Handling Water Ingress in the Interstitial Space of Storage Tanks

Water ingress into the interstitial (annular) space of double-walled or vacuum-insulated storage tanks can compromise insulation performance, increase heat ingress, and accelerate boil-off of cryogenic liquids. Timely identification and corrective actions are critical to maintain tank efficiency and safety.

1. Causes of Interstitial Water Ingress

Seal or Weld Failure: Cracks, leaks, or poor-quality welds in the outer shell allow rainwater or condensation to enter the interstitial space.

Vacuum Loss: Loss of vacuum in double-walled tanks can lead to condensation forming within the annular space.

Drainage or Venting Issues: Blocked drains or vent paths can prevent water from being removed, leading to accumulation.

Environmental Factors: Heavy rainfall, flooding, or high ambient humidity can exacerbate water ingress if tank integrity is compromised.

2. Detection Methods

Visual Inspection: External inspection may reveal water dripping or frost patterns on the outer shell.

Pressure or Vacuum Monitoring: Drop in vacuum or abnormal pressure readings can indicate water accumulation.

Moisture Sensors: Installing humidity or liquid detection sensors in the interstitial space allows early detection.

3. Corrective Measures

Drainage: Open drainage valves or ports to remove accumulated water. Ensure proper slope and flow paths for effective drainage.

Vacuum Restoration: Re-establish vacuum in double-walled tanks to restore insulation performance and prevent further condensation.

Seal and Weld Repair: Inspect and repair any compromised seals, gaskets, or welds to prevent recurrence.

Insulation Drying: In cases where insulation has absorbed moisture, controlled drying or replacement may be necessary to restore thermal performance.

Preventive Maintenance: Regular inspection of drains, vents, and tank integrity can prevent future water ingress.

4. Operational Precautions

Ensure proper sealing of access points and manways.

Avoid overfilling or introducing liquid that could lead to condensation in the interstitial space.

Monitor environmental exposure, particularly in outdoor installations, and provide protective covers if necessary.

Conclusion
Water ingress in the interstitial space of cryogenic or insulated storage tanks can reduce insulation efficiency and increase operational risks. Timely detection, drainage, vacuum restoration, and repair of seals or welds are essential to maintain tank performance and safety. Regular maintenance and monitoring prevent recurrence and ensure long-term reliability.

References

EN 14620 – Design and Manufacture of Cryogenic Vessels.

NFPA 55 – Compressed Gases and Cryogenic Fluids Code.

Barron, R.F. (1999). Cryogenic Systems, 2nd Edition. CRC Press.

Bratt, R., & Mort, P. (2015). Cryogenic Engineering: Fifty Years of Progress. Springer.

ISO 21014 – Cryogenic Vessels – Temperature and Pressure Measurement Guidelines.