Do repaired ship launching airbags need lower inflation pressure?

When it comes to ship launching airbags, safety always comes first. If an airbag has been repaired, many shipyard managers wonder: “Should we reduce the inflation pressure before using it again?” The short answer is — you should treat repaired airbags with extra caution. Lowering the pressure can be a good temporary approach, but the final decision should always come after proper inspection and testing rather than assumptions.

In this guide, we’ll explain how repaired airbags behave, why pressure adjustments might be necessary, and the practical steps shipyards follow to ensure a safe launch.

How Ship Launching Airbags Work

Ship launching airbags are heavy-duty, reinforced rubber cylinders that support and roll a vessel into the water. By inflating them to the correct pressure, they create a buoyant cushion capable of carrying hundreds or even thousands of tons.

Inflation pressure directly affects:

• Load capacity – higher pressure means greater lifting force.
• Rolling performance – consistent pressure ensures smooth vessel movement.
• Safety margins – operating outside the recommended range can cause sudden failures.

That’s why any change in the airbag’s condition — especially after repairs — requires careful evaluation.

What “Repair” Really Means for an Airbag

Not all repairs are the same. Typical damage includes:

• Surface abrasions from slipways
• Punctures caused by debris or sharp edges
• Valve leaks due to wear and tear
• Seam separation from repeated heavy launches

Repairs can range from a simple surface patch to hot vulcanization or structural reinforcement. When done by the original manufacturer using compatible materials, a repaired airbag can perform nearly as well as a new one. But field repairs using generic patches or adhesives might not restore full strength.

Understanding how and where the repair was done is the first step in deciding whether to lower pressure.

Why Repaired Airbags Can Behave Differently

Even a well-repaired airbag isn’t exactly the same as a new one. Some reasons include:

• Altered material strength – the repaired area might flex differently under stress.
• Uneven stress concentration – patches can create localized stiffness or weak spots.
• Ageing effects – if the surrounding rubber is already old, the repair doesn’t stop ongoing degradation.
• Potential leak paths – even tiny imperfections in sealing can affect long-term pressure retention.

Because of these factors, it’s safer to verify performance through testing rather than relying on past specifications alone.

Key Factors Before Deciding Inflation Pressure

Before you decide whether to reduce the pressure on a repaired airbag, consider:

• Repair quality
  • Was it done by the manufacturer or an uncertified workshop?
  • Were original materials and techniques used?
• Inspection results
  • Check for cracks, bubbles, loose seams, or surface wear.
  • Examine the repair area closely under proper lighting.
• Age & usage cycles
  • Older airbags or those used for many launches naturally lose strength.
• Environmental conditions
  • High temperatures and seawater exposure can reduce performance.
• Launch parameters
  • Heavier vessels, steeper slipways, or fewer airbags increase risk — sometimes requiring extra safety margins.

Inspection & Testing Protocol

Before returning a repaired ship launching airbag to service, shipyards typically follow these steps:

1. Visual inspection
   • Look for surface defects, seam separations, bulges, or cracks.
   • Examine the repaired area in detail.
2. Pressure retention test
   • Inflate the airbag to its standard test pressure.
   • Hold for a defined period and monitor for pressure drop.
3. Leak detection
   • Apply soapy water or use acoustic leak detectors to identify air seepage.
4. Trial run under controlled load
   • Use a partial load or dry-run setup to check rolling performance.
5. Documentation
   • Record test pressures, hold times, repair reports, and inspector signatures.

Only when a repaired airbag passes these tests should you consider restoring it to full working pressure. If there’s any doubt, lowering the pressure and increasing the number of airbags during launch adds an extra layer of safety.

Practical Guidelines from Shipyards

Many shipyards follow a conservative approach:

• Lower the working pressure temporarily until tests confirm safety.
• Use additional airbags to distribute the load during the first few launches after repair.
• Consult the manufacturer whenever possible, especially for major repairs or structural damage.

This approach minimizes risk without unnecessarily retiring a usable airbag.

When NOT to Reuse a Repaired Airbag

There are situations where lowering the pressure won’t help, and the airbag should be retired:

• Large structural tears or multiple deep punctures
• Failed pressure retention tests
• Unknown or uncertified repair history
• Severe ageing or cracking around the repaired area

In these cases, it’s safer — and often cheaper — to replace the airbag.

FAQ

1. Do repaired ship launching airbags always need lower pressure?
Not always. If a manufacturer-certified repair passes all tests, full pressure is often safe. But temporary reduction is common until testing confirms integrity.

2. How do I pressure-test a repaired airbag?
Inflate to the recommended test level, monitor pressure stability, and check for leaks using soapy water or acoustic tools.

3. Can I trust field-patched airbags for heavy launches?
Not without testing. Patches done outside manufacturer standards should always be verified before full-scale launches.

4. How long after repair can I reuse an airbag?
There’s no fixed rule — only after it passes inspection and pressure tests.

5. What documents should I keep after repairs?
Repair reports, testing logs, inspector names, dates, and photos. This ensures traceability and safety compliance.

Conclusion

Repaired ship launching airbags can be safely reused, but only after thorough inspection, testing, and documentation. While lowering inflation pressure temporarily adds a safety margin, the final decision should be based on evidence, not guesswork.

When in doubt, involve the original manufacturer or a certified inspector — it’s the safest way to avoid costly delays and potential accidents.