Recognizing 5,000+ Control Loops Using Just 3 Templates

Challenge

The client’s project involved standard utility packages where P&IDs often repeated the same control loop structure: a valve, bypass line, and pressure transmitter — repeated with minor variations across hundreds of drawings.

Despite this repetition, engineers were manually reviewing every loop, due to:

• No metadata in the PDFs
• Slight differences in tag positions or line angles
• Inconsistent vendor drawing practices

With 5,000+ such arrangements to verify, manual review became a bottleneck.

“We knew these loops were repeating — but we had no way to programmatically recognize them.”

Solution

Storm Consulting implemented a template matching system that allowed the client to:

• Select and save 3 known control loop patterns as templates
• Automatically scan new P&IDs (PDF or image) for visual matches
• Annotate matched blocks with predefined metadata (loop ID, components)
• Flag unmatched regions for manual review

Implementation Highlights

• Used OpenCV’s matchTemplate + non-max suppression to locate all matches per P&ID
• Incorporated rotation and scale invariance for higher match accuracy
• Allowed engineers to upload new templates as needed (no coding required)
• Matched loops were annotated as bounding boxes + component list
• Matching results were exported as both images and CSV data

Results

“Once the first match came through, our team’s confidence skyrocketed. It was like a ‘find and fill’ function for our P&IDs.” — Instrumentation Lead, Client Project Team

Why It Worked

• Most control loop structures varied only in tag and orientation — perfect for template recognition
• Engineers could expand the template library themselves — no dev cycles needed
• Matched results retained visual + semantic context (not just boxes)
• Minimal tuning — high match accuracy out of the box with grayscale + threshold preprocessing

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