What are the differences between the compensation wire type K KVVP-2*1.5 and the type KX-GA-VVP2*1.5?
All are flame-retardant compensation wires, which are used in pairs (positive and negative poles). The former consists of 8 pairs, allowing for 8 signal paths, while the latter is a single pair, enabling only one signal path.
Thermocouple Compensation Wire and Cable Product Standard: Compensation Wire: GB/T 4989-94 equivalent to IEC
584-3（89）；
Compensating Cable: JB/T 7495-94
Product Application: Suitable for environments with explosive hazards in the oil, chemical, and other industries that require high-level explosion-proof safety performance. Used to extend the connection between explosion-proof thermocouples and explosion-proof automatic temperature measurement instruments, forming an intrinsic safety explosion-proof temperature measurement system.
Application Features: The本质安全Explosion-Proof Temperature Measurement System uses compensation wires or cables with low capacitance and low inductance material structure, featuring explosion-proof safety performance. It is suitable for connecting explosion-proof thermocouples and explosion-proof temperature measurement instruments in environments with explosion hazards, forming an intrinsically safe thermocouple temperature measurement system.
Operating Temperature: Heat-resistant grade: -65℃ to +200℃ and 65℃ to +260℃.
Standard Grade: -40℃ to 70℃ and -40℃ to +
Three types: 105, 150℃.
Minimum Bend Radius: Compensation Wire: Not less than 8 times the outer diameter of the wire.
Compensation Cable: Sheathed, not less than 12 times the cable outer diameter; unjacketed, not less than 6 times the cable outer diameter.
Integrated temperature transmitters can actually achieve vacuum, but adjust the pressure during the circuit processing phase. Gauge pressure transmitters are equivalent to atmospheric pressure reference P0 when compared to atmospheric pressure measurement, as is the reference atmospheric pressure P2. Most on-site pressure measurements are of this nature, such as main steam pressure measurement. Differential pressure transmitters are mainly divided into level measurement and flow measurement.
A comprehensive understanding of the integrated temperature transmitter's extension as a level sensor is based on the principle that the static pressure of the measured liquid is proportional to its height. It utilizes advanced isolated diffused silicon sensitive elements or ceramic capacitor pressure sensitive sensors from overseas. These sensors convert static pressure into electrical signals, which are then temperature-compensated and linearly corrected to become standardized electrical signals.
Explosion-proof thermocouple applications
Industrial explosion-proof thermocouples are a type of temperature sensor widely used in chemical industry automatic control systems. Through temperature measurement, they ensure safe and efficient operation.
Model Naming
Temperature sensors, which convert the temperature parameters of the controlled object into electrical signals, transmit them to display, record, and control instruments, and perform detection, adjustment, and control of the system. In chemical factories, the production site often has various flammable and explosive chemical gases and vapors. Using ordinary thermocouples is extremely unsafe and can easily cause environmental gas explosions. Therefore, explosion-proof thermocouples must be used as temperature sensors in these situations.
Industry Applications
Products are widely used in industries such as steel and iron smelting, petrochemicals, mechanical manufacturing, glass ceramics, plastics and rubber, brewing and pharmaceuticals, light industry and textiles, food, tobacco, water treatment, thermal power, and nuclear industries.
Technical Information
Industrial-use thermistors, as temperature sensors and display instruments, are paired for direct measurement and control of gas, liquid, and steam temperatures in the production process. Explosion-proof thermocouples have structures, principles, and assembly methods similar to thermistors, with the main difference being that the explosion-proof product's junction box (housing) is designed from high-strength aluminum alloy die-casting, featuring ample internal space, wall thickness, and mechanical strength, as well as thermal stability of the rubber sealing rings that comply with national explosion-proof standards.
◆ Features
Multiple explosion-proof types, excellent explosion-proof performance.
Coil spring-type temperature-sensitive element, good vibration resistance.
Wide temperature range.
High mechanical strength, excellent pressure resistance.
◆ Working Principle
Explosion-proof thermocouples utilize the gap-type explosion suppression principle. They are designed with sufficient strength components such as junction boxes, sealing all parts that could generate sparks, arcs, or dangerous temperatures within the junction box cavity. In the event of an explosion inside the cavity, the fire can be extinguished and cooled through the gaps of the mating surfaces, preventing the flame and temperature from spreading outside the cavity, thereby achieving explosion suppression.
◆ Main Technical Parameters
Product Execution Standards
IEC584
IEC1515
GB/T16839-1997
JB/T5582-91
GB3836
◆ Ambient Insulation Resistance
Thermocouples exhibit an insulation resistance greater than 1000 Ω.m between the electrode and the sheath tube at an environmental temperature of 20±15°C, with a relative humidity not exceeding 80%, and a test voltage of 500±50V (DC).
Operating Principle
If a closed loop is composed of homogeneous conductors (thermocouples) made of two different components, and there is a temperature gradient at both ends, an electric current will flow through the loop. In this case, there will be a thermoelectric potential. To prevent explosion,防爆原利用间隙隔爆原理, we design components such as junction boxes with sufficient strength. All components that could produce sparks, arcs, and dangerous temperatures are sealed inside the junction box. In the event of an explosion within the box, the fire can be extinguished and cooled through the gap between the mating surfaces, preventing the flame and temperature from spreading outside the box.
Platinum Rhodium 10-Platinum Thermocouple (Type S Thermocouple) is a precious metal thermocouple. The wire diameter is specified as 0.5mm, with a permissible deviation of -0.015mm. Its positive pole (SP) has a nominal chemical composition of platinum rhodium alloy, containing 10% rhodium and 90% platinum, while the negative pole (SN) is pure platinum, hence commonly known as single platinum rhodium thermocouple. The long-term operating temperature of this thermocouple is 1300°C, and the short-term operating temperature is 1600°C.
