SF6 Gas Quantitative Leak Detector Control Box
1. Insert the gas-electric plug at one end of the probe's gas-electric pipeline into the corresponding socket on the right side of the instrument, and tighten the threaded connection.
2. Plug in the power supply and switch the status switch to the "Critical Volume" position.
3. Turn on the "Power Switch". At this time, you can hear the starting sound of the motor, and the "DC Voltage/Alarm Setting" meter should display a DC voltage of "40" volts, and the liquid crystal display on the probe should show "00".
4. After the vacuum pump runs for 10 minutes (if the ambient temperature is below 7°C, it should run for 30 minutes), pull out the "Critical Volume" potentiometer. If a faint dark purple excitation light can be seen in the window above the probe, measurement can begin.
If it does not "glow" within 10 seconds and the liquid crystal display shows "1", you can block the air inlet of the probe (needle valve) with a finger to increase the vacuum degree of the vacuum system. If it still does not "glow" within 10 seconds after blocking the probe and the liquid crystal display shows "1", you should turn off the "Critical Volume" potentiometer and the "Power Switch", wait for 15 minutes, and then repeat steps 3 and 4. Otherwise, the relevant electronic components may be damaged.
5. Adjust the "Critical Volume" potentiometer so that the speaker is in a critical state (i.e., the speaker emits a "click, click" sound). At this time, the instrument is in a standby detection state.
6. Qualitative detection: First, use a fan to blow on the detection area, then move the probe to the inspected location. If there is a gas leak, the reading on the liquid crystal display will increase, the speaker will emit an alarm sound with increasing frequency, and the laser in the ionization chamber will become brighter. At this point, the leak point can be quickly and accurately determined. If quantitative detection is required, refer to the reading on the liquid crystal display and check the corresponding K value against the quantitative calibration curve.
7. Alarm setting: After completing the above steps 1 to 4, the alarm can be set. First, switch the status switch to the alarm setting position, then adjust the "Alarm Setting" potentiometer so that the reading on the "DC Voltage/Alarm Setting" meter matches the desired setting value. Then move the probe to the detection point. If the concentration of leaking gas is greater than or equal to the set value, the speaker will emit an alarm sound.
8. After detection, first turn off the "Critical Volume" potentiometer, then turn off the "Power Switch", and finally unplug the power plug and close the box cover.
5. Calibration Method
1. Prepare sulfur hexafluoride gas of different concentrations
(1) Gas preparation: Use the syringe method;
(2) Standard gas: Qualified sulfur hexafluoride gas;
(3) Operation: Use a 1 ml syringe to extract 1 ml of pure sulfur hexafluoride gas from the cylinder, inject it into a 100 ml syringe, and dilute it to 100 ml with outdoor air, resulting in a concentration of 10000 ppm. Then use a 20 ml syringe to extract 10 ml of the 10000 ppm sulfur hexafluoride gas from the 100 ml syringe, inject it into another 100 ml syringe, and dilute it to 100 ml with outdoor air, resulting in a concentration of 1000 ppm. Concentrations of 100 ppm, 10 ppm, 1 ppm, 0.1 ppm, and 0.01 ppm are prepared sequentially using the same method.
2. Calibration of the leak detector:
After the leak detector is operated to the standby state, use a 20 ml syringe to extract about 10 ml of each of the prepared sulfur hexafluoride gas concentrations, remove the needle, connect the syringe to the probe's suction port with a rubber tube, and let the probe inhale the test gas. At this time, the signal values for different concentrations will be displayed on the liquid crystal display of the leak detector. Record each reading in Table (1) and plot the quantitative calibration curve.
