Document control for plant: drawings, as-builts and the register that keeps them findable
What document control is for, the documents a plant depends on and who owns each, the states a document passes through and what each may be used for, what a number has to carry, the register that indexes it all, tying documents to the asset, and why a modification ends with documents reissued. With a free register template.
Key takeaways
- Document control is the discipline that lets anyone find the current drawing of what is actually built, and be sure it is the current one. Without it, the plant is maintained from memory and the last modification is a rumour.
- A document has one number for life and a revision that changes. Its state says what it may be used for, and the plant runs on the as-built revision, never on the one issued for construction.
- The register is the index: every document, its revision, its state, its owner, where it is held and where copies are posted. The tags it describes are on the row, so a drawing can be found from the asset.
- Numbers carry the plant's breakdown: site, area or system, discipline, type and a sequence, with the revision kept separately. The same breakdown the hierarchy and the commissioning systems use.
- Every modification ends with the documents reissued. A change whose drawings were not updated is not finished, and the next engineer finds out in the field.
A tradesperson opens a cabinet to replace a relay and the schematic in the folder shows a different relay, because the modification three years ago was never drawn up. An engineer sizes a pump from a datasheet for the pump that was replaced in 2019. A control engineer restores a PLC from a backup taken before the last two logic changes. Each of those is a document control failure, and each costs more than the document control that would have prevented it.
This guide sets out what document control is for, the documents a plant depends on and who owns each, the states a document passes through and what each may be used for, what a number has to carry, the register that indexes all of it, how documents are tied to the asset so they can be found from the equipment, how a modification ends with documents reissued, and where it goes wrong. A register template comes with it. It sits beside the asset register and management of change guides, which are the other two legs of knowing what the plant is.
Free download
Plant document register template
A document register with the number, revision, state, owner, system of record and points of use against every document, the equipment tags each describes so it can be found from the asset, four worked rows on one conveyor, and the states and numbering elements on sheets of their own.
What document control is for
A plant is described by documents, and the plant changes. Every modification, every replacement that was not quite like for like, every logic change and every setpoint moved makes some document wrong unless it is reissued. Document control is the discipline that keeps the description matching the plant: one current revision of each document, findable, with every superseded revision withdrawn from the places people look.
Its value is in what it prevents. Work done from the wrong drawing. A hazard study run on a P&ID that lacks the bypass fitted last year. A spare bought from an old datasheet. A control system restored to a state two changes old. The asset lifecycle guide puts it plainly: what is not handed over is rebuilt later by the maintenance team at many times the cost, and documents are the largest part of what gets lost.
The documents a plant depends on
Not every document is controlled, and the ones that are share a test: would work done from an out-of-date copy be wrong or unsafe? The table lists the kinds that pass the test on most plants, who owns each for content, and what changes them. The owner is a discipline, not the document controller, because the controller keeps the revision honest and the discipline keeps the content honest.
Two kinds are most often missed. Control system configuration is a document, backed up on every change rather than on a schedule, because the backup from last month does not contain this month's logic. And the registers themselves, the asset register, the hierarchy and this one, are documents with revisions and owners like any other.
| Document | What it holds | Owner | Changed by |
|---|---|---|---|
| P&IDs | Every line, valve, instrument and interlock on the process, by tag | Process engineering | Any modification to the process. The first drawing a change touches and the last to be updated |
| General arrangements and layouts | Where everything is, in plan and elevation | Mechanical and civil | Anything moved, added or removed |
| Single line diagrams and schematics | The electrical system from the supply to each load, and the control circuits | Electrical | Any electrical change, including a changed protection setting |
| Loop diagrams and I/O lists | Every instrument from the field to the controller, terminal by terminal | Instrumentation and control | Any instrument, cable or I/O change |
| Cause and effect, functional descriptions | What the control system does and why: interlocks, trips, sequences | Control engineering | Any logic change, which is most changes |
| Datasheets and vendor documents | What each item of equipment is, its ratings, its maker's manuals and drawings | The discipline that specified it | Replacement with anything not identical |
| Control system configuration | The PLC programs, HMI projects, settings and backups | Control engineering | Every logic or display change. Backed up on change, not on a schedule |
| Procedures and job plans | How the plant is operated and maintained, step by step | Operations and maintenance | Any change that alters a step, a limit or a hazard |
| Registers | The asset register, the hierarchy, the document register itself | Asset management | Every change to what exists or what describes it |
States, and what each may be used for
A document is not simply current or not. It passes through states, and each state says what it may be used for. A draft is for its authors. A revision issued for review is for comment and nothing else. The issued-for-construction revision is what the plant is built or modified from. The as-built, reissued from the field mark-ups at handover, is what the plant is operated and maintained from. Superseded revisions are kept and never used; cancelled ones mark a subject that no longer exists.
