Asset tagging and equipment numbering: what a tag identifies, site conventions and IEC 81346, and how to retag an operating plant
What an asset tag identifies on an industrial plant, how a site convention of area, type and sequence is built, the three aspects of an IEC 81346 reference designation, the tag schemes in common use, the rules that keep a convention clean, plates and labels in the field, and how to retag a plant that is already running. With a drawing of a tag and its parts.
Key takeaways
- An asset tag names a position in the plant, not the machine sitting in it. The machine carries its own serial and asset number, so the history of the place and the history of the machine both survive a swap.
- Most Australian sites use an area, equipment type and sequence convention. IEC 81346 goes further, describing each object by what it does, what it is and where it is, each with its own prefix.
- A convention is only as good as its controlled lists. Area numbers and type codes need one owner and a published list, or every contractor invents their own.
- The same tag string belongs on the drawing, in the control system, in the CMMS and on the plate. Two numbering systems for one pump is a translation cost paid on every work order.
- Retagging an operating plant starts with a walkdown and a cross reference from old tags to new, and ends with the plates. Fitting plates first is the most common way to make it worse.
A fitter is sent to replace the gearbox on conveyor 3. The work order says CV03, the drawing says 310-CV-003, the control system calls it CONV_3 and the plate on the drive says nothing because it fell off in the last shutdown. The fitter finds the right conveyor by asking. Multiply that by every work order on a site and the cost of loose tagging is hours each week, history on the wrong equipment, and the occasional isolation on the wrong drive.
This guide covers tagging on industrial plant: what a tag identifies, how a site convention and IEC 81346 reference designations are built, the schemes in common use, the rules that keep a convention clean, the physical plates and labels, and how to retag a plant that is already running. It sits beside the asset hierarchy guide, which covers how tagged positions are arranged into a hierarchy in the CMMS. The standards named are reference points, and the right scheme depends on the owner, the industry and what is already installed.
What a tag identifies
A tag names a position in the plant, a place where equipment does a job. The pump in that position can be removed, overhauled and refitted somewhere else, and the position keeps its tag the whole time. The pump has its own identity, its serial number and asset number, which follows it to the workshop and back. In the CMMS the first is a functional location and the second is an equipment record.
Getting that distinction right is what makes the history useful. Failures recorded against the position say whether the duty is hard on pumps. Failures recorded against the pump say whether that pump is a bad one. A site that tags machines instead of positions loses the first, and a site that never records serial numbers loses the second.
The tag belongs to the hole in the plant, not to whatever is bolted into it this year.
A site convention
Most mining and process plants in Australia use a convention built from three parts: an area number for the part of the plant, a two or three letter code for the equipment type, and a sequence number that makes the tag unique within the area and type. A suffix adds components, such as the motor or the gearbox on a conveyor. The result is short, readable on a plate and easy to say on a radio.
The weakness is in the lists behind it. If the area numbers and the type codes are not written down and owned by someone, each contractor and each project adds its own, and within a few years the same kind of equipment carries three different codes. A convention needs a short document, a controlled list of areas and types, and a person who approves additions.
IEC 81346 reference designations
IEC 81346 takes a broader view. Any object can be described from three aspects. The function aspect, marked with an equals sign, says what it does. The product aspect, marked with a hyphen, says what it is. The location aspect, marked with a plus sign, says where it is. Each aspect is its own tree, so a motor can be designated by the conveyor drive function it serves, by its place in the product breakdown of the drive, and by the room or area it stands in. Part 2 of the standard sets the classes and letter codes used inside the designations.
The value is consistency across disciplines and across the life of the asset. Electrical, mechanical and control designers all work from the same structure, documents can be filed against it, as the document control guide covers, and a replacement product slots into the same function without renaming anything. The cost is discipline. Every contractor has to apply it from the first drawing, and it is much easier to specify on a new project than to retrofit.
The schemes side by side
Several schemes are in use, and a single site often has more than one: a site convention for equipment, ISA-5.1 for instruments, and an older scheme on the part of the plant built by a different owner. The aim is not to pick a winner but to know which scheme governs what, and to map between them where they meet.
| Scheme | Where it is used | How a tag is built | What to note |
|---|---|---|---|
| Site convention | Most mining and process plants in Australia | Area, equipment type code and sequence number, sometimes with a component suffix | Simple and readable. Only as good as its controlled lists of areas and type codes |
| ANSI/ISA-5.1 instrument tags | Instruments and control loops on P&IDs | Letters for the measured variable and functions, then a loop number | Covers instruments only. The equipment around them needs its own scheme |
| IEC 81346 reference designations | New projects, rail, power and infrastructure, and owners who want one scheme across disciplines | Function, product and location aspects, each a tree of codes with its own prefix | The most complete scheme. Needs discipline across every contractor from the start |
| RDS-PP | Power plants, including wind farms | An application of IEC 81346 for power plants, published by VGB | Replaces KKS on newer plants |
| KKS | Older power stations | Fixed positions for plant, system, equipment unit and component | Still on many operating stations. Mapping to a new scheme is a project in itself |
Rules that keep a convention clean
Whatever the scheme, a handful of rules decide whether it stays usable. Most of them are about stopping meaning from creeping into places it does not belong, and about keeping one string for one position in every system.
