MACHINERY | PIPE DIES
design is also possible depending on the structure of the pipe, its materials and its dimensions. In addition, Bausano has made other improve- ments to its extrusion lines and downstream equipment. And example is an internal air pipe cooling system, which cools pipes more quickly – improving their quality while taking up less space on the line. “The design of the new extrusion heads stems
from our ability to combine process consulting, technological expertise and a passion for innova- tion,” said Clemente Bausano, vice president of Bausano.
IMAGE: CONEXTRU
Right: Conextru says its multi-layer pipe head is flexible enough to make a range of pipe structures
Multi-layer RTP Pipe extruder specialist Conextru of Austria recently developed a toolset for production of multi- layer reinforced thermoplastic (RTP) pipes. The liner – or inner layer – of an
RTP pipe is typically made of PE100 or PE-RT. To reduce the length of such a line, Conextru developed a standard head with side feed connection – with the extruder position parallel to the extrusion line. The head has a helical spiral distributor system, which has advan- tages such as low pressure build-up, close wall thickness tolerance and short residence time. Common liners have a wall thickness range of 5-20mm and diameter range of 110-400mm at a production rate of up to 900 kg/h, says the company. This kind of monolayer helical spiral head – with the same spiral geometry – can also be used for monolayer liners made of PA, PVDF, PPS or other suitable materials. The multilayer head for this application can
produce a three-layer structure with PE outside, adhesive layer in the middle and high temperature- and chemical-resistant material on the inside. For best melt distribution, a triple helical spiral distributor is applied. The spiral geometries are different, depending on factors such as viscosity and throughput. Conextru says it has a library of geometries for different viscosities, which has been used in the past for other applications. In this project, a special solution was designed
to produce the liner in co-ex (PE/adhesive/PA) or mono-layer PE version. The mono-layer and multi-layer heads had the same melt feed point, so the PE extruder can stay in position in case of a change from mono-layer to multi-layer.
44 PIPE & PROFILE EXTRUSION | May 2021
Flexible pipe head Separately, Conextru has also developed a multi-layer pipe head that it says is flexible enough to make a wide range of pipe structures. “One of the important requirements for flexibil-
ity is that the position of each extruder must be the same for all pipe structures,” said Josef Dobrowsky, managing director of Conextru. “Only a short longitudinal movement of a few centimetres is allowed – for mounting to the head.” This has been achieved with a new adapter
block, which sits between the multi-spiral channel head and the extruder. The adapter block brings the melt from each extruder to the correct distributor of the head. The multi-layer head has four
different spiral distributors. They are designed for best melt distribution of low-viscosity polymers such as PVDF, PA, EVOH or adhesive, and for high-viscosity materials such as PE 100 RC or high modulus PP. Not all multi-layer pipes can be made with same die design so it is sometime necessary to have a specific die design depending on the pipe product. However, the system works with a master die set which is placed in the centring unit. ‘Add on’ die sets can be mounted onto this master die set. The horizontal die set change – combined with segmented mandrels – makes the system more flexible and user friendly. If colour stripes are needed, the best option is to apply them via a CSR colour stripe ring mounted at die end. Dobrowsky adds that the extruders themselves must be flexible enough to process different polymers without changing screw. So, instead of being optimised for high output, the extruders are optimised for a wide processing range. This can be achieved if the extruder have a corrosion resistant screw and barrel – to process corrosive polymers – as well as barrier screw design and temperate grooved intake, which can be operated at high temperature if needed.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.battenfeld-cincinnati.com �
www.tecnomaticsrl.net �
www.maillefer.net �
www.davis-standard.com �
www.bausano.com �
www.conextru.eu
www.pipeandprofile.com
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