Common Troubleshooting Methods for Gas Chromatography
When diagnosing and analyzing issues with a gas chromatograph, it is essential to be familiar with its operational procedures, as well as the structure and functions of components within its gas and electrical systems. Gas chromatograph malfunctions can be complex, and a single issue may stem from multiple causes, requiring a methodical elimination approach to narrow down the fault.
1. Gas System Faults
Common gas system issues include gas leaks, gas quality problems, and poor pressure or flow stability. These problems often lead to “ghost peaks” or cause signal peaks to disappear. In addition, aging or overheating of the chromatographic column can result in issues such as "loss of liquid phase." Therefore, the first step is to inspect the gas system. If no issues are found here, the focus should then shift to the electrical system.
2. Electrical System Faults
Troubleshooting electrical system faults is relatively complex. Technicians need a thorough understanding of the instrument’s wiring and circuit schematics, as well as foundational electronics knowledge. Wiring diagrams provide clear insights into the relationships between the control unit and the controlled elements, which aids in troubleshooting.
Most electrical faults in chromatographs occur in the temperature control system and the detection amplification system. The temperature control system consists of a silicon-controlled rectifier (SCR) and heating elements, with the SCR’s conduction angle controlling heating power and temperature regulation. Common issues include damaged SCRs, heating elements, or platinum resistors, and faults in auxiliary electronic components. Amplification system issues often involve moisture in ion signal lines, malfunctioning sensitivity switches, or degraded performance in operational amplifiers.
3. Fault Resolution Methods
When troubleshooting, it’s essential to examine both local and system-wide issues to pinpoint the cause. For example, if the baseline fluctuates or noise levels are high, first disconnect the amplifier’s signal input line and observe the baseline. If it stabilizes, the fault may lie within the gas system or temperature control system; if not, the issue might reside in the amplifier or recorder.
4. Fault Analysis Approach
Fault analysis should consider the following:
Safety Awareness: Prioritize safety to prevent electrical accidents.
Problem Identification: Link observed issues with relevant components or factors.
Avoid Blind Action: Avoid unnecessary disassembly or part replacement to prevent exacerbating the issue.
Analysis Methods:
Sequential Reasoning: Diagnose based on the operational principles.
Segmented Elimination: Systematically eliminate possible causes.
Experience-Based Inference: Use prior experience to identify causes.
Comparative Inspection: Compare data with a functioning unit to locate the fault.
Comprehensive Method: Use multiple methods to identify the fault source.
5. Common Gas Chromatograph Fault Categories
Gas System Faults: Issues such as abnormal gas input, leaks, insufficient purity, contamination, blockages, or column problems.
Electrical System Faults: Temperature control, keyboard or display malfunctions, and power issues.
Signal Output Issues: Zero-point drift, unstable signals, or lack of output.
Other Issues: Source gas problems, grid voltage fluctuations, and mechanical issues.
6. Fault Identification Methods
Know the Equipment: Understand the structure, function, and operation principles of the chromatograph.
Analyze Inputs and Outputs: Each component has an input and output. When input is normal but output is abnormal, the fault likely lies within the component. For instance, if the FID amplifier’s input (a microcurrent signal from the detector) is stable, but output is faulty, the amplifier itself may be the issue.
7. Experience Accumulation
During repairs, it is beneficial to gather fault data, keep detailed maintenance records, and build experience. Mastering and flexibly applying troubleshooting methods will enable quicker, more accurate identification of root issues.
Since its founding, Lixun Maintenance has remained dedicated to providing professional services for electronic measurement instruments across labs, research institutes, and universities. With advanced repair equipment, skilled technicians, competitive pricing, and a complete after-sales support system, we help customers reduce repair costs and minimize repair cycles.
