The SOR
The SOR should be written when an OTS is needed. It should be given to the OTS supplier with clear statements that will help the supplier to come up with a clear technical offer and price for the OTS.
The SOR should define the scope of the OTS. The best way is to add the Piping and Instrumentation Diagrams (P&IDs) to the SOR so the OTS' scope is clear.
The SOR should include the scope of the control systems and the minimum hardware performance needed. The contractor should clearly state the KPIs that will make the project a success. This will help the supplier to come up with a solution that is fit for purpose.
What should be in the SOR, then? Please refer to Chapter 6, OTS Sample Documentation, to see an example of an SOR.