In chemical plants, the production site is accompanied by various flammable, explosive and other chemical gases and vapors. The use of ordinary thermocouples is very unsafe and can easily cause environmental gas explosions. In these cases, a flameproof thermocouple must be used as the temperature sensor.
The so-called flameproof type means that the shell can withstand the explosive pressure of the explosive gas mixture inside, and prevent the internal explosion from spreading to the explosive mixture around the shell.
和普通热电偶的结构基本相同，其区别在于：隔爆型产品的接线盒在设计上采用特殊防爆结构，接线盒用高强度铝合金压铸而成，并且有足够的内部空间，壁厚和机械强度，橡胶密封圈的热稳定性均符合国家的防爆标准。 The structure of explosion-proof thermocouples and ordinary thermocouples is basically the same. The difference is that the junction box of explosion-proof products is designed with a special explosion-proof structure. The wall thickness and mechanical strength, and the thermal stability of the rubber seal ring are in line with national explosion-proof standards. Therefore, when the explosive mixed gas inside the Qin junction box explodes, its internal pressure will also damage the junction box, and the heat generated by it cannot be diffused outward.
Explosion-proof thermocouples have explosion-proof function.
The second problem is that for conductive materials, the ground point on the surface of the probe insulation layer covers the entire material and the hanging material area, so that the effective measuring capacitance is extended to the top of the hanging material. This will cause hanging material errors, and the more conductive the error, Big. But any material is not completely conductive. From an electrical point of view, the hanging material layer is equivalent to a resistor, and the part of the sensing element covered by the hanging material is equivalent to a transmission line composed of infinitely small capacitors and resistance elements. According to mathematical theory, if the hanging material is long enough, the impedance and capacitance values of the capacitance and resistance parts of the hanging material are equal, so the AC phase detector sampler can measure the capacitance and resistance, respectively.
RF admittance can completely replace capacitors. For switches, the difference between RF admittance and capacitance is obvious. Capacitance probes are two electrodes, and admittance probes are three electrodes. A shielded protective electrode is added between the measurement electrode and ground. The corresponding circuit is also the same, the added shielding protection poles play the role of anti-hanging material, so the appearance and the capacitance can be distinguished.
For switches, there are special designs from the probe to the circuit, so the admittance of the switch will be greatly improved than the capacitance resistance. For continuous quantities, the admittance and capacitance probes are the same, so they are indistinguishable from their appearance. The main difference between the two is the circuit. Two circuits are added to the admittance, the oscillation drive and the AC sampling circuit. The improvement of the admittance in the circuit to achieve anti-hanging material and improve stability.
用于何处 Where are flameproof thermocouples used
Explosion-proof thermocouple is a kind of temperature sensor. It is widely used in the chemical industry automatic control system. Through the explosion-proof thermocouple, the temperature parameter of the control object can be converted into an electrical signal and transmitted to the display, recorder and regulator. Detecting, adjusting and controlling the system.
In chemical plants, production sites are often accompanied by a variety of flammable, explosive and other chemical gases. If ordinary thermocouples are used, it is very unsafe and can easily cause environmental gas explosions. Therefore, in these occasions, explosion-proof thermocouples must be used as temperature measuring instruments. The explosion-proof thermocouples produced by our company are suitable for use in places with explosive gas dangers in the temperature range of EXdⅡCT6.
If a closed loop is composed of two homogeneous conductors (hot electrodes) with different components, and there is a temperature gradient at both ends, a current will flow through the loop, and then there will be a thermoelectric potential between the two ends.
Explosion protection principle:
Utilizing the gap explosion isolation principle, design the junction box and other components with sufficient strength, and seal all the components that will produce sparks, arcs and dangerous temperatures in the junction box. Cool down so that the flames and temperature after the explosion are not transmitted outside the cavity.
特点: Flameproof thermocouple features:
Designed according to the latest explosion-proof regulations GB3836 in compliance with international IEC standards;
Adopt two-chamber flameproof structure, easy to replace temperature measuring element, safe and reliable to use
Explosion-proof mark EXdⅡCT6, suitable for temperature measurement below IIC, ignition temperature above T6, and explosive gas-containing occasions.