How do you test and validate DCS system configuration changes before implementation?

I use a form (made by me) which include below things for DCS modifications: - Implement/Review/Approve by - Purpose, Justification - Change type: Logic or HMI or Other - Logic: Cause and Effect, PID Loop, Transmitter, Pump, Shutoff Valves etc. - HMI: Graphic Elements, New Screen, Existing Screen, Faceplates, Specify Workstation - Other: Charts, Alarms, Reports, Software updates And of course including impact on live plant. After modification, I update documents and drawings if any, train Operators and Technicians.

While testing multiple control panels of various functionality groups on different dates with different testing teams, testing strategy by understanding the process is so important. In DCS covering all functions like Boiler, Turbine, BOP etc., with same family of modules, Boiler trip emanated in Boiler Panels (tested OK during one schedule) shall be delivering redundant hardwired terminals from redundant DO Modules (in addition to soft form) to Turbine Protection panels. In next test schedule, Turbine Test team panels demonstrate the soft form Boiler trip only to trip the turbine. Hardwired terminals as DI in turbine panels for Boiler trip are absent. Engineering flaw identification by proper test plan & questioning for improvisation.

Well, DCS vendors have their own ways in simulating and testing their program before implementation. They based their program on client's Functional Design Specifications or FDS. C&E included. Client's representative enters the picture during FAT where the program is inspected and tested offline by simulating inputs, inspection of logic and monitoring the outputs. Any deviation from the client's FDS should be corrected during that stage with proper documentation. An extensive and successful FAT will reduce the margin of error during commissioning stage.

While conducting a FAT, the integrator or OEM usually provides its standard test list which is pretty generic and covers the standard features. Application specific testing should be developed by the end user in addition to the standard testing is extremely important to capture all the modifications which are tailored to the customer/enduser requirements

Well, the best way is to use Virtual System (Emerson DeltaV offers) which works in parallel to physical/production system. It helps testing, identifying any loophole, validating logic and also alerts Plant Trip, if any, in case of downloading modified logic for Safety Instrumented System.