Leak testing of radiators is a critical quality control measure to ensure that no medium (such as water, oil, coolant, etc.) leaks during operation. As an essential characteristic of heat exchangers, airtightness must be rigorously verified—whether for automotive radiators, industrial heat exchangers, new-energy liquid cooling plates, or data center cooling systems.
Below is a brief introduction to several mainstream leak testing methods currently used in the industry:
I. Water Immersion Testing
This is the most traditional, intuitive, and low-cost method, as shown in Figure 1 below.
Figure 1: Water Immersion Testing
Principle: The radiator is filled with compressed air at a certain pressure and then immersed in water to observe whether bubbles emerge.
Advantages:
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Intuitive and reliable: The location and size of bubbles can be directly observed, allowing for a rough estimation of the leak rate.
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Simple equipment: Only a water tank, an air source, and a pressure regulation device are needed, resulting in very low costs.
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Non-polluting: Environmentally friendly.
Disadvantages:
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Low efficiency: Requires manual operation and observation, with a low degree of automation, making it unsuitable for large-scale production lines.
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Subjectivity: Relies on the operator’s attention and experience, making it easy to miss minor leaks.
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Post-processing issues: The radiator must be dried after testing; otherwise, internal corrosion may occur.
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Non-quantitative: Only indicates whether there is a leak; precise measurement of the leak rate is difficult.
Applicable scenarios: Small-batch production, repair stations, laboratories, or situations where the exact location of the leak needs to be identified.
II. Pressure Decay Method
This is currently the most widely used and highly automated leak testing method, as shown in Figure 2 below.
Figure 2: Pressure Decay Method
Principle:
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Seal the radiator’s inlet and outlet, then fill it with clean compressed air or nitrogen at a predetermined pressure.
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After filling, the system enters a “pressure holding” phase, during which the air supply is cut off.
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High-precision pressure sensors monitor real-time changes in internal pressure during the holding phase.
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If there is a leak, the pressure will drop over time. The system determines whether the product passes by calculating the pressure decay value over a specific period.
Advantages:
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Efficient and automated: Can be integrated into production lines for fully automated testing with fast cycle times.
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Quantitative results: Precisely calculates the leak rate and establishes scientific pass/fail criteria.
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Clean and dry: No water is used during testing, eliminating the need for drying.
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High reliability: Eliminates human factors, providing objective and reliable results.
Disadvantages:
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Cannot locate leaks: Only indicates whether a leak exists, without identifying its location.
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Highly sensitive to temperature: Gas pressure is very sensitive to temperature fluctuations, which can cause pressure changes and lead to misjudgment. Therefore, advanced testing equipment often includes temperature compensation features.
Applicable scenarios: Most large-scale production lines, such as 100% online testing for radiators in the automotive, home appliance, and electronics industries.
III. Differential Pressure Method
An upgraded version of the pressure decay method, offering higher accuracy and stronger anti-interference capabilities, as shown in Figure 3 below.
Figure 3: Differential Pressure Method
Principle:
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Use a high-precision differential pressure sensor, with one end connected to the radiator under test and the other to a sealed “reference volume” (leak-free) at the same pressure.
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Fill both with gas at the same pressure, then hold the pressure.
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If the radiator leaks, the pressure on its side will be lower than that on the reference volume side, and the differential pressure sensor will detect this slight pressure difference.
Advantages:
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Ultra-high accuracy: An order of magnitude more precise than the direct pressure decay method, capable of detecting extremely small leaks.
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Strong anti-interference capability: Since the reference volume and the test piece are in the same environment (temperature, pressure source fluctuations), most external interferences, especially temperature changes, can be offset.
Disadvantages:
Applicable scenarios: Products with extremely high airtightness requirements, such as battery cooling plates for new energy vehicles and aerospace radiators.
IV. Helium Mass Spectrometry Leak Testing
This is currently the most sensitive and precise leak testing method, representing the “ultimate” detection solution, as shown in Figure 4 below.
Figure 4: Helium Mass Spectrometry Leak Testing
Principle:
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Evacuate the radiator, then surround it with helium (as a tracer gas) using the spray method; or fill the radiator with helium under pressure and use a sniffing probe to detect leaks externally (sniffer method).
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Use a helium mass spectrometer for detection. Helium molecules are small and easily pass through micro-leaks, and the spectrometer is highly sensitive to helium, enabling the detection of extremely trace amounts.
Advantages:
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Extremely high sensitivity: Can detect leak rates as low as 10⁻⁹ Pa·m³/s per year, unmatched by other methods.
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Precise quantification: Directly reads the leak rate value.
Disadvantages:
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Very expensive equipment.
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High testing costs (helium consumption).
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Relatively slow testing speed.
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Requires highly skilled operators.
Applicable scenarios:
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Situations with extreme airtightness requirements, such as aerospace and new energy battery cooling plates.
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Scientific research and high-end manufacturing fields.
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