I never know what someone really wants when they ask for a philosophy. Explain how you plan to configure the system. Start with your scope of work from the contract. Determine if the client has a general DCS specification that defines the client expectations or requirements. Otherwise provide your own based upon your normal practice with other client systems. You can restate their requirements as part of your philosophy.
In the case of a revamp, indicate that the initial philosophy includes a functional replacement in-kind with some enhanced alarm and data historian features. This permits capturing whether the loops are PI, PID, cascade, ratio, direct/reverse, ranges, etc. as well as recording the tuning parameters as-found. Replace strip chart recorders with historical recording and trends, etc.
Describe pre-alarms for trips or other alarm management features. Clarify that the process P&ID graphic screens will be the primary operator interface with groups, details etc. Define the dull graphic colors for normal page backgrounds with the brighter colors for alarms, etc.
Advise any scan time issues such as PID at 0.25 seconds for flow, pressure or one second for temperature, etc.
Identify whether equipment is started from the control room or locally in the field. Identify the number of normal operators at the console.
Define shutdowns as fail-safe, de-energize to trip, etc.
Define I/O to be 4-20 mA, HART, Foundation Fieldbus, etc.
Define security such as the access permitted operators, technicians, supervisors, etc.
Explain what happens upon transmitter failure.
After you pull it all together, issue it for approval. Incorporate the comments as much as practical.
