Stainless steel shock resistant axial bimetallic thermometer

Stainless steel shock resistant axial bimetallic thermometer

1、 Working principle of bimetallic thermometer:

A bimetallic thermometer is a temperature sensing device that uses a threaded bimetallic strip as a sensing element, and installs it in a protective sleeve. One end is fixed, called the fixed end, and the other end is connected to a thin shaft, called the * * end. A pointer is installed on the end axis. When the temperature changes, the * * end of the temperature sensing device rotates accordingly, driving the pointer on the thin shaft to produce an angle change, indicating the corresponding temperature on the dial.

2、 Characteristics of bimetallic thermometer products:

The advantages of bimetallic thermometers are fast response speed, small size, good linearity, and stability. Some foreign products also have high-temperature working performance.

1. The thermoelectric potential of a bimetallic thermometer is only related to the thermoelectric properties of the thermoelectric electrode material and the temperature difference between the two ends.

2. Using the same homogeneous conductor or semiconductor to form a circuit will not generate thermoelectric potential.

3. The temperature of the two junctions of the thermocouple is T, T0. If T=T0, the thermoelectric potential of the thermocouple is zero. The law of intermediate temperature laid the foundation for the development of thermocouple calibration tables.

4. High conductivity and low temperature coefficient of resistance; The configured thermoelectric potential has high sensitivity, with a linear relationship between thermoelectric potential and temperature, making it easy to * *, simple to process, and inexpensive.

Generally, bimetallic thermometers are used at low temperatures, while thermocouples are used at high temperatures. If the temperature exceeds 500 degrees, the resistance of the bimetallic thermometer will be very high, which may affect the measurement results and even lead to situations where the measurement results cannot be obtained.

Stainless steel shock resistant axial bimetallic thermometer

3、 Precautions for installation of bimetallic thermometer:

1. In order to ensure sufficient heat exchange between the measuring end of the thermistor and the measured medium, the position of the measuring point should be selected reasonably, and the installation of the thermistor near the dead corners of valves, elbows, pipelines, and equipment should be avoided as much as possible.

2. Thermistors with protective sleeves suffer from heat transfer and dissipation losses. To reduce measurement errors, thermocouples and thermistors should have sufficient insertion depth:

a、 For measuring the temperature of the fluid at the center of the pipeline, the measuring end of the thermistor should generally be inserted into the center of the pipeline (vertically or obliquely installed). If the diameter of the tested fluid pipeline is 200 millimeters, the insertion depth of the thermistor should be selected as 100 millimeters;

b、 For temperature measurement of high temperature, high pressure, and high-speed fluids (such as main steam temperature), 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 use of a hot sleeve thermistor can be adopted. The shallow insertion type thermal resistance protective sleeve should be inserted into the main steam pipeline at a depth of not less than 75mm; the standard insertion depth for hot sleeve thermal resistance is 100mm;

c、 If it is necessary to measure the temperature of the flue gas in the flue, although the diameter of the flue is 4m, the insertion depth of the thermistor is 1m;

d、 When the insertion depth of the measuring element exceeds 1m, it should be installed vertically as much as possible, or support frames and protective sleeves should be added.

4、 Classification and product parameters of bimetallic thermometers:

1. Outdoor type, heavy-duty: This bimetallic thermometer is a field detection instrument suitable for measuring medium and low temperatures, and can be directly used to measure the temperature of liquids and gases.

Accuracy level: 1.5

△ Time constant: J<40S

△ Protection tube pressure resistance: 6.3MPa

2. Electric contact type: Bimetallic thermometer is a field detection instrument suitable for measuring medium and low temperatures, which can be directly used to measure the temperature of liquids and gases.

Accuracy level: 1.5

△ Time constant: J<40S

△ Protection tube pressure resistance: 6.3MPa

△ Contact capacity: rated power 10VA (no inductance); **Voltage: AC 220V, * * working current: 1A (non inductive), contacts are upper and lower limits and normally open.

△ Header working environment temperature: -25~55 degrees Celsius

3. Seismic resistant type: The seismic resistant electric contact bimetallic thermometer is an on-site detection instrument for measuring low and medium temperatures. It can directly measure liquid, steam, and gas media within the range of -80 ℃ to+500 ℃ in various production processes

The environment is harsh and the temperature is subject to vibration.

△ Execution standard: JB/T8803-1998 GB3836-83

△ Scale dial nominal diameter: 60 100 150

Accuracy level: (1.0), 1.5

△ Thermal response time: ≤ 40S

Protection level: IP55

Angle adjustment error: The angle adjustment error should not exceed 1.0% of its range

△ Return difference: The return difference should not exceed the value of the basic error limit

△ Repeatability: The limit range of repeatability should not exceed 1/2 of the basic error limit

4. Universal type: △ dial nominal diameter: 100; one hundred and fifty

Accuracy level: 1.0, 1.5

△ Connection size: M20x1.5, NPT1/2

△ Thermal response time: ≤ 40s

Protection level: IP55

5、 Daily maintenance of bimetallic thermometer:

1. During the storage, installation, use, and transportation of bimetallic thermometers, collision with protective tubes should be avoided as much as possible, and protection should not be used Bending and deformation of the protective tube. During installation, it is strictly prohibited to twist the instrument housing.

2. The instrument should operate normally within an ambient temperature range of -30 ℃ to 80 ℃.

3. The temperature at which the instrument frequently operates can be between 1/2 and 3/4 of the scale range.

4. The length of the bimetallic thermometer protection tube immersed in the measured medium must be greater than the length of the temperature sensing element. Generally, the immersion length is greater than 100mm, and the immersion length for the 0-50 ℃ range is greater than 150mm to ensure measurement accuracy.

5. Various bimetallic thermometers are not suitable for measuring the temperature of media in open containers, and live contact thermometers are not suitable for use in control circuits with high working vibration.

6. During the storage, installation, and transportation of bimetallic thermometers, collision with the protective tube should be avoided, and the protective tube should not be bent or deformed, and the thermometer should not be used as a wrench.

7. The thermometer should be regularly inspected under normal use. It is generally recommended to do so every six months. Electric contact thermometers are not allowed to operate under strong vibrations to avoid affecting the reliability of the contacts.