I. Introduction to PE Pipe Products

Polyethylene, abbreviated as PE in English, is a thermoplastic resin produced by the polymerization of ethylene monomers. During the polymerization process, ethylene monomers are influenced by various polymerization reaction conditions, such as pressure and temperature, which result in resins with different densities. Consequently, polyethylene can be classified into three types: high-density polyethylene (HDPE), with a density ranging from 0.941 to 0.965 g/cm³; medium-density polyethylene (MDPE), with a density ranging from 0.910 to 0.925 g/cm³; and low-density polyethylene (LDPE), with a density ranging from 0.910 to 0.925 g/cm³. Internationally, based on the "Minimum Required Strength under Long-Term Hydrostatic Pressure (MRS)," polyethylene resins are further divided into five grades: PE32, PE40, PE63, PE80, and PE100. Among these, PE100 stands out for its superior overall performance—combining excellent mechanical properties, strength, and cost-effectiveness—and has now become the primary material for PE pipes.

II. Product Features of PE Pipes

Corrosion-resistant: PE pipes have an extremely stable molecular structure and are free from electrochemical corrosion. With the exception of a few oxidizing agents, they can withstand erosion by a wide variety of chemical media.

It exhibits excellent resistance to corrosion and degradation. Among various pipeline materials, PE pipes have a remarkably low corrosion rate; when conveying mineral sand slurries, their corrosion resistance is more than four times that of steel pipes.

With excellent flexibility and impact resistance, PE pipes are highly resilient materials whose elongation at break exceeds 500%. They exhibit outstanding resistance to impacts and earthquakes and demonstrate remarkable adaptability to uneven settlement of the pipe foundation.

With a long service life and high molecular weight, PE pipes exhibit excellent stability and resistance to aging. Under normal operating temperature and pressure conditions, the service life of PE pipes can be guaranteed to exceed 50 years.

Excellent hygiene and environmental performance: PE pipes are manufactured without the addition of metal stabilizers, making the material non-toxic, free from scale buildup, and incapable of harboring bacteria—thus ensuring it is a safe and hygienic piping material. Moreover, PE itself is recyclable and does not release any substances that could harm the environment.

Safe and reliable construction connection methods—PE pipes primarily use hot-melt or electrofusion connections, which essentially ensure that the material and structure of the joint are integrated with the pipe itself, eliminating any concerns about water or gas leaks.

Lightweight, easy to handle and install, with a weight only one-eighth that of metal pipes, it’s easy to transport and bend. Its welding process is simple and quick, resulting in low overall project costs and significant economic benefits.

Applications of PE Pipes

Pipes for gas use, pipes for natural gas use, ventilation pipes for coal mines, oil transportation pipelines, water supply pipes for urban and rural areas, sewage discharge pipes, fluid-conveying pipes for chemical, pharmaceutical, paper-making, and other industrial plants, drilling pipes, irrigation pipes for agricultural fields, piping systems for food processing plants handling beverages, milk, alcoholic drinks, and other food products, slurry-conveying pipelines, protective conduits for power cables, pipes for postal and telecommunications applications, and pipes for air conditioning and condensate drainage.

Construction Methods and Precautions for Polyethylene (PE) Pipes

Electrofusion Welding Construction Method

Polyethylene pipe connections in Class B are made using three methods: electrofusion welding, hot-melt socket fusion, and hot-melt butt fusion.

Electrofusion welding: Suitable for connecting pipes to electrofusion fittings; the implementation steps are as follows:

Wipe clean the connection surfaces of pipes and fittings with a clean cotton cloth.

Cut the pipe using a rotating cutting blade to ensure that the end face is perpendicular to the axis; mark the insertion depth, then use a rotating scraper to remove the oxide layer from the surface of the PE pipe.

When connecting, align the corresponding fittings so that they are on the same axis, and insert the pipe into the socket of the fitting.

Set the electrofusion welder according to the temperature indicated on the outer surface of the fittings, as well as the heating and cooling times.

Start the welding machine to perform welding.

Hot-melt socket fusion construction method:

Wipe clean the pipe and fitting connection surfaces with a clean cotton cloth.

Cut the pipe using a rotating cutter to ensure the end face is perpendicular to the axis; mark the insertion depth; then use a rotating scraper to remove the oxidation layer from the surface of the PE pipe.

Insert the pipe and fittings vertically into the hot-melt machine mold without rotation, to the specified depth, and heat them for the prescribed duration.

Immediately after heating is complete, remove both the pipe and the fitting simultaneously from the hot-melt machine. Quickly connect the pipe and fitting without any rotation, inserting them until they reach the marked depth indicator. Do not move them for at least 15 seconds, then allow them to cool naturally—connection is now complete.

Hot-melt butt fusion construction method

Check whether all components of the welding machine are operating normally.

Secure the two pipe sections onto the welding machine fixture. By adjusting the clamping bolts, ensure that the two pipe sections are aligned at the same horizontal level, with an anchorage ratio not exceeding 10% of the pipe wall thickness.

Insert the milling cutter, start the milling cutter first, then move the fixture to mill the ends of the two pipe materials, flatten the ends of both pipes, and remove the oxide layer from the pipe end surfaces.

Align the ends of the two pipes again and check the misalignment rate. The misalignment rate should not exceed 10% of the pipe wall thickness.

Place it on the heating plate and heat at the specified temperature and for the specified duration (temperature: 220 ± 10℃, heating time: 1 mm/10 s).

After placing the pipe into the heating plate, operate the hydraulic system to advance the clamp, pressing the pipe end firmly against the heating plate. At this point, continue applying pressure to ensure that the pipe end is evenly flared. Once the flaring is complete, release the pressure from the hydraulic system and start the timer to begin timing the process.

After heating is complete, promptly remove the heating plate and operate the moving fixture to join the two pipes. Once the pipes are connected, a uniform flange will form, with consistent flange height and width. At the same time, maintain the hydraulic system pressure and allow sufficient cooling time. The cooling time is also calculated based on the pipe wall thickness—specifically, a 1 mm wall thickness requires a cooling time of 1 minute.

Construction Precautions

When welding, pay attention to keeping the pipe section clean and ensuring that the pipe ends are free of oil, dirt, and other contaminants. Otherwise, this could lead to weak welds or the formation of pitting during welding.

For PE hot-melt butt fusion, heating should be stopped when uniform burrs appear on the end faces of both pipe sections; then, release the pressure and proceed with the heating time.

During the cooling phase of PE hot-melt butt fusion, do not use forced cooling methods such as air cooling or water cooling to avoid creating false welds.