Python | EasyOCR | TrOCR | Deep Learning | VLM
Situation
Risk-Based Inspection (RBI) assessments require engineers to manually review large-format P&ID and PFD documents (typically A0/A1 size) to identify and number all piping equipment, define corrosion circuits, and establish inventory groups. This manual process is cognitively demanding, time-consuming, and highly prone to human error — especially across interconnected, multi-sheet P&ID sets common in large plant facilities.
Task
To address this bottleneck, I set out to develop an intelligent P&ID analysis tool capable of automating the extraction and interpretation of the three fundamental components of any P&ID/PFD: text, symbols, and lines. The end goal was a system that could:
Automatically identify and locate all equipment and piping tags
Recognize instrument and equipment symbols to auto-generate inventory groups
Trace process lines to support corrosion circuit creation
Serve as a general-purpose P&ID analysis platform beyond RBI use cases
Action
I developed a Python-based application integrating OCR engines (EasyOCR, TrOCR) and deep learning/Visual Language Models (VLM) for symbol recognition. Key engineering challenges and solutions included:
PDF format limitation — Converted PDF drawings to high-resolution images (PNG) to enable compatibility with OCR and vision models
Image scale problem — P&ID images often exceed 10,000 px in dimension while tag text occupies only 10–20 px, exceeding model input limits. I designed a sliding window mechanism with overlapping tiles to process large images in smaller, overlapping segments, eliminating blind spots at tile boundaries
Symbol diversity — P&ID standards include hundreds of symbol variants. I curated a labeled dataset covering primary symbols (valves, flanges, instruments, etc.) and trained a deep learning model for initial recognition, with plans to expand coverage as compute resources allow
Result
Text extraction module: Successfully deployed — the tool accurately extracts every equipment and piping tag along with its coordinates, enabling instant location of any item within a P&ID without manual searching, making the equipment numbering step in RBI assessments trivial
Symbol extraction module: Functional for primary symbols (valves, flanges, instruments); model accuracy improvements are ongoing to cover the full symbol library
Line extraction module: Planned as the next development phase, to be initiated after symbol recognition reaches production-level accuracy
The tool has significantly accelerated the RBI assessment workflow, reducing both the time and cognitive load required during the P&ID review stage — a process that previously required hours of manual interpretation per document.