What Is a P&ID and Why Is Extracting Data from It Hard?
A Piping and Instrumentation Diagram (P&ID) is the primary technical drawing for any process plant or industrial facility. It shows every pipe, instrument, valve, vessel, and piece of equipment in a process system, along with the control and signal connections between them. Every significant engineering deliverable downstream — tag registers, line lists, instrument indexes, MTOs — traces back to the P&ID package.
The problem is that P&IDs are complex visual documents. The useful engineering information sits inside:
- Instrument symbols (ISA-5.1 notation)
- Line designation callouts
- Equipment tag bubbles
- Process notes and annotations
- Title block references
None of this information is in a structured format. To use it, engineers have to read it manually, interpret the notation, and key it into the appropriate deliverable. Across a package of 80–100 drawings, that reading and extraction work is measured in weeks.
What AI P&ID Extraction Means
AI P&ID extraction refers to using an AI system to read engineering drawings and convert the useful information inside them into structured data — automatically.
This is distinct from:
- OCR — optical character recognition reads text characters but does not understand what they mean in engineering context
- Smart P&IDs — digital authoring formats (SPF, AVEVA PDMS) are structured by design, but most legacy projects use PDF-format drawings
- General-purpose AI — a general language model can read text but cannot interpret P&ID symbology or maintain the structural relationships between tags, lines, and equipment
AI P&ID extraction is specifically designed for engineering drawings, with the ability to:
- Recognise instrument and equipment symbols by shape and position
- Parse engineering notation correctly (tag formats, line designations, pipe classes)
- Preserve relationships between symbols and their adjacent text
- Maintain traceability from each extracted value back to its source drawing
What an AI P&ID Extraction System Produces
The outputs from P&ID extraction are the structured deliverables the engineering team needs to build:
| Output | What It Contains |
|---|---|
| Tag register | All tagged items: instruments, valves, equipment, piping lines |
| Line list | All piping lines with service, class, and from/to connections |
| Instrument list | All instruments with type, tag, line, and datasheet reference |
| Equipment list | All tagged equipment with description and P&ID reference |
| Valve list | All valves with type, tag, size, class, and actuator details |
| Mismatch report | Tags and attributes that conflict across drawings |
These are the deliverables the team would have produced manually. AI extraction produces them systematically, in a fraction of the time, with every value linked back to its source.
The Five Steps in Novek's P&ID Extraction Pipeline
Step 1 — Package ingestion
The drawing set is loaded as a package. Drawings are organised by sheet number and revision, with relationships between sheets tracked.
Step 2 — Visual symbol recognition
Each drawing is scanned visually for engineering symbols. ISA-5.1 instruments, valve types, equipment items, and line flow indicators are identified by shape and context — not by reading text alone.
Step 3 — Notation parsing
Adjacent text is parsed together with each symbol. Tag numbers, line designations, service abbreviations, and equipment references are extracted as structured attributes linked to their source symbol.
Step 4 — Cross-drawing consolidation
Tags and lines that appear across multiple sheets are consolidated. A flow transmitter that appears on three P&IDs is one entry in the tag register, with all three references captured.
Step 5 — Source-linked export
Each extracted row links to its source drawing page and position. Engineers can verify any value against the source without re-reading the full drawing.
Why General-Purpose AI Tools Struggle With P&IDs
A common question is why tools like general-purpose LLMs (GPT, Claude, Gemini) cannot just read a P&ID and produce the same outputs.
There are three structural reasons:
Symbols are not text. ISA-5.1 instrumentation symbols are geometric shapes. A circle with a line through it means a specific type of instrument. A rectangle with specific line types means a different type of equipment. Language models trained on text cannot reliably interpret these.
Relationships are spatial. The relationship between a tag number and its instrument is defined by proximity on the drawing — not by any explicit linguistic connection. General AI models that convert drawings to flat text lose these relationships.
Consistency matters. A tag register built by sampling a few drawings and extrapolating is not useful. EPC deliverables need to be complete — every drawing, every tag, every line. Systems designed for this task have completeness checking built in. General-purpose tools do not.
A Practical Example: What Changes on a Real EPC Project
Consider an EPC team receiving a 100-drawing P&ID package for a process facility expansion. The conventional workflow:
- Assign 2–3 engineers to read drawings and build tag register: 2 weeks
- QA check — cross-reference against drawing set: 3 days
- Build line list from same package: 2 more weeks
- Build instrument list: 1 additional week
Total: approximately 6 weeks to produce the foundational deliverables.
With AI P&ID extraction:
- Run extraction across the full package: hours
- Engineering review using source-linked outputs: 1–2 days
- Export in project template format: immediate
Total: 2–3 days for the same set of outputs, with full traceability throughout.
The engineering team's role shifts from data collection to review — which is a better use of their specialist knowledge, and a faster path to client-ready deliverables.
Frequently Asked Questions
Does AI P&ID extraction work with PDF-format drawings?
Yes. Novek is designed for standard PDF-format P&IDs used in most legacy and current projects. Smart P&ID formats are not required.
What about P&IDs with non-standard conventions?
Every project has its own drawing conventions. Novek adapts to the project's specific notation, and any notation it encounters that falls outside its model is flagged for engineering review.
How is accuracy verified?
Every extracted value stays linked to its source drawing page and position. The engineering team can verify any row by clicking through to the source — no re-reading of the full drawing required.
What happens when drawings are revised?
Updated drawing revisions can be re-processed. The system shows what changed between the old and new extraction — new tags, removed tags, modified attributes.
Can the outputs be exported in our project template?
Yes. Output format maps to the client's project template — column names, attribute selection, and field order are configurable per project.