Stopping the refrigerant circulation in the refrigeration circuit is a critical malfunction, which is often accompanied by a lack of cold in the chambers, but the compressor can work endlessly or turn off due to overload. Capillary tubebeing a throttling device, it has microscopic internal diameter, which makes it extremely vulnerable to any contaminants that enter the system. In most cases, the problem lies not in a freon leak, but in a banal blockage that blocks the movement of the working substance.
The process of restoring patency requires from the master not only theoretical knowledge, but also the presence of specialized equipment, such as a vacuum pump and a cylinder with dry nitrogen. Independent cleaning without appropriate experience can lead to depressurization of the system or damage to thin-walled copper. However, understanding the physics of the process helps to correctly diagnose the problem and choose the right method for restoring the functionality of the unit.
In this article we will analyze in detail the causes of traffic jams, consider professional methods for eliminating them and answer frequently asked questions that arise when repairing refrigeration equipment. It is important to understand that any repair associated with a violation of the tightness of the circuit should ideally be completed by replacing the filter-drier and evacuating the system.
Causes of clogging of the capillary system
The main reason for blocking a narrow channel is most often moisture that entered the circuit during poor maintenance or due to microcracks in the evaporator. Interacting with the refrigerant and oil, water forms ice crystals or acidic compounds that clog the passage. Hydraulic blockage can be temporary (ice blockage) or permanent (oxidation products).
The second common cause is mechanical contamination, such as copper shavings remaining after soldering, or decomposition products of engine oil when the compressor overheats. Oil plug often occurs in systems where the compressor has been operating for a long time with broken winding geometry or when using the wrong type of refrigerant. Also, solder particles that got inside the tube during careless soldering can cause blockages.
⚠️ Attention: Attempting to clean the system by simply blowing it with your mouth is strictly prohibited, since the exhaled air contains moisture, which will aggravate the situation and lead to the formation of a new one ice plug after a short time.
To prevent repeated breakdowns, it is necessary to strictly follow the soldering technology, using filler material containing phosphorus or silver, and be sure to flush the pipes with nitrogen during heating. Copper oxidation the passage inside the tube also narrows, so the access of oxygen to the soldering site must be blocked by a flow of inert gas.
Diagnostics of the condition of the capillary
Before taking active steps, it is necessary to accurately determine the location and nature of the blockage. Primary diagnostics are carried out visually and by ear: if, when the compressor is running, the condenser (grid at the back) remains cold or warm only in the initial part, and the evaporator inside the chamber does not cool, this is a sure sign circulation problems.
A more accurate method involves disconnecting the capillary tube from the filter-drier. If air (or freon) does not come out forcefully from the disconnected end of the filter when the compressor is running, it means the filter or discharge line is clogged. If there is blowing from the filter, but there is no flow from the capillary tube itself, disconnected from the evaporator, then this is where the problem lies.
- 🔍 Visual inspection: search for traces of oil at the joints, indicating previous leaks through which moisture could have entered.
- 👂 Acoustic method: listening for a characteristic hissing or gurgling, which may be absent when completely blocked.
- 🌡️ Temperature analysis: checking the heating of the condenser and the temperature of the compressor suction tube (it should not be hot).
Sometimes the blockage may not be complete, but partial, which leads to a decrease in system performance. In such cases capillary tube the refrigerant passes through, but in insufficient volume, which is why the refrigerator works longer than expected, trying to gain temperature.
Preparation of equipment and tools
To perform high-quality work on cleaning the throttling device, you will need specific a set of tools without which repairs will be ineffective or even dangerous. The main element is a cylinder with dry nitrogenequipped with a reducer that allows you to regulate the gas supply pressure.
You also need a powerful vacuum pump capable of creating a deep vacuum in the system, and a burner (gas or oxygen-acetylene) to heat the soldering areas. Do not forget to prepare a new filter drier, since the old one must be replaced after the circuit is opened and moisture enters.
☑️ Tools for repair
Special solvents for flushing the system may be required as auxiliaries, such as like R141b or isopropyl alcohol if chemical cleaning is planned. All connections must be tight, so stock up on high-quality solder and flux for copper pipes.
Purge with nitrogen under pressure
The most common and effective way to clear a blockage is to purge the circuit with dry nitrogen under high pressure. The essence of the method is to create excess pressure, which pushes out foreign particles or destroys the ice plug. To do this, nitrogen is supplied to the circuit from the compressor side or through a cut capillary.
The pressure during purging must be controlled, usually in the range of 10–15 atmospheres, so as not to damage the thin walls of the tubes or heat exchangers. Inert gas does not react with oil and metal, which makes it an ideal cleaning agent. The procedure is often repeated several times at short intervals.
⚠️ Attention: If compressed nitrogen is suddenly released from the tube, oil and contaminants may be released with great force, so be sure to use safety glasses and point the end of the tube into a safe container or rag.
