Instrument Cable Layout

Instrument Cable Layout shows routing of instrument cables according to plant or platform layout. In addition, instrument cable layout shows the details related to instrumentation cable such as:

  • Location of field devices to be wired
  • Location of junction box
  • Cable number
  • Cable going up/down


Reference drawing: Instrument Location Plan

  • From Instrument Location Plan, disregard the instrument which does not require wiring such as Gauges, Pressure Safety Valve, etc.
  • Route the electronic instrument to the nearest junction box accordingly (make necessary separation to junction box for analog or digital, SIS or BPCS or Fire & Gas, IS or Non-IS).
  • Route the multi-pair/multi-core cable from junction box to control room/other rooms.

Cable routing should be as short as possible, however consider some factors which should be avoided such as high interference noise, hot source, etc. Please refer to API 552.

The purpose of instrument cable layout
Instrument cable layout together with interconnection block diagram are to be used as a reference for preparing instrument cable schedule in determining the following:

  • List of the cable required and its length
  • The point of source and destination of cable end connection

Instrument cable layout is also a reference to identify the existence of all instrument cables in the plant or platform.

No example is provided here since instrument cable layout depends on plant or platform layout. However below symbols may be used for items related to instrument cable layout.

Note that, above example shows symbols which may differ among projects. The important thing is one shall be consistent with the symbol in the entire instrument cable layout drawing and shall list the symbols in the legend section.

Instrument Drawing