Common Faults of Freeze Dryer_Treatment Steps

Refrigeration system failure

1. The expansion valve is blocked

A. Symptoms: The refrigerant does not flow through the sight glass, the outlet of the expansion valve freezes and frosts, the high-pressure pipe becomes hot or the high-voltage trips.

B. Causes: Dirty blockage, ice blockage, thermal capillary breakage

C. Processing steps:

Adjust the superheat of the expansion valve; adjust the opening degree of the expansion valve;

Increase the superheat of the temperature sensing package and increase the PS pressure; such as covering the temperature sensing package with your hands, or putting the temperature sensing package into warm water;

Increase the high pressure of the refrigerant (the setting value of the fan switch), close the hot gas bypass valve, and impact the dirty blockage.

2. Clogged dry filter

A. Symptoms: There is an obvious temperature difference between the inlet and outlet of the dry filter, or condensation occurs at the outlet of the filter.

B. Processing steps: replace the dry filter

Note: When the system is blocked and the equipment is running without load, the high and low pressure values may be within the normal range; when the load is running, the high pressure is seriously high, and even the high pressure trips. During long-term operation, a large amount of high-temperature and high-pressure gas is directly returned to the low-pressure return air pipe from the hot gas bypass throttling, which will cause the compressor to become hot, and the temperature of the high-pressure return air pipe will rise to hundreds of degrees, and even cause the motor to burn out. When the compressor is overheated, the internal thermal protection of the compressor starts to work and protect; only after the compressor temperature cools down naturally can it be restarted.

3. Compressor failure

A. Causes: excessive load, motor burnout, long-term abnormal operation of the cold dryer, leakage, damage to the starting capacitor (miniature machine), etc.

B. Judgment method:

①Measure the motor resistance to judge

Three-phase motor:

ROA=ROB=ROC

Two-phase motor: ROA=ROB+ROC

(ROB=ROA+ROC)

(ROC=ROA+ROB)

② Measure the grounding resistance of the compressor;

③ Check the capacitor of the compressor (ND-05～ND-100AC air dryer is equipped with it)

Capacitance detection method: adjust the gear of the multimeter to the maximum range (above 200 megohms), and connect the two probes to both ends of the capacitor. Whether it is an electronic or pointer multimeter, the displayed value is very small for an instant, and then slowly increase. The larger the capacity of the capacitor, the slower it increases. If the measured capacitor resistance value is 0 or ∞, and there is no change, it can be judged that the capacitor is leaking or breakdown.

④ Observe whether the compressor moves (or makes abnormal noise) after starting up, and feel whether the middle part of the compressor is hot; Turn on the machine and observe whether the compressor works;

⑤ Measure the running current of the compressor with an ammeter to judge whether it is normal.

4. Refrigeration system leaks fluorine

A. Symptoms: After shutdown, the refrigerant high pressure gauge and refrigerant low pressure gauge show that the pressure is zero or the pressure is below 0.4MPa. During operation, the surface temperature of the compressor and the high-pressure pipe is high and hot, and the high and low pressure of the refrigerant often appear in a low state; if there is a serious fluorine leakage, it will cause a low-pressure alarm.

B. Processing steps: check for leaks, make up for leaks, and fill with fluorine for re-commissioning.

C. Judgment method for internal leakage of evaporator:

① Stop the work of the cold dryer, discharge the refrigerant in the refrigeration system (note that it should be fully discharged, that is, the pressure gauge shows zero), and the needle valve is closed;

② Open the compressed air inlet valve to let the compressed air pass through the evaporator. At this time, observe the change of the refrigerant pressure gauge. If the evaporator leaks, the pressure on the refrigerant pressure gauge will gradually increase after a period of time, reaching the pressure of compressed air. In this way, it can be judged that it is an internal leakage of the evaporator.

D. If there is no change on the refrigerant pressure gauge for a long time after the compressed air is introduced, or there is only a slight increase, it is not necessarily the internal leakage of the evaporator. The reason is that a small part of Freon will be dissolved in the freezing oil and then released slowly.

Air system failure

1. The air system has a pressure drop between the equipment inlet and outlet

Processing steps:

A. Ice is blocked inside the evaporator, and the low pressure of the refrigerant is low; adjust the low pressure of the refrigerant above 0.35Mpa;

B. Compressed air pre-filter element fails;

C. The air pressure gauge is broken;

D. Severe air leakage in the drainage system

2. Poor water removal in the air system

Processing steps:

A. Compressed air inlet pressure is seriously low;

B. The drainage system does not drain, and the time setting of the electronic drain is short;

C. The float drainer is dirty and blocked, and the manual drainage is not timely.

D. Replace the filter element.

Electrical system failure

1. The high and low voltage switch is disconnected

Processing steps: It is a protection measure, manually reset and check the condition of the refrigeration system

2. The thermal relay is disconnected

Processing steps: check the current direction of the thermal relay, and check the actual current value

3. Press the start button without starting

Processing steps:

①Poor contact;

②High and low voltage switch protection, or temperature switch protection;

③The delay time has not arrived;

④ Check the control system.

4. Turn on the air switch

Processing steps:

A. Check whether there is a short circuit or poor contact in the line, resulting in phase loss;

B. Check the electromagnetic contactor;

C. Measure the actual operating current value;

D. Check the resistance of the compressor motor to determine whether the compressor is working.

5. The fuse of the control system is burned

Processing steps:

A. Check whether the resistance value of the electronic drainer coil is short-circuited;

B. Check the short circuit according to the schematic diagram of the control system.

6. The compressor does not run when connected to the power supply

Processing steps:

① Check the phase sequence of the power supply, and then check the schematic diagram.

②The incoming power line does not meet the requirements.

③Compressor failure

Drainage system failure

1. Ice blockage at the drain: adjust the low pressure of the refrigerant to the normal value.

2. Float drain is dirty and blocked: clean the float drain.

3. The electronic drain does not drain water: check the coil of the electronic drain and the electrical schematic diagram.

The importance of the drainage system: when the condensed water is removed by the cold dryer, it cannot be drained in time, and the flow rate of the air will bring the condensed water out of the cold dryer to the user’s air point, bringing water in the air source. Therefore, users should often use the manual drain button ESC to drain, observe the drain time of the electronic drain, and reset the drain time.

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