Re: [foxboro] How to limit SP when dialed in a wrong value?
- From: "Subbiah, Srinivasan" <Srinivasan.Subbiah@xxxxxxxxxx>
- To: "'foxboro@xxxxxxxxxxxxx'" <foxboro@xxxxxxxxxxxxx>
- Date: Thu, 2 May 2013 12:34:24 -0600
Thank you. This is really a good one.
Regards,
Srini
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Rguercio@xxxxxxx
Sent: Thursday, May 02, 2013 10:52 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] How to limit SP when dialed in a wrong value?
Just reading the last in this series, so don't know if the following idea
was presented, but this is how I implement what I call "setpoint change
delta protection".
Create a CALCA block that reads in the current setpoint of the PIDA
setpoint you are trying to 'protect'. Put the largest change you want to allow
at any given time into a RI or MEM location. Use that value to both add to
and subtract from the current setpoint value, and tie those results to
SPHLIM and SPLLIM, respectively, in the PIDA block. If you want or need to get
fancy, you can put the max increase and max decrease into two locations
and use each in its own calc whose output is tied to its respective SP clamp
as above.
This has a few benefits: prevents those 'order of magnitude' setpoint
changing errors, and allows repeated small changes in pretty rapid sequence if
you really do want a large change.
Rick Guercio, P.E.
RG Consulting
918 E Desert Shrub Drive
Washington, UT 84780
713-805-8742 cell
In a message dated 5/2/2013 10:30:31 A.M. Eastern Daylight Time,
Joe@xxxxxxxxxxxxx writes:
Standard PIDA Features
The features are:
♦ Setpoint limiting, SPCLMP
♦ Local setpoint ramping by rate or time to target, SPROPT
SPCLMP Setpoint Clamp is a configurable short integer that specifies the
limits to
be used when clamping or limiting the Supervisory setpoint (SUP_IN),
Remote setpoint (RSP), and local setpoint (SPT).
0 = clamp using the measurement scale limits (HSCI1 and LSCI1)
1 = clamp using the setpoint limits (SPHLIM and SPLLIM)
2 = reject values outside of the setpoint limits (SPHLIM and SPLLIM)
Joseph M. Riccardi
386-441-0250 Office
386-451-7607 Cell
Joe@xxxxxxxxxxxxx
"To give real service you must add something that cannot be bought or
measured with money; and that is sincerity and integrity." - Donald A. Adams
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Subbiah, Srinivasan
Sent: Thursday, May 2, 2013 10:14 AM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: [foxboro] How to limit SP when dialed in a wrong value?
Hi,
There was an incident that the operator dialed in a wrong SP; 445 instead
of 345 and the reactor pressure shot up. I know in Honeywell, there is a
parameter that does limit the "rate of change of SP". In this case the SP
will not jump to 445 instead would be 375 or so for example.
I was trying to find such a parameter in PID or PIDA block, however no
success. During my Invensys training, I understand that there is no such
mechanism rather PIDA block can only ramp at a rate but still the SP will get
to
445 eventually.
Any thoughts please on how to limit the SP. Is it such that I am not yet
completely trained?
Thank you,
Regards,
Srini
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anyway, waive privilege or confidentiality. If you have received this E-Mail in
error please immediately delete it and notify sender at the above E-Mail
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and outgoing E-Mail. We encourage and promote the use of safe E-Mail management
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you receive for the presence of viruses. The sender and Agrium accept no
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