Box-type experimental electric furnace (hereinafter referred to as box-type furnace) is composed of a furnace body and a controller, which can also be combined as a whole, and the furnace body is generally a table. The heating element is made of electrothermal alloy. The shell of the furnace is made of treated steel (the outer surface is sprayed with heat-resistant protective paint), and the lining is selected to provide heat-resistant materials for the performance requirements of the box-type furnace. Box-type furnace is an experimental equipment used in coal, electric power, petrochemical, military industry, metallurgy and coal-related industries. It is mainly used in coal and electric power industry with large consumption and high frequency. Therefore, it is very important to calibrate the box furnace. The current testing literature is the national standard, but the operation is complicated, some calculations are not reasonable, this paper has carried out the relevant experiment and calibration method research, the following several aspects to talk about the box furnace calibration method and calculation.
1. Determination of working area
To calibrate the box furnace, the working area of the furnace should be determined first. The second is to use the "workspace size" provided by the calibrated customer to determine the workspace.
2. Determination of temperature measurement points
According to the size of the working area of the box furnace, design the size of the temperature measuring frame, determine 5 temperature measuring points and 1 monitoring point. The five temperature measuring points were located at the middle point of the working area and at the four corners of the front and lower left, front and upper right, back and upper left, back and lower right. The monitoring point is located in the working area where the extension direction of the temperature control thermocouple endpoint is no more than 150mm. If the extension direction of the intermediate point is no more than 150mm from the temperature control thermocouple measuring point, the intermediate point shall be deemed as the monitoring point.
3. Selection of temperature calibration device
The temperature calibration device is composed of measuring instrument, thermocouple and supporting equipment, etc. The introduced extended uncertainty should meet the calibration requirements for the temperature uniformity of the box-type furnace.
4. Calibration process
Calibration is usually performed in an empty furnace. Before calibration, the measuring end of the testing thermocouple is fixed on each temperature measuring point position of the temperature measuring frame and marked. Then, the temperature measuring frame is installed into the furnace, the thermocouple reference end is removed from the furnace, and the measuring instrument is connected with the transfer switch according to the marked serial number. Close the furnace door, send electricity to heat up, set the temperature control meter of the box furnace to the required calibration temperature.
When the furnace temperature reaches the calibration temperature, start reading after stabilization. Within 60 minutes, record the monitoring point, temperature measuring point and temperature displayed by the thermometer every 3 minutes, 20 times in total. Each time, the monitoring points, temperature measuring points and the temperature displayed by the thermometer should be recorded within 1min.
On 2018-08-08 11:45:46
