Electric heating tube knowledge
Electric heating tube is a common electric heating element, which mainly appears in metal tube, also called heating tube or heating tube. Its shell tube mainly includes stainless steel tube, copper tube, and iron tube. The electric heating tube mainly includes four parts: metal tube, heating wire, magnesium oxide powder, and port.
As a traditional electric heating device, electric heating tube has the characteristics of simple structure, high mechanical strength, high thermal efficiency, safety and reliability, easy installation and long service life. The products are widely used in rubber machinery, plastic machinery, food machinery, spraying equipment, baking equipment , Electroplating equipment, electronic equipment, electrical equipment, air conditioners, wave soldering furnaces, microwave ovens, electric water heaters, coffee pots, ovens, heaters, and shoe machines and other industries.
1. Pipe and temperature design
Stainless steel SUS316L: 700°
Stainless steel SUS321: 700°
Stainless steel SUS304: 650°
Cu (nickel plating): 250°
Fe (copper plating): 450°
2. The highest surface load of commonly used heating medium (W/cm2)
Generally, the watt density of electric heating tube is 5W/cm2 or 6 W/cm2. The watt density of the empty heating tube should not exceed 9 W/cm2, and the watt density of boiling water should not exceed 30 W/cm2.
Three, heating wire
1. The heating wire of the high temperature electric heating tube is Ni-Cr wire, with a temperature resistance of 1400oC;
2. The heating wire of the medium and low temperature electric heating tube is Fe-Cr wire, with a temperature resistance of 1500oC. Disadvantages: easy to oxidize and short life.
3. The watt density at the R angle of the electric heating tube is lower than that of the straight part. The temperature difference between the two will be about 20oC during heating, and it will be controlled at about 10oC after oil pressure treatment.
4. The diameter of the heating wire is between 0.12 and 0.6.
Four, fill (Mgo)
The gap of the electric heating tube is filled and compacted with magnesium oxide powder with good insulation and thermal conductivity
1. Put the cut empty tube on the powder adding machine and add magnesium powder to the empty tube.
2. Remove the powdered tube, pour the magnesium oxide powder 1-2mm away from the tube mouth, and then insert the rubber sheet.
3. The electric heating tube with added powder must be tested for 2000V/0.5MA withstand voltage before shrinking the tube.
4. The shrunken electric heating tube should be tested and marked according to the designed terminal length, and it must be within its tolerance range.
5. Sealing and fasteners
According to the customer's needs, inject the required sealing agent into the two nozzles, insert silicone or ceramic beads into the electric heating nozzle, and rotate to make the sealing agent evenly distributed around the nozzle.
Electric heating pipe fasteners generally include iron and copper materials, and Teflon wires or rubber sleeves can be used according to customer needs.