Abnormal increase in pressure

Reason: The sample size exceeds the standard (such as solid>0.2g), the organic matter reacts violently, or the heating rate is too fast (>5 ℃/min).

Solution: Reduce the sample size to within 10% of the tank volume, add a pre digestion step (such as maintaining 80 ℃ for 30 minutes), and switch to a gradient heating program. A laboratory caused a can explosion due to uncontrolled sample size, and the problem was solved by strict weighing (solid ≤ 0.1g) and staged heating.

Prevention: Regularly replace the pressure relief valve spring (at least once a year) and avoid using acid systems containing sulfides without oxidants.

Abnormal/no change in pressure display

Reason: Damaged pressure sensor, blocked pressure pipe, or aging sealing ring.

Processing: No load test (only running the program with water), clean the pressure tube with 5% HNO 3 ultrasonic for 30 minutes; Replace the PTFE sealing ring (with a lifespan of 50-100 cycles).

2、 Temperature control system malfunction

Temperature reading drift/jump

Reason: Sensor corrosion (HF corrosion), loose connection wires, or signal interference.

Solution: Use a multimeter to test the platinum resistance (PT100 should be 100 Ω at 0 ℃), clean the probe (wipe with an anhydrous ethanol cotton swab); Upgrade shielded twisted pair cables to avoid sharing circuits with high-power devices.

Insufficient heating rate

Reason: Magnetron power attenuation (>15%) or turntable imbalance.

Processing: Symmetrically load samples (with a quality difference of ≤ 0.1g), professionally test the power of the magnetron, and replace it if necessary; A certain chemical plant experienced slow heating due to wear and tear of the rotary table bearings. After replacing the bearings, it returned to normal.

3、 Mechanical and sealing failures

Leakage of digestion tank

Performance: Acid stains on the outer wall of the tank and fluctuations in the pressure curve.

Reason: O-ring aging (>50 uses) or improper torque (<15N · m or>25N · m).

Solution: Immediately stop the machine, replace the sealing ring, and calibrate the torque wrench (standard 15-20N · m).

Abnormal vibration of the turntable

Reason: Bearing wear or asymmetric loading.

Solution: Manually rotate to detect stuttering, apply molybdenum disulfide grease; Reload to ensure mass balance (deviation ≤ 0.5g).

4、 Microwave and electrical system malfunction

No microwave output

Reason: The high-voltage fuse has blown or the door interlock switch has failed.

Solution: Replace the fuse (specification 10A/250V), check the door switch linkage device; A laboratory experienced microwave leakage due to aging door seals, which were resolved by replacing the door seals.

Frequent tripping

Reason: Poor grounding (resistance>4 Ω) or power harmonic interference.

Solution: Install an isolation transformer or power filter to ensure that the grounding resistance is ≤ 4 Ω.

5、 Software and data failures

Program loss/communication interruption

Processing: Restore data from backup USB drive (FAT32 format), clean fiber optic interface (wipe with isopropanol); A user lost data due to not backing up the program, and subsequently established a regular backup system.

Touch screen malfunction

Solution: Restart the control system and calibrate the touch points; If it is a hardware failure, the touch screen needs to be replaced.

6、 Sample related faults

Incomplete dissolution

Reason: Improper acid ratio (such as not using alkaline system for hexavalent chromium).

Solution: Use NaOH+Na ₂ EDTA system and maintain at 100 ℃ for 20 minutes.

Turbidity of digestion solution

Reason: Residual silicates (insufficient HF).

Solution: Add 1-2 mL of HF and extend the digestion time at 180 ℃.

7、 Maintenance and preventive measures

Regular calibration: Perform two-point calibration on the sensor every quarter using boiling water (100 ℃) and ice water (0 ℃).

Consumable replacement: Immediately wipe the sensor with 5% boric acid after HF digestion to avoid acid corrosion.

Safety ban: Prohibition of perchloric acid and concentrated sulfuric acid; Samples containing organic matter need to be pre carbonized.

Operation specification: After freeze-drying the sample, digest it and control the sample volume (solid ≤ 0.2g, liquid ≤ 5mL).

Through systematic fault diagnosis and preventive maintenance, the operational stability of microwave digestion equipment can be significantly improved, the equipment life can be extended, and experimental safety and data accuracy can be guaranteed.