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Moyses

Batch Process Control

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Hello, Our batch process was installed and started up in 1996. Originally it was composed of a SLC504 with 3 ten slot chassis in the main panel, a RIO jaguar scale head for mix tank weigh scales, an RIO ten slot chassis on one channel in a remote panel, and another RIO channel with two more ten slot chassis. Our original HMI was a custom VB application. We batched in 3 10000 gallon mix tanks and transferred our finished goods to 4 hold tanks to supply two packaging lines. The recipes reside in a MSAccess database. The batch would sequence through each step as target weight was reached. Add a bunch of years and growth and it became a bohemoth, more mix tanks, hold tanks, ingredients in the tank farm, etc. We transitioned to RSView 32 for the HMI application some years ago mostly because the VB application took a great deal of work to maintain and modify.We've added several sub-processes along the way that are composed of multiple components that have to be mixed with a high shear process. We have added several ingredients that are slurries instead of our original powder adds. We kept adding RIO and upgrading to newer and larger processors. This January we transitioned to the Control Logix platform. We just added a small rack with the processor and DHRIO modules to use our SLC field I/O as RIO. The code was converted, not re-written. The old SLC datatables are now data arrays of the same int type as before. The limitations that we had with the SLC were only partially overcome with the conversion since the datatypes currently emulate the SLC that we had. As I said, the original batching control system allowed one ingredient to be added at a time and since we used weigh scales, multiple adds didn't make much sense anyway. Now I have mass flowmeters on the majority of ingredients and multiple ingredient adds that make sense chemically can be accomplished. The code through the years has lost the standard, consistent, sequence that it originally had, and now every time I look at it, I get a little queasy because while it made perfect since as a SLC, as a Control Logix control it seems stupid and clunky. It gets a little harder to keep the maintenance guys up to speed as well and they tend to be intimidated by it. I don't have time to sit down and do a complete re-write. I'll have some problems justifying a contractor expense to re-write. Nobody really cares much about it but me, anyway. I keep hacking more code in that is functional but ....Everyone cares about what goes in and what comes out but the black box in the middle doesn't really mean too much. Okay, now some questions. Where can I see some good examples of what is being done in industry? I realize that code is money, but how about some conceptual stuff? How about some discussion around what some UDT's would be applicable? Or some AOI's with parameters that help get some modularity and consistency back? I am talking to Rockwell Engineering and my local vendor's tech guy is helpful, but I can't get my head wrapped around it good enough yet. Rockwell will try to sell Batch and I don't really see what the benefits would be to me. Too much? Then maybe an encouraging word or two....

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Hi, I empathise, I really do. I work in a manufacturing facility that has also become neglected over the years. One area did successfully motivate a control system upgrade a few years ago. It works. FactoryTalk Batch running ControlLogix PLCs. I continually use this area as motivation to upgrade the other areas. FYI, the other areas are running on Modicon 984s using IEC ladder, IEC FBD and 984 ladder with zero consistency inside a every controller. Reading it is like trying to build a puzzle of a picure of baked beans. There is a big catch though: buying the hardware and control system software alone won't help you at all. It needs to be coded according to an international standard, e.g. S88, and your own site standard while adhering to the vendor specifications all the way. Our system was designed around the S88 standard and the site standard uses very well thought out control modules. What it comes down to is that it doesn't matter what solution you take, it will cost you a lot of money and take a lot of time and effort. My suggestion to you is to develop some decent standards and control frameworks and then have a system integration company execute the work for you. Get as much information handy before you embark on anything. This goes for everything including P&IDs, Conceptual Functional Specification, Electrical diagrams etc. If you don't button these down before you start, your upgrade work will never complete as people will just add work onto your project. Should you take on this project, I suggest you plan it very carefully w.r.t. your standards and future expansion plans and also to commission it thoroughly. Pull this off and it is your ticket into financing for future control system upgrade project. Don't allow your new system to perform worse than your old one after commissioning, then you are screwed for future. Good luck.
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The S88 method is definatlkey your best way to go i read a book a few years ago by a couple of guys who implemented S88 batch into a Ben and Jerry's ice cream factory. The book was very easy to understand and gave me some great ideas of how to break code down and how to structure it. I think it was call apllying S88. and when i do a search this is the only referance i can find http://www.amazon.co.uk/s/ref=nb_sb_noss?u...ds=applying+s88. If you want a taster of this book email me and i might be able to dig it out

