What are the dangers if the protective jacket of an explosion-proof thermoresistor is disconnected?
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My workshop is an explosion-proof workshop, and most of the instruments used are Yokogawa explosion-proof instruments. It seems that the explosion-proof properties of the explosion-proof thermoresistors in the workshop don’t receive enough attention from the instrument manufacturers; quite a number of these thermoresistors have unsealed wire outlets, and the wire ends inside can be seen on site. The instrument indicated that there was no voltage at the thermistor. In some thermal resistors, the protective sleeves at both ends corrode and fall off; what explosion protection does such an explosion-proof thermal resistor still have? Additionally, I would like to know that for a thermistor to be able to send signals back to the system, it needs to be supported by an electrical circuit; what voltage does the system’s power supply provide to this thermistor? If this power cord breaks at the work site and comes into contact with the equipment, will arcing occur? We are in an explosion-proof area. I hope everyone can help clarify this.
The power supply for instruments is usually 24V, so I don’t think there will be any electric sparks! Personal opinion
Is there danger as long as there is electricity? In explosion-proof areas, there is no distinction between high voltage and low voltage; a voltage of 3V can also generate sparks, which in turn can ignite flammable gases. I just want to know if the field power supply for explosion-proof thermoresistors is 24V (DC)?
This definitely won’t work; the original poster didn’t clarify what type of explosion protection is needed – intrinsically safe or flameproof? Flame isolation goes without saying – it’s necessary to isolate the device from combustible gases in the surrounding environment. With the connection terminals exposed, it’s simply a matter of risking one’s life. Although intrinsically safe systems have safety barriers that can limit current and voltage, explosion protection is still required wherever terminals are exposed. For example, in the case of an on-site junction box, if it is placed in an explosion-proof area (Zone 1), even though the signals inside the junction box pass through safety barriers, the junction box still needs to be of an explosion-proof or other suitable explosion-resistant design.
Immediate corrective action is required; a low voltage (below 5V) also poses safety risks.
First, we need to determine whether a temperature module, also known as a temperature transmitter, is installed in the heat-resistant resistor junction box. If it is present, the signal line will have voltage; it outputs a signal of 4–20 MA, with a voltage of 24 VDC. **This standard safe voltage does no harm to humans. The normal 220 VDC voltage is converted to 24 VDC using a current-voltage conversion controller – and this is one way of doing it. Secondly, if the junction box for the thermoresistors designed for shock protection does not contain a temperature sensor, and the signal lines that transmit the data have no voltage at all, then it simply transmits the resistance temperature as a signal to the system; of course, the system converts this signal into 4–20 MA. In such cases, as long as there is no dangerous electricity present in the workshop, these thermoresistor signal lines will have no current or voltage. Then, regarding the sealing issue, companies with sufficient funds generally use flexible tubes (either explosion-proof or non-explosion-proof) to create a section for the thermistor signal output cable. Finally, if the explosion-proof thermal resistance protection tube is corroded or broken, it indicates that the medium being measured by the thermal resistor is highly corrosive. For the material of such protection tubes, steel pipes made of corrosion-resistant materials such as 316, 3030, or 3039 should be used; alternatively, applying corrosion- and wear-resistant coatings to these tubes can also yield good results. However, the prices vary, and it depends on your company’s choice!
The protective tube can be made of 316 material, or it can have a Teflon lining or a sintered Teflon layer. An explosion-proof flexible tube can be used at the outlet; feel free to contact me on QQ if needed