Advances in Inline Biaxial Stretching for PVCO

Evolution of PVCO Production

Early commercial production of biaxial oriented PVC (PVCO) pipe utilized a batch-based mould system. While this method was effective, it had limitations, such as the potential lack of true axial stretching and material waste from cut-off pipe ends.

More recent developments focused on inline systems, where the stretching process occurs continuously as the pipe exits the extruder. These inline methods, like those pioneered by Vinidex (Australia) and Wavin (Europe), allowed for better control over the stretching process and pipe dimensions.

The Latest In-Line Biax Process

The latest development in inline PVCO production is the dry in-line Biax process. This system features integrated wall controls, essential for maintaining precise pipe geometry.

A key innovation in this process is the design that facilitates an easy start-up. This is achieved through a preform design with a "thick nose 30", which enables the pipe to be blown up easily to the mandrel diameter without requiring high forces or extremely narrow temperature conditions. The less strict temperature requirements for the preform contribute to shorter start-up and cleaning times.

The system utilizes a solid mandrel, offering robustness compared to alternative methods involving inflatable balloons which can be wear and tear sensitive, especially during start-up or interruptions. Furthermore, the simple tie bar design, not requiring internal hot and cold water circuits with thermal separation, allows for a smaller diameter. This potentially enables the production of a smaller stretched pipe diameter relative to the preform bore limitation.

This advanced inline technology focuses on process stability, reproducibility, and ease of operation, contributing to higher overall equipment effectiveness (OEE).

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