The S-type thermocouple boasts advantages such as accuracy, stability, wide temperature measurement range, and long service life within the thermocouple series. It exhibits excellent physical and chemical properties, with good thermal electromotive force stability and resistance to oxidation at high temperatures, making it suitable for oxidizing and inert atmospheres. Due to its superior comprehensive performance, the S-type thermocouple, which conforms to international temperature scales, has long been used as an internal calibration instrument for international temperature standards. Although "ITS-90" stipulates that it will no longer serve as an internal calibration instrument for international temperature standards, the International Temperature Consultative Committee (CCT) believes that the S-type thermocouple can still be used to approximate the international temperature scale.
The S-type thermocouple has drawbacks such as lower electromotive force, lower electromotive force rate, low sensitivity, decreased mechanical strength at high temperatures, high sensitivity to contamination, and expensive precious metal materials, thus requiring a significant one-time investment.
(R-Type Thermocouple) Platinum Rhodium 13-Platinum Thermocouple
Platinum Rhodium 13-Platinum Thermocouple (Type R Thermocouple) is a precious metal thermocouple. The wire diameter is specified as 0.5mm, with a permissible deviation of -0.015mm. The nominal chemical composition of the positive pole (RP) is platinum rhodium alloy, containing 13% rhodium and 87% platinum, while the negative pole (RN) is pure platinum. The long-term operating temperature is 1300°C, and the short-term operating temperature is 1600°C.
The R-type thermocouple boasts advantages such as accuracy, stability, wide temperature measurement range, and long service life within the thermocouple series. It has excellent physical and chemical properties, good thermal electromotive force stability, and excellent oxidation resistance at high temperatures, making it suitable for oxidizing and inert atmospheres. Due to its comparable overall performance to the S-type thermocouple, the R-type thermocouple has been difficult to promote in China. Its application in temperature measurement is mainly limited to imported equipment, with little use domestically for temperature measurement. Between 1967 and 1971, the UK's NPL, the US's NBS, and Canada's NRC conducted a cooperative study, which showed that the R-type thermocouple has better stability and reproducibility than the S-type thermocouple. China has not yet conducted research in this area.
The R-type thermocouple has limitations such as a low electromotive force, low electromotive force rate, low sensitivity, reduced mechanical strength at high temperatures, high sensitivity to contamination, and the high cost of precious metal materials, thus requiring a significant one-time investment.
Type B Thermocouple: Platinum Rhodium 30-Platinum Rhodium 6 Thermocouple
Platinum Rhodium 30-Platinum Rhodium 6 thermocouples (Type B thermocouples) are precious metal thermocouples. The wire diameter is specified as 0.5mm, with a permissible deviation of -0.015mm. The positive pole (BP) has a nominal chemical composition of platinum rhodium alloy, containing 30% rhodium and 70% platinum, while the negative pole (BN) is also a platinum rhodium alloy with 6% rhodium content, hence commonly referred to as double platinum rhodium thermocouples. The long-term operating temperature of this thermocouple is 1600°C, and the short-term operating temperature is 1800°C.
Type B thermocouples offer high accuracy, stability, wide temperature measurement range, long service life, and high temperature measurement limit in the thermocouple series. They are suitable for oxidizing and inert atmospheres and can be used short-term in a vacuum, but not in reducing atmospheres or those containing metallic or non-metallic vapor. A distinct advantage of Type B thermocouples is that they do not require compensation wires, as the thermoelectric potential is less than 3μV within the 0~50℃ range.
The disadvantages of Type B thermocouples include lower electromotive force, lower electromotive force rate, lower sensitivity, reduced mechanical strength at high temperatures, high sensitivity to contamination, and the expense of precious metal materials, thus requiring a significant initial investment.
Type K Thermocouple - Nickel-Chromium to Nickel-Silicon Thermocouple
Nickel-chromium-nickel silicon thermocouples (Type K thermocouples) are the most widely used inexpensive thermocouples, accounting for the total usage of other thermocouples. The nominal chemical composition of the positive pole (KP) is Ni:Cr = 90:10, and the nominal chemical composition of the negative pole (KN) is Ni:Si = 97:3. Their operating temperature range is -200 to 1300°C.
The K-type thermocouple boasts excellent linearity, high thermal electromotive force, high sensitivity, good stability and uniformity, strong anti-oxidation properties, and affordability. It is suitable for use in oxidizing inert atmospheres and is widely adopted by users.
Type K thermocouples should not be used directly in high-temperature environments with sulfur, reducing or reduced atmospheres, alternating oxidation, or in vacuums. They are also not recommended for use in weakly oxidizing atmospheres.
Type N Thermocouple: Nickel-Chromium-Silicon-Nickel-Silicon Thermocouple
Nickel Chrome Silicon-Nickel Silicon Thermocouples (Type N Thermocouples) are a type of economy metal thermocouple, an internationally standardized thermocouple. Developed by Australian laboratories in the early 1970s, it overcomes two significant drawbacks of Type K thermocouples: the instability of the electromotive force due to the short-range ordered crystal lattice of the nickel-chromium alloy between 300-500°C; and the instability of the electromotive force caused by preferential oxidation of the nickel-chromium alloy around 800°C. The nominal chemical composition of the positive pole (NP) is Ni:Cr:Si = 84.4:14.2:1.4, and the nominal chemical composition of the negative pole (NN) is Ni:Si:Mg = 95.5:4.4:0.1. The operating temperature range is -200 to 1300°C.
The Type N thermocouple boasts excellent linearity, high electromotive force, high sensitivity, good stability and uniformity, strong antioxidant properties, affordability, and is unaffected by short-range ordering, making it superior in comprehensive performance to the Type K thermocouple. It is a thermocouple with great potential for development.
