In this article7 sections
IFR, IFA, IFC and AFC are the status codes an engineering drawing is issued under on its way from first draft to the field, and on projects that use all four they come in that order. IFR, issued for review, sends the drawing out for comment. IFA, issued for approval, sends it to the client or owner for a formal decision. IFC, issued for construction, releases it to be bought against, fabricated and built. AFC, approved for construction, records the owner's approval to build: on some projects it is a separate stamp that follows the IFC issue, and on others it is the project's own name for IFC. After construction the drawing is reissued once more, as As-Built.
The status states what a reader may do with the sheet. An issued for construction drawing can be built from and an IFR drawing cannot, and the instrument index, the I/O list and the other registers taken from a drawing inherit that difference. Each register row has to carry the revision and status of the sheet it came from.
No single public standard fixes these codes. Each project defines them in its document control procedure, so the meanings here are the common ones, with variants noted where practice splits.
The status codes in order
Each column answers a question a document controller or engineer asks of an incoming sheet.
| Code | Full name | Issued by | What it permits | What may still change | What the registers do |
|---|---|---|---|---|---|
| IFR | Issued for Review | The originating discipline, to other disciplines or the client | Comment, coordination and early planning. Nothing is bought or built from it | Anything: tags, lines, equipment, layout | Rows open as provisional, at the revision letter. Counts feed estimates only |
| IFA | Issued for Approval | The engineering contractor, to the client or owner | A formal decision, returned with a review code | Anything the approval comments touch | Rows move to the new letter. A deleted tag keeps its row, marked deleted, and is not reissued |
| IFD | Issued for Design, where used | The lead discipline, to the disciplines that design from it | Downstream design: datasheets, piping layout, cabinet sizing | Anything still under review or approval | The index becomes the basis for datasheets and requisitions, rows still provisional |
| IFC | Issued for Construction | The engineering contractor or engineer of record, through document control | Purchase, fabrication and construction, outside any held area | Only through a numbered revision under change control | Baseline at the IFC revision. Channels and terminations assigned. Held rows stay listed and unreleased |
| AFC | Approved for Construction | The owner, or the contractor where AFC replaces IFC | Construction with the owner's approval on record | As for IFC | Release to purchase and wiring follows whichever stamp the contract names |
| As-Built | As-Built | Engineering, from construction and commissioning redlines, accepted by the owner at handover | Operation, maintenance and later change start from it | Only through the operating site's management of change | Rows reconcile to the as-built revision and go into the handover set |
Two fields travel together and are easy to conflate. The status says why the sheet was issued and the revision says which issue it is, so a drawing can stay at IFC through revisions 0, 1 and 2. A document register records both on each line.
A third field arrives when the sheet comes back. The review code records what the recipient decided, and the CFIHOS reference data lists six returns a principal can give a contractor's document: approved, approved with comments, reviewed with comments, reviewed with no comments, rejected, and not reviewed. A drawing returned rejected at IFA goes out again as IFA at the next letter, and one approved with comments usually goes to IFC with the comments incorporated.
Statuses outside the main sequence
Projects add codes on either side of the four.
- IFI, issued for information. Sent so the recipient knows the content. No approval is expected and nothing is built from it.
- IFB or IFT, issued for bid or tender. The pricing basis for bidders, with no authority to build.
- Issued for HAZOP. Some projects issue the P&IDs formally for the hazard study, so the team reviews one fixed revision, then reissue them with the recommendations incorporated.
- ISO 19650 suitability codes. Projects run to ISO 19650, common in buildings and infrastructure, replace the words with codes: S1 to S4 for information shared for coordination, for information, for review and comment and for stage approval, A for authorized and accepted, B for partial sign-off with comments, and CR for the as-constructed record.
On a project with several contractors the same letters can mean different things on two transmittals in one week. The transmittal legend is the authority, and the document register records each status exactly as issued.
AFC and IFC, one stamp or two
Three arrangements are common.
- AFC in place of IFC. Some projects, engineering and infrastructure work in particular, print AFC where others print IFC, with the same authority to build.
- AFC after IFC. The contractor issues the drawing for construction, the owner reviews it, and construction proceeds from the sheet carrying the owner's AFC stamp. IFC is the contractor's statement that the design is complete, and AFC is the owner's acceptance of it.
- Approval before IFC. The IFA return licenses the IFC issue and no separate AFC stamp exists. Vendor drawings often follow this route, with the customer's approval code releasing the vendor to issue for construction or fabrication.
UK legal commentary describes IFC as an industry term with no definition in legislation or case law, so its effect comes from the contract. For the registers the rule holds under all three arrangements: find the stamp the contract names as the release to build, and release rows to purchase and wiring on that stamp alone.
How a revision identifies itself
The status sits on a stamp or in the title block. The revision identifies the issue, and its conventions show whether anyone may have built from the previous one.
