Thermocouple features

Flameproof thermocouple features

Designed in accordance with the latest explosion-proof code GB3836 of international IEC standards;

The two-cavity flameproof structure is adopted, which is easy to replace the temperature measuring element and safe to use

Flame-proof mark d Ⅱ CT6, suitable for Ⅱ C below level, ignition temperature above T6, with explosive gas temperature measurement.

Notes:

Please disconnect the power during maintenance

Flameproof thermocouple flameproof principle

If a closed circuit consists of two homogeneous conductors (thermal electrodes) with different components, a current flows through the circuit when there is a temperature gradient at both ends, and a thermoelectric potential exists between the two ends (as shown in the figure below)

Principle of flameproof:

Based on the gap flameproof principle, the junction box and other components with sufficient strength are designed to seal all the zero parts that will generate spark, arc and dangerous temperature in the junction box. In case of explosion in the cavity, the flame and temperature after explosion can be extinguished and cooled by the joint surface clearance, so that the flame and temperature after explosion will not be transmitted outside the cavity

Overview of explosion-proof thermal resistance

Overview of explosion-proof thermal resistance

Explosion-proof thermal resistance is usually used together with display instruments, recording instruments, etc. The temperature of liquid, steam and gas medium and solid surface in the range of 0 ~ 500℃ in the presence of hydrocarbon explosion at production site is directly measured.

Technical parameters of explosion-proof thermal resistance

Pressure spring type temperature sensor, good vibration resistance; High measurement accuracy; High mechanical strength, good pressure resistance; Imported thin film resistance elements, reliable and stable performance; Explosion-proof level: Exd Ⅱ CT4 Exd Ⅱ CT6 ExiaCT4 / ExiaCT6 IP65 protection grade electrical outlet M20 x 1.5 1/2 'NPT explosion protection working principle of the thermal resistance of thermal resistance using the clearance flame-proof principle, design has enough strength of the junction box, and other components, will all produce spark, arc and dangerous parts are sealed in the junction box cavity temperature, when the explosion cavity, can remove from heat and cooling by joint clearance, made after the explosion flame temperature and not reach outside the cavity, thereby for temperature measurement.

Explosion-proof thermal resistance system composition

(1) The temperature measuring system of thermal resistance is generally composed of thermal resistance, connecting wires and display instruments. The following two points must be noted:

(1) The dividing number of the thermal resistance and the display instrument must be consistent

(2) In order to eliminate the influence of the change of resistance of the connection wire, the three-wire connection method must be adopted. See the third chapter for details.

(2) Armored thermal resistance Armored thermal resistance is a solid body composed of temperature-sensing elements (resistance body), leads, insulation materials and stainless steel sleeves. Its outer diameter generally means 1~ 8mm, and the minimum is up to mm. Compared with ordinary thermal resistors, it has the following advantages:

Small volume, no internal air gap, thermal inertia, small measurement hysteresis;

(2) Good mechanical properties, vibration resistance, impact resistance;

(3) can bend, easy to install

Long service life.

(3) End face thermal resistance The end face thermal resistance temperature sensing element is made of specially treated resistance wire and is attached to the end face of the thermometer. Compared with the general axial thermal resistance, it can reflect the actual temperature of the measured end face more accurately and quickly, and is suitable for measuring the end face temperature of bearing bush and other parts.

(4) the flameproof thermal resistance flameproof thermal resistance through the special structure of the junction box, its shell internal explosive mixed gas by sparks or electric arc resistance such as shadow to the circuit repair is bound to change the length of the wire resistance and impact resistance, resistance to replace the new body is good, if the repair welding, after welding to be calibrated before use.

Installation requirements for explosion-proof thermal resistance

Attention should be paid to the installation of thermal resistance, which is conducive to accurate temperature measurement, safe testing and easy maintenance, and does not affect equipment operation and production operation. To meet the above requirements, the following points should be paid attention to when choosing the installation position and insertion depth of the thermal resistance:

1. In order to have sufficient heat exchange between the measuring end of the thermal resistance and the measured medium, the location of the measuring point should be reasonably selected and the dead Angle of the valve, elbow, pipe and equipment should be avoided as far as possible.

2. The thermal resistance with a protective sleeve has heat transfer and heat dissipation losses. In order to reduce measurement errors, the thermocouple and thermal resistance should have sufficient insertion depth:

(1) For the thermal resistance to measure the fluid temperature in the center of the pipeline, the measuring end should generally be inserted into the center of the pipeline (vertical installation or inclined installation). If the diameter of the pipe is 200 mm, the insertion depth of the thermal resistance should be 100 mm.

(2) For the temperature measurement of high-temperature, high-pressure and high-speed fluids (such as the temperature of the main steam), in order to reduce the resistance of the protective sleeve to the fluid and prevent the protective sleeve from breaking under the action of the fluid, shallow insertion of the protective tube or the thermal resistance of the hot sleeve can be adopted. The shallow-inserted thermal resistance protection bushing shall be inserted into the main steam pipe at a depth not less than 75mm; The standard insertion depth of hot-sleeve thermal resistance is 100mm;

(3) If the temperature of the flue gas needs to be measured, even though the diameter of the flue is 4m, the insertion depth of the thermal resistance is 1 m.

(4) When measuring elements are inserted at a depth of more than 1m, they should be installed as vertically as possible, or with support frames and protective sleeves.