Your launder is costing you more than you think

Author : Leslie Du | Published On : 25 Aug 2026

Most aluminum casters spend serious money on degassing units and ceramic foam filters, then let the metal travel through a launder that undoes half that work in the last 10 metres before the mold. I’ve watched plants measure hydrogen at the furnace exit at 0.09 mL/100g, then pour a sample at the casting station and get 0.18 – and they blame the degasser. It wasn’t the degasser. It was the launder.

Here’s what actually happens in a typical under‑performing launder:

Temperature drop of 15–25°C over 10 metres – so the holding furnace is run 20°C hotter than needed, which accelerates hydrogen pickup and oxide formation before the metal even leaves the furnace.
Open joints or poorly sealed covers that pull in humid air, re‑introducing the moisture you just spent energy removing.
Turbulence at transitions – every height drop or sharp bend folds in a fresh oxide film that your filter can’t catch because it forms right downstream of the filter box.

If any of these sound familiar, the launder is your real bottleneck.

Fix the basics first – they’re simple and cheap:

Check your slope. The standard rule is 1–2% gradient (1–2 cm per metre). Less than 1% gives sluggish flow and cold spots; more than 2% creates turbulence at the outlet. Measure it with a digital level – don’t guess.
Upgrade the insulation. Switch from standard ceramic fibre board to microporous panels. They give the same thermal performance at one‑third the thickness, which means you can add more insulation without changing the channel geometry. Temperature loss drops from 20°C to under 5°C per 10m – that’s a 15°C gain you can use to lower your holding furnace setpoint.
Seal every cover and joint. Use ceramic rope gaskets and check them weekly. A 1 mm gap at a cover edge loses more heat than you’d think, and it’s a direct path for atmospheric moisture. Keep covers closed except when you absolutely have to open them – and pre‑heat the launder before every shift to avoid thermal shock cracking.
Inspect the hot‑face lining after every campaign. Look for cracking, erosion, and aluminium penetration. If you see metal stuck in cracks, grind it out and patch before the next run – that penetration expands on the next heat and turns a small crack into a full reline job.
Clean the channel regularly. Dross buildup reduces effective cross‑section and changes flow velocity. Remove it while it’s still soft – once it hardens, you’re scraping refractory off with it.

These aren’t theoretical. I’ve seen plants cut temperature loss by two‑thirds with just better insulation and seal discipline, and their scrap rate from oxide‑related leakers dropped by over 40% in two months. The payback on a launder upgrade is usually under six months – not from some spreadsheet model, but from real fuel savings, longer refractory life, and fewer rejected castings.

If you want the full breakdown – refractory material grades, flow velocity calculations, recommended pre‑heat ramps, and how to size the launder for your specific casting speed – the article below walks through every component with real numbers. It’s the same guide I use when I’m troubleshooting a line that’s struggling with inconsistent quality.

Read the detailed launder system guide here: [launder system design, materials, and maintenance parameters]

Start by measuring your temperature at the furnace tap and again at the casting station. If the drop is more than 8°C, your launder is costing you more in scrap and energy than a proper insulation upgrade would ever cost. Don’t wait until your customer’s X‑ray rejects another batch – the fix is straightforward, and the data is right there on your thermocouples.