Re: [foxboro] Ladder Logic
- From: Corey R Clingo <corey.clingo@xxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Thu, 3 May 2012 20:59:47 -0500
Another nice thing about these systems (well, brand R's at least, in my
experience) is that they don't care whose box you run the
HMI/gateway/historian/configurator software on. As long as it meets some
minimum hardware specs, you can buy any PC or server you want, from anyone
you want. And when one of the boxes dies, you just buy a newer PC (again,
from anyone you want), load your existing software on it, and go. You
don't have to repurchase all your software along with the new PC from the
control systems vendor, and possibly upgrade other parts of your system
because the software is too new to be compatible with the rest of what you
have.
They also often give you the option of running open-standard industrial
protocols on Ethernet as the control network. Which means you can buy
whatever network gear you want from anyone you want as well.
Corey Clingo
From: "Campbell, John C" <john.campbell@xxxxxxxxxxxxxxxxx>
To: <foxboro@xxxxxxxxxxxxx>
Date: 05/03/2012 03:46 PM
Subject: Re: [foxboro] Ladder Logic
Sent by: foxboro-bounce@xxxxxxxxxxxxx
I brought this issue up many, many years ago at one of the user
conferences open session. I came aware with two impressions: a) I was
respectfully listened to, and b) nothing would happen as this would be a
costly change.
Within our company DCS's are a dying breed for a number of reasons:
a) yes they are more powerful than your standard PLC's, but is this
power really needed?
b) Brands "R" and "S" are considered hybrids. Able to do anything a PLC
or DCS can do.
c) These PLC mfg's can do Function Block, Ladder and sequential logic on
the same controller. Limit is only based on memory and the power of the
processor. You can get a lot of programming in these processors. Plus
these programs are easy to troubleshoot and understand. Inter-mixing of
programs is logical and easy.
d) PLC vendors have integrated their safety functions on their back
planes. Most safety functions dealing with machine guarding (ISO-13849)
are predominately ladder logic type. This means you can work with one
system, one brand.
e) Technicans/Technologists from our community colleges have been
trained on brand R and S systems because these companies have "donated"
their systems and services to these colleges. These graduates
understand ladder, they understand how to read, diagnose PLC's.
f) Foxboro's competitors are agressively targeting the process
industries. Brand R regularly holds Process User conferences and I'm
seeing more and more petro-chemical involvement.
g) instrument tech's prefer function block, electricans prefer ladder.
With companies optimizing their maintenance staff, we are quickly moving
to "control" tech's who must do both.
Foxboro has a great product, but if they don't make themselves more
flexible (PLB doesn't cut it). Then I won't be allowed to have them bid
on our future projects. A few years ago I had one project that was
worth $5 Million to the vendor. Foxboro was asked to bid (the divergent
phase of the investigation) and was quickly eliminated at their request
because 60% of the job was to replace a system using ladder logic. The
process unit had two objectives: a) do an in-kind replacement (no
improvements at this time) and b) they only wished to deal with one
brand. (this replaced 2 plc's and 1 DCS).
When I/A first came out (yes there are a few of us left), Foxboro was
able to quickly capture market share because the system was designed to
be flexible (hardened, no grounding issues and powerful).
The future are hybrid systems. Vendor's who keep to one or two
languages will end up in niche markets.
Sorry for the rant but Foxboro has always been my choice, but this one
item is forcing me to abandon them.
John Campbell
my 2 cents
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