When ventilating hygroscopic substances in IBC containers, the use of respiratory dryers is essential. These protect the contents from contact with atmospheric moisture and thus guarantee consistently high product quality.

Negative pressure in IBC

If an IBC contracts laterally due to the use of a silica gel filter when it is almost completely empty, this is due to the operating criteria. If an IBC is emptied at a high rate and aerated with a valved adsorber, there will be too much negative pressure for the plastic shell. This happens when emptying the IBC (1000l) within a few minutes and only becomes visible when more than 2/3 of the IBC has been removed.

Reasons for the vacuum

At a high removal rate, an adsorber must generate a minimum negative pressure. This is the case with a sufficiently large dimensioning and the absence of the valves. A small diameter of the silica gel fill as well as an additional constriction by the valves build up a negative pressure which causes the IBC to contract.

Proper adsorber

To avoid negative pressure in the IBC, an adsorber should not have any valves. This reduces the pressure difference considerably.  The two graphs below show the clear pressure difference of an adsorber without valves (left) and with valves (right). (right).

The diameter of the adsorber also plays an influential role. If an adsorber is dimensioned too small, the air has to pass a smaller diameter and is more strongly congested. The graphs below show the adsorbers with different diameter (2L – diameter 90 mm; 3M – diameter 110 mm).

Conclusion

If an IBC is emptied at a high rate, the adsorber should be as large as possible and without valves → GIEBEL Adsorber VV-D / VV-R 3M

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