Application Of HDPE Water Supply Pipe

Plastic pipes have achieved great development and improvement in design theory and construction technology in construction, and have accumulated rich practical experience, which has promoted plastic pipes to occupy a very important position in building water supply and drainage pipeline engineering, and form a an unstoppable development trend.

HDPE pipe adopts advanced production technology and technology, and is formed by hot extrusion. It has the characteristics of corrosion resistance, smooth inner wall, low flow resistance, high strength, good toughness and light weight. HDPE pipes are the second most consumed plastic pipes in the world after PVC-U drainage pipes.

1. Development of HDPE water supply pipes

In the water supply and drainage pipeline system, plastic pipes have gradually replaced traditional pipes such as cast iron pipes and galvanized steel pipes and become the mainstream pipes. Compared with traditional pipes, plastic pipes have significant advantages such as light weight, corrosion resistance, low water flow resistance, energy saving, simple and rapid installation, and low cost, and are favored by the pipeline engineering community. At the same time, with the rapid development of the petrochemical industry and the continuous progress of plastic manufacturing technology, the output of plastic pipes has increased rapidly, and the types of products have become more diversified.

HDPE pipes are the second most consumed plastic pipes in the world after PVC-U drainage pipes. Medium or high density polyethylene pipes of PE80 and PE100 grades should be used for gas transmission; medium or high density polyethylene pipes of PE80 and PE100 grades are usually used for water supply pipes, and PE63 has gradually been eliminated. In terms of water delivery, the fastest growing is PE100 pipeline system, which is expected to grow by more than 10% in the next five years.

In Europe, HDPE pipes have been developed and applied more rapidly, and HDPE pipes have gradually replaced the status of PVC-U pipes and become the main consumption pipes. At the same time, HDPE pipes are gradually being used outside Europe.

2. HDPE pipe specifications and connection methods

The diameter of HDPE pipes ranges from DN32 to DN1000, and is divided into 26 grades. The pressure level is between 0.6Mpa ~ 1.6Mpa, with a total of 5 levels.

The HDPE pipe will be melted at a temperature between 190°C and 240°C. Using this feature, the two melted parts of the pipe (or pipe fittings) are fully contacted and maintained under appropriate pressure. After cooling, the two can be firmly integrated. Therefore, the connection method of PE pipe is different from that of U-PVC pipe. Usually, two methods of electric hot melt connection and hot melt butt are used. According to the size of the pipe, it can be divided into: when DN≤63, injection molding hot melt socket connection is adopted; When DN ≥ 75, use hot melt butt connection or electrofusion socket connection; when connecting with different materials, use flange or thread connection.

In terms of pipeline repair methods, there are expansion pipe construction method and lining HDPE method.

3. Application areas of HDPE

HDPE pipes are mainly used for: municipal engineering water supply systems, indoor water supply systems in buildings, outdoor buried water supply systems and residential quarters, buried water supply systems in factories, repair of old pipelines, water treatment engineering pipeline systems, gardening, irrigation and other fields of industry water pipes, etc.

However, it should be noted that HDPE pipes cannot be used for hot water lines.

4. Advantages of HDPE water supply pipeline in application

HDPE water supply pipes are widely used, mainly because they have incomparable advantages over other pipes:

(1) It is easy to form a closed anti-seepage system by butt welding and electrofusion welding. When laying along the trench, the amount of earthwork excavated and the amount of accessories can be reduced.

(2), light weight and easy to install and handle;

(3), strong wear resistance and excellent hydraulic performance, no need for outer protection in buried pipelines. It can be applied to earthquakes and soil subsidence areas in mining areas, and can also be laid on the bottom of rivers by submersion method.

(4), chemical corrosion resistance, resistance to internal, external and microbial corrosion, strong corrosion resistance, and healthy. It is suitable for conveying acidic and alkaline substances, sewage, natural gas, gas and other substances;

(5), good environmental adaptability and frost resistance. Can be used for indoor and outdoor water supply pipes.

(6), long service life, with a service life of more than almost 50 years;

(7), easy to recycle.

5. Matters needing attention in the application of HDPE water supply pipes

(1) It is recommended to take shading measures for outdoor laying in the open air, where there is sunlight.

(2) Buried HDPE water supply pipes, pipelines with DN ≤ 110 can be installed in a serpentine shape in summer, and pipes with DN ≥ 110 can resist thermal stress due to sufficient soil resistance, so there is no need to reserve pipe length; in winter, No need to reserve pipe length.

(3) When the HDPE pipeline is installed, if the operation space is too small (such as pipeline well, construction in the ceiling, etc.), the electrofusion connection method should be used.

(4) When the hot-melt socket is connected, the heating temperature should not be too high or too long, and the temperature should be controlled at 210±10℃, otherwise it will cause too much molten slurry extruded in the fittings and reduce the inner diameter of the water; At the same time, pay attention to control the angle and direction of the pipe fittings to avoid rework.

(5) When the hot-melt butt connection is made, the voltage is required to be between 200 and 220V. If the voltage is too high, the temperature of the heating plate will be too high, and the voltage will be too low, and the docking machine will not work normally; the docking interface should be kept aligned when docking. Otherwise, it will result in insufficient butt joint area, insufficient welding strength, and improper curling; when the heating plate is heated, the pipe interface is not cleaned, or the heating plate has impurities such as oil stains, sediment, etc., which will cause the joint to detach and leak water; The heating time should be well controlled, the heating time is short, and the heat absorption time of the pipe is not enough, which will cause the welding lip curling to be too small, and the heating time is too long, which will cause the welding junction curling to be too large, which may cause virtual welding.