For heavy-duty trucks—workhorses of logistics and construction—even tiny leaks can trigger chain reactions: brake failure, emission violations, or accelerated component wear. Air tightness testing isn’t just a "routine check"—it’s a core line of defense for safety, compliance, and operational efficiency. This blog breaks down the critical application scenarios, practical detection methods, and standardized processes of heavy-duty truck air tightness tests.

1. Core Application Parts & Test Purposes

Different components of heavy-duty trucks require air tightness tests for distinct safety and performance reasons:

Part	Core Purpose of Test
Pneumatic brake pipeline	Avoid brake failure by detecting leaks at welded/bent positions (ensures stable air pressure during braking).
Exhaust pipe & aftertreatment device	Meet National VI emission standards: Prevent exhaust leakage (maintains purification efficiency and reduces environmental pollution).
Axle oil-lubricated wheel hub	Prevent lubricating oil leakage and component wear (avoids driving safety hazards caused by hub malfunctions).
Tire	Ensure stable pressure (improves handling, shortens braking distance, and optimizes fuel economy).

2. Mainstream Detection Methods

Choose the right method based on component precision, cost, and efficiency:

• Soap Water Detection Method

  • Low cost & easy operation; suitable for preliminary tests (e.g., exhaust pipes).

  • Process: Pressurize the part → spray soap water on joints → bubbles indicate leaks.

  • Scenario: Quickly check leaks at the engine-exhaust pipe joint of National VI heavy-duty trucks.

• Instrument Positive Pressure Detection Method

  • High accuracy; ideal for precision parts (e.g., brake pipelines).

  • Process: Seal the part → connect to a tester → set parameters (e.g., 100kPa for brake pipelines) → monitor pressure changes in real time.

  • Judgment: Parts with leakage exceeding the upper limit are unqualified.

• Helium Detection Method

  • For parts with extreme air tightness requirements (rarely used in routine tests due to high equipment/helium costs).

  • Process: Evacuate the part’s inner cavity → fill helium outside → detect leaked helium with a mass spectrometer.

• Water Immersion Detection Method

  • Traditional method (gradually replaced by integrated test benches): Immerse pressurized parts in water and observe bubbles.

  • Drawbacks: Low efficiency, high risk of missed judgments, and water pollution.

3. General Test Process (For Precision Components)

Take precision parts (e.g., brake pipelines, wheel hubs) as an example:

1. PretreatmentClean surface oil/stains → seal open ends with plugs/hot melt adhesive (avoids interference from seal leaks).

2. Equipment ConnectionConnect the sealed part to a test bench: e.g., place the hub on the positioning boss, or connect the brake pipeline to the tester via a quick connector.

3. Parameter SettingAdjust pressure values and time parameters (e.g., 20s inflation, 10s detection, 300Pa leakage upper limit for brake pipelines).

4. Start DetectionInflate the part → monitor pressure changes in real time (some test benches use indicator lights for intuitive results).

5. Result Judgment & Follow-up

   • Qualified: Leakage within the set range; record data and proceed to the next process.

   • Unqualified: Locate leak points, repair, and retest.

For heavy-duty truck manufacturers and maintenance teams, mastering air tightness testing is non-negotiable. By matching the right method to each component and strictly following standardized processes, you can not only meet safety and emission standards but also cut long-term maintenance costs and improve fleet reliability. Whether it’s a brake pipeline or a National VI aftertreatment device, every leak checked is a risk eliminated.