The fill cap on top of an IBC, commonly 6″ on a standard tote, comes in vented and sealed versions. Ordering the wrong one creates a small problem that is annoying to fix in the field.
Vented
A vented cap lets air in or out as the contents expand and contract with temperature. That matters because the bottle is fairly rigid.
Use vented when:
- The product is water-based or an edible oil.
- The tote will see significant temperature swings.
- You will drain by gravity through the bottom valve, so air must replace the liquid.
Sealed
A sealed cap is airtight. Use it for products that should not be exposed to air or that give off vapor.
Use sealed when:
- The product is solvent-based and you want to limit vapor escape.
- The product is sensitive to oxidation.
- Your shipping rules call for it. Check current DOT/UN rules for hazmat.
- You will discharge by pump rather than gravity.
The small annoyance
A sealed cap on a gravity-drained tote slows the flow and can pull the bottle inward as it empties; loosen the cap or use a vent while draining. A vented cap on a product that should be sealed can lose vapor or let in moisture. Tell the partner supplier what you will store, and ask which cap is fitted.