1. What is a radiant tube?

A radiant tube refers to a pipe extending in a straight line from the center to all directions. Refers to non-central pipelines (or trunk pipes), which transport the material of the trunk pipe to designated or non-designated addresses. Radiant tubes are widely used in heating furnaces and are the main heating elements of heating furnaces. The radiant tubes currently in use are mainly divided into two categories: gas radiant tubes and electric heating radiant tubes.

2. What are the typical structures of electric heating radiant tubes?

(1) Linear spiral surrounding electric heating radiant tube This kind of electric heating radiant tube is composed of heat-resistant alloy steel sleeve and heater, as shown in Figure 3-4-18. The heater is generally made of a 43~5mm resistance wire wound on a heat-resistant insulating ceramic core with a spiral groove. The working voltage is 220V and the power is 5~7kW. It is made of segmented cores for the convenience of manufacturing and processing resistance wires. The composition is called the grouped die structure.

(2) The structure of this heater is basically the same as the structure of the belt spiral surrounding the electric heating radiant tube. Only the heating element is made of a resistance band. The resistance band is generally 2mm in thickness and 15-20mm in width.

Axial corrugated cage frame type electric heating radiant tube At present, this type of radiant tube is used more abroad, and it has been serially produced. Radiant tubes of various lengths, diameters and powers can be manufactured according to the needs of the furnace. The structure is shown in Figure 3- 4-19.

(3) Outer frame type spiral resistance wire radiant tube. This structure is basically the same as the third structure, except that the heating element is wound into a spiral resistance wire, which is generally suitable for radiant tubes with lower power; see figure 3-4-20.

(4) Graphite heating element radiant tube `The American IPsen company uses graphite as the heating element of the electric heating radiant tube, which has been used in sealed box furnaces and continuous gas carburizing furnaces. This kind of electric heating radiant tube is made of ceramics, the diameter of the graphite rod is about 20mm, 12 pieces are connected in series, and nitrogen is introduced into the tube. As long as the seal is reliable and the nitrogen cabinet has fewer stars; the surface power of the heating element can reach 80-100W/cm, and the service life can reach 4 to 5 years. This kind of radiant tube is mostly installed vertically, the length of the protection tube is between 450 and 900 mm, and the diameter is not more than 150 mm.

3.What are the advantages of electric heating radiant tubes?

(1) The controllability of the atmosphere in the furnace can be ensured.

(2) Installation, testing and maintenance are all very convenient, all of which are carried out outside the furnace. There is no need to shut down or cool down the furnace temperature to maintain and replace the electric heating device. Under normal production conditions, the replacement only takes about 10 minutes, which greatly reduces labor intensity and improves productivity.

(3) Temperature control, convenient installation and maintenance, and easy to seal.

(4) Since there is no muffle furnace in the furnace, the furnace capacity is increased and the production capacity is improved.

(5) Compact structure, stable performance, single power supply, and service life several times that of ordinary electric heating tubes. Therefore, it is an ideal new product for drying equipment tunnel kiln.