When the refrigerator stops freezing and the compressor hums idle or turns off due to overload, one of the likely causes is a clogged refrigeration circuit. Most often, the problem lies in the thinnest part of the system - capillary tube, the diameter of which is only a few tenths of a millimeter. This is where moisture gets stuck, turning into an ice plug, or oil oxidation products and paraffins accumulate.
To restore refrigerant circulation, it is necessary to perform a comprehensive flushing of the system, but the key step is cleaning capillary. The procedure requires precision, special tools and, most importantly, the right choice flushing liquid. Errors at this stage can lead to complete failure of the unit, so it is important to understand the chemical and physical processes occurring inside the circuit.
In this article we will look at which solvents are really effective and which can cause irreparable harm to the system. You will learn about the technology of nitrogen purging, the features of working with various types of blockages and the nuances that novice repairmen often miss when restoring refrigerators.
Causes and types of blockages in the capillary tube
Before choosing how to flush the system, you need to understand the nature of the obstacle that has formed. The capillary tube of a refrigerator is a bottleneck where the pressure drops sharply and the temperature drops. Any impurities that enter the circuit tend to settle here. There are two main types of blockages: oil-paraffin and humidity (ice plugs).
Oil-paraffin deposits are formed due to poor quality oil in the compressor or its aging products. When in contact with freon and the metal of the tubes, the oil can oxidize, forming a viscous mass that hardens over time. This type of blockage is the most difficult to remove, as it requires not just dissolution, but also mechanical washing out of dense fractions.
The second type is moisture. Even a small amount of water that gets into the system due to poor installation or depressurization freezes in the throttling zone. The ice plug blocks the freon current, and the refrigerator stops cooling. Rinsing in this case, it is aimed at removing moisture and acid residues that could have formed during the reaction of water with oil.
⚠️ Attention: An attempt to blow out the capillary with air without preliminary cleaning and evacuation will lead to the entry of moisture and oxygen into the system, which is guaranteed to cause re-clogging and oxidation of the compressor.
To diagnose the type of blockage, technicians often use the method of local heating or cooling, but the most accurate answer is provided by a visual inspection of the cut-off tube and analysis of the pressure behavior when purging with nitrogen. If the tube is tightly clogged, nitrogen does not pass through at all or passes through with great resistance.
Requirements for flushing liquids and solvents
The choice of flushing agent is a critical moment. The liquid must have a high dissolving ability with respect to mineral and synthetic oils, but at the same time be chemically inert with respect to the metal of the tubes and rubber seals. The ideal solvent should evaporate quickly without leaving any residue.
One of the main characteristics is the lack of hygroscopicity. If the flushing fluid absorbs moisture from the air, you risk introducing even more water into the system than was present before the repair. Therefore, popular household products such as acetone or alcohol require extremely careful handling and immediate sealing of the system after use.
- 🧪 Oil solubility: The product must effectively break down old compressor oil and paraffin deposits, turning them into an easily removable emulsion.
- 💨 Volatility: After flushing, the liquid should completely evaporate under vacuum, leaving no traces that could mix with the new refrigerant.
- 🛡️ Safety for materials: The solvent should not cause corrosion of copper, steel or aluminum, nor destroy the insulation of the compressor windings.
Many craftsmen argue about whether it is possible to use Galosh gasoline or white spirit. These substances dissolve oil really well, but they leave a greasy residue and take a long time to evaporate. The use of such aggressive media requires repeated repeated rinsing with cleaner solvents, which increases labor costs.
Review of effective products: what is the best way to rinse
The professional market has formed a list of the most effective products that service centers use. Already remains the leader freon R141b. This is a unique liquid that combines the properties of a refrigerant and a powerful solvent. It is non-flammable, perfectly washes out oil and is easily removed by vacuuming.
However, R141b is an ozone-depleting substance, and its production is limited by international agreements. As an alternative, high purification is often used. It is less aggressive to rubber parts than some hydrocarbons and mixes well with water, helping to remove wet plugs. isopropyl alcohol high purity. It is less aggressive to rubber parts than some hydrocarbons and mixes well with water to help remove wet plugs.
Specialized fluids such as Dupont Fluflush or HCFC-123 are formulated specifically for these goals. They are safer for the environment and have excellent solvent properties. Some craftsmen use a mixture of alcohol and freon in certain proportions to enhance the effect.
| Remedy | Effectiveness against oil | Safety for rubber | Difficulty of removal |
|---|---|---|---|
| Freon R141b | High | High | Low (easily evaporates) |
| Isopropyl alcohol | Medium | Average | Medium (requires vacuum) |
| Gasoline "Galosh" | Very high | Low (corrodes) | High (remains plaque) |
| White spirit | High | Medium | High (long drying) |
⚠️ Attention: It is strictly forbidden to use water, antifreeze or water-based liquids for flushing the freon circuit. Water in the system will lead to the formation of acids and instant failure of the compressor.
When choosing a product, it is also worth considering the type of oil in the compressor. Some solvents are suitable for mineral oils, and others for polyester oils (POE). Using the wrong chemicals can lead to oil coagulation and the formation of an even denser plug.
Technology for flushing the circuit with nitrogen and solvent
The process of cleaning the capillary tube is not limited to simply pouring liquid. The most effective method is cyclic washing under pressure using technical nitrogen. Nitrogen creates the necessary pressure to push the solvent through a narrow section of the tube and wash out contaminants.
