How to Detect Leaks in a Type C Air Conditioning Hose?

In industrial refrigeration and automotive air conditioning systems, Type C air conditioning hoses are widely used due to their high pressure resistance, corrosion resistance and strong flexibility. However, during long-term operation, loose hose joints, material aging or mechanical wear may lead to refrigerant leakage, resulting in energy efficiency loss, system failure and even environmental damage.
1. Necessary preparations before testing
Safety protection
Wear goggles and antifreeze gloves (refrigerant contact with skin can cause frostbite), make sure the working environment is well ventilated, and avoid the accumulation of refrigerants such as R134a/R1234yf in confined spaces.
System pretreatment
Turn off the compressor and let the system stand for 30 minutes to stabilize the pressure in the hose to the typical working pressure range of 0.8-1.2MPa. At this time, use an infrared thermometer to detect the temperature difference on the hose surface. Areas with a temperature difference of more than 3°C may indicate phase change endothermic absorption caused by leakage.

Second, the process of four-level precision inspection
1. Visual screening (primary inspection)
Use a 10x magnifying glass to check the hose surface: ▸ Cracks in the rubber layer (crack width ＞0.2mm needs special attention) ▸ Exposed metal braided layer ▸ Annular wear marks at the clamp
Focus on the stress concentration area where the hose bending radius is less than 5D (D is the hose diameter)
2. Soap bubble development method (intermediate inspection)
Mix distilled water and soap-based solution in a ratio of 3:1, and use an atomizing spray gun to evenly cover the hose surface. When the system pressure is ≥0.5MPa, a stable bubble with a diameter of ≥2mm will form at the leak within 60 seconds. This method can detect cracks ≥0.1mm, but is not sensitive enough to micro-leakage (<0.05mm).
3. Electronic leak detector verification (advanced detection)
Use a helium mass spectrometer leak detector with a resolution of 5ppm or an infrared sensor leak detection gun:
Move the probe along the axial direction of the hose at a speed of 15cm/s
Set the alarm threshold to the leakage rate corresponding to 0.5% of the system charge/year
Focus on scanning the O-ring sealing surface and Schrader valve core
4. Fluorescence tracer method (precise positioning)
Inject refrigerant containing UV dye (naphthalene fluorescent agent compatible with POE lubricant is recommended), and run the system for 20 minutes:
Use ultraviolet light with a wavelength of 365nm to illuminate
The leak point will show a bright green light spot with a diffuse diameter
Use an industrial endoscope with a resolution of 50μm to detect leakage in hidden parts
III. Leak classification and treatment recommendations
Leak grade Feature description Repair plan
Grade I (micro-leakage) Annual leakage <50g Apply fluororubber sealant on the surface for temporary treatment
Grade II (medium leakage) Monthly leakage >15g Replace the clamp and re-flare the connection
Grade III (heavy leakage) Visible bubbles continue to be generated The entire hose must be cut off and replaced
IV. Preventive maintenance strategy
Periodic detection: electronic leak detection every 2000 working hours or quarterly
Stress monitoring: install optical fiber strain sensors to monitor hose deformation in real time
Material upgrade: composite hoses with HNBR rubber layer + 304 stainless steel braided layer are preferred
Special note: According to the requirements of the Montreal Protocol, residual refrigerant must be recovered by a recovery unit after detection, and direct discharge is strictly prohibited. It is recommended to establish a digital file for hose detection and predict the life cycle through big data analysis such as vibration frequency and pressure fluctuations.

Through the combined application of multimodal detection technology, the leakage detection rate of C-type air conditioning hoses can reach more than 99.7%. Standardized detection procedures can not only reduce maintenance costs by more than 30%, but also effectively avoid the greenhouse effect caused by refrigerant leakage (R134a with a GWP value of 1300 is particularly critical). It is recommended that enterprises establish a preventive maintenance system in accordance with the SAE J2791 standard to ensure the long-term and stable operation of the refrigeration system.