Site measurement and approval drawings
What to measure, how to photograph it and what the approval drawing has to show before fabrication starts.
Custom ductwork goes wrong at the interface. The component is built correctly and does not fit, because the duct was not what the drawing said. Careful measurement before fabrication is the cheapest insurance available.
What to measure
The duct section at four points along the length where the component will sit, not just at the flange, because ducts bow. The flange bolt pattern including bolt size and pitch. The distance to the nearest obstruction in all four directions. The available clearance for the actuator and for removing it later. The lifting route and the headroom.
How to photograph it
One wide shot showing the whole position, one close shot of the flange face with a tape measure held across it, and one shot of the actuator side showing what is in the way. Four photographs with a tape measure in frame are worth more than a page of description.
What the drawing shows
Overall dimensions, flange drilling, shaft centres, actuator envelope including the removal clearance, weight and lifting points, the fixed and sliding anchor points, and the design conditions the component was designed for. The last item is often omitted and it is the one that matters when the plant later changes its operating temperature.
Approval
The client marks up and returns the drawing. We do not proceed on a verbal approval, and we do not proceed on an email that says "looks fine" without the drawing attached. Once approved, the drawing becomes the specification and any later change is a variation with a date on it.
Fabrication tolerance
We state it on the drawing so nobody argues about it later. Typically ±2 mm on flange faces and bolt patterns, ±5 mm on overall dimensions, and a stated flatness for seat surfaces. If the site needs tighter, say so before the drawing is issued.
Talk to us about this duty
Send the duct section, design temperature, pressure difference and the duty point. We reply with the gate type, the material selection, the drive and a general arrangement drawing for approval.