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A tail with a twist

Plastic container manufacturer PrimePac Ltd gained 60% energy savings and 30% production improvement when they replaced a 23 year old blow molding machine.

In Northern Ireland there is a blow molding machine that, after 23 years of loyal service, had started to underperform. The machine, belonging to PrimePac, makes a variety of plastic bottles and it had started to create what is known as a “long tail”. This is excess plastic that extends from the bottom of a bottle and needs to be trimmed and recycled.

The slower the machine, the longer the tail and the fewer bottles are made each minute. Sometimes the entire bottle loses its shape and needs to be scrapped. In fact, the more plastic that is trimmed, or scrapped in this way, the higher the energy consumption. This is because the excess plastic needs to be cut from the bottle, fed back into the hopper, chopped and melted, repeating an energy intensive process that, in effect, is making the same bottle that had been manufactured a few minutes earlier.

Enter ABB’s authorized value provider for Northern Ireland, Advantage Control. The company’s David Watt carried out an energy assessment. This initially suggested a 30 percent energy saving if the blow molder’s hydraulic drive and motor was replaced with ABB’s all-electric synchronous reluctance motor (SynRM) and industrial drive package.

Additionally, the SynRM offers an unprecedented speed holding accuracy, meaning that bottles of a uniform length and weight can be produced, thereby eliminating “long tails”. The SynRM is much more accurate than a traditional induction motor and when coupled with the encoderless feedback offered by the direct torque control technology of the ABB industrial drive, the result is highly accurate speed holding.

Plastic bottles coming out from refurbished blow molding machine.

And, sure enough, once installed the SynRM package proved its worth. Whereas previously 63 percent of extrusions successfully turned into bottles, today this has increased to 96 percent – an outstanding 30 percent more bottles are fit for purpose. Because there is less waste, the 18.5kW granulator used to recycle the waste is used less. ‘’Approximately 5 percent of the energy saved comes from reduced load on the 18.5 kW granulator’’, explains Watt.

But, there was to be an unexpected, and hugely beneficial, twist associated with the SynRM installation.

In addition to investigating how to improve the efficiency of its existing blow molding machine, PrimePac had also wanted to install another new all-electric blow molding machine. This second project was challenging as the site had already reached its electrical capacity and a £250,000 ($356,000) investment was needed to upgrade its 600 kVA electrical supply to cope with the additional equipment.

However, once the 55 kW, IE4 SynRM package was installed on the blow molder, the plan not only generated some 80 tonnes less of carbon dioxide per year but also actual energy savings of over 60 percent were more than double the 30 percent initially predicted. This extra saving alone freed up enough electrical capacity to allow the electric machine to be installed. “This is beyond our wildest ambitions,” says PrimePac’s Engineering Manager, Clifford Craig. “We have managed to salvage our old blow molder machine, massively increase our production, reduce wastage, lower our energy bill and install a new machine at the same time, just by installing one SynRM package from ABB.”

Learn more about the PrimePac case.

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