In Chapter 02, I made a point of saying that RevE copies drawings exactly, typos and all. If the sheet says EUIPMENT, the record says EUIPMENT, because a fabrication drawing is a contract document and nobody should quietly edit it.
I still believe that. But it left an obvious question hanging, and my fabricator friend asked it the moment he saw the review screen: "Fine, you copied my mistake perfectly. Can you also tell me it's a mistake?"
That question opened a second job for RevE. Reading a drawing correctly is one thing. Checking that the drawing itself is correct is another, and it turns out that drawings get things wrong in two very different ways.
Kind one: words that are wrong
The first kind is familiar. Drawings are typed by busy people, copied from older drawings, and revised for years. Spelling mistakes creep in and then get copied forward, job after job.
When we ran RevE's new spelling finder over the sample drawings, it found exactly the eight typos on one heat-exchanger sheet: EXHANGER, TRIAGULAR, STRIGHT, CORROSSION, ALLOWANVCE, JPINTS, LIFTNG and BONET. Other drawings had their own: BAFFEL, NOZZEL, STIFFNER, PERPEDICULARITY, TORISHPHERICAL, REQUISION and more. Some of these had clearly been carried from drawing to drawing for years.
Building a spelling checker for engineering drawings is harder than it sounds, because an ordinary spell checker would have a nervous breakdown. TUBESHEET, SORF, SCH, ASTM and B16.5 aren't in any dictionary. So the rules lean hard towards precision: it's better to miss a typo than to flood the engineer with false alarms. A word is left alone if it's an English word, an engineering word on our list, a British spelling, or simply a fragment of a longer word. It's only suggested when it's one letter away from a known word starting with the same letter. And engineering words win: REQUISION becomes REQUISITION, not REVISION.
Then there's wording, which a spell checker can't catch at all. "Shall be provide" should be "shall be provided". "Equally spaces" should be "equally spaced". "As per ASMT" should be "as per ASTM". "Tele tale hole" should be "tell-tale hole". These are phrase rules that a shop can extend, plus simple checks for doubled words and unbalanced brackets.
All of this runs on the laptop. No AI is involved.
The original is never touched
This is where the principle from Part 2 survives intact. RevE doesn't fix the original drawing. Each suggestion appears in the review list with its place on the sheet, and a person decides: accept the correction, edit it, or keep the word as printed.
Accepted corrections go into two places:
- a corrected copy of the drawing, with a matching review copy where every change is marked in blue;
- every new drawing made from that template from then on. The typo that has travelled for years stops travelling.
The system learns as it goes. A correction accepted on one drawing is suggested on every drawing, and a word deliberately kept as printed is never suggested again. Before any new drawing is produced, the wizard lists typos in the values the person typed and any wording on the template that hasn't been decided yet.
Kind two: a drawing that contradicts itself
The second kind of error is far more dangerous, and it's the one I'm prouder of catching.
A fabrication drawing states the same fact in many places. On a typical exchanger sheet, the number of tubes appears in a note on the elevation, in the parts list, in the tubesheet hole views (as actual drawn holes) and in the drilling notes beside them. The tube pattern, triangular or square, appears in the notes, in a small pitch sketch, and in the way the holes are actually laid out in two or more views.
When someone revises a drawing by hand, it's easy to update four of those places and miss the fifth. The sheet then speaks differently in different places, and the shop floor builds whichever version the welder happens to read.
So RevE now runs an integrity check. It reads every place a fact appears: printed text, lettering drawn as shapes (read with local OCR), notes split across several lines, tables printed sideways, and the holes physically drawn in the tubesheet views. Then it asks one simple question: does every place say the same thing?
The test that convinced me was simple. We took a design where the tube layout had been changed from triangular to square, with 45 tubes. On RevE's generated drawing, every place agreed: 45 holes in five places, square in nine, pitch 24 in eight. Then we checked an un-updated copy of the same sheet. RevE flagged the pitch sketch, both bold notes, the "44 TUBES / TRIAGULAR PITCH-24" text and all four drawn hole views. Exactly the places a tired draughtsperson might miss.
On the templates themselves it raised no false alarms. Where a fact isn't printed, or can't be read, it's skipped and never guessed, and the screen shows how many places each fact was found in.
It learns what "fine" means
Not every difference is a mistake. Sometimes a note deliberately mentions an old value, or a phrase looks like a count but isn't. A parts-list item number "04 TUBES" is a row number, not four tubes, and RevE knows to ignore it.
When a check flags something that's actually fine, the engineer says so with one click. RevE remembers that wording, with the numbers masked out, and leaves it out of every later check on every drawing. The checker gets quieter and sharper the more it's used, which is exactly the opposite of how most alarm systems age.
The bug the checker found in our own work
My favourite moment came from turning the checker on ourselves.
When RevE changes a tube pattern on a new drawing, it redraws the holes. The first version of that feature covered the old holes in white and drew the new ones on top. On screen and on paper, it looked perfect.
The integrity check didn't agree. When it read the hole views, it found the old holes still there, hidden under white paint. They would have appeared in the AutoCAD file, where white on white is just another layer of lines. The fix was to remove the old holes properly, take out every path that touched them, and redraw each new hole as its own clean shape, so it can be read back and checked.
A check that only verified what we thought we'd done would never have caught that. A check that reads the finished drawing the way a stranger would caught it at once.
What comes next
For now the integrity check covers the tube-bundle facts: tube count, holes, pitch, pattern and tube size. The rules live in a simple file, so new facts can be added without new code. Next on the list are baffle count and cut, tie-rod count and size, shell diameter and length, nozzle sizes against the nozzle schedule, and parts-list quantities against the views.
In my steel-plant years, the most expensive problems were rarely the obvious failures. They were the quiet inconsistencies: two systems that each looked right on their own and disagreed with each other. Drawings are no different. A drawing that disagrees with itself is a defect waiting for a shop floor to find it.
RevE now finds it first.
Next, in Part 4: making the next drawing from an approved one, without drawing anything.
#QualityAssurance #EngineeringDrawings #IndustrialAI #Fabrication #HeatExchangers #DesignReview #Manufacturing #ZeroDefects #Engineering #SandurTech
Disclaimer
This series introduces SandurTech RevE, a product in development for AI-assisted engineering drawing analysis and generation. Examples reflect our current capabilities and ongoing validation. Outputs should be reviewed by qualified engineers and verified against approved drawings, standards, and project requirements before use.
