Many in the cement industry have already opted to make the switch from paper to plastic bags. What was their rationale, and has it given them what they expected? There are a number of reasons to switch over with each having their own benefits. A pioneering choice, it would appear. Is making a choice so simple? Unfortunately not. There are a number of systems each with their own advantages and disadvantages. So, make sure you get some good advice. Arodo was the first company to start packaging cement in plastic and can offer various systems currently on the market. So, it is certainly worth taking some expert advice
The advantages of cement in plastic bags
“Around the turn of the century a customer in the UK asked us to develop a machine for packaging cement in plastic bags”, explains Frank Goris, Sales Director at Arodo. “As we always try to meet to the needs of our customers, we rose to the challenge and started carrying out some tests.”
The advantages were soon clear:
- Environmental-friendly solution
- Less wastage
- Easier to recycle
- Lower packaging costs
- Better printing possibilities with nicer bags
- Substantial longer life expectancy
- Storage -Transport
- Water and weather resistant, unprotected open air storage
- Cleans storage: no leaks
- Dust and spillage free
Fully automatic packaging in plastic bags
Opting for cement in plastic bags is a logical choice. But then we have the packaging process. Fully automatically packaging in plastic is technically not a simple matter. If you look at valve fillers at the cement plants it’s obvious straight away. The product is pressed into the bag, while bags are made round so the maximum amount of product with air can be put inside. Then the bags are flattened so the air can escape through the many holes in the bag, and the bags can be stacked on a pallet. This process does not however work well with a closed plastic bag. The air leaving the product/mix causes an air inclusion that cannot escape.
We at Arodo offer the following bag types to counter this phenomenon:
- A perforated bag with small openings so the air can escape but water can also enter. These types of bags are therefore not usually used for pure cement.
- A labyrinth bag, being a technique where the bag has openings so the air can gradually escape and water cannot penetrate the bag.
- A fully sealed bag that cannot be deaerated after closing. The air is removed (vacuum percentage) before the bag is sealed.
The technology for filling the different types of bags is also different. Perforated bags and labyrinth bags can be processed on the same machine. The fully sealed bag must be filled using vacuum technology. For cement-based products that absorb (nearly) no air (e.g. concrete) we can use yet another technique. The different bag types with associated packaging technology give different results. The differences can be seen in pallet stability, being dustproof, etc. and obviously the price of the bag.
The bag price largely depends on the weight of the empty bag. The perforated bag has the lowest weight. A labyrinth bag needs extra foil to create the labyrinth along the whole length of the bag. The fully sealed bag then needs an extra length at the top of the bag. The reduced pressure on the bag means the fully sealed bag can be made with thinner foil than a labyrinth bag. The total weight of the labyrinth bag and of the fully sealed bag will be approximately equal for this reason.
With the manufacture of lay flat tube, a tube is first made, the bag is cut in the longitudinal direction and then printed. After printing the foil is again joined in the longitudinal direction to form a tube. Cutting though is not necessary if more simple colouring is chosen for printing. Printing is in that case less expensive for the perforated or fully sealed bag.
It is best to be assisted by a professional when deciding on the bag and associated technology. Bag price, pallet stability, appearance of the bag… each element is important when making your choice. Arodo has all the necessary expertise in-house. We have the most extensive range of machines for cement and cement-based products. But that's not all: we produce machines for the perforated bag, the labyrinth bag and sealed bag.