Keep melamine powder in its closed bags inside a clean, dry, ventilated warehouse at ambient temperature, on pallets, out of rain and sun, with big bags stacked no higher than the producer allows. The rest of the risk sits in transit: a container that sweats on the voyage, or cold bags opened into warm, humid air on arrival.
Why Melamine Powder Cakes
Packed melamine cakes when it stays in contact with moisture from the air for long enough. Two conditions besides the moisture itself help a powder cake: temperature and humidity that rise and fall over time, and the weight of bags stacked on top.
Storage Conditions for Melamine Powder
Melamine powder belongs in a clean, dry, well-ventilated warehouse, under a roof and away from heat sources. The Azomureș melamine SDS adds a single-level building of brick or concrete with a flat, dry floor, cleaned before and after each delivery.
No producer we checked sets an air-change rate for a melamine store. Bulk melamine arrives in clean, dry, sealed silo tanks, and a receiving silo should stay as sealed and dry as the tank that filled it.
Temperature
Store melamine powder at ambient temperature. For caking, keeping that temperature steady matters more than any particular figure.
Humidity
Keep the store dry and the humidity steady; no producer or national standard we checked sets a relative-humidity limit for melamine powder. Without a figure to hold to, the working rule is to remove the sources of damp: roof leaks, wet floors, and doors left open in wet weather.
Rain and Sunlight
Melamine powder should not be stored outdoors. A tarpaulin over pallets in a yard keeps out neither the sun’s heat nor the damp.
Keep Bags Sealed Until Use
Leave every bag closed until it goes to the process, and close a part-used bag again as soon as material has been taken out.
For a lined bag or big bag, close the inner liner first and then the outer bag or spout; a cut-open valve bag cannot be closed tightly, so empty it or tip the rest into a container that seals. Use opened bags before full ones.
Stacking Height for Bags and Big Bags
There is no single industry limit for stacking melamine big bags: each producer sets its own for its own bags, and the strictest is not to stack them at all.
- OCI (SDS): big bags over 1,000 kg are not stacked, bags of 1,000 kg or less go no more than two on top of each other, and its SLP grade is not stacked at all.
- Azomureș (SDS above): 1,000 kg bags are stacked no more than 2 rows.
- Metafrax (product sheet): stacking big bags or transport packages on top of each other is not recommended.
Follow the rule in your producer’s SDS, and where it is silent, keep big bags one high. No producer we checked gives a pallet stacking height for 25 kg melamine bags.
Stand every bag on a pallet: Metafrax specifies pallets at least 5 cm off the floor. Keep stacks back from outside walls.
Preventing Condensation in Transit and Storage
Condensation is prevented by keeping everything packed with the bags dry and by controlling when warm, damp air meets cold surfaces.
These measures apply to every container of bagged melamine:
- Dry packing materials: no wet pallets, dunnage or packaging go into the container.
- A breathable cover on top: paper or nonwoven fabric over the top layer catches drips, while a plastic sheet only moves the condensation to its underside, against the bags.
- Stowage out of the sun: below deck where possible.
Ventilate and open the container according to its route; the German Insurance Association’s container handbook gives opposite advice for the two directions. Heading toward cooler climates, leave the ventilation openings open or use a ventilated container; the doors may be opened in port.
Heading into the tropics, seal the vents and door gaps, and do not open the container on arrival until the cargo has had time to warm up, otherwise warm, humid air condenses on the still-cold bags; a customs inspection should open it only briefly.
Bags moved from a cold container or store into a warm, humid warehouse should stay closed until they reach the temperature of the room.
Shelf Life of Melamine Powder
No melamine producer we checked prints a shelf life or expiry date: QAFCO, OCI and Azomureș describe melamine as stable under normal storage conditions. Only Metafrax gives a number: a guaranty period for melamine storage of 1 year from the date of manufacture, provided its transport and storage rules are followed. That is a warranty term and does not mark when the powder degrades.
Ship stock out first-in, first-out. A lot that has caked or passed a guaranty period is judged on a moisture retest against the water limit on its COA rather than on its date.