Galvanising lines: coating weight set with a safety margin
Why coating lines apply more zinc than the specification needs, what the margin costs, and how to check a computed coating weight first.
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Zinc coating weight is set with a margin
What happens. The coating weight is measured after the fact, at a few points or on a few samples, and the specification is a minimum. To be safe, the line runs with a higher weight than needed. Air-knife pressure and strip speed are set by experience and corrected when the gauge reading drifts.
What it costs. Zinc is a large cost on a coating line. Every extra bit above the minimum goes into the product for nothing, on every metre of strip or every batch of parts.
Why the usual fix fails. Running closer to the minimum by hand works until bath conditions, speed or strip width change. The gauge reading arrives late, so the correction always chases the last change.
How a fixed-price remote diagnosis checks it. From line logs (speed, knife pressure and distance, bath temperature, gauge readings) I estimate the coating weight as it is applied. The fixed-price remote diagnosis shows whether the margin can be reduced with a computed value and tighter knife control, and what the data would have to cover.
Background: Computing unmeasured states for control
Check it on your plant first: a fixed-price remote diagnosis
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