I solved similar problems by adding a PIC to control the upper limit of the
FIC.
Recently, I have been wondering if it would not be more efficient to link
the output of the PIC to the BIAS input of the FIC. (The output of the PIC
would have a range of -100 low to 0 high.) But what I have done works, so I
am reluctant to change anything. The only advantage that I see to this new
scheme would be that the upper limit would still be available for operator
(or engineer) use, if needed.
Chuck Jones
Refinery Automation Technologist
A.E. Staley Mfg. Co. -- Lafayette South Plant
765.477.5324 - Office | 765.420.4431- Pager
-----Original Message-----
From: Lance Dusing [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 06, 2001 9:12 AM
To: Foxboro DCS Mail List
Subject: Process Control
Hi everyone,
Here is a process control question I have been pondering.
Under normal process conditions, the control looks like this...
|--|
|FT|--
|--| |
|
|--| |---| ->|---| |---|
|LT|--->|LIC|--->|FIC|--->|VSD|
|--| |---| |---| |---|
However, if the pressure in the line with the VSD gets to large, corrective
action needs be taken.
How is the best way to control this?
Limit the FIC hi output limit with logic?
Switch to a PIC?
Anything else?
Lance
-----------------------------------------------------------------------
This list is neither sponsored nor endorsed by the Foxboro Company. All
postings from this list are the work of list subscribers and no warranty is
made or implied as to the accuracy of any information disseminated through
this medium. By subscribing to this list you agree to hold the list
sponsor(s) blameless for any and all mishaps which might occur due to your
application of information received from this mailing list.
To be removed from this list, send mail to
[EMAIL PROTECTED]
with "unsubscribe foxboro" in the Subject. Or, send any mail to
[EMAIL PROTECTED]
This e-mail and any files transmitted with it are confidential and intended
solely for the use of the individual or entity to whom they are addressed.
If you are not the intended recipient or the person responsible for
delivering the e-mail to the intended recipient, be advised that you have
received this e-mail in error, and that any use, dissemination, forwarding,
printing, or copying of this e-mail is strictly prohibited. If you have
received this e-mail in error, please notify the TLNA HELPDESK at
800-404-2436 or e-mail [EMAIL PROTECTED]
-----------------------------------------------------------------------
This list is neither sponsored nor endorsed by the Foxboro Company. All
postings from this list are the work of list subscribers and no warranty
is made or implied as to the accuracy of any information disseminated
through this medium. By subscribing to this list you agree to hold the
list sponsor(s) blameless for any and all mishaps which might occur due to
your application of information received from this mailing list.
To be removed from this list, send mail to
[EMAIL PROTECTED]
with "unsubscribe foxboro" in the Subject. Or, send any mail to
[EMAIL PROTECTED]