| Convention | What it looks like | What it tells the reader | Where practice varies |
|---|---|---|---|
| Lettered revisions | Rev A, B, C on IFR, IFA, IFD and HAZOP issues | The sheet is not released to build, and the next issue can change anything | Some owners number preliminary issues and letter the construction ones. Manufacturing drawings often start at revision zero or a dash, then use letters |
| Revision 0 | The first IFC issue | The construction baseline | Some projects clear the lettered history from the revision block at revision 0, and others keep it |
| Numbered revisions | Rev 1, 2, 3 after IFC | Someone may have acted on the previous issue, so each change needs its own record | Some firms number formal issues from 1 and give internal issues a letter suffix, such as 1A and 1B |
| Cloud and triangle | A cloud around each change, with a triangle carrying the revision number | Where the latest revision changed the sheet | The previous revision's clouds are usually removed at each issue. A P&ID with many changes may point to a separate revision list |
| Hold cloud | A cloud marked HOLD, often with a hold number | The content inside is not released, even on an IFC sheet | Some owners refuse an IFC issue that still carries holds |
| As-Built | The next revision, status As-Built, with the redlines incorporated | What was installed, and the base for operation and later change | In building practice the contractor's marked set is the as-built and the designer's clean compiled set is the record drawing |
| As-Installed | A status or title used on some projects | Usually another name for the record set | A project that uses both terms defines the difference in its status legend |
A hold cloud is easy to misread. The sheet is released and the clouded content is not. Holds usually wait on vendor data, such as nozzle orientations or a package's own instruments, and each carries a number on a hold list beside the document register. Work proceeds around a hold and not inside it, and lifting the hold is a numbered revision of its own.
One drawing through six issues
Take PID-001, sheet 1, on Unit 34, showing inlet separator V-201 and its two pumps, P-302A and P-302B. The drawing and its tags are invented for this example. The table follows the sheet from first issue to as-built, with what each issue did to the two registers built from it.
| Issue | What changed on PID-001 | Instrument index | I/O list |
|---|---|---|---|
| Rev A, IFR | First issue for interdiscipline review: PT-101 and LT-103 on V-201, then FT-101, TT-104 and control valve FCV-302 on the pump discharge line 4"-CS-101-A1A | Five rows opened, provisional, at revision A | A count for the estimate: four analogue inputs and one analogue output. No channels |
| Rev B, IFA | Review comments add LSL-402, a low-level switch protecting the pumps. Returned approved with comments: the owner asks for a separate high-high pressure trip | LSL-402 added. All rows on the sheet rechecked and moved to revision B | One digital input added. Still a count |
| Rev 0, IFC | Comments incorporated: PSHH-401 and SDV-306 added on the inlet, both on the cause and effect matrix. Suction strainer ST-602 and PDT-105 across it clouded HOLD for pump vendor data | PSHH-401, SDV-306 and PDT-105 added. Baseline at revision 0, status IFC. PDT-105 carries its hold number and is not released for purchase | Channels and terminations assigned to released rows. PDT-105 listed as held, with no channel |
| Rev 1, IFC | Vendor data received. Hold lifted, PDT-105 range and connections confirmed, triangle 1 at the strainer | PDT-105 released for purchase | PDT-105 assigned an analogue input |
| Rev 2, IFC | A change request raised during construction adds FSL-403, low-flow protection for the pumps. Triangle 2 cites the change number | FSL-403 added, carrying the change number | One spare digital input used. Loop and termination drawings follow under the same change |
| Rev 3, As-Built | Redlines incorporated: TT-104 installed upstream of FCV-302 instead of downstream as drawn, and a drain valve added on the discharge line | TT-104 location corrected. Every row reconciled to revision 3, status As-Built | Reconciled to revision 3 and handed over |
Three things in that history are easy to lose. The lettered issues produced real work, an estimate and a first cabinet layout, and nothing in them was released to buy or build, so the rows stayed provisional. After revision 0 the I/O list changed only when a numbered revision told it to: once to release a hold, once to add a signal under a change number. And the as-built moved a transmitter without changing a tag, which is why reconciliation checks location and line as well as the tag list.
Changing a drawing after IFC
Before IFC, revising a drawing is how the design develops. The next lettered issue replaces the last, and nothing has been bought or built from it.
After IFC, other people have acted on the sheet. Procurement has ordered against it, a fabricator may have cut spools, and the I/O list has sized the cabinets. A change now has consequences outside the drawing, so it passes through change control before the drawing is touched, under whatever name the project uses: change request, design change notice, field change request, or a technical query answered by a site instruction. The change is raised, its effect on cost, schedule, safety and the other documents is assessed, the authority the project names approves it, and only then is it issued as a numbered revision whose cloud and triangle cite the change number. The document freeze taken before the IFC issue fixes the revision this route starts from.
After handover the same discipline moves into the operating site's management of change procedure. In the United States, for processes covered by OSHA's process safety management standard, the employer's procedures must address the technical basis, the safety impact, the procedure changes, the duration and the authorization before a change is made (29 CFR 1910.119(l)), and the process safety information, which includes the P&IDs, must be updated to match. Owners and regulators elsewhere set their own requirements, and the site procedure is the authority.
A redraw with no change record leaves the sheet correct and its history broken. The new row in the instrument index has no reason attached, and an auditor cannot walk from the row to the decision that put it there. That gap is how registers drift from the plant, the subject of MOC and P&ID documentation.
Keeping the registers on the drawing's revision
The status codes are a short vocabulary with a contract behind each word: what may be built, from which revision, on whose approval. The registers derived from a drawing inherit that contract, and they hold up when each row names the drawing, sheet, revision and status it came from. Four habits carry most of the weight:
- Treat rows taken from lettered issues as provisional.
- Baseline the registers at the release to build, and record the transmittal that released it.
- Change nothing after IFC without the revision and change number that authorize it.
- Reconcile to the as-built before handover.
The columns that carry those fields are set out in the instrument index, field by field and I/O list columns explained.
Tagsight gives a project team the instrument index and I/O list for each issued revision of a P&ID set, so the registers can be compared issue against issue. The work at each issue is the same: an engineering record kept true through every revision, from the first IFR to the as-built.