Storage conditions are among the foremost factors determining how a paperboard tube performs. A tube manufactured to the right dimensions and the right strength will not deliver as expected if it is stored badly.
Why does moisture matter so much?
Paperboard is made of cellulose fibre and is a hygroscopic material: it takes up moisture from its surroundings and gives it back. When it takes up moisture the bonds between fibres weaken and the compressive strength of the wall falls.
That loss leaves no visible damage. The tube can look sound from the outside while going oval during winding. This is what makes the source of the problem hard to find.
The second effect of moisture is dimensional. Paperboard expands somewhat when it takes up moisture and contracts as it dries. In applications with a narrow inner-diameter tolerance, that change can cause problems when mounting on the spindle.
Storage conditions
Rules that are workable in practice:
- Enclosed, dry space. Open areas, canopies and damp basements are not suitable.
- Raise off the floor. Tubes should be kept palletised and should not be in direct contact with the floor. Concrete floors carry moisture upwards.
- Distance from walls. External wall bases are the points most prone to condensation. Leaving a gap is advisable.
- Avoid sudden temperature changes. Material brought from a cold store into a warm production area can form condensation on its surface.
- Protect from direct sun and rain. This applies during shipping and loading as well.
The role of packaging
Tubes are generally shipped in stretch wrap or boxes. That packaging serves not only for transport but also as a moisture barrier.
Not opening the packaging of tubes that will not be used, and re-closing packaging that has been opened, are simple but effective measures.
Stacking
Stack height determines the load on the tubes below. Paperboard kept under high load for a long period may not fully recover its shape once the load is removed — this is known as creep.
Practical recommendations:
- Keep stack heights moderate
- Do not lay boxes on their sides; tubes are more resistant upright
- Prevent forklift forks from coming into direct contact with the boxes
- Do not place damaged boxes in the upper rows
Stock rotation
Paperboard tubes have no "use by" date; what is decisive is storage conditions. Even so, good practice is to operate a first-in, first-out principle in stock rotation.
With batches that have been in stock for a long time, it is worth checking a few tubes by eye and by hand before use: are the ends sound, does the wall retain its resilience, is there any sign of moisture on the surface?
When a problem arises
If a particular batch is producing deformation, first check where and for how long that batch was stored. When some tubes of the same size cause problems and others do not, the cause is usually storage.
The Kafkas Masura approach
The tubes we manufacture are made of paperboard, and the conditions above apply to all paperboard tubes.
We can assess together how your storage conditions affect tube dimensions; wall strength is set on the basis of that information, particularly for products that will sit in stock for an extended period.