |
| Axial movement | EN 13445-3/ Clause 14.10 | required anchor and additional guides | Yes | Table 26-1 | Yes | Yes |
| Lateral deflection | EN 13445-3/ Clause 14.10 | Yes | Yes | Table 26-1 | Yes | Yes |
| Universal | No | required anchor and additional guides | No | Table 26-1 | No | Yes |
| Single-ply | Yes | Yes | Yes | Yes | Yes | Yes |
| Multiple-ply | Yes | Yes | No | Yes | No | Yes, max 5 |
| Calculation of the allowable number of cycles | Yes | Yes | Yes | Yes | App. 5-1 (d): Not required, only specified by Pressure vessel manufacturer | Yes |
| Stresses and Instability due to internal pressure | Yes | Yes | Yes | Yes | Yes | Yes |
| Fatigue evaluation | Yes | Yes | Yes | Yes | Yes | |
| External pressure design | EN 13445-3/ Clause 14.7.5 | Yes | Yes | Yes | No | Yes |
| Design general | EN 13445-3/ Clause 14 | Yes | Yes | para. UHX-1: If max. Design Temperatures higher than Table 26-1.2: Design requirements for bellow expansion joints in Section VIII, Div. 2, Part 4.19 | App. 5-3; UHX-1: If max. Design Temperatures higher than Table 26-1.2: Design requirements Section VIII, Div. 2, Part 4.20 | Yes |
| Unreinforced U-shaped bellows | EN 13445-3/ Clause 14.5 | Section 6.2.3 | Yes | Table 26-1 | No | Yes |
| U-shaped reinforced bellows | EN 13445-3/ Clause 14.6 | Section 6.2.4 | No | Table 26-1 | No | Yes |
| Toroidal bellows | EN 13445-3/ Clause 14.7 | Section 6.2.5 | No | Table 26-1 | No | Yes |
| Fabrication | EN 13445-3/ Clause 14.8 EN 13445-4 | Section 7 | No | App. 26-10 | App. 5-4 | Yes |
| Inspection and testing | EN 13445-3/ Clause 14.9 EN 13445-5 | Section 8 | No | App. 26-11 | App. 5-5 | Yes |
| Marking | Assmembly marking by name plate incl. CE Marking; No additional requirements | Separate marking by name plate | Code requirements | App. 26-13 ASME U2 Stamp incl. Partial Data Report | App. 5-6 | No |
| Operating/installation instruction | Required EN 13445-5 | Section 8.7.3 | No | Pressure Vessel Code requirements | Pressure Vessel Code requirements | Yes |
| Installation and shipment | EN 13445-3/ Clause 14.4.6 | Section 10.3 Annex C | No | No | No | Yes |
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Metal Bellows Expansion Joints for pressurised piping systems: Applicable Codes and Standards
