Re: [foxboro] Block Equivalents List

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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