The codes vary by site and contractor. The rule that does not vary is that the plant runs on the as-built. A site whose drawings stop at issued-for-construction is maintained from what was intended, and the gap between intended and built is exactly where the problems are.
1Draft
Rev A, B, C
Being written or checked. Not issued
Nothing outside the authoring team
2Issued for review
Rev IFR
Circulated for comment by the disciplines and the owner
Comment. Not construction, not operation
3Issued for construction
Rev IFC, revision 0
Approved. The document the plant is built or modified from
Construction, procurement, commissioning
4As-built
Rev AB, revision 1 onward
Marked up from the field at handover and reissued to show what was actually built
Operation, maintenance, the next modification
5Superseded
Rev S
Replaced by a later revision. Kept, never used
History only. Withdrawn from every point of use
6Cancelled
Rev X
The subject no longer exists. Kept with the decommissioning record
History only
→ The number never changes. The revision does
The plant runs on the as-built, withdrawn from every point of use when superseded
| State | Revision code | What it means | May be used for |
|---|---|---|---|
| Draft | A, B, C | Being written or checked. Not issued | Nothing outside the authoring team |
| Issued for review | IFR | Circulated for comment by the disciplines and the owner | Comment. Not construction, not operation |
| Issued for construction | IFC, revision 0 | Approved. The document the plant is built or modified from | Construction, procurement, commissioning |
| As-built | AB, revision 1 onward | Marked up from the field at handover and reissued to show what was actually built | Operation, maintenance, the next modification |
| Superseded | S | Replaced by a later revision. Kept, never used | History only. Withdrawn from every point of use |
| Cancelled | X | The subject no longer exists. Kept with the decommissioning record | History only |
What a number carries
A document number is a location, not a label. It places the document in the plant's structure, the same structure the asset hierarchy and the commissioning systems use, so that everything about one area can be found by one prefix. The elements below are the usual ones. The format, the separators and the codes are the site's choice, made once and never changed, and IEC 81346 gives the reference designation structure they should follow.
Two rules follow. A number is never reused, because a cancelled document's number resurfacing on a new one makes the history unreadable. And the revision is not part of the number, because a number that changes on every revision cannot be referenced from a job plan or a procedure.
| Element | What it says | Example |
|---|---|---|
| Site or project | Which facility the document belongs to | PRJ, or the site code |
| Area or system | Where in the plant, from the same breakdown the hierarchy and the commissioning systems use | CR for crushing, 200 for the conveyor system |
| Discipline | Which discipline owns it | P process, M mechanical, E electrical, I instrumentation, C civil, S control |
| Document type | What kind of document, from a fixed list | PID, GA, SLD, LOOP, CE, DS, PROC |
| Sequence | A number that makes it unique within the above | 0012 |
| Revision | Its state and issue, carried separately so the number never changes | C, IFC 0, AB 1, AB 2 |
The register
The register is the index of every controlled document: number, title, type, discipline, area, revision, state, issue date, owner, where the master is held and where copies are posted. The two columns that make it useful rather than merely complete are the equipment tags, so a drawing can be found from the asset rather than from a folder tree, and the points of use, so that when a revision is superseded every posted copy can be withdrawn. The columns are the template's.