First, the system must be depressurized and the remaining old refrigerant removed. Then a nitrogen cylinder is connected to the process fitting of the compressor through a reducer. The pressure is regulated within 10-15 atmospheres so as not to damage the connections, but to ensure sufficient pressure. The solvent is introduced into the circuit with a syringe or through a special dispenser.
☑️ Checklist for preparing for washing
Rinsing is performed in several stages. First, a portion of the solvent is supplied, then the nitrogen pressure increases sharply, creating a hydraulic shock that knocks out the contaminants. The liquid coming out of the opposite end of the tube is drained into a transparent container for visual control of cleanliness.
The cycle is repeated until the emerging liquid becomes absolutely clean and transparent. After this, the system must be thoroughly purged with pure nitrogen to remove all remaining solvent. Only after this can a new filter drier be sealed and vacuuming carried out.
It is important to ensure that when washing, the solvent does not get inside the compressor windings if the washing is carried out through the suction line. Aggressive chemistry can damage the varnish insulation of wires, which will lead to an interturn short circuit.
Tools and equipment for high-quality cleaning
A gas cylinder alone is not enough to perform high-quality work. You will need a specialized tool to control the process. The main device is a nitrogen cylinder with a pressure gauge, which allows you to accurately set the pressure in the circuit. A reducer is also required. It is the quality of evacuation that determines how well it will be possible to remove residual flushing fluid and moisture from the system. A weak pump will not be able to evaporate the solvent at low temperatures. gearbox for a nitrogen cylinder with a pressure gauge, allowing you to accurately set the pressure in the circuit.
A powerful vacuum pump with a residual pressure of at least 0.5 mbar (micron) is also required. It is the quality of evacuation that determines how well it will be possible to remove residual flushing fluid and moisture from the system. A weak pump will not be able to evaporate the solvent at low temperatures.
- 🔥 Burner: To desolder the tubes and filter-drier, an oxygen-propane torch or equipment for soldering with silver-containing solder is required.
- 🔧 Pipe cutters: A high-quality pipe cutter will ensure an even a cut without burrs, which could again cause a blockage in the future.
- 🌡️ Thermometer: Controlling the temperature of the compressor and tubes is important so as not to overheat the oil or defrost the plug prematurely.
Do not forget about personal protective equipment. Vapors from solvents and freon can be toxic, and working with an open flame and high pressure requires gloves and safety glasses.
Why can’t you use the compressor of the refrigerator itself for purging?
Using a standard compressor to pump the solvent is dangerous. An aggressive liquid can damage the valves, wash out the lubricant from the rubbing pairs, or cause a hydraulic shock that will jam the piston group. In addition, the compressor is not able to create the necessary pressure pulse for effective cleaning.
Frequent errors during self-flushing
Independent repair of refrigerators is often complicated by typical errors that nullify all efforts. One of the most common is using too little solvent. Craftsmen save liquid, as a result of which the contaminants only soften, but are not completely removed, settling a little further along the tube.
Another mistake is neglecting to replace filter-drier. This item is disposable. After any opening of the circuit or washing, the old filter is no longer able to effectively retain moisture and acidic residues. Its reuse guarantees quick re-clogging.
Insufficient vacuuming time is also critical. Many people think that 15-20 minutes of pump operation is enough. However, it may take several hours to completely remove solvent vapors and moisture from the porous structure of the oil in the compressor, especially when using compressor heating.
⚠️ Caution: Never leave the system open to air longer than is absolutely necessary to connect the tool. Copper actively absorbs moisture from the atmosphere, which will negate all drying work.
It is also a mistake to ignore the condition of the compressor itself. If metal shavings are visible in the oil or it has a burning smell, simply flushing the capillary will not help - replacement or repair of the compressor unit is required.
FAQ: Answers to questions about flushing the capillary
Is it possible to flush the capillary without unsoldering it from the refrigerator?
Theoretically, you can try to push the blockage with nitrogen through the process fitting, but the effectiveness of this method is extremely low. Without unsoldering the filter drier and the possibility of direct flushing of solvent through the tube itself, you will not be able to reliably remove oil breakdown products. Most often, it is necessary to cut off the capillary for direct washing.
How many times should the washing cycle be repeated?
The number of cycles depends on the degree of contamination. Typically 3 to 5 runs of solvent under nitrogen pressure are required. The stopping criterion is the visual cleanliness of the flowing liquid and the absence of oily stains on the white napkin onto which the solution is drained.
What to do if nitrogen does not pass through the capillary?
If nitrogen under a pressure of 15-20 atmospheres does not pass, it means the blockage is mechanical or the paraffin plug is too dense. In this case, the capillary tube often has to be replaced with a new one, since it is physically impossible to clean it without damaging it. A new tube is selected of the same diameter and length.
Is it necessary to heat the compressor during evacuation?
Yes, heating the compressor (up to 60-70°C) during evacuation significantly speeds up the process of removing moisture and solvent residues from the oil. However, you need to heat it carefully, using a special heating belt or a fan heater, controlling the temperature so as not to damage the varnish insulation of the windings.
Which filter drier to choose after washing?
The choice of filter depends on the type of refrigerant and oil. For modern freons (R134a, R600a) and polyester oils, filters with zeolite filler are used (for example, UAD or DANFOSS brands of the corresponding series). It is important that the filter is hermetically sealed and opened immediately before soldering.