Copper tube of evaporator coil repeatedly expands and contracts with cyclic temperature swing. Long term thermal cycling causes thermal fatigue risk on tube and weld joints. Temperature change from defrost and cooling mode creates repeated stress on copper material. Weld seams are the weakest position to develop micro cracks. Xindacool coil adopts full annealing copper tube and optimized welding craft to improve ductility and resist thermal fatigue damage. Rigid pipe connection without flexible connector transfers stress directly to coil nozzle. Thermal movement cannot release and accelerates crack generation. Frequent defrost cycles increase temperature variation frequency. Cold rooms with high humidity have more thermal cycles and higher fatigue risk. Vibration superimposed with thermal stress greatly speeds up metal fatigue. Combined load is more destructive than thermal change alone. Coating corrosion on tube surface creates stress concentration point. Tiny corrosion pits become crack initiation positions under cyclic temperature change. Pressure test after coil production verifies weld integrity. But micro fatigue cracks may appear only after thousands of cooling and defrost cycles. During annual inspection, focus visual check on tube welds and bending sections. These positions bear the largest thermal and mechanical stress. Once micro crack appears, refrigerant leakage occurs slowly. Early leakage is hard to detect and can only be captured by regular leak detection work. Proper pipe support and flexible joints release thermal displacement, reducing stress accumulation on coil copper tubes and weld seams.
Q: What causes thermal fatigue on evaporator copper coil? A: Repeated expansion and contraction caused by cyclic temperature change in cooling and defrost process. Q: Where do fatigue cracks most easily appear? A: Welding seams and tube bending sections where stress concentrates during temperature fluctuation. Q: How flexible pipe connector protect coil? A: Release thermal displacement and avoid stress transferring directly onto coil copper tube and welds. Q: Why high humidity cold storage has higher fatigue risk? A: More frequent defrost brings more temperature cycles and increases thermal stress times. Q: What effect when vibration and thermal stress act together? A: Combined load accelerates metal fatigue and speeds up crack formation greatly. Q: Can factory pressure test find future fatigue cracks? A: It verifies initial weld quality, but fatigue cracks may form after long time cyclic operation. Q: What spot to inspect annually for coil fatigue risk? A: Welding joints and tube bending areas for micro cracks and corrosion pits. Q: How corrosion pits affect thermal fatigue? A: Corrosion pits form stress concentration points and become starting positions of metal cracks.
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