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Join Date: Feb 2009
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Assigning I/O Types to Instruments

02/17/2009 12:50 PM

Hello everyone!

Can anybody help me determine the type of I/O to be assigned in certain instruments? I am currently working on INtools and taking off instruments from P&ID. I am quite confused on the I/Os that i'm inputting in our database, kinda new in this task. Example, all my transmitters are AI. All my control valves are AO. How about those DI, DO, SAI, SAO, SDO, SDI? In which instruments should i use those I/O types?

Thanks and best regards,

AJ

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#1

Re: Assigning I/O Types to Instruments

02/18/2009 12:48 AM

Hi there,

You are obviously very new to this - so let us try and make this simple for you.

Firstly - I hopw your P&ID's follow the ISA standard. If so then this will be very easy.

All loops should have at least a primary and secondary indentifier. This means the first and second letters that identify the loop. For example the first letters mentioned below:

F - Flow

P - Pressure

L - Level

T - Temperature

The second letter can be something like the following:

E - Element

T - Transmitter

I - Indicating

S - Switch

C - Control

And so the list goes on. You can download these standards from the ISA website - at a cost. There is help though - your P&ID's should have come with a lead sheet that will give you these descriptions.

Now the easy part.

Your AI values - pretty much anything that has the second letter value of T for transmitter.

Your AO values - anything that looks like FCV, PCV, LCV, TCV. Look at the above table to work out Flow Control Valve etc. Why - because it has the seondary indentifier - Control

Your DI values - anything like FSL, PSL, LSL etc. The secondary identifier - Switch - gives it away. Flow Switch Low etc etc.

Your DO Values - anything like XV.

Basically your have things that will give you feedback - things you get information from - Inputs and things you need to drive - outputs. The things that you can get more than two states of information from - analogue, and the things you can only get two states of information from i.e. on/off - digital.

The same applies to outputs - on/off or more than two states or degrees of information.

Regards,

Craig

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Active Contributor

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Posts: 10
#4
In reply to #1

Re: Assigning I/O Types to Instruments

02/18/2009 12:12 PM

How about the serial tags? I know in completing a database, system type should should also be considered.

For example:

In DCS system,

FIT - AI

FI - Soft

FAH - Soft

FAL - Soft

In ESD system,

FIT - AI

FI - SAO

FAHH - SDO

FALL - SDO

Kindly check and explain if my inputs are correct.

Then, when can i use SAI and SDI I/O types?

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Participant

Join Date: Jun 2012
Location: Indonesia
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#7
In reply to #4

Re: Assigning I/O Types to Instruments

06/13/2012 2:12 AM

hi AJ,

actually, i have heard about SAI, SDI, ect. as you mentioned in my previous project. the 'S' here was about the system of the instrument go through, which was 'ESD/Safety/Shut Down System'. so, for SAI means an Analogue Input that is used for instruments in Shut Down System.

otherwise, maybe you also ever found about PAI/PAO that means an AI/AO that is used for instrument in 'DCS/PCS/PSD System.'

CMIIW

Regards,

Sandra

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#2

Re: Assigning I/O Types to Instruments

02/18/2009 1:08 AM

I agree with most of what was said with the exception of that on your P&ID's a second identifier "S" can be an analog input signal as this is a safety device.

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#3

Re: Assigning I/O Types to Instruments

02/18/2009 1:20 AM

Hi there,

If S is used as the first identifier - then it is Speed, If it is used as the second identifier it could be switch or safety. ISA-5.1-1984(R1992)

I have never heard of S as the second identifier being used for analogue. This could be because you are not following ISA standards.

Regards,

Craig

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#5

Re: Assigning I/O Types to Instruments

02/23/2009 2:02 AM

Hi Armando,

FIT - Flow Indicating Transmitter - hardware - physical analogue input

FT - Flow Transmitter - hardware - physical analogue input

FI - Flow Indication - Indication - Software Analogue

FSH - Flow Switch High - hardware - physical digital input

FAH - Flow Alarm High - Alarm - Software digital bit

FY - Flow Acutuator - hardware - physical analogue output

This principle applies to DCS/PLC/ESD

If it is an indication - it is something you will see on your SCADA/HMI - therefore it is software. If it is a transmitter - it is something physical and will therefore need an input. The same applies to the xSx because it is a switch.

Regards,

Craig

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Guru
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#6

Re: Assigning I/O Types to Instruments

02/26/2009 5:33 AM

Hi AJ,

I am familiar with AI, AO, DI and DO but never seen SAI, SAO, SDI and SDO.

AI (Analog Input) - this is where your transmitters signals go in.

AO (Analog Output) - this is where you connect your control valves or external indicators to.

DI (Digital Input) - the signals for this can come from limit switches, proximity sensors, pushbuttons, selector switches, or any device that sends an on/off signal.

DO (Digital Output) - this is where you connect devices that are either switched on or off such as: indicator lights, solenoid valves, relays, contactors, alarm horns/bells, etc.

You mentioned that the "S" devices are serial. By that I take it to mean that they are connected to a common bus (fieldbus devices perhaps?). If this is the case, these devices go into a single port and you don't necessarily need to have separate ones for input or output.

In any case, giving you a complete lesson here is going to take too much time. You're either going to have to ask for help from someone in your location. When I was still learning, I made a request to my boss for training. As a supervisor myself, I wouldn't want my crew to working by themselves on something they know nothing about. I would either send them to assist a more experienced person (who I expect to teach the newbee).

regards,

Vulcan

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