| Rule | Why it matters |
|---|---|
| One tag per position | The tag names the place in the plant. The machine in it carries its own serial and asset number, so a pump swapped for a rotable keeps the history in the right place |
| Controlled lists | Area numbers and equipment type codes come from a published list with one owner. A new code is a change, not a choice made on the day |
| Fixed format | The same number of characters and the same separator in every segment, so tags sort, filter and validate |
| No meaning in the sequence | The sequence number makes the tag unique and says nothing else. Encoding size or service into it breaks when the plant changes |
| Never reuse a tag | A retired tag stays retired, or old records attach to new equipment |
| One string everywhere | The same tag on the drawing, in the control system, in the CMMS and on the plate. A second numbering system is a permanent translation cost |
| Tag where the work is | Down to the level where work orders are raised and failures recorded, and no further. Parts below that are on the bill of materials |
Plates, labels and codes
A tag in a system is only half the job. The person in the field needs to read it on the equipment, in the light and conditions where the work happens. The plate needs to survive the environment and stay with the position, which means fixing it to the structure rather than to a guard that comes off at every service. Barcodes, QR codes and RFID add a quick lookup from a phone or tablet, and are worth the cost where the field crew actually carries a device.
| Carrier | Suits | What to watch |
|---|---|---|
| Engraved stainless steel plate | Outdoor, wet, hot or abrasive areas, and anything washed down | Fixing by rivet or tie to the structure, not to a removable guard |
| Engraved laminate plate | Indoor equipment, switchrooms and panel fronts | Fades and goes brittle in sun. Check the colour convention for the site |
| Printed label | Cabinets, cable cores and small instruments | Rated for the temperature and the chemicals in the area |
| Barcode or QR code | Work order lookup from a phone or tablet in the field | Encode the tag itself, not a link that will break when the system changes |
| RFID or NFC tag | Inspection routes and proof that a person was at the equipment | Needs readers, and metal surfaces need tags designed for them |
Retagging an operating plant
Retagging a running plant is a data project first and a plate project last. The walkdown usually finds equipment that is on no drawing, records in the CMMS for equipment long gone, and control system tags that match neither. Each change to a tag is a change to the plant record, and the cross reference from old to new is kept for good so that old drawings, old work orders and old trends stay searchable.
| Step | What it involves |
|---|---|
| Agree the convention | Areas, type codes, format and rules, written down and signed off before any plate is made |
| Walk the plant | Record what is actually installed and where, against the drawings and the CMMS. The three rarely agree |
| Reconcile the systems | Match every walked item to its drawing tag, control system tag and CMMS record, and list the gaps |
| Build the cross reference | Old tag to new tag for every item, kept permanently so old records and drawings stay searchable |
| Change the systems together | CMMS, control system descriptions, historian and drawings move to the new tags in one planned change |
| Fit the plates | Last, once the systems match, so nobody in the field reads a tag the CMMS does not know |
Where tagging goes wrong
- Machines tagged instead of positions, so the history leaves with every rotable.
- Type codes invented on each project, so one kind of equipment carries several codes.
- Meaning packed into the sequence number, such as size or duty, which breaks the first time the plant changes.
- The CMMS numbering designed separately from the drawings and the control system.
- Plates fixed to guards and covers, so they end up in the bin after the next shutdown.
- Retired tags reused for new equipment, so old failure records land on the wrong machine.
- New plates fitted before the systems are changed, so the field and the CMMS disagree for months.
Common questions
What is asset tagging on an industrial site?
Asset tagging gives every piece of equipment in the plant a unique identifier, the tag number, and fixes it to the equipment on a plate or label. The tag is used on drawings, in the control system and in the CMMS, so a person in the field, an engineer reading a P&ID and a planner raising a work order all mean the same thing. It is a different job from IT asset tagging, which labels portable items such as laptops for a fixed asset register.
What is IEC 81346?
IEC 81346 is the international standard series for structuring principles and reference designations of industrial systems. Part 1 sets the rules for building a reference designation and Part 2 sets the classes and letter codes for objects. An object can be described by its function, its product and its location, each a separate tree with its own prefix: an equals sign for function, a hyphen for product and a plus sign for location. Many power, rail and infrastructure owners specify it, and RDS-PP for power plants is built on it.
What is the difference between a tag number and an asset number?
A tag number names the position, such as the drive motor on a particular conveyor. An asset number or serial number identifies the physical machine. When a motor fails and a rotable is fitted, the tag stays the same and the asset number changes. Keeping the two separate in the CMMS lets the history of the position and the history of each motor be read on their own, which is how ISO 14224 and most CMMS products treat functional locations and equipment.
How should equipment tag numbers be structured?
Most sites use an area number, an equipment type code and a sequence number, sometimes with a suffix for components. The segments have a fixed length and a fixed separator, the area numbers and type codes come from controlled lists with one owner, and the sequence number carries no meaning beyond making the tag unique. A tag is never reused once it is retired. Where an owner wants one scheme across every discipline, IEC 81346 gives a fuller structure.
What should an equipment tag plate be made of?
Engraved stainless steel for outdoor, wet, hot or washed down areas, engraved laminate for indoor equipment and switchrooms, and printed labels rated for the environment for cabinets and small instruments. The plate should be fixed to the structure or the equipment base, not to a guard or cover that is removed for maintenance. A barcode or QR code on the plate can let a phone open the work order history, as long as it encodes the tag rather than a web link that may change.
Key terms
Plain-language definitions from our glossary for the concepts this article leans on.
Standards and further reading
- IEC 81346-1:2022 Industrial systems, installations and equipment: structuring principles and reference designations, basic rules (IEC)
- IEC 81346-2:2019 Structuring principles and reference designations, classification of objects and codes for classes (IEC)
- ANSI/ISA-5.1-2024 Instrumentation and control symbols and identification (ISA)
- ISO 14224:2016 Collection and exchange of reliability and maintenance data for equipment (ISO)
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