Re: [foxboro] Block Equivalents List
- From: "Doucet, Terrence" <tdoucet@xxxxxxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Mon, 27 Mar 2006 20:02:45 -0500
Jack,
Think of it this way:
If you want to know which way the wind is blowing:
1. Use a precision wind direction instrument - equate this to the CP STATION
display in IA.
2. Stick a wet finger in the air and sense the cool side of your finger -
equate this to the CP loading spreadsheet
3. Stick a gloved finger in the air and see if you can sense the cool side -
equate this to Block Equivalents!
There is really no cheap and easy way to predict the CP load and be correct
every time. FoxWatch is able to help you in this area for a running system.
(There is big value in this service)
The CP loading spreadsheet has a large number of presumptions made that in 98%
(my estimate) of CP's it will give a very good approximation of the CP's
performance. In the CP10 days (1985 technology) CP's were overloaded a lot and
the spreadsheet could predict it! CP's that were given the OK by the
spreadsheet were never overloaded, in my experience.
I never had one CP30 or 40 or 60 that ended up overloaded when my spreadsheet
said it would be OK. I had quite a large number of CP's that no one ran the
spreadsheet on until there was trouble and when we ran the spreadsheet, it too
said that the CP was overloaded. Included in this bunch of overloaded CP's were
some CP60 upgrades from 30A and 40A where the CP60 spreadsheet predicted that
the CP60 (fieldbus) would be overloaded but the 30A and 40A ran OK.
Use the spreadsheet to verify loads on your running CP's to become familiar
with it. You should get close to the CP Station display numbers.
There is a Help Hint for using SOM and RSOM. Sorry, cannot remember the number.
I believe that Foxboro also provides training in these tools as part of the
Alliance course. There is value in being trained by experts.
Terry
________________________________
From: foxboro-bounce@xxxxxxxxxxxxx on behalf of Jack.Easley@xxxxxxx
Sent: lun. 2006-03-27 17:17
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Block Equivalents List
Does anyone have a handy-dandy list of I/O Loading block equivalents for
the most common Foxboro blocks they are willing to share? I know Foxboro
has spreadsheets available for this, and that other factors affect CP/GW
loading, but I could use a better grasp of block equivalents to quickly
check loading problems.
A list of other CP/GW loading factors such as peer-2-peer, display,
historian, and PI connections and how one calculates (rsom, sipc, etc)
how significantly they affect CP/GW loading would be useful to most of
us also.
Appreciate it ...
Jack Easley
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