Selection of Electric Heating Tube Shapes in Electric Heaters
1.Electric Heating Tube
Electric heating tubes come in various shapes such as straight single-end, straight double-end, U-shaped, W-shaped, special-shaped, and spiral. In chemical plant electric heaters, the commonly used types are single-end heating tubes and U-shaped heating tubes, two structures.
2.Characteristics of Electric Heating Tubes
Single-end electric heating tubes, i.e., single-end inlet and outlet electric heating tubes, can be designed as detachable, with threaded connection for fixing. The advantage is that the heating elements can be replaced on-site, making maintenance easy and short; the disadvantage is that the threaded connection increases the equipment size and cost.
U-shaped electric heating tubes are connected to the tube sheet by welding. The advantage is that the equipment shell is small and the cost is low; the disadvantage is that maintenance is complicated. If the heating tube elements are severely damaged, they need to be returned to the factory for repair, which takes a long time.
3.Selection of Electric Heating Tube Type
It is recommended to use U-shaped electric heating tubes with welded sealing; the internal connecting conductors and the spacing between them and the metal tube should be reasonably maintained; the internal connecting conductors and the heating element should be crimped or brazed, and comply with the minimum electrical clearance and minimum creepage distance specified in GB3836.2-2000; the tube end of the metal tube should be sealed with insulating material and fully insulated and moisture-proofed, and tested according to the requirements of GB3836.1-2000 "General Requirements for Explosion-proof Electrical Equipment for Explosive Atmospheres". The surface power of U-shaped electric heating tubes is relatively small, generally below 2.3g/cm². The reason is that when selecting U-shaped electric heating tubes, the longest single-end straight tube can reach 18m, so when the heating power of the tube is determined, the surface power can be selected to be relatively small.
4.Calculation of Electric Heating Tube Length
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