The Headache of Cold Spots in Glass Lehr Tunnels
Most infrared lamps stop at 1 or 1.5 meters. That sounds like plenty, but when you’re running a glass lehr tunnel, those tiny gaps between the lamps are a nightmare. They create cold spots. And in this business, a cold spot is just a fancy way of saying “defective glass.” We fixed this by building custom units that push past the 2-meter mark. The struggle with length You can’t just stretch a piece of quartz and call it a day. When you go long, physics starts fighting you. You deal with voltage drops and thermal expansion that can warp everything. If you just cram too many watts into a long tube without balancing the voltage, you’ll end up burning out the ends. It’s a waste of money and time. We spend a lot of time dialing in the wattage so the heat stays steady from one end to the other. No surprises. Getting the layout right We stick with high-purity quartz because it can actually handle the stress without cracking. The goal here is to kill the “zebra effect.” You know the one—those annoying alternating hot and cold stripes that ruin a temper. We array our units in a tight, continuous sequence to make sure the heat is a solid wall, not a picket fence. Depending on how deep you need the heat to soak into the glass, you can go with shortwave or medium-wave. Oh, and we use heavy-duty connectors. Why? Because conveyor belts vibrate. A lot. You don’t want your wiring shaking loose in the middle of a shift. The honest trade-offs Look, longer units make your life easier in some ways. You have fewer electrical connections to wire up, which cleans up the whole footprint of the machine. But there’s a catch. A 2-meter tube is fragile. If a piece of glass shatters or someone bumps it with a tool, you’re replacing a much more expensive part than you would with a tiny 500mm tube. You’ve got to be obsessive about your guarding. Also, these things put out a massive amount of heat. If your exhaust system isn’t sized right, you’ll get heat soak, and that’s a quick way to damage your oven shell. It’s worth double-checking your ventilation before you flip the switch.