As a key equipment for accurately mixing multiple gases, gas mixers are widely used in industrial manufacturing, scientific research experiments, medical and other fields. The debugging process needs to balance safety, accuracy, and stability. The following outlines the key points of debugging from the preparation stage to functional verification.

1、 Preparation before debugging

1. Environmental and equipment inspection

-Environmental requirements: Ensure good ventilation in the debugging area, keep away from fire and heat sources, and control the temperature between 5-35 ℃ (to avoid gas expansion or condensation).

-Tool preparation: high-precision pressure gauge, flow meter, soap water or electronic leak detector, adjustable gas source (including inert gases such as nitrogen and compressed air), explosion-proof wrench, and anti-static equipment.

-Technical data: Check the equipment manual, gas compatibility table (such as hydrogen and chlorine cannot be mixed), and safety data sheet (MSDS).

2. System blowing and pre cleaning

-Blow the pipeline with inert gas (such as nitrogen) to remove manufacturing residues (such as metal shavings and oil stains) for at least 10 minutes until the outlet is free of impurities.

-If the mixer comes into contact with corrosive gases (such as Cl ₂, NH3), the pipeline should be cleaned with acidic or alkaline solution, then rinsed with clean water and dried.

2、 Hardware installation and parameter settings

1. Gas path connection and sealing test

-Pipeline assembly: Connect the air source, filter, solenoid valve, mass flow controller (MFC), and mixing chamber step by step according to the direction of airflow to avoid cross contamination.

-Sealing test: Apply pressure to 1.2 times the working pressure, apply soapy water or spray leak detection solution, and hold the pressure for 5 minutes without bubbles to be qualified.

2. Control parameter initialization

-Flow calibration: Set the reference flow rate of each channel gas through the calibration function of standard flow meter or mass flow meter (such as setting the air to 20L/min, with an error of ≤± 1%).

-Proportional setting: Based on the target mixing ratio (such as O ₂: N ₂=21%: 79%), input the weight of each gas flow rate in the controller and enable closed-loop feedback regulation (PID parameters are initially set to proportional 0.5, integral 0.2, and derivative 0).

3、 Staged functional debugging

1. No load operation test

-Disconnect the outlet of the mixing chamber, start the equipment, and observe the sequence of action of each solenoid valve (such as opening and closing delay ≤ 0.5 seconds) and MFC response speed (step change ≤ 1 second).

-Check the communication status of the control system (such as whether the RS485/MODBUS signal is normal), and ensure that the data refresh frequency of the touch screen or upper computer software is ≥ 1Hz.

2. Single gas flow verification

-Introduce a gas (such as argon) separately, adjust the flow rate to the upper limit of the range (such as 100L/min), and compare the actual value with the set value deviation (allowable ± 2% FS).

-Record the flow fluctuation under different pressures (such as 5-10 bar) and correct the MFC compensation coefficient.

3. Multi gas mixing accuracy testing

-Static mixing experiment: fix the total flow rate (such as 50L/min), adjust the proportion of each gas (such as CH ₄: CO ₂=30%: 70%), use an infrared gas analyzer to detect the outlet concentration, and the error should be<± 1.5%.

-Dynamic response test: For sudden changes in the set value (such as increasing the O ₂ ratio from 21% to 30%), record the time it takes for the system to reach a new steady state (which should be ≤ 30 seconds).

4、 Safety interlock and alarm verification

1. Over limit protection function

-Manually set faults for overpressure (such as exceeding 15% of rated pressure), undercurrent (such as a channel flow rate below 10% of the set value), and overheating (sensor temperature>80 ℃), check if the sound and light alarm is triggered and if the emergency shut-off valve is closed.

-After simulating power outage recovery, verify whether the system automatically restarts and retains the original parameter settings.

2. Emergency response to leakage

-Introduce a small amount of leakage (such as releasing a small amount of helium gas) at the mixing chamber or pipeline interface, detect the leakage alarm threshold (usually ≤ 5% LEL), and start and stop the linked exhaust device.

5、 Performance optimization and recording

1. Parameter fine-tuning

-Optimize PID parameters based on test data: increasing the proportional gain to 0.7 can accelerate response, shortening the integration time to 0.1 seconds to reduce steady-state error.

-For highly reactive gases such as silane, add a purging program (such as introducing nitrogen gas for 5 minutes after each shutdown).

2. Long term stability monitoring

-Run continuously for 72 hours, record the mixing accuracy and equipment status every hour, and draw the flow fluctuation curve (peak deviation should be<3%).

3. Document management

-Prepare a debugging report, including equipment model, gas type, calibration data, fault handling records, and maintenance recommendations (such as monthly calibration of MFC).

6、 Common exceptions and solutions

-Mixing ratio deviation: Check MFC zero drift and recalibrate; Confirm that the gas supply pressure is stable (fluctuation<± 5%).

-Electromagnetic valve misoperation: Check for electromagnetic interference sources and install filters or shielding layers.

-Sensor failure: When replacing electrochemical sensors (such as detecting H ₂ S), zeroing calibration must be performed.