Upgrade PLC vs DCS vs Hybrid system?

I am looking at upgrading a mineral processing control system in Queensland Australia and would appreciate comments on the relative
merits and pitfalls of each of the possible scenarios. The upgrade is due to increasing maintenance costs due to obsolecence of the installed equipment and the problems caused by the historical effects of just tacking bits on whenever a new facility was installed at the site. Its a bit of a tangle now with an extensive (and slow) network. The control equipment is spread over 30 odd facilities on site and consists of mainly allen bradley plc's of various vintages and a littleYokogawa DCS (microxl/CS3000) with 15,000 IO, around 20 plant OIT's and a control room with a half dozen OIT's and the usual mix of servers, historians, engineering workstations, networking and plant management packages. Its complicated by the fact it will need to be cutover in stages during routine facility shuts.
What it boils down to is as follows Go to fully PLC (AB) ControlLogix with RSView32 - What does this signify for the HMI compared to a DCS? Go to fully DCS - Yokogawa CS3000? Go to an updated hybrid say ControlLogix/Yokogawa CS3000 -or another vendor?
What are the options? Pitfalls? Pro's & con's? Relative costs? Repercussions for cutover/maintenance/operations/thirdparty support? Should I look at other vendors & what would they offer? Citect/Emerson/ABB....?
Whatever we do it will need to be able to be supported for a while (say to 2020?) and allow for expansion.
I would appreciate any suggestions as cutting through the manufacturers hype has been a frustrating exercise to say the least.
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On 3 Jan 2007 18:18:46 -0800, snipped-for-privacy@bigpond.com proclaimed to the world:

Are you doing the install or hiring the work out?
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Paul M wrote:

That decision is one of the outcomes of what I am looking at! A lot of the config/installation will have to be contracted out of course but how and why etc depends on what kind of conclusions I reach. Hopefully I can get a clearer more unbiased view of the issues involved from someone who has been there before me.
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This is clearly a major exercise, it needs close involvement all the way through of people with specific experience of every stage involved, from basic architecture design, through platform selection, design, installation, integration, cutover, commissioning and training. If you want to keep it platform-vendor independent up front, then you'll need the involvement of an outfit that can handle all the front end engineering. Building your own implementation team without having a fair amount of experience yourself is a chancy business in its own right. Good luck.
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On Thu, 4 Jan 2007 19:00:59 +0900, "Bruce Varley"

I have a lot to say about this having been involved several times in cleaning up the mess left over after everyone involved in a project gets mad and goes home, leaving the people left to try and operate the plant, dazed and bitter.
If I don't get the chance to say anything else about this, I would urge you to hire someone with a history of sucessful projects of this type and make sure that a single firm has the finacial responsibility of seeing it all work.
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I hate to push my own barrow, but you will need to engage a firm of Consulting Engineers to help you though this. Our job is to give you answers to exactly the questions you pose above.
Norton Consultants has been involved with similar projects (for ACI Minerals) in the dim distant past and is currently engaged on similar upgrades for the major Oil Companies. You can find us on the web at www.nortonconsultants.com
There are many others around who can help you, some good, some bad. Maunsell have a control systems division in Melbourne (called 'Mamic' last I checked) and I could give you a contact name if you like, there's Patterson Flood Engineers and countless others...
We look forward to being of assistance. A small hint in passing - ControlLogix is not all it's made out to be and if you are not *really* careful with your systems design, you could find yourself in very deep poo...
HTH, Cameron:-)
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Cameron Dorrough wrote:

Thanks to all the posters who answered. The replies were pretty much what I was aware of. The answer to the technical issues will drop out following deeper investigation and in the mean time I am gleaning small nuggets of wisdom from a myriad of sources.
The small hint above intrigues me. Have you had a specific problem in the past or is that a general observation? I have been getting more information from Rockwell on possible obsolescence of their product line and as a consequence will probably install more ControlLogix.......?
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Paul and Jake have spelt out the complexities of control systems design far better than I could. We have used and continue to use ControlLogix (and Yokogawa and others as well) for a variety of different clients and applications and no two systems are ever exaclty alike.
The biggest issues I, personally, have with ControlLogix are (1) that it is marketed as "the solution for everyone", (2) it is heavily software-based and each update brings new "undocumented features" which you are left to find yourself and hence (3) none of the Rockwell people I have ever met have even the faintest idea of it's limitations (and there are some) and how they might affect your plant.
If I'm going to recommend a system to a client, particularly one connected to another system hybrid fashion that they can blame when stuff goes wrong, I'd want to be extra careful defining the interfaces..
I hope this helps, Cameron:-)
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snipped-for-privacy@bigpond.com wrote:

