What is Instrument I/O List?

Instrument I/O List is a document containing list of instrumentation which serve as an input or output of control system.

Therefore, only the tag number that physically has a cable which connects to the control system appears on I/O List.

When there are more than one control system in a plant (let say PCS and SIS), the I/O list shall clearly indicates which instruments is assigned to which control system or may separate them to different section in the document.

Instrument I/O List

In I/O list, the following information should be stated but not limited to:

  • Tag number
  • Loop Number
  • Service description
  • P&ID Number
  • Type of Instrument
  • Location
  • I/O Type
  • Control System
  • Range or set point

The information column in which I/O list contains may be as simple as above, however some project require I/O list to be detailed by having alarm list, controller action, logic “0”/“1”descriptor.

Later on, I/O list would include I/O number assignment (rack, slot, channel number) which information to be provided by control system vendor.

Reference document

  1. Instrument Index

Filter all tag numbers that has an Input Output to make the I/O list

The purpose of I/O List

I/O list is used to determine the size of control system required by project, by counting how many I/O exists within a plant by each control system

Example of I/O list document shown in above image.