- Now that AOC's plan to abolish oil&gasis foiled, it is time for future planning.
- APC implementation is a slow and steady evolution.
- Operator acceptance is required to reap the benefits of APC.
- Long term maintenance is the key to sustainability of APC as a technology.
- In-house APC team should start implementing simple non-commercial algorithms using Windows 10. For example, Heater Pass Balance, automatic PID tuning etc.
- Operators are never going to be removed from control room because of APC. That confidence building is necessary.
- Good Chemical engineers must be hired for APC.
Automatic PID Tuning guideline.
- Buy and install a data communication software to do input/output between DCS and Windows 10. Check the functionality on a dummy DCS tag using a VC++ * console app. Look for vendor samples. Do not choose C#, VB.net, Java, Fortran as these are dying languages and are hack-able. Learn C++ here. Stay away from funky languages like Python.
- Choose one PID running on the DCS that has a tuning problem.
- Collect DCS values for the following in your Windows 10, using VC++ *; PV(process value), SV, MV, P, I, D, save them on a text file, one line a sample ( 1 min) as your database. VC++(MFC) has got classes for these. CFile, SetTimer, Serialization. Learn from StackOverflow.com how to samples.
- If PV is noisy, check if instrument needs maintenance.
- If sporadic MV saturation is present, slow down the PID manually, until MV freely moves.
- Detect offset: use a 1st order filter on PV to detect if average of PV is always away from SV by a constant.
- Detect Cycles: detect upper peaks and average distance between these peaks. Do the same for lower peaks. They should be same over a long time.
- Use a textbook algorithm using offset and cycle to calculate future P, I, D values, cut them down to 40% or less.
- Send newly found P, I, D values to DCS. Observe the for better results, if textbook algorithm works fine. (Everyone is a PID tuning expert.)
- If you succeed in PID tuning algorithm implementation, you will find Pass Balance easy and fun too. Always check what you expect to happen is happening, and nothing else is happening. These will prepare the team for a full scale MHEMPC design, implementation and deployment.
- Learn bumpless transfer between computer mode and DCS mode when Windows 10 is removed on Pass Balance.
- One licence allows you to implement as many MHEMPCs on the computer as needed(max limit 5 for a i7 computer for threading limitations), so keep them small instead of cramping the whole plant into one MPC. If one variable is found in more than one MPC, we can make cooperative MPCs at a later stage.