There is no magically "good" answer. There are only issues of usability, maintainance, expense, stability, security, short term costs, long term costs, and so forth.
Manufacturing hype can be cut through by understanding what these folks are really selling. I suggest taking introductory courses to find out how the systems are configured, how they work, and what networks they support.
Also, you should consider what these systems offer in the way of maintainance features, and where you might need to improve your own maintainance staff. Consider what tools they'll need. Consider what record keeping you want them to do, and what system features might be helpful.
Finally, consider where you may need to go with your regulatory environment. Look at what reporting features they offer. Figure out who is supposed to do those things and how hard they are to implement.
Cameron's suggestion of retaining an engineering firm is a good first step toward making these decisions. You will need someone's help getting started. The fact that you have to ask these questions at all shows that you really need this sort of help.
In the long run, however, I'm a big believer in the do-it-yourself philosophy. While you get your act straightened out, train some new engineers. Pay them reasonably well to keep them on staff. With a knowledgeable engineer on staff you can make changes to the system on the fly. They'll have good information on what is and isn't working well for the company. They'll be able to help you build the next generation of control systems too. You may still need assistance from an outside consulting firm at that time, but you'll be a much smarter consumer at that point and you'll be able to control costs of the upgrade much more effectively.
One thing is certain, however: If you install one of these systems, tie a ribbon around it, and say this is it, we're never going to change anything here --then you'll be missing out on one of the very best features of modern control systems: You can make changes rapidly at very little expense.
That's what separates the kids from the adults in this business.
Jake Brodsky (I'm a control systems engineer for a water utility, so what I'm posting here is free advice, unencumbered by a consulting business or the need to sell anyone's product)
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On Sun, 07 Jan 2007 23:45:05 -0500, Jake Brodsky

This is good advice. I too do control systems engineering and until recently owned and operated a company that maintained and upgraded water treatment and industrial instrumentation & control systems. My last job was as an independent consultant in addition to the engineering firm hired to design and let out contracts to upgrade a regional waste water treatment system. My full time job for over a year was to cut through all the hype and make sure they had a sustainable and flexible system for the next 25 years. I had a long history with this customer. The system installed in the 1080's when the plant was built was failing and the company that installed it no longer had anyone who knew anything about it. Many times parts were unavailable.
They spent a lot of money hiring me, but they saved more from having someone like me, working in their best interest and the only way to do this is to remove any incentive to sell you something. Even the firm you hire to design the system have some motives that may end up costing you time and money. A mistake I have seen engineering firms make is to spec equipment based on how neat the engineer thought it was. Another is trying to integrate the system too much. Keep it simple and provide points in the system that provide easy interface to new systems. It makes upgrading to new equipment easier.
You have a fantastic opportunity here to make your plant a much nicer place to work while increasing the profit or you can find yourself cursing the new system and wishing for the good ol days were back. Making the first option come true requires the controls engineer talk with the operators and look at the processes to see if a better way is possible.
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On 3 Jan 2007 18:18:46 -0800, snipped-for-privacy@bigpond.com proclaimed to the world:

While Allen Bradley has a good record for supporting their equipment, the RSView lacks a lot. I would only use RSView for local interface if needed.
Use a common networking protocol.
Use an HMI that can do supervisory control for DCS and PLC.
I cannot advise what combination of DCS and PLC you should use. This depends on the process. While both can do the other's job, one does some thing better than the other. Sometimes it is best to have a DCS supervising several PLC.

Pitfalls I discussed in another post. Relative costs between system types is not very much. There can be a lot of cost differences in brands.

A lot of effort should go into making sure the system can be maintained with the resources you have there. You need to decide how you will do this. It is possible to keep it in house.

What they offer will vary between here and there. It's possible to save a bunch of money by using generic equipment. The "open source" approach also makes it easier to change brand and/or model in the future. Again, it all comes down to how well the system is designed. Hybrid has a lot going for it. You can pick out each system's strong points and combine them into your system.

Depending on you expectations, this can be done. Don't expect not be running a 10 year old system in ten years. There will be better stuff available and the PC interface and protocols will evolve and change. Expect some changes to the system over they years, but it should be supportable and most of the equipment should last that long. Mineral processing can be pretty nasty on equipment.
What are your processing and how? We have a lot of mining and processing plants around here (Virginia USA) and I have done a lot of work for them in the past. Most of the stuff is closed down now but we had gypsum, lead, zinc, salt, iron and limestone all have been mined here and we have coal and natural gas production and lots of power plants. We also have hydroelectric plants that have supplied cheap power for mining since the turn of last century. Worldwide availability of the former mentioned minerals closed most of the production down several years ago. What part of Queensland are you in? I am not familiar with what natural resources are found down there? Most of the rock contact I have seen in pictures appear to be sandstone.
Paul Montgomery, President Progressive Gauging & Controls Inc.
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