Proper Use and Maintenance of Quartz Tubes in Tube Furnaces

In our interactions with customers, we often receive inquiries from users of tube furnaces looking to purchase quartz tubes. To assist our customers in properly using quartz tubes within tube furnaces, we are sharing some practical tips on usage and maintenance. These methods not only ensure the efficient operation of the equipment but also help to minimize wear and extend the lifespan of quartz tubes.

Structure of Tube Furnaces

A tube furnace consists of a heating body and a waste heat recovery system. The heating body features a chimney baffle, with a high-temperature gas outlet located below the baffle. The waste heat recovery system includes an air preheater, which comprises both non-condensing and condensing air preheaters. Tube furnaces are primarily used for experiments and small-scale production in universities, research institutes, and industrial enterprises. The equipment offers advantages such as reliable operation, simple design, high temperature control accuracy, good insulation, wide temperature range, uniform furnace temperature, multiple temperature zones, and optional atmospheres, including vacuum conditions.

Usage and Maintenance of Quartz Tubes

Due to the unique structure of tube furnaces, the furnace tube plays a critical role as the reaction chamber and working area in production testing. The operation of the furnace tube is closely linked to gas, pressure, and operating methods. Thus, it is essential to pay attention to the following aspects when using quartz tubes in tube furnaces:

1. Softening Point and Usage Duration of Quartz Tubes

• The softening point of quartz tubes is 1,270°C. At 1,200°C, the continuous usage should not exceed 3 hours.

2. Hydrogen Usage Restrictions

• The use of hydrogen in tube furnaces is generally not recommended unless it is under non-explosive concentrations. If hydrogen must be used, appropriate safety measures should be taken.
• If the furnace tube is not sealed at both ends, stainless steel tubes should be used. Stainless steel tubes require water cooling at both ends to prevent O-rings from overheating and losing their sealing capability.

3. Cleaning and Handling of Furnace Tubes

• The interior of the furnace tube should be kept clean, and materials that react with SiO2 should not be left inside.
• When burning materials, avoid placing them directly on the furnace tube; instead, use crucibles or other fixing devices to extend the lifespan of the quartz tube.

4. Use of Ceramic Plugs

• Ceramic plugs should be inserted into the furnace tube during heating to prevent excessive temperatures at the ends of the tube. This helps maintain the sealing effect of the O-rings on the flanges and promotes a balanced temperature field within the furnace.

5. Use of Alumina Plugs

• Alumina plugs should be placed in the furnace tube during heating, with two plugs on one side and two on the other, for a total of four plugs. The distance between the two plugs on each side should be about 450mm.
• If plugs are not used, the temperatures at the ends of the furnace tube may be higher, causing the inner O-rings of the flanges to lose sealing capability. Placing plugs at both ends of the tube helps achieve a balanced temperature field.

6. Heat Resistance and Purity of Quartz Tubes

• The heat resistance of quartz tubes is directly related to their purity. The higher the purity, the greater the heat resistance.

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