A decrease in the cooling efficiency in the freezer or a complete lack of cold when the compressor is running often indicates a critical violation of the refrigerant circulation. Capillary tube is the narrowest section of the freon line, where a sharp drop in pressure and temperature occurs, turning the gas into liquid. This is where ice or mud plugs most often form, blocking the movement of of the refrigerant.
Restoring the patency of this element requires not only an accurate understanding of the device refrigeration circuit, but also the availability of specialized equipment for working with high pressures. An independent attempt at cleaning without the proper skills can lead to depressurization of the system or damage to the compressor.
However, for experienced craftsmen and enthusiasts, knowledge of methods for removing blockages is a key skill in repairing household appliances. Below we will analyze in detail the physics of the process, the necessary tools and step-by-step action algorithms.
Causes of blockages in a thin-walled line
The main enemy of any freon system is moisture, which gets inside the circuit due to poor installation or depressurization. When passing through a low-pressure zone, water freezes, forming an ice puck that completely covers the cross-section of the tube with a diameter of less than a millimeter. This type of malfunction is often called hydraulic clogging.
The second common cause is solid mechanical particles formed as a result of oxidation of the internal walls of pipelines or destruction of the insulation of the motor-compressor windings. Oil and varnish breakdown products mix with the refrigerant and accumulate in the narrowest point of the system. This phenomenon is especially typical for old units or after combustion of an electric motor.
⚠️ Attention: If the blockage is caused by combustion of the compressor, simply cleaning the tube will not help - acidic residues will quickly damage the new motor.
The third factor is poor-quality oil or its excess, which under certain temperature conditions can wax and harden, creating a viscous plug. It is impossible to determine the exact nature of the blockage visually; an analysis of the symptoms of the system operation is required.
Necessary tools and preparation of the workplace
To perform work to restore the patency of the capillary system, you will need not only a standard set of plumbing tools, but also specific equipment for working with freons. The basic element is a cylinder with dry nitrogen, since it is the inert gas under pressure that is used for purging and checking for leaks.
It is also necessary to have a pressure gauge station (manifold), which allows you to control the pressure in the circuit in real time. Without accurate readings pressure gauges it is impossible to determine whether the blockage has been cleared or whether the pressure is rising due to another obstacle.
- 🔧 Set of pipe cutters and flaring tools for working with copper
- 🔥 Torch with solder and flux for soldering connections
- 💉 Syringe or pump for pumping flushing liquid
- 🧪 Solvent (alcohol, freon R141b or specialized liquid)
Do not forget about personal protective equipment, since the work is carried out with chemically active substances and open fire. Gloves and goggles are required to prevent burns and contact of reagents with the skin.
Methodology for diagnosing the condition of the capillary system
Before starting active actions, it is necessary to localize the blockage and make sure that the problem lies in the capillary tube, and not in the filter-drier or the compressor itself. Primary diagnosis is carried out by disconnecting the condenser from the rest of the system and applying pressure. If the pressure gauge shows a rapid increase in pressure, it means that the condenser and the compressor discharge valve are working properly.
Then the patency of the capillary tube is checked separately. To do this, the filter drier is sealed off and nitrogen is supplied through the capillary. The resistance to gas flow in a working tube should be certain, but not zero. If the pressure does not drop or drops extremely slowly, there is a complete blockage.
It is important to distinguish between an ice plug and a mud plug. The ice plug often thaws when heated with a hairdryer, and the system temporarily starts working, but after a few hours or days it freezes again. Mud blockage is permanent and requires mechanical or chemical cleaning.
How to distinguish ice from dirt?
An ice blockage is often accompanied by a whistling sound when the compressor is operating, which stops after stopping. A dirt blockage usually “muffles” the system without the characteristic sounds of flow.
Nitrogen purging and solvent flushing technology
The most effective and safe way to clean the internal cavity of copper tubes is a combined method that combines chemical dissolution of deposits and mechanical blowing. First, flushing liquid is poured into the system, which dissolves oily deposits and paraffins. Then compressed nitrogen is supplied, creating a shock wave that throws the dissolved dirt out.
