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dembous (Electrical)
20 Aug 07 10:02
Helllo Guys!!!

I am an EIT (not yet familiar with DCS) and my supervisor asked me to compare the Remote I/O capabilities of different vendors.

The thing is that I went through vendors documentation and I still can't decide the features that are really important for the sacke of comparison. I tried to find some infos in our (the company) specifications but nothing...

Based on your experience, could you tell me what's really important to check!!?
Thanks guys!!!!
JLSeagull (Electrical)
20 Aug 07 12:14
Some DCS and PLC I/O are rated for the hazardous area classification Class I Division 2.  This is important in the hydrocarbon business.

The temperature limits are important for any remote I/O consideration.  Typically they publish an upper limit at 40, 50 degree C etc.  The low end is important too.  Humidity is a consideration.

Can the I/O board be changed without being disconnected from power (maintainable)?

Can the same analog input I/O module work where the I/O powers the transmitter and with field powered instruments?

Are the digital I/O points configurable for input or output?

Is there a termination strip that permits pulling the I/O card without disconnection the I/O wiring?

...
controlnovice (Electrical)
20 Aug 07 12:37
JLSeagull has some good points.

Also compare the type of communication between the main controller and the Remote I/O.  Is it the same DCS/PLC network, or is it proprietary, or a 3rd party.  I recommend Remote I/O that uses the same network communication provided by the vendor.

______________________________________________________________________________
This is normally the space where people post something insightful.

itsmoked (Electrical)
20 Aug 07 15:10
All excellent.

And just "what do you need"?;
Analog IN? <Voltages>
Digital IN? <Voltages>
Digital OUT? <Voltages/Current>
Analog OUT? <Voltages/Current>
Something else?

Won't matter what else 'it' can do if it doesn't provide 'what' you need.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

dembous (Electrical)
20 Aug 07 16:13
Thanks so much to all!!! I've got a pretty good basis now for my work.

Cheers!!!
Ashereng (Petroleum)
20 Aug 07 18:21
Just to add to the excellent list:

Vibration - in some applications (pulp and paper) vibrations can not be avoided.

Hardened - in some applications (pulp and paper) you will have chemicals in the air (chlorine, caustic, water) that you can not protect agains (eg. with a positive pressure enclosure) and the I/O boards are left to fend for them selves. Moore had an excellent hardened I/O boards - they used to demonstrate it by pouring Coke (TM) on it, letting it sit for the whole day, and then re-inserting it back. They also used to literally throw it across the room, and then re-inserting it. Quite robust.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
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JLSeagull (Electrical)
21 Aug 07 10:53
A lot of people address tropical treatment for I/O boards in tropical locations.  Ashereng mentions paper plants.  Hydrogen sulfide will eath the copper off printed circuit boards.  If the remote location includes a nasty ambient you need to treat the environment or the enclosure.  Make the installation easy for the technician to service.  One manufacturer used to address remote I/O enclosures out in the weather like a junction box.  Don't do that.
dembous (Electrical)
23 Aug 07 9:57
Controlnovice, can you tell me the reason why you prefer a network communication provided by the vendor rather than a 3rd party one?
controlnovice (Electrical)
24 Aug 07 10:22
Basically,

- no finger pointing when something goes wrong.

- Usually easier configuration when using the same vendors communication and configuration packages. A 3rd party communication many times consists of 'additional' configuration to make the systems match.  However, in the last 5 years or so, the DCS and PLC providers have worked closely with each other and offer multiple communication networks for their systems to provide the most flexibility.  Your system may be one of them.

______________________________________________________________________________
This is normally the space where people post something insightful.

dembous (Electrical)
24 Aug 07 15:41
Thanks a lot !!!

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