1、 Core fault types and detailed analysis (sorted by frequency of occurrence)

1. Decreased evaporation efficiency (most common)

Fault manifestation: Under the same feed amount, the concentration of concentrated solution does not meet the standard and the yield of distillate decreases; The device's running time is prolonged but the processing effect is poor.

Core causes:

Scale formation on the heat exchange surface (high salt and high organic wastewater is prone to produce calcium and magnesium salt scale, and organic matter adhesion);

Insufficient vacuum degree (vacuum system leakage, vacuum pump failure, condenser frosting/blockage);

Insufficient temperature of heating medium (insufficient steam pressure, malfunction of heat transfer oil heater, inaccurate temperature sensor);

Unstable feed flow rate (feed pump failure, pipeline blockage or leakage).

Key points of investigation:

Check the surface of the heat exchange tube/plate heat exchanger for white scaling or black attachments (requiring regular chemical cleaning or physical descaling);

Use a vacuum gauge to measure the vacuum level of the system. If it is lower than the set value (usually 0.08-0.095MPa), check for leaks in the vacuum pump oil level, seals, and pipeline interfaces;

Check the inlet and outlet temperatures of the heating medium, and confirm whether the pressure of the steam boiler or the power output of the heat transfer oil heater is normal.

2. Vacuum system malfunction

Fault manifestations: inability to reach the set vacuum level, frequent fluctuations in vacuum level, abnormal startup of vacuum pump, or excessive noise.

Core causes:

Pipeline/equipment sealing failure (aging flange gaskets, damaged sealing rings, inadequate sealing of observation windows);

Vacuum pump malfunction (oil contamination/insufficient oil in oil type vacuum pump, clogged dry vacuum pump filter element, pump body wear);

Frost formation or blockage in the condenser (under low-temperature conditions, the vapor of the distillate may freeze and frost, blocking the condensation channel);

Excessive non condensable gas (due to the presence of a large amount of air in the feed, or equipment exhaust valves not opening properly).

Key points of investigation:

Apply soapy water to the pipeline interface, flange, observation window, and other parts to observe for bubbles (to determine the leakage point);

Check the oil color of the vacuum pump (if it turns black or emulsified, it needs to be replaced), oil level, and cleanliness of the filter element;

Check if there is frost on the condenser shell, and if necessary, activate the defrosting function or clean the condensation channel.

3. Equipment icing/freezing blockage

Fault manifestation: Ice formation on the heat exchange surface, pipeline or discharge port, resulting in poor material circulation; In severe cases, the device cannot start.

Core causes:

The evaporation temperature is set too low (below the freezing point of the material);

Excessive feed concentration (high salt wastewater concentration approaching saturation, prone to crystal precipitation and freezing);

Decreased heat transfer efficiency (due to insufficient heat transfer caused by scaling, resulting in localized cooling and freezing of materials);

Failure to clean up residual liquid in a timely manner after shutdown (residual liquid freezes and blocks the pipeline in a low-temperature environment).

Key points of investigation:

Adjust the evaporation temperature to above the freezing point of the material (usually 5-30 ℃ according to the composition of the wastewater);

Check the feed concentration and dilute it if necessary before processing;

After shutdown, rinse the interior and pipelines of the equipment with warm water to remove residual liquid and crystals.

4. Motor/pump malfunctions

Fault manifestations: Failure to start vacuum pump, feed pump, circulation pump, excessive noise, severe heating or tripping.

Core causes:

Unstable power supply voltage and poor circuit contact;

Pump impeller blockage (solid particles in the material entering the pump body);

Wear and insufficient lubrication of motor bearings;

Overload operation (excessive feed flow, increased equipment resistance leading to motor overload).

Key points of investigation:

Check the power supply voltage, whether the line connectors are loose, and whether the grounding is good;

Disassemble the pump body and clean the solid impurities or crystals inside the impeller;

Check the temperature of the motor bearings (normally below 70 ℃), add lubricating grease or replace worn bearings.

