In a shell and tube exchanger the pressure parts are rarely what limits the design. What limits it is the tubesheet, and behind the tubesheet the differential expansion between a hot bundle and a cold shell that were welded together at ambient temperature.
Techso carries out the mechanical design of shell and tube exchangers to ASME VIII Division 1 and EN 13445, with construction to TEMA and API 660, and verifies the cases that fall outside the standard calculation methods.
Configuration
The TEMA designation is a decision about maintenance and thermal behaviour before it is a decision about geometry: whether the bundle can be pulled, whether the shell side can be cleaned mechanically, whether differential expansion is absorbed by the tubes, by a bellows, or by letting one end float.
- Fixed tubesheet: simplest and cheapest, expansion taken by the shell or a bellows
- U-tube: expansion free, bundle removable, tube side not mechanically cleanable
- Floating head: bundle removable and expansion free, at higher cost
- Shell type selection and its effect on the mechanical design
Tubesheet design
- Tubesheet calculation for fixed, U-tube and floating head configurations
- Differential thermal expansion between shell and tubes
- Expansion joint design and verification where the shell cannot absorb it
- Ligament efficiency and perforated plate treatment
- Load cases: each side alone, both together, with and without thermal expansion
Tube-to-tubesheet joint and bundle
- Expanded, seal welded or strength welded joints, and when each is appropriate
- Joint qualification and the testing it requires
- Baffle spacing and unsupported tube span
- Flow-induced vibration screening of the bundle
What you receive
- Mechanical calculation report for all governing load cases
- Setting plan and fabrication drawings
- Nozzle load evaluation against the connected piping
- Verification of an existing exchanger against new operating conditions