Re: [foxboro] Rate of Change Alarming
- From: "Wilson, Brad" <brad.wilson@xxxxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Fri, 4 May 2007 11:34:32 -0400
There is nothing in REALM that allows you to qualify how it calculates
the rate of change - I'm guessing it compares inputs from scan to scan
which could result in very erratic reading for flows & pressures.
Temperatures are more steady, so perhaps you slow down the scan rate for
the REALM and see if that helps.
Brad Wilson
brad.wilson@xxxxxxxxxxxxxxxx
Invensys Systems, Inc
1090 King Georges Post Rd, Suite 204
Edison, NJ 08837
732-874-0087
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Jaudon, Mike
Sent: Friday, May 04, 2007 11:28 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Rate of Change Alarming
Thanks Brad.
I understand better how the ROC works now BUT...as the "clients of the
D.C. Madam" say, here's what I really want is... if that 1.67 Deg/sec
rate is sustained for 5 minutes then alarm.
Is there an easy way of doing that without bringing that "alarm bit"
into a logic block and "DON" for 5 minutes?
Regards,
Michael L. Jaudon
TRONOX, LLC
(Technology Group-Hamilton, MS)
(662)343-8710 Office
(662)304-0313 Cell
mike.jaudon@xxxxxxxxxx
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-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Wilson, Brad
Sent: Friday, May 04, 2007 10:08 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Rate of Change Alarming
I just did a test with a RAMP and REALM and it worked as expected. The
trick is to get the units correct ... the RAMP.OUT is units/min and the
REALM.ROCVAL is units/sec. When I RAMPed at 50 %/min it showed up on the
REALM.ROCVAL as 0.833 %/sec.
In your case I would try
Make your REALM input scaling the same as the AIN that feeds it
REALM.ROCLIM =3D3D3D 1.67 (deg F/sec or 500 deg in 5 min)
REALM.ROCTIM =3D3D3D 5 (mins)
REALM.ROCOPT =3D3D3D 1 (enable ROC alarming)
Now, this will alarm if the instantaneous rate ever goes over 1.67
deg/sec. ROC alarming is absolute value, so you'll also get an alarm if
it falls 1.67 deg/sec. You might be able to "dampen" the alarming by
using a filter in the AIN block, but that is questionable.
Brad Wilson
brad.wilson@xxxxxxxxxxxxxxxx
Invensys Systems, Inc
1090 King Georges Post Rd, Suite 204
Edison, NJ 08837
732-874-0087
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Jaudon, Mike
Sent: Friday, May 04, 2007 10:40 AM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Rate of Change Alarming
List,
=3D3D
Can anyone tell me how and what to set on a REALM block to make the ROC
work? In the past I have set up on a test bed and used a RAMP block to
test but it never works as I think it should.
=3D3D
I want an alarm to be generated when the temperature goes up 500 DegF in
5 minutes. The temp normally operates at a constant value but if it
increases by the 500 Degrees within 5 minutes then I want an alarm.
=3D3D
In the past I have accomplished this by building two AIN blocks and
changing the "period" on one and sending these to a REALM block (MEAS &
DEVSPT). One problem I have now is there is no period with a 5 minute
execution. Besides if I could configure the REALM correctly I would
only have to create one block instead of two.
=3D3D
Anyone with any ideas?
Michael L. Jaudon =3D3D
TRONOX, LLC =3D3D
(Technology Group-Hamilton, MS) =3D3D
(662)343-8710 Office =3D3D
(662)304-0313 Cell =3D3D
mike.jaudon@xxxxxxxxxx =3D3D
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=3D3D
=3D3D
=3D3D
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