Quartz Heater

The tube is the fragile part and it needs room to move

Quartz grows as it heats and shrinks as it cools, and it does that thousands of times. Holders must let one end slide. Anything that pins both ends — a too-tight clamp, a tube pushed into a housing that has closed up, an end cap bolted hard — cracks the tube on an early cycle, usually near an end cap where nobody thinks to look.

Long tubes also sag. Above about a metre they want support at the middle, or they bow towards whatever is beneath them and touch it.

Fingerprints are a real failure mode

Skin leaves salt and oils on the quartz. At 1000 °C that mark changes the structure of the glass at that spot, and the tube devitrifies and fails there. Fit tubes with clean gloves, and if a tube has been handled, wipe it down with alcohol before the first run. This is one of the few maintenance rules that is absolute rather than a matter of degree.

Medium wave is what most work actually absorbs

Water, most plastics and paint films take up medium-wave infrared in the top fraction of a millimetre of the surface. That is exactly where the heat is wanted for drying, shrinking and forming. It is why quartz is the default radiant element for a shrink tunnel or a drying line, while short-wave halogen belongs on metal and long-wave ceramic on gentle, even work.

It can be turned down as well as off

Unlike a halogen lamp, a quartz tube has no minimum output it must run above. A thyristor can hold it at twenty per cent all day. That matters on a line that runs at different speeds, or one that idles between batches — instead of cycling full on and full off, the bank can simply sit at a lower power, which is gentler on the tubes and steadier for the process.

Replace a bank together and keep the spacing honest

A tube that has been in service puts out slightly less than a new one. Mix them and the work gets a pattern. Where the tubes make up one heating zone, change them as a set and note the date.

Spacing matters as much as power. The rule of thumb is to space tubes at roughly the distance between the tubes and the work, so the patterns overlap by the time they arrive. Wider than that gives stripes; much closer and the tubes see each other, which raises their own temperature above what they were designed for.

Keep water off a hot tube

A cold splash onto a tube at working temperature cracks it immediately. On lines where the product is wet, or where there is washdown nearby, either guard the tubes or interlock the heaters so they are off while the area is being cleaned. This is the failure that most often gets blamed on tube quality.