Shanghai Automation Instrument Third Factory WRN-240A Flameproof Thermocouple Industrial Intrinsically Safe One Batch Start

(1)WRN-640Introduction to Flameproof Thermocouple Products

Industrial flameproof or intrinsically safe thermocouples are a type of temperature sensor widely used in chemical industry automation systems. Through temperature sensors, the temperature parameters of the controlled object can be converted into electrical signals, transmitted to display, record, and adjust instruments, and the system can be detected, adjusted, and controlled.

In chemical plants, the production site is often accompanied by various flammable, explosive and other chemical gases and vapors. If ordinary thermocouples are used, it is very unsafe and can easily cause environmental gas explosions. Therefore, it is necessary to use explosion-proof or intrinsically safe thermocouples as temperature sensors in these situations. The explosion-proof or intrinsically safe thermocouple products produced by our factory are suitable for places with explosive gas hazards within the temperature range of d Ⅱ BT4 to d Ⅱ CT6, ib Ⅱ BT4, ia Ⅱ BT4, and ia Ⅱ CT6.

The technical performance of explosion-proof or intrinsically safe thermocouples complies with JB/T9238-1999 Technical Conditions for Industrial Thermocouples and GB/T16839.1-1997, GB/T16839.2-1997 Industrial Thermocouple Graduation Tables and Permissible Errors. At the same time, the products comply with the General Requirements for Explosion proof Electrical Equipment in Explosive Atmospheres GB3836.1-2000, GB3836.2-2000 standards. The national explosion-proof safety supervision and inspection station for instruments and meters specially approves and approves the product drawings, technical documents, and prototypes, And issue an explosion-proof certificate.

At present, our factory produces two types of industrial explosion-proof thermocouples: nickel chromium nickel silicon (K-type) and nickel chromium copper nickel (E-type).

Intrinsically safe thermocouples must use intrinsically safe compensating wires, and their distribution parameter control range is: total inductance ≤ 2mH, capacitance ≤ 0.06 μ f. When using associated equipment safety barriers, the selection of associated equipment should follow the following principles. When using thermocouples (must be insulated) with low internal resistance secondary instruments, MTL75/ac, Z605/EX, LB95/ac should be selected. When using high internal resistance secondary instruments, MTL760/ac, Z960/ac, LB960/ac safety barriers should be selected. The specific wiring of the safety barriers can be found in the manufacturer's manual.

(II)WRN-640Main technical specifications of explosion-proof thermocouple

◆ Range specifications

Note: "t" represents the measured temperature of the temperature sensing element.

◆ Thermal response time: When there is a step change in temperature, the time required for the output of the thermocouple to change to 50% of the step change is called the thermal response time, denoted by T0.5.

◆ Nominal pressure: generally refers to the static external pressure that the protective tube can withstand without rupture at room temperature, and the test pressure is generally 1.5 times the nominal pressure. In fact, the allowable nominal pressure is not only related to the material, diameter, and wall thickness of the protective tube, but also to its structural form, installation method, insertion depth, and the flow rate and type of the measured medium.

◆ Thermocouple insulation resistance: The test voltage for insulation resistance at room temperature is: DC 500 ± 50V. The atmospheric conditions for measuring insulation resistance at room temperature are: temperature 15-35 ℃, relative humidity 45%, and atmospheric pressure 86-106kpa.

For thermocouples with a length exceeding 1 meter, the product of their insulation resistance at room temperature and their length should not be less than 100M Ω. m.

Namely: Rr L>100M Ω · m L>1m

In the formula: Rr - The insulation resistance value of the thermocouple at room temperature (M Ω)

Length of L-thermocouple (m)

For thermocouples with a length equal to or less than 1 meter, their room temperature insulation resistance value should not be less than 100M Ω.

◆ Insulation resistance of armored thermocouple (insulated type): When the relative humidity is not more than 80% at an ambient temperature of 20 ± 15 ℃, the insulation resistance between the thermoelectric electrode and the outer sleeve should be greater than or equal to 100M Ω. m *, and the test voltage should be 500V DC. (* The insulation resistance is expressed in M Ω. m, which is the product of the insulation resistance at room temperature and the length of the armored thermocouple)

◆ Explosion proof type and level group

Explosion proof group: d Ⅱ BT4 or d Ⅱ CT4 d Ⅱ BT6 or d Ⅱ CT6

Intrinsically safe group: ia Ⅱ BT4 or ia Ⅱ CT4 (multi pair) ia Ⅱ BT6 or ia Ⅱ CT6 (multi pair)

Shell protection level: IP65

(III)WRN-640Principle and structure of explosion-proof thermocouple

The structure and principle of flameproof or intrinsically safe thermocouples are basically the same as those of assembled thermocouples. The difference is that the junction box (shell) of flameproof or intrinsically safe products adopts an explosion-proof special structure in design. The junction box is made of high-strength aluminum alloy die-casting, and has sufficient internal space, wall thickness, and mechanical strength. The thermal stability of the rubber sealing ring meets the national explosion-proof standard. So, when the explosive mixture inside the junction box explodes, its internal pressure will not damage the junction box, and the resulting heat energy cannot diffuse outward and transmit the explosion.

Due to the use of the above-mentioned explosion-proof special structure, the product fully complies with the explosion-proof category range of d Ⅱ BT4 to d Ⅱ CT6, ibIIBT4, iaIIBT4, and iaIICT6. As long as users strictly follow the product usage rules, the product can achieve reliable explosion-proof effects.

(IV)WRN-640Explosion proof signs, categories, levels, and temperature groups for explosion-proof thermocouples

Explanation of temperature groups for the category and level of electrical equipment:

Electrical equipment is divided into two categories

Class I - Electrical equipment used underground in coal mines

Class II - Electrical Equipment for Factory Use

◆ Explosion proof level: The explosion proof level of explosion-proof and intrinsically safe thermocouples is applicable to explosive gas mixtures with a maximum safety gap or a minimum ignition current ratio of A, B, C, and III.

Temperature group: The temperature groups of explosion-proof and intrinsically safe thermocouples are divided into six groups based on the highest surface temperature of their exposed parts, T1 to T6.

(V)WRN-640Model representation of explosion-proof thermocouple

（6） Specification Table for Flameproof and Intrinsically Safe Multipair Thermocouples

* n represents the number of armored components, with 4.5.6.7.8.9 for user selection

（7） Types and specifications of flameproof and intrinsically safe thermocouples

Note: Explosion proof flanges are flat flanges according to the instrument industry standard JB/T5219-1991.

（8） Specification Table for Flameproof and Intrinsically Safe Armored Thermocouples

*Special specification orders must be negotiated and decided by both parties

（9） Specification Series Table for Flameproof and Intrinsically Safe Thermocouples