| When taking a shell-and-tube heat exchanger with a removable tube bundle such as a bayonet-tube type heavy fuel oil service heater out of service, to avoid thermal shock what statement represents the correct operating procedure? |
| A) Secure both the steam and heavy fuel oil simultaneously and immediately to avoid thermal shock. |
| B) Secure the heavy fuel oil first, then gradually secure the steam to avoid thermal shock. |
| C) Secure the steam and heavy fuel oil simultaneously and gradually to avoid thermal shock. |
| D) Gradually secure the steam first, then secure the heavy fuel oil to avoid thermal shock. |
