DCS System vs. SLC/PLC/Wonderware Combo

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Thread Starter

Gwinup, David

I am trying to put together a comparison between a small DCS system (like Plantscape or Delta-V) and a user assembled "system" of single loop controllers, PLC's to manage the SLC's via RS-485 & Wonderware on a PC as the user interface.

If anyone has URL's pointing to comparisons, or has any comments on their experiences please let me know.

Thanks,
David Gwinup
 
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George Robertson

It has been my experience that DCS or smaller Hybrids have a higher capital cost to install than systems of PLCs and controllers. The cost of
ownership, maintenance and modifications tends to be higher with the latter system. I would lean toward a Hybrid unless I were sure that the person who implemented the system will stay with it for the life of the process.

(just my never-to-be-humble opinion.)

[email protected]
George G. Robertson, P.E.
Manager of Engineering
Saulsbury Engineering and Construction
 
B
I have not had the opportunity, but I have always wanted to make a process control system out of a network of single loop controllers and a PC running a VB or C program. Actually, I passed the opportunity when I was less experienced and have always regretted it.

You can use as many serial ports as you need to get the required screen update rate. Single loop controllers do an admirable job of control and
they are simple and reliable. Most have multidrop serial ports as an option.

Why would you use the PLC? For sequencing? I would have the PC talk directly to the loop controllers. This would be excellent for MMI, recipe management, alarms, and data logging.

Bill Sturm
 
I have always felt the use of OPC although
I was not much familiar with it i would like to know some suggestions for it
my id is [email protected]
please send me a reply

N.Gopi












> I am trying to put together a comparison between a small DCS system (like Plantscape or Delta-V) and a user assembled "system" of single loop controllers, PLC's to manage the SLC's via RS-485 & Wonderware on a PC as the user interface.

>

> If anyone has URL's pointing to comparisons, or has any comments on their experiences please let me know.

>

> Thanks,

> David Gwinup
 
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Kevin Totherow

David,

This reply may be too late but the first thing to do is look at the process that you want to control. Continuous verses discrete, and the sophistication of the control algorithms to be used. Where will this process go in the future -- intergation into a plant historian, will you want web capability? Who has to keep the system running? Will maintenance personnel get training?

When you have those questions answered you move over to the choice of controllers that will serve best.

In many cases the Wonderware over the SLC will be a less expensive system that is easier to maintain, easier to modify, easier to upgrade, easier and cheaper to add in new process areas and will be more feature rich along the way. I can't really see many places where some of the new "hybrid" DCS is best.

Look at my article in April 2000 Control Magazine.
 
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Vance Newman

David, You are trying to compare Apples and Oranges. Trying to compare the two technologies at this time in point is not a good Idea. Wonderware compared to an Proprietory HMI such as ABB Baileys PCV ( QNX) or Conductor NT is impossible. Wonderware doesn't compare. MOORES Procidia comes very close and succeed in providing a good DCS type configuration solution for a small PLC type system. Check www.procidia.com. Vance Newman I&C Technologist
 
This reply may be too late but the first thing to do is look at the process that you want to control. Continuous verses discrete, and the sophistication of the control algorithms to be used. Where will this process go in the future -- intergation into a plant historian, will you want web capability? Who has to keep the system running? Will maintenance personnel get training?

When you have those questions answered you move over to the choice of controllers that will serve best.

In many cases the Wonderware over the SLC will be a less expensive system that is easier to maintain, easier to modify, easier to upgrade, easier and cheaper to add in new process areas and will be more feature rich along the way. I can't really see many places where some of the new "hybrid" DCS is best.

Look at article in April 2000 Control Magazine.
 
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