Corroded Moulds

User: Coca Cola H.B.C. AG, Thessaloniki, Greece

For cooling the moulds of the PET bottle production a closed cooling loop is used. The water is cooled down by plate heat exchangers.

As a small amount of water is added to the cooling loop continuously, also limescale and free oxygen enters the cycle. Therefore the moulds need to be cleaned every two weeks. The dirt did consist of corrosion and rust more than limescale. The reason for this is the high content of oxygen in the system.

If the cleaning is done too late, the quality of the bottles suffers.

Merus Ring in the cooling loop

We installed one Merus Ring in the cooling loop. It is located between heat exchanger and moulds. As the goal is to reduce corrosion in the moulds we installed it close to them. Thus we could achieve the best results there.

Before – After

Right after the installation we started to take water samples every day. Its iron content was measured on a daily basis and recorded by the customer. In a fully closed loop the iron content is expected to increase in the period following the installation. The reason for this is that the existing rust in the moulds is solved in the water and circulates in the loop. As soon as all rust is flushed out the iron content will decrease significantly until it is on the level of the feed water.

In this case a small amount of water left the cycle and was replaced by fresh water. This was enough to flush out the rust right from the beginning. Therefore the iron content in the samples decreased day by day.

A visual inspection showed, that no new rust or limescale formed after the installation. What was especially remarkable is that since the Merus Rings have been installed no special chemical cleaning of the moulds was necessary.

This has a positive effect on production quality and volume as no downtimes are needed for servicing.