Copper Capillary Tube

What are the common causes of copper capillary blockage?

Copper capillary, as a throttling element widely used in refrigeration systems, plays a vital role in household air conditioners, commercial refrigerators, car air conditioners and other equipment. It controls the refrigerant flow between the compressor and the evaporator through a slender pipe structure, so that the system can achieve the expected refrigeration effect. However, in actual application, copper capillary blockage is common, which not only affects the refrigeration efficiency, but also may cause compressor damage, frequent system start and stop, and even equipment scrapping.
Welding residue blockage
The welding process is an inevitable link in the installation of copper tubes, especially when high-temperature welding methods such as silver soldering and phosphor copper soldering are used when connecting or repairing the system. If the operation is improper, flux residue or metal slag may enter the copper capillary, and eventually accumulate in the narrow part of the pipe as the refrigerant circulates, causing blockage.
Industry experience: Zhejiang Jingliang Copper-Tube Products Co., Ltd uses automatic cleaning systems and online detection processes in the manufacturing and post-processing of copper capillary tube to effectively control the cleanliness of the capillary cavity and reduce the probability of welding pollution entering the system.
Failure of the dry filter causes water to mix in
The refrigeration system is usually equipped with a dry filter to absorb moisture and impurities in the refrigerant. Once the filter is saturated with adsorption, or the seal fails due to improper installation, moisture will enter the system and react with the refrigerant to form ice crystals, especially quickly freezing at the capillary throttle, forming an "ice blockage" phenomenon.
Technical response: Zhejiang Jingliang Copper-Tube Products Co., Ltd actively guides customers to reasonably select and regularly replace dryers in cooperative projects, and also provides customized services for capillary-dryer integrated components to further optimize the stability of system operation.
Oxide scale or copper chips remain
During the extrusion, drawing, annealing and other processing of copper capillary tube, if they are not fully deoxidized, copper chips or oxide scales are easily left on the inner wall of the pipe. Although these tiny particles do not affect the operation of the system in a short period of time, they are easily carried by the refrigerant to the thinnest part of the capillary after long-term operation, forming mechanical blockage.
Enterprise advantages: Zhejiang Jingliang relies on its complete industrial chain system, from copper ingot smelting, extrusion molding to precision drawing and annealing, and adopts clean processing + multi-channel inner wall cleaning detection technology throughout the process to ensure that the product eliminates residual impurities from the source and significantly reduces the risk of blockage.
Refrigerant or lubricant pollution
In the refrigeration system, the purity of lubricants and refrigerants is extremely critical to the smooth operation of copper capillary tube. If substandard lubricants or recycled refrigerants are used, a large amount of insoluble matter, metal particles or carbides may be entrained. These foreign objects are easily deposited in the narrow channels of the capillaries under the action of high pressure difference to form blockages.
Industry practices: As a company that has been deeply involved in the copper tube industry for more than 30 years, Zhejiang Jingliang insists on making professional suggestions on material purity and system compatibility in the process of cooperation with global refrigeration equipment manufacturers, and provides personalized design services, such as capillary products with different finish levels to adapt to specific refrigeration oil or environmentally friendly refrigerant systems.
Non-professional installation and use
The capillary system has extremely high requirements for the installation environment and technology. If the installation process is excessively bent, squeezed, or the inside is contaminated, or if it is frequently started and stopped during operation, or improper refrigerant substitutes are used, the blockage may be aggravated.
Customer service: Zhejiang Jingliang is not only a producer of copper capillary tube, but also a provider of system solutions. The company has a technical service team to provide customers with full-process support from selection, installation, fault diagnosis to maintenance, helping customers to operate the system stably and reduce after-sales maintenance.
Sludge deposition after long-term operation
In the refrigeration system after long-term operation, the sludge formed by lubricating oil and impurities will gradually deposit at the bottom of the system or the inner wall of the pipe, especially the capillary because of its extremely small diameter, it is very easy to become a deposition point. Once the sludge accumulates to a certain extent, it can cause the system flow to decrease, and then completely block.
Quality control: Zhejiang Jingliang uses high-precision drawing technology and bright annealing technology to make the inner wall of the capillary smoother and reduce the adhesion of oil stains, slowing down the speed of sludge formation from the source and increasing the service life of the product.

What is the impact of the length and inner diameter of copper capillary on the performance of refrigeration system?

