Iowanews Headlines

I. Copper Tube LeakageCopper Tube leakage is a fatal defect of air conditioners. Once leakage occurs, all the refrigerant of the air conditioner will overflow. The air conditioner will fail due to the lack of heat transfer medium. The causes of Copper Tube leakage are relatively complex, and the common causes are elaborated below.

1. Manufacturing Reasons

• Eddy current flaw detection missed inspection. GB requires 100% eddy current flaw detection for Copper Tubes, and specifies the diameter of artificial defects (through holes) on the sample tubes used to calibrate the flaw detector. This ensures the sensitivity of eddy current flaw detection and prevents missed inspection of excessive defects. Regular large-scale Copper Tube factories can fully guarantee this requirement, as flaw detection is an online inspection. This online eddy current flaw detection ensures that all lengths of the tubes are inspected by eddy current, achieving 100% flaw detection. However, some Copper Tube factories do not follow this practice; they either skip eddy current flaw detection or conduct random inspections with low-standard eddy current flaw detectors. This leads to missed inspection or non-inspection of excessive defects in Copper Tubes, resulting in air conditioner leakage during user use.
• Defects detected by eddy current flaw detection but no marks or inaccurate, unclear marks on the Copper Tube surface. During the production of Copper Tubes, defects detected by eddy current flaw detection are required to be covered with ink marks to allow users to remove defective Copper Tubes during use. However, due to reasons such as insufficient adhesion of the ink selected by the manufacturer, improper adjustment of the inkjet spray gun, incomplete drying, and fading of the ink composition at high temperatures, users cannot identify and pick out the defects detected by eddy current flaw detection during use. Once defective Copper Tubes are used in air conditioners, leakage is inevitable.

2. User Usage Reasons

• Misuse of defective tubes detected by eddy current flaw detection. Under normal Copper Tube production conditions, eddy current flaw detection not only marks the number of defect points on each coil of tube but also applies black marks to the defect locations. This allows users to identify and pick out these “black tubes” during use. Air conditioning and refrigeration enterprises should clearly inform operators, especially new employees, to prevent such defective tubes from being installed in air conditioning and refrigeration equipment. During our in-depth user services, we have found this problem many times. Some workers asked us about the black marks on the tubes, and in some cases, when dissecting unqualified products, it was precisely because the “black tubes” were installed in the products that caused the leakage of the air conditioning and refrigeration equipment.
• Processing issues. In the process of forming the two heat exchangers, the main air conditioning tubes go through bending, expanding, flaring, welding and other links.
• Leakage caused by poor welding. After the Copper Tubes are inserted into the perforated aluminum foil, the tubes need to be connected with small elbows. For firm connection, solder is used to weld the small elbows to the Copper Tubes during production. The welding methods are manual and automatic. During welding, due to reasons such as poor solder quality, improper flaring of Copper Tubes, and foreign objects on the welding surface, insufficient welding (virtual welding) is caused, leading to refrigerant leakage.

II. Copper Tube CrackinCopper Tube cracking mainly occurs in the tube expanding and flaring processes. In the production of the two heat exchangers, tube expanding and flaring are a continuous process, often combined into one process. There are many reasons for Copper Tube cracking, and the main reasons are as follows:

1. Reasons Related to the Quality of Copper Tubes ThemselvesThe quality problems of Copper Tubes themselves can be divided into external surface defects, internal surface scratches, internal surface oxidation, etc. During the cold working deformation of tube expanding and flaring, the surface of the Copper Tube is stretched by tensile stress and elongates. When there are deep scratches on the external surface of the Copper Tube, it cannot bear the surface tensile stress, resulting in tensile fracture, which is the external surface cracking of the Copper Tube we see. The cracking mechanism caused by internal surface scratches is similar to that caused by external surface scratches. When there is oxidation on the internal surface of the Copper Tube, during tube expanding, the friction force on the oxidized internal surface is different from that on the non-oxidized internal surface. This causes inconsistent upsetting length dimensions of Copper Tubes of the same length. During flaring, the Copper Tube with small upsetting amount has a long extension length, leading to excessive flaring and cracking.2. User Usage ReasonsIn the use of copper tubes, coil straightening and cutting to length are usually carried out, and chipless cutting is often used. The surface of the copper tube is relatively soft after heat treatment. During chipless cutting, if the cutter is dull or the cutting depth is too large, excessive necking or burrs of the copper tube will be caused, resulting in port burrs and port hardening, leading to cracking during flaring. A heat exchanger is composed of many “U”-shaped tubes. The consistency of the length of each “U”-shaped tube and the length of the two ends of each “U”-shaped tube is required to be very high. When bending the “U”-shaped tubes, due to equipment or adjustment reasons, the difference in the length of each “U”-shaped tube and the length of the two ends of each “U”-shaped tube is too large (greater than 2mm). Therefore, during flaring, excessive flaring and cracking will occur due to the excessive extension length of the copper tube caused by the too long port.III. Wrinking and Fracture of Bent TubesWrinkling and fracture of copper tube bending occur in the process of making “U”-shaped tubes, and many copper tubes are scrapped in this process.

Media Contact
Company Name: Shenzhen Hongdingye Metal Co., Ltd.
Email: Send Email
Country: China
Website: https://www.hdycopper.com/