Any specific comments/suggestions you may have is highly valued for someone trying to decide between the two systems. Also, if you know of anyone in your network who has gone down this decision path, please forward this inquiry as I would like to ask for their comments/suggestions as well. Thank you for your time.
Sam Roe, Sr. Electrical/Automation Engineer, BPB America
ANSWERS:
THE ARCHITECTURE of the system is important. This applies to hardware architecture as well as software architecture. The central component of hardware the architecture is the control-network. Without a doubt this shall be based on standard Ethernet. I stress standard Ethernet, not modified "industrial" Ethernet requiring specialized hardware and which does not use IP. For availability it is important that true duplicated "DCS style" redundancy is supported, not just ring topology. The application protocol on top of IP is critical for interoperability between devices from different manufacturers as well as package unit integration. Do not go for proprietary protocols over Ethernet and IP. These criteria pretty much narrows the control-network platform down to Foundation fieldbus HSE.
Siemens does not support HSE, Allen-Bradley does to some extent, but there are other options you should also look at.
At the core of the software architecture you need a technology to exchange data between hardware and software, and between the different software applications. Without a doubt this shall be OPC, including the principal flavors OPC-DA, OPC-A&E, and OPC-HDA. Both Wondwerware and WinCC support at
least OPC-DA. Wondwerware maps it to their own solution loosing some of the easy of use - this could have changed. I have no experience with WinCC. There are other options you should also look at. There are other software technologies you should make sure are supported: SQL/ODBC/OLE_DB/ADO database access, ActiveX graphics components and OLE container, DDE for legacy, VBA for script, and HTML for web viewing etc.
For OPC and other software technologies, take a look at the book "Software for Automation: Architecture, Integration, and Security." ISBN: 1-55617-898-0; Publisher: ISA.
For Ethernet, take a look at the book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance." ISBN 1-55617-760-7; Publisher: ISA
IS THERE some reason you've limited your evaluation to the two combinations indicated? A good reason might be that there's already expereience with all of these products elsewhere in your company.
On the other hand, if there's not a particularly strong reason to impose such a limitation, you might want to include at least a couple other possibilities:
- In the PLC area, Modicon (Schneider Automation) especially, and perhaps GE Fanuc.
- In the HMI area, Intellution Fix (now owned by GE), and RSView32 (Rockwell Automation/Allen-Bradley), and perhaps CiTect.
As for PLC's, I have personal experience with Modicon (584, 984, Quantum) and Allen-Bradley (PLC-5, SLC-500, ControlLogix) in pulp and paper and food industry applications and find both to be solid products, but have slight preference for Modicon.
As for HMI's, I have personal experience with Wonderware and Intellution, more hands-on experience with Wonderware, but, slight preference for Intellution for technical and commercial reasons.
This may not have helped - more opinion based on personal experience. My Modicon preference comes from ealy days employed in the Cellulose and Specialties division of Procter and Gamble, where we chose Modicon over Allen-Bradley as the std. for that division of the co. because it could better meet higher performance reqt's in the pulp and paper mills.
Of course, keep in mind that most leading HMI's will integrate well with most leading PLC's. There may be some minor advantages in pairing ControlLogix-RSView, both Rockwell-AB products.
R. H. (Rick) Meeker, Jr., P.E. , Reliable Power and Controls Corp./Process Control Solutions, Inc., Tallahassee, Fla.
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