5. Concentrated liquid crystallization blockage

Fault manifestation: Blockage of concentrated liquid discharge outlet, increased pipeline pressure; The equipment frequently alarms and shuts down.

Core causes:

The feed concentration is too high or the evaporation intensity is too high (causing the concentration of the concentrated solution to exceed the saturation concentration and precipitate crystals);

The temperature of the discharge pipeline is too low (crystals quickly deposit and block at low temperatures);

Equipment mixing function malfunction (mixer stops running, material is locally concentrated excessively).

Key points of investigation:

Reduce the feed concentration or adjust the evaporation intensity to control the concentration of the concentrated solution below the saturation concentration;

Track the discharge pipeline with heat (such as wrapping with heating tape) to prevent crystal deposition;

Check the operation status of the mixer to ensure uniform mixing of materials and avoid local concentration.

6. Temperature sensor/control system malfunction

Fault manifestation: Abnormal temperature display (high, low, or fluctuating violently); The device cannot automatically adjust temperature and vacuum degree.

Core causes:

The temperature sensor probe is scaled, damaged, or installed improperly;

Control system (PLC, touch screen) program error, parameter setting error;

Malfunction of the actuator (such as jamming of solenoid valves and regulating valves, unable to respond to control signals).

Key points of investigation:

Disassemble the temperature sensor, clean the surface scale of the probe, or calibrate it with a standard thermometer (if the deviation exceeds ± 1 ℃, it needs to be replaced);

Verify control system parameters (such as evaporation temperature, vacuum setting, PID adjustment parameters);

Check if the solenoid valve and regulating valve are functioning properly, and if necessary, disassemble, clean or replace them.

2、 Core Measures for Fault Prevention in Industrial Scenarios

Regular maintenance:

Clean the heat exchange surface and condenser scaling every week (using chemical cleaning agents such as citric acid and hydrochloric acid for cyclic cleaning);

Check the oil level, quality, and sealing components of the vacuum pump every month, and replace the vacuum pump oil every 3-6 months;

Calibrate temperature and pressure sensors quarterly, check motor bearings and lubrication conditions.

Pre treatment of incoming materials:

Remove solid particles from the feed (through filtration, precipitation, etc.) to avoid clogging the pump body and heat exchange tubes;

Control the feed concentration and temperature (the concentration should not be too high, and the temperature should be close to the set evaporation temperature to reduce equipment load).

Standardized operation:

Strictly follow the equipment manual to set parameters (evaporation temperature, vacuum degree, feed flow rate) to avoid overload operation;

Before shutting down, turn off the feed and continue running for 10-15 minutes to drain any remaining liquid from the equipment;

In low temperature environments (below 0 ℃), it is necessary to rinse the pipeline with warm water after shutdown to prevent freezing.

Emergency Management:

If there is a blockage in the pipeline, stop the machine first to relieve pressure, soak it in warm water or chemical solvents, and then clear it. Violent tapping is prohibited;

When the vacuum degree suddenly drops, priority should be given to identifying the leakage point, followed by checking the vacuum pump and condenser;

After the motor trips, it is necessary to investigate the cause of overload (such as blockage or leakage), eliminate the fault before restarting, and avoid frequent closing.

3、 Supplementary Applicable Scenarios

The malfunction of low-temperature evaporators is closely related to the characteristics of the processed materials (such as high salt, high COD, and crystalline substances) and operating conditions (temperature, vacuum degree, feed flow rate). The above types of faults are applicable to mainstream scenarios such as industrial wastewater treatment (such as electroplating wastewater, chemical wastewater, saline wastewater), material concentration (such as food and pharmaceutical intermediates), etc. The focus of investigation can be adjusted according to specific industry needs (such as electroplating wastewater needing to focus on scaling and crystallization issues, and pharmaceutical intermediates needing to pay attention to vacuum stability).