How to Check the Airtightness of a Pneumatic Fender?

A pneumatic fender absorbs berthing energy by compressing the air inside.
Once airtightness becomes an issue, the fender’s energy absorption performance drops sharply, and in serious cases, it can even create safety risks.

That’s why airtightness checks are essential—not only during factory inspection, but also during site acceptance and routine maintenance.

Below, we’ll explain how to check the airtightness of a pneumatic fender in a clear and practical way.

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Why Is Airtightness Inspection So Important?

Some people may think:
“The fender doesn’t look damaged and it still works—so why worry?”

In reality, it’s not that simple.

When a pneumatic fender starts to leak air, you may see the following problems:

• The internal pressure drops below the design value, reducing energy absorption
• Local deformation appears, causing uneven load distribution
• Slower rebound during berthing, or even abnormal sliding
• Long-term use accelerates rubber fatigue and damage

In short, airtightness directly determines whether the fender is actually working as designed.

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What Should You Prepare Before Checking Airtightness?

Before starting the inspection, it’s best to do the following:

• Inflate the fender to its rated pressure (commonly 50 kPa or 80 kPa)
• Place the fender on flat, clean ground without sharp objects
• Prepare the necessary tools:
  • An accurate pressure gauge
  • Soap water or a professional leak detection liquid
  • A timing or recording tool
• For long-term tests, record the ambient temperature

These steps are simple, but they significantly improve inspection accuracy.

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Method 1: Pressure Retention Test (The Most Basic and Important Method)

This is the most commonly used method and the one that best reflects overall airtightness.
After production, pneumatic fenders are usually tested this way at the factory. After a period of use, the same method can be used for reinspection.

Overall, this is the most accurate and reliable airtightness test available.

How to do it:

• Inflate the fender to its rated pressure
• Close the inflation valve and record the initial pressure
• Measure and record the pressure regularly over 24 or 48 hours

How to judge the result:

• If the pressure remains stable with only minor fluctuations, airtightness is normal
• If the pressure keeps dropping or drops significantly, air leakage is likely

This method is especially suitable for:

• Factory inspection
• Project delivery and acceptance
• Condition assessment after a period of use

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Method 2: Soap Water Leak Test (Quick Leak Point Detection)

When you suspect air leakage at a specific area on site and need to locate the leak, this is the fastest and most practical method.

Key areas to check include:

• Inflation valve and valve core
• Flange connection areas
• Rubber layer joints
• Reinforced areas at both ends of the fender

How to judge:

• Continuous bubbles indicate air leakage
• No bubbles mean the area is airtight

This method is simple and intuitive, and most on-site personnel can use it easily.

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Method 3: Long-Term Static Observation

If time allows, a more conservative approach can be used to confirm airtightness.

How it works:

• Inflate the fender and leave it unused for several days
• Record the pressure daily or every few days
• Monitor changes in ambient temperature at the same time

Suitable scenarios:

• Factory quality control
• Large project acceptance
• Applications with higher airtightness requirements

This method is more effective for identifying small but continuous air leaks.

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Where Do Airtightness Problems Most Commonly Occur?

Based on real-world experience, air leakage usually occurs in the following areas:

• Aging inflation valves or damaged sealing components
• Scratches or punctures on the rubber outer layer
• End areas where stress is concentrated
• Material fatigue caused by long-term overpressure or underpressure use

That’s why inspection should never focus only on surface damage—internal pressure is the key factor for pneumatic fenders.

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What Should You Do If Air Leakage Is Found?

Once leakage is confirmed, the solution depends on the severity:

• Minor leakage:
  • Replacing the valve core or sealing components is usually sufficient
• Clear damage location:
  • Professional rubber repair is required
• Severe or structural problems:
  • Factory repair or full replacement is recommended

Relying on repeated reinflation instead of proper repair is not recommended, as it increases operational risk.

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How Often Should Airtightness Be Checked?

A practical inspection schedule is as follows:

• Before leaving the factory: mandatory airtightness testing
• Before installation or delivery: reinspection
• During normal operation:
  • Every 6–12 months
  • More frequently for high-intensity or frequent berthing operations

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FAQ

1. How long should a pneumatic fender hold pressure during an airtightness test?

Under normal conditions, a pneumatic fender should maintain stable pressure for at least 24 to 48 hours. Minor fluctuations caused by temperature changes are acceptable, but continuous pressure loss indicates air leakage.

2. Is a soap water test enough to check airtightness?

No. A soap water test is useful for locating specific leak points, but it cannot evaluate overall airtightness. For reliable results, it should always be combined with a pressure retention test.

3. Does temperature affect pressure readings during testing?

Yes. Ambient temperature changes can cause slight pressure variation. That’s why temperature should be recorded during long-term tests, especially for factory inspection or project acceptance.

4. Where does air leakage usually occur on a pneumatic fender?

Air leakage most commonly occurs at:

• Inflation valves or valve cores
• Sealing components
• Rubber joints or seams
• Reinforced end areas where stress is concentrated