I have always been amused at the complete distrust the petrochem industry has
for electronic communications of control data. Possibly this stems over from
the early days of electronics when hardware was not reliable.
The practice here has always been to not allow CB-LAN regulatory control. I
have, however, set up several control schemes which use the LAN to pass
feedforward data.
On the flipside, the nodebus is used for regulatory control in many instances
here.
Basically, my opinion is that the control-databus should be robust enough to
handle any type of control, "timing" being the only limitation (e.g.
ControlNet). If we distrust Foxboro's nodebus/LAN, then we probably should not
be using their control systems to run our processes as their design is
apparently suspect.
Kirk's little two-cents....
____________________
Kirk Carver
ExxonMobil Chemical
Beaumont Polyethylene Plant
PO Box 2295
Beaumont, Texas 77704
Phone: 409-860-1314
[EMAIL PROTECTED]
"Murphy, Daniel J" <[EMAIL PROTECTED]> on 03/30/2000 04:53:54 PM
Please respond to "Foxboro DCS Mail List"
<[EMAIL PROTECTED]>
To: "'Foxboro DCS Mail List'" <[EMAIL PROTECTED]>
cc: (bcc: Kirk D Carver/Beaumont/Mobil-Notes)
Subject: RE: Detection of nodebus-failure
I would be interested to know what the concensus is out there for doing
regulatory control across the carrier-band LAN. For example, one PID block
in one node talking to an AOUT block in another node.
Here we don't trust the CB-LAN to do basic regulatory control. We prefer to
hardwire the signal via FBM's. Anyone else do the same?
The same question applies to peer-to-peer communications within a node.
Anyone hardwire these connections as well?
Dan Murphy
BP Amoco Refinery
Brisbane Australia
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