In modern refrigeration systems, copper capillary is widely used as a throttling component in household air conditioners, freezers, refrigerators, car air conditioners and heat pump equipment. It limits the flow of refrigerant through a narrow and thin structure, so that the high-pressure liquid refrigerant enters a low-pressure state after passing through the capillary throttling, thereby absorbing heat in the evaporator to achieve a refrigeration effect. The length and inner diameter of the copper capillary are key parameters that affect system stability, cooling output and energy efficiency ratio (COP). Whether the matching is reasonable directly determines the operating efficiency and life of the whole machine.
Brief description of the throttling principle of copper capillary
The copper capillary relies on its own narrow diameter and the extension of the pipeline length to produce significant pressure loss when the high-pressure liquid refrigerant passes through, so that the refrigerant changes from a high-pressure state to a low-pressure and low-temperature state, providing a suitable working condition for the evaporator.
Among them, the inner diameter of the capillary determines the baseline value of the flow resistance, and the length extends the process of pressure drop on this basis. The two together determine the amount of refrigerant passing through per unit time.
The impact of inner diameter on system performance
The smaller the inner diameter, the greater the flow resistance and the stronger the throttling effect.
Small inner diameter capillary tubes are suitable for refrigeration systems with small cooling capacity or low load conditions. It can effectively limit the excessive refrigerant flowing into the evaporator, avoid overcooling or liquid return, and improve system stability.
If the inner diameter is too large, it may cause excessive liquid supply, liquid hammer or uneven frosting of the evaporator.
If the system load is insufficient but the inner diameter of the capillary tube is too large, the refrigerant will not be able to fully evaporate, which will not only be inefficient, but may even cause impact on the compressor.
Matching the type of refrigerant is also crucial.
Different refrigerants (such as R134a, R410A, R290, etc.) have different densities, viscosities and expansion characteristics, and the inner diameter design needs to comprehensively consider the physical parameters. Zhejiang Jingliang has a special database in the R&D link to provide customized inner diameter parameters according to the media used by customers to achieve precise matching.
The regulating effect of length on system operation
The longer the capillary tube, the greater the pressure drop and the less refrigerant passes per unit time.
Suitable for systems with high evaporation temperature requirements or small cooling loads, it can extend the residence time of the refrigerant in the pipeline and improve the throttling accuracy.
If the capillary is too short, it will cause insufficient throttling, too fast refrigerant supply, and cause system overcooling or abnormal compressor load.
Zhejiang Jingliang uses precision cutting equipment and automatic length detection system to ensure that the length error of each capillary product is within ±0.5mm, greatly improving the energy saving and stability of the system.
In the heat pump system, the capillary length design needs to take into account both cooling and heating conditions.
Such systems often use double capillary design or bypass throttling structure. Zhejiang Jingliang can provide parallel structure capillary solutions to meet the challenges of system performance balance under multiple working conditions.
Comprehensive matching relationship between length and inner diameter
The length and inner diameter of copper capillary are not isolated parameters, but variables that affect each other. Generally speaking, under the condition of ensuring the same pressure drop, the smaller the inner diameter, the shorter the required length, and vice versa. However, due to the significant differences in the actual working conditions (condensing temperature, evaporating temperature, compression ratio, etc.) of the refrigeration system, the ratio needs to be combined with system simulation or experimental correction.

What process requirements should be paid attention to when installing copper capillary tube

In modern refrigeration systems, copper capillary tube are key components for controlling the flow of refrigerants and are widely used in household air conditioners, commercial refrigerators, automotive air conditioners, heat pump systems and other equipment. copper capillary tube have a precise structure and small size, and their performance stability has a decisive influence on the operating efficiency and reliability of the whole machine. However, even the best copper capillary products may cause blockage, leakage, abnormal liquid supply and other problems if the process control is improper during the installation process, resulting in abnormal system operation or equipment damage.
Preparation work before installation
Pretreatment and cleaning of pipes
Although copper capillary tube have passed multiple cleaning processes before leaving the factory, there may be contamination during transportation or storage. Before installation, dry anhydrous nitrogen should be used for purging to ensure that there is no dust, oil, moisture and other foreign matter inside. Zhejiang Jingliang's factory capillaries are all packaged with high-pressure nitrogen to provide customers with a "ready-to-use" level of cleanliness.
Size verification
Before installation, it is necessary to strictly check whether the length and inner diameter of the capillary are consistent with the design parameters. Different types of refrigeration systems have different requirements for the throttling capacity of the capillary. Once the specification is selected incorrectly, the efficiency will decrease at best, and the system will be paralyzed at worst.
Environmental cleanliness requirements
The capillary is an open component. The installation environment should be controlled in a dust-free, dry, and non-corrosive gas place to prevent impurities from entering the system with installation tools or air.
Key process control in copper capillary installation
Avoid excessive bending or sharp turns
The copper capillary has a small diameter and limited mechanical strength. Excessive bending can easily cause deformation of the inner wall or partial collapse, forming a potential blockage. It is recommended to use professional capillary bending tools to control the minimum bending radius within 3 to 5 times the outer diameter of the capillary. Zhejiang Jingliang repeatedly emphasized the installation principle of "bending without death, bending without obstruction" in product training.
Fine welding operation
Welding is the most problematic link in the installation of copper capillary. When using silver soldering or phosphor copper soldering, the flame should be avoided from directly burning the middle of the capillary to avoid oxidation or burning through. At the same time, ensure that the solder joint is smooth and free of spatter to prevent welding slag from falling into the tube. It is recommended to use low-temperature precision welding process and halogen-free flux. Zhejiang Jingliang provides capillary-dryer-filter integrated welding module OEM service for large refrigeration equipment customers to effectively reduce welding risks.
Prevent welding "back-absorption" pollution
When welding the capillary connection, a trace amount of nitrogen protection should be continuously introduced to avoid the "suction effect" during the heating process, which will absorb external impurities into the pipe. This is one of the common but easily overlooked details in the industry.
Secondary cleaning after welding
After welding, dry nitrogen should be used to purge the capillary channel again to thoroughly remove the trace welding slag or dust that may remain, laying a good foundation for system vacuuming and refrigerant charging.
System commissioning and testing after installation
Air tightness test
After installation, a nitrogen pressure test of 1.5 times the working pressure is required to check whether there is a micro-leakage at the capillary connection. Especially in the connection part of the high-pressure side of the refrigeration system, any small leakage may cause the refrigerant flow control to be unbalanced.
Observe the throttling effect of the system
After the capillary tube is installed, the throttling should be judged by observing the sight glass or the operation of the evaporator. If the evaporator is frosted unevenly, the compressor is frequently started and stopped, etc., it may be caused by the mismatch of the capillary length or inner diameter. Zhejiang Jingliang provides capillary matching simulation verification services for specific customers, combined with different load point adjustment parameters to ensure the matching of the optimal refrigeration solution.
Insulation and fixation
Although the capillary tube is not a mainstream refrigeration pipeline, it may also experience thermal expansion in a high temperature environment to affect the flow distribution. Therefore, the pipe should be coated with heat-resistant insulation material and fixed on the system bracket to prevent displacement or fatigue fracture due to vibration.