At a small plant the register is a controlled spreadsheet with the files in a structured folder that mirrors the numbering. At a larger one it is the metadata of an electronic document management system, with the revision workflow enforced by the system. The system matters less than the discipline that every document on the plant is on the register and every document on the register is where it says.
| Column | What goes in it |
|---|---|
| Document number | Never reused and never changed. The revision is in its own column |
| Title | As it says |
| Type | As it says |
| Discipline | As it says |
| Area or system | From the plant breakdown |
| Equipment tags | The tags the document describes, so it can be found from the asset |
| Revision | As it says |
| State | As it says |
| Issue date | As it says |
| Owner | The person or role accountable for its content |
| Held in | The system of record and its path or id |
| Points of use | Where copies are posted: control room, substation, the CMMS job plan |
| Change reference | The management of change or project that produced this revision |
| Supersedes | The revision this replaced |
Tied to the asset
A document that cannot be found from the equipment is a document that is not used. The tags column on the register is one half of the tie; the other is the link from the CMMS, where the job plan for a task lists the drawings it needs by number, and the functional location carries the documents that describe it. A tradesperson opening the work order sees the loop diagram and the schematic, by number, with the current revision, and does not go looking in a folder.
The same tie is what makes management of change work in reverse. A change request names the equipment, the register lists the documents that describe that equipment, and the change is not closed until each of them is reissued. Without the tie, the list of documents to update is made from memory, and memory misses the cause and effect every time.
If the drawing is not on the work order, the job is done from whatever was in the cabinet.
Where it goes wrong
- Drawings that stop at issued-for-construction, so the plant runs on what was intended rather than built.
- Field mark-ups made at commissioning and never drawn up, filed in a box with the project.
- Modifications closed without the documents reissued, so the next engineer finds the bypass in the field.
- Control system backups taken on a schedule, so the restore is two changes old.
- Numbers reused, or carrying the revision, so references in job plans and procedures break.
- A register that nobody owns after the project, so it stops being true the month after handover.
- Documents held in the contractor's system, in the contractor's format, with the native files never delivered.
- Copies posted in substations and control rooms with no record of where, so superseded revisions stay on the wall for years.
Common questions
What is document control?
The practice of numbering, revising, approving, distributing and withdrawing the documents a plant depends on, so that the current revision of each is the one in use everywhere and superseded revisions cannot be mistaken for it. It covers drawings, schematics, datasheets, procedures, job plans and control system backups, and it is what makes the as-built state of a plant knowable years after the project left.
What is an as-built drawing?
A drawing reissued after construction or modification to show what was actually built, from the field mark-ups made during commissioning, as distinct from the issued-for-construction revision that showed what was intended. The plant is operated and maintained from the as-built, and every later modification starts from it. A plant without as-builts is maintained from drawings that are wrong in ways nobody has written down.
What should a document numbering system include?
Elements that place the document in the plant and say what it is: the site or project, the area or system from the same breakdown the asset hierarchy uses, the discipline, the document type from a fixed list, and a sequence number to make it unique. The revision is carried separately, so the number never changes. Formats vary by site and contractor; the elements and the rule that a number is never reused are what matter.
What is the difference between a document register and a document management system?
The register is the index: a list of every controlled document with its number, revision, state, owner, location and points of use. The document management system, or EDMS, is the software that holds the files, enforces the revision workflow and serves the register from its metadata. A small plant can run the register as a controlled spreadsheet with the files in a structured folder. A large one needs the system. Either way the register is what has to be right.
Who owns plant documents after a project hands over?
The owner's organisation, through a document controller or the asset management function, with each document type owned for content by the discipline that would change it: process engineering for P&IDs, electrical for single lines, control engineering for the configuration backups. The project's document control ends at handover; the plant's begins there, and the handover has to include the register and the native files, not a box of PDFs.
Which standards apply to plant document control?
IEC 81346 for the reference designations that tie documents to the plant's structure, IEC 81355-1 for classifying the kinds of information a plant holds through its life, ISO 15489 for records management in general, and ISO 55001, which requires an asset management system to control the information it depends on. None of them dictates a numbering format; they give the structure that a site's own format should carry.
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 (IEC)
- IEC 81355-1:2024 Classification and designation of information: basic rules (IEC and ISO)
- ISO 15489-1:2016 Records management: concepts and principles (ISO)
- ISO 55001:2024 Asset management system requirements (ISO)
- ISO 14224:2016 Collection and exchange of reliability and maintenance data for equipment (ISO)
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