Automation & Controls:
- After an auto-migration ensure all the OBs, FCs, FBs are the same as the original program. Attention to some of the functions that may have been migrated automatically to another version. For example the PID CONT_C in the migrated software may be migrated to a Technology Object rather than a FC. The DB numbers, tags, HMI connections may be changed.
- Remove all the obsolete or unused IO from the code.
- Improve the industrial network in the new project if possible, e.g., by adding a redundant PROFINET network.
- Check the analogue signals NORM_X and SCALE_X are appropriate normalized and scaled in the new hardware.
- Test as much as possible in the workshop and FAT, everything from IO, networking (PROFINET and PROFIBUS, DP-DP Couplers, PN-PN Couplers), simulation, HMI trends, alarms.
- Check the PID settings, scan time, parameters. Monitor the process and be flexible to adjust the PID settings accordingly.
- Retain, save set-point values in the new PLC and make a first scan routine to initialize them.
- Edit the Starting values of the Set-points or parameters.
- Check for filters in the software, e.g., moving averages used to analog input values. Add filter if required, as the new hardware will run and process data much faster than the older.
- Do a Watch Table with all the IO. Attention to the reverted IO like fail-open valves and fail-open control valves.
- In case the program has been re-written, do a cross reference in all IO making sure they are all being used and were not forgotten during the new implementation.
- Ensure the PID is properly operating. A good starting point for the tuning parameters are displayed below:
tscan-rate = 0.1 x td
Td = 0.5 x td
Ti = 2-4 x td
Electrical:
- Review existing power supplies and improve or do a new one if necessary. If there are more than one power supply, ensure there is no difference in their voltages and references, if not possible to merge them into one.
- Ensure compatibility between existing and new IO termination.
- Ensure existing drawings are available.
- Ensure output cards meet the current requirements, e.g., relay output cards.
- Ensure power supplies and racks are earthed.
- Ensure shield bar on analog cables, e.g., analog input, telefast, RTD, analog output is present.
- If system is connected to more than one SCADA, ensure the communication to all SCADA systems are healthy.
- Evaluate if hardwired communication between PLCs through multi-core cable and relays is simpler than networked.
- Check polarity of analog output signals.
- Use 500ohm resistor to convert between 4-20mA and 0-10V during tests with a current source meter.
- Ensure there is no additional power supply incorrectly introduced to existing instrumentation and incorrectly supplying the field wiring.
- Note any resistors (e.g., 500ohm resistors used for 4-20mA conversion to 0-10VDC) used for current/voltage conversion that are present either in the terminals or in the IO cards themselves. Ensure they are not wrongly removed during the change-over. Note that they may be located in the IO terminals or in the terminal blocks used to connect the field wiring to the panel wiring.
- Use a network tester to validate that all the ethernet connections and cables are healthy. They should blink all the 8 cores plus the Ground, in the correct order (i.e., 1 to 8 plus G).
- Set the electronic fuses to the correct current rate, e.g., 0.5A for 16-channel digital inputs and 2A for digital outputs. Leaving them at higher than required, such as the 6A default in the new electronic fuses, will be an issue as it won't trip as expected.
Process:
- Talk to operators and process engineers that work on site with this equipment to better understand how it works. Have a deep understanding how the process works and what are the key points to get it correct.
- Take the opportunity to improve some simple existing issues, e.g. too small alarm page, trend issues.
- Take a photo of all the HMI screens and faceplates before migration.
- Attention to run-away processes, e.g., exothermic chemical process, oxidisation, pH, etc.
Project:
- Take a phased approach to reduce risks.
- Identify the risks and create alternative plans.
- Take detailed photos from all the electrical cabinets, including the settings of all the rotary switches.
No comments:
Post a Comment