The process requires care: the liquid is poured through a syringe into a sealed tube, after which the system is sealed to expose the reagent. Exposure time depends on the type of pollutant, but is usually 10-15 minutes.
After chemical treatment, a nitrogen cylinder is connected. The pressure should be raised smoothly, monitoring the readings of the pressure gauge, so as not to tear the thin walls evaporator. A sharp surge in pressure can deform the aluminum plates of the heat exchanger
☑️ Washing algorithm
Replacing the filter-drier and evacuating the system
Any operation Depressurization of the freon circuit requires mandatory replacement of the filter-drier. This element contains zeolite or silica gel, which, upon contact with atmospheric air, are instantly saturated with moisture and lose their properties. Installing an old filter will negate all efforts to clean the system.
After successfully cleaning the capillary tube and installing a new filter, it is necessary to carry out a deep vacuum. This process removes not only air, but also water vapor, which can refreeze in the capillary during operation. The vacuum pump must operate for at least 30-40 minutes until a residual pressure of several tenths of Pascal is reached.
Weight according to the passport (±10 g)
Pressure stability 24 hours
| Work stage | Required equipment | Control parameter |
|---|---|---|
| Purge of the circuit | Nitrogen cylinder, reducer | Pressure 15-20 atm |
| Evacuation | Vacuum pump, valve | Residual pressure < 50 µm Hg. Art. |
| Refrigerant charging | Scales, freon, manifold | |
| Crimping | Nitrogen, pressure gauge |
Ignoring the vacuum stage is the most a common mistake leading to the re-formation of ice plugs after a short time.
Common mistakes and safety precautions during repairs
One of the biggest mistakes is trying to clean the capillary tube without disconnecting it from the evaporator. In this case, all the dirt and flushing liquid will get into the thin channels of the heat exchanger, which are almost impossible to clean without completely replacing the unit. Always work with cut-off sections of the line.
Another risk is associated with the use of open flames near the refrigerant. Some types of freons, upon contact with an open flame, disintegrate to form phosgene, a chemical warfare agent. Before any soldering, you must make sure that there are no gas residues under pressure in the tubes.
⚠️ Attention: Never use oxygen to purge or pressurize the circuit! A mixture of oxygen with oil and freon is explosive.
It is also not recommended to exceed the pressure during pressure testing above 25-30 atmospheres, as this can lead to rupture of solder joints or deformation of the compressor housing, especially if it is of the type LBP (Low Back Pressure).
When a complete replacement of the capillary tube is necessary
In some cases, cleaning does not give the desired effect, and the only solution is to replace the element. This is necessary if the inner surface of the copper is severely corroded or if the blockage is caused by the collapse of the tube walls due to external mechanical influence.
The new tube must strictly match the original in terms of internal diameter and length. Even a minimal deviation in geometry will lead to a change in the throttling effect: a tube that is too long will reduce the cooling capacity, and a short one can cause liquid freon to enter the compressor (water hammer).
The process of selecting an analogue requires calculations or reference to correspondence tables for a specific model. refrigeration unit. Making a capillary yourself at home is impossible due to the requirements for calibration accuracy.
Is it possible to clean a capillary without nitrogen? cylinder?
It is almost impossible to properly clean the system without a source of dry compressed gas (nitrogen). Compressors from refrigerators or car pumps do not create sufficient pressure and flow to blow out tight plugs, and can also introduce moisture and oil into the circuit.
What is the danger of tampering with the freon circuit yourself?
The main risks: the possibility of being burned by hot solder or refrigerant, the risk of explosion when using the wrong gases, and There is also a high probability of permanently causing the refrigerator to fail, after which repairs will become economically unfeasible.
How much does it cost to replace a capillary tube during service?
The cost consists of the price of materials (tube, filter, freon) and the complexity of the work. On average, the price varies widely depending on the region and model of the refrigerator, but usually this is one of the most expensive procedures in the repair of household appliances.