Analysis and Treatment of Faults in Coal Mine Gas Chromatograph

In this paper, the chromatographic technicians of Wuhan Tetworth Technology Co., Ltd. proposed the treatment measures to solve the fault through the typical failure phenomenon of coal mine gas chromatograph, and carried out the summary analysis, which greatly improved the work of chromatograph maintenance. effectiveness. Wuhan Tetworth Technology Co., Ltd. is located in Jiangxia District, Wuhan, China, specializing in the production of gas chromatographs. When using the gas chromatograph, you must understand these principles in detail so that they can be used conveniently. If you have technical support, please call Wuhan Tentworth Technology Co., Ltd.

1 characteristics of gas chromatograph

When the gas chromatograph malfunctions, to find out which system the fault exists in, which component, first understand the basic structural composition of the instrument, the division of the system and the mutual connection, which is to gradually narrow the scope of the fault to one. Necessary conditions within the system or a component. The gas chromatograph system is divided into a pneumatic system, a circuit system, a detector system, an electronic system (a power supply component, a temperature measurement and control component, an amplifier component, a dedicated microcomputer system, an external event control component), and a data processing system. Correct understanding of the role and requirements of each component of the gas chromatograph is very important for our analytical work.

The gas chromatograph analysis system utilizes the difference in gas physical properties. The gas sample is carried into the column through a specific carrier gas. The gas sample component is distributed multiple times between the gaseous phase and the stationary phase. Although the carrier gas flow rate is the same, due to the fixed relative The adsorption capacity of each component is different, resulting in different flow rates of the components in the column. After a certain period of flow, the separation is carried out, and the column is passed through the column to enter the detector system, and different signals are amplified and processed through data processing. The peaks of the components are displayed on the host. According to the peak position (time), the name of the component is determined, and the content is determined according to the peak area (or peak height value).

2 gas chromatograph failure cause judgment processing

Gas chromatography is an important precision instrument for gas component analysis. It is especially important to strengthen the observation of its condition during the operation process, especially the correctness of the judgment, analysis and processing flow after the failure, and the normal operation of the recovery instrument. Has a decisive role. Therefore, the following summarizes the typical faults and treatments that occur in the gas chromatograph to ensure accurate and efficient operation of the chromatograph.

(1) The gas path system has a phenomenon such as blockage, leakage, no pressure indication, no gas output. Treatment measures: 1) Check whether the gas cylinder and gas generator are normal; 2) Observe the gas pressure gauge to judge whether the gas input is normal; 3) Check whether the external gas path such as the filter is normal; 4) Check whether the gas output of the injection gas path is normal Normal; 5) Check whether the regulator valve to the column is normal; 6) Check whether the gas input and output of the detector are normal; 7) Appropriately block the gas system and observe the change of the indication of the corresponding pressure gauge. Is there a leak?

(2) The temperature control part does not rise or the temperature is unstable. Treatment measures: 1) When the temperature is unstable, the temperature of the oven can be lowered, and the temperature of the detector can be observed. If it is normal, it is the fault caused by the grid voltage or the grounding wire; 2) When the temperature is abnormal, check the voltage and grounding wire. Whether it is normal; the temperature control of the oven is not normal, check whether the corresponding relay and thyristor are normal; 3) If the temperature control of a certain channel is not normal, check whether the platinum resistance and heating wire of the corresponding temperature control are normal. If the platinum resistance, heating wire, etc. are normal, the microcomputer board is faulty.

(3) The FID detector cannot be ignited or turned off. Treatment measures: 1) Check whether the carrier gas and auxiliary gas enter the detector normally; 2) Check whether the shape of the ignition wire is normal, whether there is any open circuit or short circuit, or poor contact; 3) Check if the ignition relay is normal, and the ignition current is Normal; 4) Check whether the detector mechanism is contaminated or blocked; 5) Check whether the flow ratio of various gases is appropriate.

3 gas chromatograph routine maintenance points

During the use of the instrument, it is often judged whether there is a problem based on the comparison between the instrument startup state and the analytical spectrum. Abnormal spectra often reflect problems in operating conditions or instrumentation systems.

In the daily operation of the chromatograph, the temperature of the external environment will change, causing the abnormal peak spectrum of the chromatograph. The specific examples of the processing are as follows: (1) The peak time of the channel moves forward, indicating the flow rate in the gas path. Increased, it is easy to cause peak overlap. This phenomenon indicates that the corresponding carrier gas flow control is not good. It is necessary to check the carrier gas flow rate and pressure of the corresponding channel to control the flow rate reduction. (2) The channel does not have a peak, indicating that the detector hydrogen, air, and nitrogen flow ratios are not suitable. Causes the hydrogen flame to turn off. The hydrogen, air, and nitrogen flow ratios should be properly adjusted to maintain hydrogen: air = 1:5-10; (3) The peak time of the channel is delayed, indicating that the gas flow rate is low, and the peak is incomplete. Need to increase the corresponding channel gas flow rate or check if the air path filter media needs to be replaced. Judging the working state of the chromatograph through the peak of the spectrum is one of the important basis for the operator to deal with the initial failure of the instrument.

For instrument troubleshooting, maintenance personnel need to pay attention to the following points: (1) Carefully observe the fault phenomenon and record the details of the fault phenomenon. Check and analyze whether there are errors in the operation steps; (2) Query the use and maintenance records of the instrument to see if the same or similar phenomenon has occurred in the past; (3) According to the observed phenomenon, reference drawings, self-diagnosis manual and maintenance guide Analyze the general location where the cause of the fault may be distributed; (4) Test according to the planned steps, and judge the exact position and extent of the fault distribution according to the test result; (5) During the fault judgment process, always pay attention to whether each connector and the connecting line exist. Open circuit, short circuit and poor contact.

In the process of troubleshooting, the accuracy of the analysis, testing and judgment of the fault will play a decisive role in the success or failure of the entire maintenance work.

Gas chromatography is a relatively expensive precision instrument. In order to be safe to use and obtain good working results, you must know the basic knowledge about the installation, maintenance and maintenance of the instrument. When the instrument fails, it can judge the occurrence of a certain accessory or gas path of the analysis system according to the phenomenon (instrument pressure, channel flow rate, peak characteristics, etc.). To solve the malfunction of the chromatograph, "prevent the right medicine", avoid unnecessary loss or expand the fault range during the maintenance process, and improve the efficiency of instrument maintenance.

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