Tagging Philosophy for Junction Box, Cable, and Cable Drum

Tagging of the junction box, cables, and cable drums is very important during front-end engineering design for the preparation of the JB schedule, cable schedule, cable drum schedule, etc.

In this article, we are going to discuss the tagging philosophy for junction boxes, cables, and cable drums.

Junction Box Tagging

Junction Box Numbering

The given above is the basic structure of junction Box tagging philosophy

It includes,

  • Unit Number
  • Junction Box Code
  • Sequence Number

Unit Number

Refer to the below article for details regarding the unit number

Junction Box Code

Each junction box is associated with an instrumented facility comprising of a series of letters depicting that junction box details based on the type of signals.

Below table indicates some of the junction box types

JBEAnalogue (BPCS)
JBSControl – Solenoid Outputs (BPCS)
JBFFFieldbus Foundation (BPCS)
JBEXAnalogue (SIS)
JBSXControl – Solenoid Outputs (SIS)
JBAFAlarm (F&G)
JBEFAnalogue (F&G)
JBPFPower (F&G)

Also Read: Instrumentation Project Documents

Junction Box Schedule

Junction Box Schedule

Reference drawings required for the preparation of the JB Schedule are

  • Specifications for instrument junction boxes
  • Specifications for cable glands
  • Instrument cable schedule
  • Junction box tagging philosophy

Cable Tagging

The below discussed the different ways where we used the cable tagging.

Field Instrument to Junction Box

Individual cables running between field instruments and junction boxes are normally identified by the instrument tag number itself.


Field Instrument Unit Number

Junction Box to Control Room

The below image shows the basic structure of cable tagging for cables from the junction box to the control room.

Basic Structure of Cable Tagging for Cables

It includes,

  • Unit Number
  • Junction Box Code
  • Sequence Number of Cable
  • Cable Suffix

Cable Schedule

Signal Cable Schedule

Reference drawings required for the preparation of the cable schedule are

  • Instrumentation Index
  • Cable Tagging Philosophy
  • Cable and Junction Box Specification
  • Instrumentation Design Basis 

Instrument Cable Drum Tagging

Instrument Cable Drum Tagging

Given above is the basic structure of the Instrument cable drum numbering system.

It includes,

  • Zone
  • Cable Drum Number
  • Sub-Contractor Name
  • Cable Code
  • Sequence Number

Cable Code

Cable code indicates all details regarding that cable type. There is always a description associated with each cable code.

Given below is an example of cable type and description

Cable Code

Zone details and subcontractor details are entered as per the project execution details.

Cable Drum Schedule

Cable Drum Schedule

Reference drawings required for the preparation of cable drum schedule are,

  • Specification for Instrument Cables
  • Cable Drum Tagging Philosophy
  • Instrumentation Design Basis
  • Instrument Cable Schedule
  • Instrument Index
  • Fire & Gas Index

Author: Greeshmesh TP

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