Tie-ins are connection of piping inside a plant to outside world e.g. to utility supply company piping, or also to existing plant. Proper MTO for such tie ins must be ensured. Here is a typical checklist for taking out proper MTO for such tie ins.
| Sr | Check Item | Done |
| 1 | Tie-in materials are considered and separated from new line MTO. Additional temporary materials like blind flange, gasket, bolt, etc. are considered as applicable. | |
| 2 | Flange rating or pipe schedule matching with existing/project interface/ vendor supply items is verified. If site survey data is available, flange dimensional standard to be correctly captured (e.g. B16.47/MSS-SP-44). | |
| 3 | Material required for early tie-in is considered in MTO, if applicable. | |
| 4 | Material required for Hot tapping is considered in MTO, if it is not in vendor scope. |