I. Introduction to PE Pipe Products

Polyethylene, abbreviated as PE in English, is a thermoplastic resin produced by the polymerization of ethylene monomers. PE pipes for gas applications represent a replacement for traditional steel and polyvinyl chloride (PVC) gas pipes. PE resin is synthesized through the polymerization of ethylene monomers. Depending on the polymerization conditions—such as pressure and temperature—the density of the resulting resin varies, leading to distinctions among high-density polyethylene (HDPE), medium-density polyethylene (MDPE), and low-density polyethylene (LDPE). When processing different types of PE pipes, it’s essential to select the appropriate resin grade based on the specific application requirements. Moreover, the requirements for extruders and molds also differ accordingly. In the plastic pipe industry, PE pipes, PP-R pipes, and UPVC pipes all hold significant market positions; among these, PE pipes enjoy an exceptionally broad range of applications. Among them, PE water supply pipes and PE gas pipes are the two largest application markets for PE pipes.

II. Product Features of PE Pipes

1. 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.

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

3. 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.

4. Long service life—PE pipes have a high molecular weight, offering 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.

5. 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 bacterial growth—thus qualifying as a safe and hygienic piping material. Moreover, the PE material itself is recyclable and does not release any substances that could harm the environment.

6. 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 risk of water or gas leakage.

7. Lightweight, easy to handle and install, with a light weight—its specific gravity is only 1/8 that of metal pipes—making it easy to transport and bend. It features simple and rapid welding processes, 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 connection: 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. The connection is now complete.

Hot-melt butt fusion construction method

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

2. 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.

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

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

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

6. 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 undergoes uniform flanging. Once flanging is complete, release the pressure from the hydraulic system and start the timer to begin timing. After heating is finished, quickly remove the heating plate, activate the moving clamp, and join the two pipes together. Upon completion of the connection, a uniform flange will be formed, with consistent flange height and width. Meanwhile, maintain the hydraulic system’s pressure and allow the pipes to cool gradually. The cooling time is also calculated based on the pipe wall thickness: for every 1 mm of wall thickness, the cooling time is 1 minute.

Construction Precautions

1. During welding, pay attention to keeping the pipe section clean and free of oil stains, dust, and other contaminants on the pipe ends; otherwise, this could lead to weak welds or the formation of pinholes during welding.

2. 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.

3. 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 causing false welding.