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Q1: What is the difference between the temperature of corundum and ceramics?
A: Corundum also belongs to the category of ceramics. Corundum belongs to high-purity alumina, with an alumina content of 99.5%, and its high temperature resistance is very good! The ceramics cover a wide range, silicon carbide, silicon nitride, alumina composite silicon dioxide are all ceramics!
Q2: What is the reason why the temperature fluctuation is especially large and the number of jumps is zero?
A: Like this kind of hundreds of jumps, I do not know whether it is a high jump or a low jump. The high jump must be electromagnetic interference. The low jump is a decrease in the dielectric strength. The reason may be: Some areas of the compensation wire are damp and some places are aging. And there are places where the terminals are rusted. In this case, like the material of many terminals is brass, stainless steel, and the additional potential generated after rusting. In the case of thermocouples, the potential of the thermocouple increases.
Q3: Nowadays in many petrochemical industries, most of the installed thermocouples are installed by welding. How can the problems be discovered in a timely manner after installation? Is it possible to weld multiple crossings?
Answer: The best welding is not used, welding is prone to accidents, and the risk factor is higher! The flanges in the petrochemical industry are welded, and if they are welded, their pressure capability is relatively low. In the event of a leak, the consequences are serious. Regarding welding of multiple crossings, personally think that it is best not to use it. Although the overall cutting cost is relatively high, but it can absolutely guarantee safety. In terms of welding, the strength of the welding part is only about 50% higher than that of the normal part. The strength is very low, and the weld can only weld the thickness of about 2-8 mm in the surface layer. Although it looks like it is welded up, it is actually empty inside. Arc welding is easy to have trachoma, certainly not enough, there is no trachoma in argon arc welding, but the weld is generally 3-5 mm in the surface, even if it is double-sided welding, the middle is empty, it is unsafe.
Q4: The thermocouples in our company's cracking furnace are K series thermocouples, and the furnace temperature is between 1100-1250 degrees. There may be SO2, SO3, S, sulfuric acid mist (sprayed acid), CO2, CO, N2, water Steam and other components, the original design was the use of corundum casing, but after the installation of the oven after the completion of the process, the alumina casing cracked, and then replaced the stainless steel, and then after more than 10 days, close to the burner A thermal couple (1-2 m) was damaged by corrosive corrosion. The other rear thermocouples were examined and corroded, but the corrosion was not severe. ·What is the guarantee that a thermocouple of this type can be used for a long period of time?
A: There is no problem with the thermocouple in the cracking furnace. Nowadays, many materials can be replaced. The cermet can be used. It is resistant to high temperatures, oxidation and vulcanization.
Q5: How many degrees can the current couple measure? What temperature measuring element is used for measuring about 350 degrees? What is the material used to measure hydrogen? (Hydrogen gas density is easily penetrated and hydrogen embrittlement occurs)
A: The tungsten germanium series can measure more than 2000, and the platinum thermal resistance of PT100 is the best for 350 degrees. Hydrogen can be used for thermocouples.
Q6: How is the range of the thermal resistance set in the system or on the safety barrier?
A: The thermal resistance is set on the system. If it is set on the DCS, there is a reminder on the top of the system itself.
Q7: Do you consider the flow rate when selecting thermal resistance and thermocouple?
A: Generally, the flow rate should be taken into account when selecting thermal resistance and thermocouple. For boilers and high-pressure pipelines in power plants, welded and protected protective tubes must be used. If there is no pressure, ordinary protective tubes are acceptable. In general, higher flow rates are recommended. Tapered protective tubes are recommended. Cone-shaped protective tubes are more resistant to turbulence in the flow.
Q8: Does the compensation wire need to use a shielding layer?
Answer: Compensation wires are now large industries. Many of them use DCS. It is recommended to use shielded compensation wires as much as possible. It is better to shield the interference resistance of the compensation wires. There are many electromagnetic interferences that are not intended and will interfere with the DCS system. In the former small-scale industry, there were no DCS systems, too many frequency converters, and no high-power electrical appliances, etc. It was possible to use shielded compensation wires. Nowadays, many large companies have high-power electric shocks on the spot, and they are connected to DCS. It is recommended to use shielded compensation wires.
Q9: How about the application of infrared temperature measurement technology?
A: Infrared temperature measurement is not the same as the spectral refraction, different objects are not the same, so in use, the common temperature measurement point can be used after correction, but for measuring different parts, because different spectral refraction is not the same, it will not be accurate, The actual parameter error will be very large.
Q10: Regarding field installation, one type is flange mounting. One is socket welding installation, how to protect the thermocouple in the socket welding, and check the trachoma in the welding, sometimes the welding is no problem, but after high-pressure vibration, it will cause leakage, leakage of liquid will enter the wiring chamber After leaking through the cable gap to the engine room, how can we prevent it, or how to deal with it, and inspection methods, we can not complete the installation of a thermocouple welding radiation detection?
A: Regarding the inspection of welding installations, there are not many on-site welding, many power plants are welding, each power plant is portable, a simple flaw detector, a general thermocouple enterprise, and qualified petrochemical industry suppliers all have X-rays. machine.
Q11: Now that most of the thermal resistance is 3-wire, what kind of occasion is the 4-wire system used?
A: The 4-wire system is a high-precision material. High-precision measurement uses a double-bridge circuit to eliminate the resistance. Generally speaking, it is not necessary. Double bridges have more 4-wire systems in the petrochemical industry.
Q12: What is the recommended distance when the thermocouple compensation wire and the power line are inevitably parallel to each other?
A: Generally speaking, electrical erection individuals are not professional, and the crossover should be as far away as possible. Parallel intervals are about 2-3 meters, because the compensation wire is sometimes shielded.
Q13: What thermocouple materials are currently resistant to erosion and high temperatures? We are now using high-iron cast iron, the site temperature is 500?
A: The protective tube, now the cobalt-chromium-molybdenum-tungsten alloy, the traditional old material of high-iron cast iron, is now lagging!
Q14: Colleagues in the gasifier install two B-type thermocouples. One display shows 60-70 and the other shows negative 100. What are the reasons?
A: Because the B-index thermocouple is basically no matter how it is displayed below 400 degrees, it can be ignored. Below 800 degrees, the accuracy is not considered. The temperature is too low and the meter does not feel it.
Q15: Request for detailed explanation of welding pressure rating?
A: The welding pressure rating: 4 MPa or less, the traditional is this, and now many large industries will reach 40 MPa or less, 40 MPa will use the overall cutting. If the petrochemical industry is used in a hazardous explosion environment, there must be redundancy. For example, the previously mentioned 40 MPa should be lower than this, adding more redundancy.
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