If simple purging does not help, use the “water hammer” method, briefly increasing the pressure to the maximum values permissible for a given system. However, this method requires experience, since there is a risk of rupture of the weakest link (the weakest point) in the circuit, for example, an aluminum evaporator.
Safety precautions when working with nitrogen
The nitrogen in the cylinder is under enormous pressure (about 150 atmospheres). The use of a gearbox is mandatory. Do not direct the gas stream at people or animals. When the cylinder heats up, the pressure increases, so store it away from heat sources.
Chemical flushing of the system
In cases where mechanical purge does not produce results, chemical flushing of the system with special solvents is used. This method is effective against oil plugs and complex organic contaminants that do not dissolve in the refrigerant. Most often, liquid R141b or specialized cleaners for refrigeration systems are used.
The solvent is poured into the system under nitrogen pressure, after which the circuit is left for some time to dissolve deposits. This is followed by a thorough nitrogen purge to remove chemical residues and dissolved dirt. It is important to ensure that there is no moisture left in the system, as solvents can be hygroscopic.
| Type of contamination | Cleaning method | Efficiency | Risks |
|---|---|---|---|
| Ice plug | Warming + Purge | High | Low |
| Copper shavings | Nitrogen purge | Medium | Medium (stuck) |
| Oil clot | Chem. flushing | High | Chemical residues |
| Combustion products | Replacement of area | Maximum | Soldering |
After chemical cleaning, it is necessary to especially carefully vacuum the system to remove solvent vapors. Residues of aggressive chemicals can destroy the insulation of the compressor windings or react with new oil, so this method is considered a last resort.
Thermal method and replacing the area
If the blockage is localized in a specific place, which often happens with ice plugs at the beginning of the capillary, local heating is applied. The site of the suspected blockage is heated with a burner to a temperature of 200–300 degrees, after which a sharp blowdown is performed. Thermal expansion and liquefaction of contaminants help to break through the channel.
In the most difficult cases, when it is not possible to clean the tube or it is damaged by corrosion, a decision is made to replace capillary pair. This is a labor-intensive process that requires selecting a tube of exactly the same length and internal diameter, since the pressure in the system depends on these parameters.
When replacing, it is necessary to carefully desolder the old section, observing the temperature, so as not to melt the adjacent aluminum parts, and solder in a new one. After replacement, the system must be evacuated for 30–60 minutes and charged with the exact amount of refrigerant indicated on the nameplate.
Common mistakes during repairs
One of the most common mistakes is ignoring the replacement of the filter-drier. Many technicians, having cleaned the capillary, simply solder the system, believing that the problem is solved. However, the old filter is already saturated with moisture and contaminants, which in a short time will again clog the thin channel.
Another mistake is insufficient vacuuming time. Moisture in the system is the main enemy. If you do not remove it completely, it will freeze in the capillary during the first operation of the refrigerator, creating a new plug. Vacuum pump It should work until the pressure gauge needle freezes at the deep vacuum mark.
- 🚫 Lack of nitrogen: Soldering without nitrogen purging leads to the formation scale inside the pipes, which will inevitably cause a new blockage.
- 🚫 Incorrect refrigerant: Filling the system with freon of a different type or brand can change the properties of the oil and cause sediment to form.
- 🚫 Overheating: Long-term heating the soldering area without heat removal can damage the varnish insulation of the compressor windings.
⚠️ Attention: Technical characteristics of refrigerators (refrigerant type, capillary length, oil type) may vary depending on the manufacturer and year of manufacture. Always check the technical documentation of the specific model before starting work.
FAQ: Frequently Asked Questions
Is it possible to clean a capillary tube with a syringe with water or alcohol?
Using a medical syringe will not create enough pressure to break through a serious blockage. Water is strictly prohibited as it will freeze. Alcohol can help dissolve some contaminants, but without subsequent powerful nitrogen purging and vacuuming, this method is ineffective and dangerous to the system.
How long should you vacuum the refrigerator after cleaning?
The minimum operating time of the vacuum pump should be 30 minutes for household refrigerators. For larger volume systems or if moisture is suspected, the time should be increased to 1 hour. The end criterion is the stable position of the pressure gauge needle in the vacuum zone after stopping the pump.
What to do if, after cleaning, the refrigerator begins to freeze worse?
This may indicate incomplete removal of the blockage, the presence of an “air lock” in the system, or an incorrect length of the installed capillary tube (if a replacement was made). It is also possible that there is an excess amount of oil left in the system, which is interfering with heat transfer.
Is it necessary to flush the system with oil after cleaning?
Flushing the system with oil (injecting fresh oil to displace dirt) is an old method that is now rarely used due to the difficulty of removing flushing oil. The current standard is to flush with nitrogen and replace the filter. Excess oil in the system is just as harmful as its lack.