How Do You Prevent Leakage During Shipping and Storage?

The Short Answer

Leakage almost always comes from one of four places: insufficient closure torque, a sealing element that cannot tolerate the product or the pressure, a container that deforms under stacking or temperature, or a filling process that leaves product on the sealing surface. Preventing it is a matter of controlling torque, choosing a seal that suits the formula, validating the pack under transport conditions, and keeping the sealing land clean during filling.

Closure Torque and Its Stability

Torque applied at the filling line is not the torque the consumer sees. Removal torque falls as the sealing element takes a set, and it can also fall further when the pack is vibrated in transit or when the product warms and the internal pressure rises. A pack closed at the low end of its torque window may be leak-free on the line and leaking on arrival. Measuring removal torque after vibration, rather than only at capping, gives a realistic picture, and specifying a torque window rather than a single target allows the line to work within a range that survives transport.

Sealing Element Compatibility

The liner or gasket must resist the formula, not merely the water used in a leak test. Oils swell some foam liners, solvents attack adhesives, and surfactants can wick through a material that appears solid. Once the seal is compromised, no amount of torque will restore it. Compatible material selection, followed by storage testing with the actual product at elevated temperature, is the only reliable check. Where the product is aggressive, an induction seal or a plug seal may be more robust than a flat gasket.

Container Deformation

Plastic containers creep under sustained load, and a stack of cartons in a warm container is exactly that. A jar that ovalises slightly at the neck will no longer hold its closure evenly, and leakage follows. Thin walls, tall stacks and high temperatures compound the effect. Compression testing at elevated temperature, and specifying a carton strength that matches the stack height actually used, prevents the problem. Where a pack is known to be sensitive, reducing stack height is cheaper than increasing wall thickness.

Process and Packing Discipline

Product on the sealing land is a frequent and entirely preventable cause of leakage. It comes from nozzles that drip, from fills that are too close to the neck, and from caps applied while product is still foaming. Simple countermeasures include a drip tray, a slower withdrawal of the nozzle, and a short settling distance before capping. On the packing side, cartons should hold packs upright and prevent them from rubbing against each other, since abrasion can wear through a printed cap and expose an unsealed edge.

Verification Checklist

• Measure application and removal torque on production samples.
• Vibrate cartons and re-measure torque afterwards.
• Store filled packs inverted for 72 hours at elevated temperature.
• Compression test at the real stack height and temperature.
• Inspect sealing lands for product residue at the capping station.
• Leak test using the bubble emission method on sampled packs.
• Check carton dividers prevent pack-to-pack contact.

Temperature, Altitude and Pressure

A sealed pack is a pressure vessel. Warm air expands, and air freight exposes packs to lower external pressure, both of which push product toward the closure. A pack that is tight at sea level and room temperature can weep in an aircraft hold or in a delivery van in summer. Where the product is volatile or the route includes air freight, the closure should be tested after a thermal cycle, and the fill level should leave enough headspace that thermal expansion does not bring product into contact with the liner.

Designing the Carton for the Pack

The carton is part of the sealing system. A carton that allows packs to lie on their side converts a small closure weakness into a visible leak; one that holds them upright with dividers prevents it. Corrugated strength must match the stack height actually used in the warehouse and container, not the height assumed in a drawing. Where packs are heavy or glass, individual cells are essential; where they are light plastic, a well-fitted divider is usually sufficient.

Conclusion

Leakage prevention is a chain of small controls: a defined torque window, a compatible seal, a container that resists creep under the real stack, and a filling process that keeps the sealing land clean. Testing after transport simulation, rather than at the end of the line, is what converts those controls into confidence.

References

• ASTM D3078-02(2021), Standard Test Method for Determination of Leaks in Flexible Packaging by Bubble Emission.
• ASTM D4169-22, Standard Practice for Performance Testing of Shipping Containers and Systems.
• ASTM D642-20, Standard Test Method for Determining Compressive Resistance of Shipping Containers.
• ASTM D3474-20, Standard Practice for Calibration and Use of Torque Meters.
• USP <671>, Containers — Performance Testing.
• ISO 4180:2019, Packaging — Complete, filled transport packages — General rules for performance testing.