New Advances in the Forming Processing Technology of Large-Diameter HDPE Pipe Extrusion

In recent years, driven by the robust development and large-scale expansion of the domestic PE industry—and capitalizing on inherent advantages such as being non-polluting, long-lasting, and possessing superior physical properties, excellent resistance to corrosion and aging, good cold resistance, abrasion resistance, and high impact strength—PE piping has emerged as the preferred choice for large-diameter pipelines in the municipal water supply and drainage sector. This success is attributed to its light weight, ease of installation, superior jointing methods, excellent flow characteristics, and cost-effectiveness, presenting a highly promising outlook for future growth. Currently, the PE piping market is dominated primarily by HDPE products, a category that encompasses solid-wall pipes for water supply and drainage, single- and double-wall corrugated pipes, steel-reinforced corrugated pipes, gas pipelines, pipes for conveying mineral slurries, sand, and silt, agricultural drip irrigation tubing, and various other composite, modified, and cross-linked pipe systems.

Classification of PE Pipe Raw Materials

First and foremost, the selection of HDPE material is critical; different grades of HDPE possess distinct performance characteristics and must be screened based on actual production requirements. For instance, when manufacturing large-diameter PE pipes, the preferred HDPE grade is PE100. This material exhibits outstanding resistance to pressure, impact, and corrosion, while simultaneously meeting the rigorous strength requirements inherent to large-diameter piping.

However, for the production of thick-walled pipes, it is advisable to select grades that feature "anti-sag" properties. During the manufacturing process of thick-walled pipes—due to the substantial material thickness—there is a propensity for "melt sag" to occur. HDPE materials endowed with anti-sag capabilities maintain superior stability at elevated temperatures, thereby guaranteeing the quality and structural integrity of the finished pipes.

Beyond the two scenarios mentioned above, several other factors warrant consideration. For example, pipes intended for prolonged exposure to outdoor environments should be manufactured using HDPE grades that demonstrate superior weather resistance; conversely, pipes designed to convey corrosive media require HDPE grades characterized by exceptional corrosion resistance.

Consequently, when selecting HDPE materials, it is imperative to identify the most suitable grade based on specific production demands, thereby ensuring that the manufactured pipes are capable of meeting operational requirements across a wide spectrum of complex environments. Furthermore, during the production process itself, meticulous attention must be paid to processing techniques and quality control measures to guarantee that the resulting pipes exhibit stable and reliable performance.

To meet specific extrusion process requirements, extrusion machine must possess corresponding capabilities, primarily encompassing aspects such as screw design, melt temperature control, pipe mold design, vacuum control, traction speed ratio control, and automatic cutting mechanisms.

JWELL LARGE DIAMETER PIPE EXTRUSION LINE

Extruder Section

For the production of large-diameter HDPE pipes, JWELL Machinery employs a proprietary main extruder series featuring a length-to-diameter (L/D) ratio of 40, paired with a spiral feed bushing. This configuration ensures high output rates while simultaneously guaranteeing optimal material plasticization and low melt temperatures. For pipe specifications with an outer diameter (OD) of 800 mm or greater—and wall thicknesses corresponding to SDR 11 or higher—the extruder is equipped with a rear-mounted melt cooler. This device reduces the melt temperature before the material enters the die, thereby minimizing "melt sag" as much as possible while simultaneously allowing for a reduction in the length of the vacuum cooling tank; ultimately, this ensures exceptional uniformity in the pipe's wall thickness.

Mold design

The single-layer or multi-layer die features a spiral structure, incorporating a multi-spiral flow distributor design as well as air and oil cooling mechanisms to minimize material residence time within the die and further stabilize the melt temperature.

Vacuum Control

During the vacuum cooling and forming stage of pipe production, the implementation of a fully automated negative-pressure closed-loop control system ensures rapid pipe formation and provides a swift dynamic response. Furthermore, the system is capable of detecting vacuum leaks in real time and automatically compensating for them, thereby enhancing the stability of the vacuum sizing process. Additionally, by automatically regulating the rotational speed of the vacuum pump, the system not only significantly reduces noise levels within the vacuum tank but also achieves substantial energy savings, with an energy-saving rate exceeding 50%.

Stable Traction

The system employs a "one-to-many" synchronous control scheme—where a single drive unit simultaneously powers multiple permanent magnet synchronous servo motors—offering the advantage of stable torque output at low frequencies. Furthermore, its wide speed regulation range ensures a smoother production process and minimizes potential product waste. Regarding the traction tracks, a self-expanding contour-following mechanism is utilized to ensure a tight, precise fit between the chains and the guide rails, thereby guaranteeing the accuracy of the traction speed.

Automated Cutting

It features a fully automated, dust free cutting mechanism capable of cutting thicknesses up to 160 mm. Furthermore, it is equipped with a "one-touch automatic diameter adjustment" function, rendering the dust free cutting of ultra-thick pipes remarkably simple and intuitive—enabling the rapid cutting of pipes with varying specifications.

Overall, selecting appropriate materials and matching equipment, optimizing production processes, and enhancing the level of automation and quality control can effectively improve the production quality and efficiency of large-diameter HDPE pipes.