Major Need to Understand My Process Control

I am relatively new to PLC & Panelview. I am studying both and am coming along, but I have a process where I work that I need to understand quickly and am hoping that someone from this site may be able to help me. In my operation we have a SLC 500 that controls everything. We also have two HMIs (Panelviews). The process that I need help understanding is this; A large steam-jacketed kettle for heating a food-product. The kettle uses an RTD input to the PLC for monitoring the steam-jacket/product temperature. This RTD signal is registered on the Panelview display. The RTD goes back to the PLC (and uses instructions (including PID instruction ... which I do understand) to send a 4-20 mA signal to a steam control vlv. The vlv. opens and closes steam to the kettle jacket according to the HMI setpoint & temperature. That is it. There does not seem to be alot to it, but I do not understand how it all works, like I would if it was all relay logic. I have alot of good Panelview & SLC study material, and am going at it hard, but I really need to get a good understanding of this particular process now. I have access to all of the program, and can copy & fax (or e-mail) anything.

Well....
If you won't get in trouble, and you don't mind the world seeing it, post the code for both. Easiest way is to zip them up and attach them to a post.

Just guessing, it appears that you have a pretty straight forward application.
Standard PID instruction with the RTD input as your PV, and the steam control valve as your CV. The Panelview is most likely reading the RTD input via the PLC, and the setpoint is written to the PID instruction via the Panelview.

If you have a copy of the program on disk, and the original programmer was half way decent, the labels and comments should give you a pretty good idea of what's going on.

What exactly are you having problems with? You say you understand the PID protion, which can confuse at times, is it the analog inputs/outputs?


If you can't post your code, can you post the part numbers of all the components in the system? Different AB I/O modules, have slightly different behavior.

Since this is used for a food making process, I would assume any and all changes would have to go through some sort of validation process.

Greetings mmarch,







if you can post your .RSS and .PBA files then we can probably give you some detailed help ... without those files, the best we can do is give you some general hints ... what part of the operation is most confusing to you right now? ...

There does not seem to be alot to it, but I do not understand how it all works

Click to expand...

I’m afraid that without those files, we’re not going to be able to tell you much more than you’ve already told us ... remember, we only know as much about your system as you can tell us ... but those files would tell us a LOT ...







and it would be very helpful to know your deadline on this project ... please note that “As Soon As Possible” is not a valid answer ... are we talking hours, days, weeks, or what? ...





PS Edit ... it looks like I’m on the same track as my distinguished colleague Ken Moore ... and obviously he’s a faster typist than I am ... post the files ... let’s nail this down ...

and one more thought ... is it working and you just need to understand it? ... or is it broken and you need to fix it? ... or what? ... the more we know, the more we can help ...