Shell and Tube Heat Exchanger Start-up and Shutdown Procedures
Shell and tube heat exchangers are designed to eliminate problems from differential thermal expansion of the shell and the tubes. When the temperature difference between the hot fluid and the cold fluid is large, a removable bundle or a floating head is used to avoid damage from the different thermal expansion rates of the tubes and the shell.
For extreme temperature differentials, the metal temperatures should be analyzed carefully. Mechanical stress calculations should be performed to determine the consequences of any thermal shock on the heat exchanger.
In some cases, differential thermal expansion can be a problem at start-up or shutdown. Many shell and tube heat exchangers have suffered damage during start-up and shutdown because the fluids were not introduced or removed in the proper sequence.
The table below offers suggestions on the order in which the hot and cold fluids should be introduced at start-up or removed at shutdown for different applications.
Exchanger Type | Fluid Location | Start-up Procedure | Shut-down Procedure | |
Shell Side | Tube Side | |||
| Fixed Tubesheets | Liquid - HOT | Liquid - COLD | Start both fluids gradually at the same time | Shut down both fluids gradually at the same time |
| Condensing gas - HOT | Liquid or Gas - COLD | Start hot fluid first, then slowly start the cold fluid. Avoid temperature shock | Shut down cold fluid first, then hot fluid | |
| Gas - HOT | Liquid - COLD | Start hot fluid first, then cold fluid | Shut down cold fluid gradually, then hot fluid | |
| Liquid - COLD | Liquid - HOT | Start both fluids gradually at the same time | Shut down both fluids gradually at the same time | |
| Liquid - COLD | Gas - HOT | Start cold fluid first, then hot fluid | Shut down hot fluid first, then cold fluid | |
| Removable Bundle u-tubes floating head | Liquid - HOT | Liquid - COLD | Start hot fluid first, then cold fluid gradually | Shut down hot fluid first, then cold fluid |
| Condensing gas - HOT | Liquid or Gas - COLD | Start hot fluid first, then cold fluid gradually | Shut down hot fluid first, then cold fluid gradually | |
| Gas - HOT | Liquid - COLD | Start hot fluid first, then cold fluid gradually | Shut down hot fluid first, then cold fluid | |
| Liquid - COLD | Liquid - HOT | Start cold fluid first, then hot fluid gradually | Shut down hot fluid first, then cold fluid | |
| Liquid - COLD | Gas - HOT | Start cold fluid first, then hot fluid gradually | Shut down hot fluid first, then cold fluid | |