How to Unclog Expansion Valve?

Figure 1: A clogged expansion valve.

In the air conditioning and refrigeration system, the blockage fault of expansion valve often occurs. The general blockage faults mainly include "ice blockage" and "dirty blockage". When there is a certain amount of fiber, iron filings, copper filings, welding slag and other impurities in the system, it is easy to get dirty and blocked; When there is more moisture in the system, ice blockage is easy to occur.

1. Common Blockage of Expansion Valve

1.1 Dirty Blockage

Figure 2: An expansion valve with serious dirty blockage.

Under normal circumstances, dirt blockage is easy to appear on the drying filter. The filter intercepts the impurities in the system resulting in dirty blockage. In case of dirty blockage, the superheat and temperature of the return gas will rise. When the dirty blockage is serious, it will affect the normal operation of the system. The system will not operate if the impurities in the system cannot be cleaned in time.

1.2 Ice Blockage

Figure 3: An expansion valve with serious ice blockage.

Ice blockage is easy to occur at the throttle of the expansion valve, because the temperature there is the lowest and the aperture is the smallest in the whole system. When the air conditioning system stops cooling, the overall temperature of the system will gradually rise, which will make the ice jam begin to melt slowly. When the system restarts and starts refrigeration, the overall temperature of the system will gradually decrease with the operation of the system, so ice blockage will occur again. Therefore, it can be said that ice blockage occurs repeatedly.

The reason for ice blockage is that the system contains too much water (moisture). The ways to produce moisture are as follows:

(1) The vacuum pumping time was not enough during installation, so the moisture in the pipeline was not pumped out. Or the welding process at the pipeline connection is not good (there are air leakage points).

(2) When filling the system with refrigerant, the air in the connecting hose is not blown out of the hose.

(3)Air enters the expansion valve when replenishing lubricating oil for the system.

2. Signs of blockage in the expansion valve

The expansion valve plays a throttling role in the air conditioning system. When the system works, the refrigerant flow and system pressure can be adjusted by controlling the opening of the expansion valve to make the system work normally. Dirty blockage of the expansion valve will cause the system to fail to increase the refrigerant flow even if the expansion valve is opened to the maximum. And then it will lead to excessive differential pressure before and after the valve.

If the expansion valve is blocked, the cooling effect of the air conditioning system will be poor, and the expansion valve will freeze. The compressor will run with noise, abnormal cooling, etc.

3. How to eliminate the blockage of expansion valve

So how can we effectively eliminate the blockage of expansion valve? If the dirty blockage of the expansion valve is not serious, the problem can be solved only by replacing the drying filter. If the expansion valve is seriously dirty and blocked, we should clean the impurities at first. Then draw a vacuum for the system and charge the refrigerant.

If the ice blockage of the expansion valve is not serious, what we should do is applying a hot towel outside the ice blockage. If the ice blockage of the expansion valve is serious and the system cannot work normally, we should replace the filter dryer. Dispose the water in the pipeline, vacuum it, and then charge the refrigerant.

Related Info