Autoclave project advice

There are purpose-built devices that can control P & T.  Wire it up, configure for the specific requirements for that system and you are done - until something fails or slowly wears out.

very quick online search came back with this:

https://toepia.com/ego-temperature-controller

Much less work than making a PID work, and likely much less expensive.

IngTecDiStasio

Hello dear experts!

Im considering implementing a S7-1200 PLC program for a clients Autoclave.

It clearly involves PID control of both vapor pressure and temperature.

Could anyone give me any advice on the general strategy to build the program?

Should the PID's be cascaded or in a timed sequence?

Perhaps a simpler strategy is in order.

Any special warnings?

Thanks so much for your help!

I understand now that the full project scope has been provided.

Very different reply now that enough information has been provided.

An S7-1200 can certainly accomplish the required tasks.

It does sound like a PID_TEMP to control temperature is in order.  What feedback hardware will you use?  A S7-1200 TC or RTD AI module, or a single TC/RTD with signal conditioner connected to one of the 2 built-in Analog Inputs?

General strategy for coding:

Get I/O tags created (you can export the tag table to excel, clear out the tag table, update in excel and import the tag table back to into the project.  Will be faster after you do a couple export / clear / import (and always work from a "backup" or "Save As" project when you are about to wipe out the tag table -- prevents losing work).

After PLC tags for I/O are created, create some global DB used for regular PLC tags (rather than M-tags).  

First, get analog scaling block(s) working (you can and should use the LGF - library of general functions - from this support site and integrate any blocks you find helpful.... then look for process control and other blocks for the HMI/PLC as well as sample applications for working with SCADA systems and so on so you can use Siemens-maintained code within your code. In this way, you can save yourself lots of time. 

At the same time, on the SCADA system PC, I suggest creating a "Documentation" folder.  Break it up as you see fit, but every single PDF you refer to and use anything from, copy into that docs folder, renaming as appropriate so it's more obvious what is inside the PDF.  This goes for hardware and software.  And when you are done with the schematics, export to PDF and save to that same docs folder - organized something like "c:\docs\electrical\schematics" folder.

PID(s) should be whatever is required to control the system correctly in every possible situation.  If that means from time to time a PID gets turned off, or "manual" control of the PID is required, make sure your logic enables it, or at least _can_ enable it with relative ease.

By that I mean, do not make it a complete rewrite just to add manual PID control, or to allow for local / remote PID turning off.  Make sure when the PID is off the PLC can be only be controlled in a manual mode and ensure there is someone there.  Probably not a good idea to run with a heater on 100% unattended without any oversight.

That said, have a contactor enable the heater controller (SSR?).  Further, have the contactor coil power flow through an overtemp switch set at the appropriate temperature to prevent fire, damage to whatever is inside the system or to whatever surrounds the system, and placed such that it would require tools to access / remove, and in a good world, security screws protecting any safety device (like an overtemp switch).

Keep It Simple Silly (or "Stupid" as the old saying goes), or the  KISS Principle applies.

Once a piece of logic works, create an FB or FC (or OB & related FBs/FCs), and put it in there.  If you find an FB or FC used more than once, don't repeat yourself and create a proper FB/FC with only internal parameters used in the FB/FC logic - no global tags / DBs used).

Follow the S7-1200 Programming and Style Guildlines provided by Siemens on this support site.  It will really help as the project complexity goes up.

Any special warnings? --> Consider all current safety regulations for your area for people safety, equipment safety, process safety, and cybersecurity -- since you intend on connecting to unknown and potentially unsecure network devices.  I know it sounds like bogus, but you need to at least spend 1 minute considering it and either do something or not depending on the safety outcome of someone breaching security on any connected devices (including HMI and SCADA and other data friendly --but maybe not very cybersecurity conscious devices).

Keep in mind, you asked and provided basically nothing about your background and familiarity, so I shot-gunned my reply (spraying lots of info at you from many directions).

Be careful what you ask for.  You might just get exactly what you ask for - and more!

IngTecDiStasio

Thanks for your input but Im looking for a modern PLC implementation because the client requires full integration with scada systems and other data-friendly platforms.

The system will include an HMI screen for parameter configuration, trend graphs, etc.

I'll keep the device in mind anyway.