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Don't ahve anything specific I can share but I work in a plant with a mixture of batch processes and sequential material handling processes. Our Corporate Gurus developed a coding standard some years ago for SLC and PLC which was migrated to CLGX. I can't say enough for having a standard and being able to open most any PLC/SLC or CLGX and know what the code is going to look like. One of the biggest gains for us is the standard modules which are for both PLC and HMI. To add a new motor I simply need name it {and there is a standard for doing that} copy and paste in the generic motor control code for the type it is, substituting the actual name for generic placeholders. And then call the HMI programmer and give him the screen location and tag name of the motor control pop up and in a matter of mintues new motor is fully programmed.

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hmiman - It seems that I woke up one day and realized that I am the leader. I am the most senior and most experienced in my plant. Our corporate guys don't care about controls, per se. I talk to my boss and he makes me realize that the vision is supposed to come from me. Holy cow, man, I don't have vision. Couple that with some issues I have with delegation (especially to contractors) and I have some freaking out to do. I will endeavor to overcome all of this. Thanks for your comments. I know the importance of under promising and over delivering, it's one of my mantras. I hear you on the S88 compliance. PLC_Man_Stan - I read that book. There is good information there. Our code does most of the things that the book recommends. Recipes outside of PLC, units taking ownership of resources until released, checking inventory levels before ingredient delivery, batch suspension (pause), etc. BobLfoot - Oftentimes I'm a one man show. Sometimes that's good, other times not so much. I'll get through the next few hurdles and keep the goals of standardization and implementation of S88 compliance close in mind. I also realize that I won't be able to do it myself and at minimal cost no matter how bad I want to. Thanks. Edited by Moyses

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Keep in touch with this forum, its a great place just to vent your frustrations and at best it's the best learning tool i've ever used Good luck, your never on your own!

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I would disagree with this approach. IF you could bring an SI, you are better off letting them drop in their standards and methods, learn from them. Trying to develop your own standard, then asking a Systems Integrator to implement well that will just cost more money and more headache, and you'll end up with less functionality. Let the pros do what they do, they have years of experience that just raise the bar when it comes to this sort of thing. As others have said, S88 is where you want to be, but to get there the "right" way is an investment. Considering the original design concepts of your system are almost 20 years old, it's time to consider modernizing it Maybe it won't happen right away, but in 5 - 10 years, management can't believe that their 25 year old methods are efficient. So your company really needs to begin to create a rough plan for a migration strategy now so it can be though-out, budgeted as a capitol project in 5 years. It's great that you've converted to CLX, but unfortunate the system wasn't re-written at that point. As you've discovered, converting the software to a CLX is quick, fairly easy and cost-effective but you still have constraints due to the original platform. When it comes to S88 and CLX, you really want to become educated, and start using Phase Manger in the CLX. "Phases" are the key to S88, it maintains modular code, it ensures standard code, and it allows dynamic code. Phase Manager is also Rockwell's solution on the PLC level to adhere to the concepts of S88. If you've been talking to Rockwell at all, you are probably aware of this. Unfortunately S88 software licensing (FactoryTalk Batch, WW InBatch) isn't cheap. Our software standard is completely based on S88, but we use the S88 concepts for everything. Batching, Continuous process....in my opinion I can program just about anything with the S88 philosophy. I've done a few batching projects now, and the biggest reason to use FactoryTalk Batch or WonderWare InBatch is for recipe management. Dedicated batching software, and PLC code which is all S-88 compliant really gives you a lot of creativity as to how your recipes are created and executed. As you've mentioned, you now have mass flow meters and you could do simultaneous additions, well that is pretty easy to change the recipe to handle that with dedicated batching software.

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