Large blowing machinery for tanks up to 10,000 litres


PHOTO: The massive machine is to produce 7000-litre tanks for a customer in Saudi Arabia, at a rate of 8 tanks per hour, which is vastly faster than the roto process

INDUSTRIAL blow moulding machine manufacturer Rikutec Richter Kunststofftechnik showed off its technology for blow moulding very large containers – up to 10,000 litres – at a joint stand at the NPE show with fellow German exhibitor Kautex Maschinenbau.

The portfolios of extrusion blow moulding machines available from the two manufacturers complement each other: Kautex essentially supplies machinery for containers and tanks with capacities of up to about 1,000 litres while the range of RIKUTEC machinery only starts around that size. So it is only natural that since 2010, both companies have been exploiting synergies and cooperating successfully.

In the currently most exciting project, RIKUTEC is constructing the world’s largest blow moulder, a GBM S10.000 LD unit for a customer on the Arab peninsula. The machine with a clamping force of 6,000 kN (600 tons) will produce hollow bodies of a capacity of as much as 10,000 litres.

This four-layer co-extrusion machine is equipped with a 400 litre accumulator head and four extruders, each with a diameter of 150mm and an L/D ratio of 25. Each extruder provides a minimum throughput of 650kg per hour making for a total throughput of 2,600 kg/hr. The maximum shot capacity of the accumulator head is 330kg.

The machine will be used to produce above-ground water tanks with a capacity of 7,000 litres and a net weight of 250kg that will be provided with a white UV-stabilized outer layer for better reflection of the sunlight. An inner layer of food grade material is followed by two black middle layers to prevent the formation of algae. These two middle layers are fed by extruders also processing post-industrial and purchased regrind. The screws comprise special mixing zones and – like the barrels of the extruders for the middle layers – are especially hardened, which allows the incorporation of calcium carbonate (CaCO3), not only for cost reasons. Since the above-ground tanks can be exposed to summer temperatures of as high as 55 C, the calcium carbonate also serves to increase the stiffness of the processed polyethylene.

While roto moulded tanks of this size draw their stiffness from a 25-30mm thick wall with a foamed core layer comprising about two-thirds of the total wall thickness, the blow moulded tanks have a wall thickness of only 10-12mm. As a consequence, the more cost-efficient blow moulding process permits the production of about eight tanks per hour, while the rotational molding machine may need a full hour for a single tank. Moreover, the fully automatic blow moulding process can be controlled by a just one machine operator, whereas roto moulding requires up to four people.

“RIKUTEC has been active in ‘ultra large’ blow moulding machine projects for more than 30 years”, says Stefan Eichelhardt, head of the company’s Blow Moulding Machinery business unit.

“Our focus is on the manufacturing of machinery, and together with Kautex Maschinenbau we are excellently placed.”