What is an Input-Output List or mostly said I O list?
IO list is a document that contains the list of instrumentation serving as an input or output of the control system. Tag numbers that physically has a cable that connects to the control system will appear or be named on the IO list. For example, transmitter switches, pushbuttons, detectors, solenoid valve Positioner of a control valve and alarm are on the list but not Fence for example.
When there is more than one control system in a plant, let’s say PCS (Process Control System), SIS(Safety instrumented system) and F&G (Fire and Gas), the Io list shall clearly indicate which instruments are assigned to which control system or may separate them to a different section of the document.
In the IO list, at least the following information should be stated for each tag number
tag number,
service description,
drawing number,
type of instrument,
Location,
Io type
control system
range or set point.
loop number, (For DCS and process control, not applicable for most Assembly Lines)
| NO | Tag Number | Loop Number | Instrument Type | Service Comment | Drawing Number | Location | IO Type | System | Calibration Min | Calibration Max | Setpoint | Engineering Unit | Rack ID | I/O Address |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | LIT-0100 | L-0100 | Level Indication Transmitter | Water Level Control | P-CPP-PID-00-01 | Field | AI | PCS | 0 | 100 | – | % | FL00A0 | I:1.0 |
| 2 | FIT-0100 | F-0100 | Flow Indicate Transmitter | Gas Outlet | P-CPP-PID-00-01 | Field | AI | PCS | 0 | 150 | MMScfd | FL00A0 | I:2.0 |
The information column in which the IO list contains may be as simple as the above table. However, some projects require the IO list to be detailed by having an alarm setpoint, the controller action etc.
In the next step, the IO list will include IO number assignments such as rack number, slot number and PLC IO Address
For preparing an input-output list. We may need an instrument index as a reference document in some big plants. Otherwise in smaller projects equipment list which is prepared in step 2 (FDS) would be enough.
Instrument Index document containing lists of instrument devices within a plant this document shall include tag number of all physical instruments for example field instrument physical alarm and indicator and pseudo instruments which commonly name soft tag, for example, DCs indication alarm and controller in an instrument index document the following information should be stated but not limited to tag number loop number type of instrument location service description P and ID number line number or equipment number input-output type control system range or setpoint along with engineering unit used applicable reference documents such as instrument datasheet number hookup drawing number instrumentally outnumber and loop drawing number package number manufacturer model number.
Although the IO list mostly does not include IO wiring type, it would be informative to look at below subject
Electrical Engineer 