Re: [foxboro] RAMP block question

I appreciate it. The process works better with your help.

Regards,
 
Alex Johnson
Invensys Process Systems
Invensys Systems, Inc.
10707 Haddington
Houston, TX 77043
713.722.2859 (voice)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Airhart, Chad M.
Sent: Wednesday, January 26, 2005 10:34 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] RAMP block question

Thanks Alex.  We will put in a CAR.

Chad M. Airhart
Senior Engineer (Instrument, Electrical and Control Sys)
Lyondell Chemical Co.                             Victoria Plant
Ph. (361)572-2568
Fx. (361)572-2541
Cell. (361)935-3230

-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Johnson, Alex (Foxboro)
Sent: Wednesday, January 26, 2005 8:57 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] RAMP block question

Chad,

This is a defect in our cascade handling. Would you please enter a CAR
on
this? Include the write-up below as the description. We need a customer
entered CAR to give this some priority.


As it turns out, all control blocks that participate in cascade handling
have the following anomaly.=20

When the cascade is opened, or closed, or when an initialization request
to
the upstream block is made, the downstream block requests the upstream
block
to run immediately on the next BPC regardless of the period/phase of the
upstream block. This logic was created many years ago to provide fast
initialization of the cascade when the upstream blocks run slower than
the
downstream block.

The flaw in the cascade logic is that the downstream block should check
to
see if PRIBLK=3D1 before issuing a demand run of the upstream block. If
this
were done in this case, the RAMP block would not run additional cycles
and
the calculation would be correct.


Regards,
=20
Alex Johnson
Invensys Process Systems
Invensys Systems, Inc.
10707 Haddington
Houston, TX 77043
713.722.2859 (voice)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On
Behalf Of Airhart, Chad M.
Sent: Tuesday, January 25, 2005 5:18 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] RAMP block question

One of our specialists wanted me to put this question out on the list.
He has built a RAMP block that will be used to ramp the remote setpoint
of a PIDE block in a control scheme.  The RAMP is supposed to move 12000
SCF ( actually from 0 to 12 ) in 15 minutes.  He set the ramp rate at
0.8 or 12/15.  When he runs the block as stand alone, and times it, it
works great.  0.8 the first minute, 1.6 the second etc...  When he makes
the one necessary connection to the remote set point of the PIDE it
ramps twice as fast.  The actual output of the ramp is twice as fast
i.e. 1.6 in the first minute instead of 0.8.  Any ideas why?
P.S. KSCALE is set at 1.0, Range in and out is the same, scale is the
same, engineering units are the same.  Period and phase are even
matched.  Every block in compound are on 1 second period phase 0.  Only
5 blocks in the compound.  Version 6.3 system running display manager
and legacy historian.  When he adjusts the ramp rate to 0.4 or half it
ramps at the rate he wants but we want to know why.

Chad M. Airhart
Senior Engineer (Instrument, Electrical and Control Sys)
Lyondell Chemical Co.                             Victoria Plant
Ph. (361)572-2568
Fx. (361)572-2541
Cell. (361)935-3230


=20
=20
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
=20
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         =
mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Djoin
to unsubscribe:      =
mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Dleave
=20
=20
=20
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
=20
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         =
mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Djoin
to unsubscribe:      =
mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Dleave
=20
 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
 
 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave

Other related posts: