SECT skin current heating method skin effect heating cable system
Information source: Anhui Cable Group Views: 6635 Release time: 2014-03-14
I. Overview <br /> The skin current heating method (skin current method or SECT method for short) is a new type of pipe heating system that appeared in the mid-1960s. "SECT" should be the abbreviation of "SKIN ELECTRIC CORRENT TRACING", which translates to "skin effect heating". Due to its simple structure, safety and reliability, long life, easy automation, and high energy efficiency, the heating system is gradually gaining attention and research at home and abroad.
The SECT skin effect heat tracing cable (skin current heating) system was first applied in Japan, and later extended to the United States, Canada and other countries, and has been increasingly used. SECT skin effect heat tracing technology began to be applied in China in the 1980s. Based on long-term electric heat tracing technology reserves and practices, Anhui Cable Group now has mature product design and perfect system installation to provide users with safe and reliable heat tracing devices. Each skin effect heating device is designed, manufactured and installed by the company.
Second, the skin effect heat tracing principle
The principle of the SECT skin effect heating cable (skin current heating) system is based on the "skin effect ring effect" and "proximity effect" of alternating current. The so-called skin effect is a phenomenon in which the current passing through a carbon steel conductor gradually skins on the surface of the conductor; the ring effect is a special effect that occurs because the cable core wire is surrounded by a steel tube; the current on the outer wall of the steel tube Squeeze to the inner wall, and the proximity effect is a kind of electromagnetic phenomenon between a pair of electric bodies with equal current in the opposite direction. When a current is passed between the cable in the heating pipe and the outer pipe, the current on the outer heat pipe gradually becomes skin on the inner wall of the heating pipe It is the Joule heat generated by this thin outer wall to meet the needs of heat tracing. SECT skin effect heating cable (skin current heating) system generates Joule heat mainly from three parts:
1. When the heating tube is energized, the heat emitted from the heating tube. This heat is the main source of heat for the SECT skin effect heating cable (skin current heating) system.
2. Heat generated by cables inside the heating tube.
3. Hysteresis loss in the heating tube generates part of the heat.
In a SECT skin effect heating cable (skin current heating) system, an insulated wire (SECT wire) passes through a ferromagnetic steel pipe and is connected to the end of the steel pipe. The first end of the steel pipe and the insulated wire are respectively connected to the power supply. Neutral and phase wires are subjected to common-frequency or intermediate-frequency AC voltage, and electric current forms a loop through the wire and steel pipe to generate Joule heat. Because there is a certain relationship between the size, material, and frequency of AC power, AC power does not flow uniformly through the cross-section of the steel tube, but concentratedly flows through a certain depth from its inner surface. The current density decreases exponentially. The outer surface voltage and current are almost zero, which is very safe. Therefore, the SECT pipe can be directly welded to the conveying pipe, making it an efficient heat source. The heat generated by the SECT pipe is quickly transferred to the conveying pipe through the weld and the thermally conductive glue, which plays a role of heat tracing.
Main technical parameters of SECT skin effect heating cable (skin current heating) system:
Composition of skin heat tracing device
The skin effect heat tracing technology device for pipes is basically composed of transformers, heating power supplies, infusion tubes, heat tracing tubes, skin heat tracing cables, thermal insulation layers, and protective shells. The heating power is divided into industrial frequency heating power and intermediate frequency heating power. The infusion tube and heat tracing tube are ordinary steel pipes, the diameter of the heat tracing tube is 15-40mm, intermittently welded to the infusion tube; the skin cable is worn in the heat tracing tube, and the outside is Thermal insulation and protective shell.
Fourth, technical characteristics
1. High tensile strength and resistance to mechanical damage;
2. High heat-resistant temperature, the highest heat-resistant temperature is 360 degrees;
3. Large heating power: ≥100W / m;
4. The power of the pump heating part: ≥350W / m;
5, good energy saving effect, compared with ordinary heating cable energy saving of 35%;
6. Strong adaptability, wide application range, suitable for all long, medium and short distance infusion tubes;
7. Pipe insulation and heating;
8. Reliable installation and easy maintenance.
9, fully automatic control, with short circuit, open circuit, over current protection, automatic temperature adjustment.
Five, skin heating system uses
The SECT skin effect heating cable (skin current heating) system is very suitable for heating long-distance pipelines for material transportation between tank farms, process units and loading and unloading facilities. Its flexibility can be used for temperature maintenance, freeze protection and heating. The SECT skin effect heat tracing cable (skin current heating) system can adapt to different site conditions above and below ground and cross the terrain with variable elevation. Compared with the conventional resistance heat tracing for long-distance pipelines, skin heat tracing is the only system that can heat up to 30 km of pipelines, and only requires single-ended power supply instead of parallel power supply.
6. Skin heat tracing design <br /> Because each pipe has different working parameters and different pipeline lengths, each SECT skin effect heat tracing cable (skin current heating) system is designed and selected by our company in detail. type. It also provides a full range of services from calculation of pipeline heat tracing, selection, installation and commissioning of skin heat tracing systems. The user only needs to provide the following parameters, and the rest will be completed by our company.
1. The exact length of the pipeline, the number of valves (types) and pipe supports, and the material of the pipeline.
2. The heat tracing of the pipeline maintains the temperature, allowing the highest surface temperature of the pipeline.
3. The material and thickness of the thermal insulation layer, and the thermal conductivity at the temperature of the pipeline.
4, can provide power capacity (voltage level) and location.
5. The environmental conditions of the pipeline.
6. Working requirements.
7. The medium in the tube, the temperature at which the medium enters the tube, whether the pipeline needs to be heated or heated, and whether it needs decoagulation.
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