Why Short-Wave Infrared Heating Lamps Turn Black or White

The short-wave infrared heating lamp is a tubular heater that uses the infrared principle. It has the characteristics of high quality, high thermal efficiency, high power density, rapid heating, power saving, and long life.

Quartz near-infrared lamps use transparent quartz glass as the tube shell to generate near-infrared radiation spectrum. Infrared is a kind of electric wave, which is transmitted at the speed of light, carries high energy, and the radiation intensity of different types of infrared rays with the same power The intensity is different depending on the wavelength.

Shortwave Infrared (i.e. near infrared) Features:

With 1-3 seconds heating and cooling time, the heating process is more flexible. The high-efficiency and durable gold-coated reflective layer of single tube and twin tube can achieve a radiation efficiency of more than 96%, and a long service life, generally more than 5000 hours .It is especially widely used in the drying and curing of high-speed printing equipment. It can quickly heat the surface of plastics, water and other solvents, and has the characteristics of being quickly absorbed by the water film to reach the drying effect.

Because the quartz tube material is hard and brittle, has low strength, and is difficult to process, improper processing or use during production and use is likely to cause poor quality problems, such as yellow, blue, whitish and black lamps.

1. The lamp tube turns yellow and white or blue

Reasons:
   The reason why the lamp tube is whitish and blue is because the lamp tube is leaking, and the tungsten filament in the lamp tube loses its gas protection at high temperatures and reacts with oxygen in the air to produce different products of tungsten.。

1）W+O2→WO2.9(Blue Oxide)；

2）W+O2→WO3(Yellow Oxide)；  

WO3 undergoes a sublimation reaction at a temperature of 1400°C to 1700°C, and then condenses on the lamp tube when the glass bulb is cooled. The WO3 condensed on the lamp tube is white or light yellow powder.

2. The Lamps Tube turns black

Reasons:

1). The cold end of the filament in the tube is black, which is also a common problem in the production process of the tube. This problem is mainly caused by the impurity that is not completely removed when the filament is shaped or the surface of the filament is contaminated during the assembly process. There are dust and low-melting impurities. These impurities will volatilize when the filament is heated and adsorb on the inner wall of the nearby lamp. So as to make the lamp tube black;

2). The overall blackening of the lamp tube is mainly due to the high heating temperature of the filament and insufficient protective gas concentration in the tube. The evaporation rate of the filament is greater than the rate of tungsten halide reduction, so that excess tungsten vapor adheres to the lamp tube and forms a black circle.

How to avoid this kind of problem？

   In view of the whitening and blackening of the lamp, the following points need to be paid attention to in the daily production process：

1). During the filament cleaning process, try to remove the graphite layer on the surface;

2). In the process of filament shaping, heat thoroughly to completely remove surface impurities;

3). During the filament assembly process, the countertop should be kept clean, and the assembler should wear gloves to prevent contamination of the filament surface;

4). The lamp tube is fully heated during the exhaust process to remove the residual air and moisture inside the lamp tube;

5). The lamp should be handled with care during the transportation process, to avoid collision, causing the lamp to crack and cause air leakage;

6). Be careful during the installation of the lamp to prevent excessive force from causing air leakage;

7). The protective gas in the lamp tube should be selected according to the filament temperature and the space of the lamp tube.