Re: [foxboro] Calculations
- From: "Murray, Steve" <SMurray@xxxxxxxxxx>
- To: "foxboro@xxxxxxxxxxxxx" <foxboro@xxxxxxxxxxxxx>
- Date: Tue, 14 Jun 2011 12:40:58 -0700
Hi Dale,
We are doing the exact thing you need to do, except we use six minute opacity
averages.
We bought the Foxboro FoxCEM environmental reporting package in 1998 and our
discrete six minute opacity averages are calculated in a series of IND, MON, &
TIM blocks. There are much simpler ways to calculate the averages though -
most of the complexity of the FoxCEM is due to the user interface and data
packaging features.
To alarm on three consecutive periods >20% I bring the average opacity (from
a FoxCEM block) into a separate AIN block and set an alarm at 20%. This alarm
does not go to any alarm manager, I just have the HAI parameter linked to an
ACCUM block running at one second. When I get a high alarm the ACCUM block
starts accumulating by one every second, and if it gets to 720 seconds (12
minutes) without getting reset by the AIN block HAI alarm clearing, then I send
a pre-target alarm to our operators and the Alarm Manager from the ACCUM block.
This gives me an alarm if the opacity is >20% for eighteen minutes. You
would need to change the ACCUM time to suit your needs.
Steve Murray
Asarco
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Gillis, Dale
Sent: Tuesday, June 14, 2011 8:23 AM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: [foxboro] Calculations
Hello List
Just wondering if any one has done something similar to the following?
I've been asked to:
Program a calculation block to calculate the 3 minute arithmetic average of
instantaneous opacity reading and send this average to PI. (this is 3 minute
block average not rolling average). Create an alarm if the arithmetic three
minute average (block not rolling average) is 20% or above for more than 4
minutes in any 30 minute period. (2 peaks of 4 minute average in a 30 minute
period). Alarm banner to state "Opacity Exceedence..... log Exceedence"
I was thinking of using a calca block and maybe a DTIME block. Any ideas?
Thanks in advance
Dale
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