Hot-melt welding of pipes in urban drainage systems

As an important part of urban infrastructure, urban water supply and drainage systems are responsible for transporting and discharging domestic water, industrial water and rainwater. PE (polyethylene) pipes have been widely used in urban water supply and drainage systems due to their excellent physical properties, corrosion resistance, economy and ease of construction. However, the connection quality of PE pipes directly affects the operating efficiency and safety of the entire system. Hot-melt welding, as an efficient and reliable connection method, has become the preferred method for PE pipe connection. This article will discuss in detail the solution for hot-melt welding of PE pipes in urban water supply and drainage systems, in order to provide a reference for related engineering practices.

Overview of hot-melt welding of PE pipes

The hot-melt welding of PE pipes is a method of connecting pipes by heating the surface of the pipe so that the plastic molecules fuse with each other in a molten state. This method has the advantages of high connection strength, good sealing and strong adaptability, and is suitable for PE pipes of various calibers and pressure levels. Hot-melt welding includes hot plate welding and electric heating welding, each of which has its specific application scenarios and operation steps.

Hot plate welding method

The hot plate welding method is one of the most commonly used methods for hot-melt welding of PE pipes. The steps include preparation, heating the hot plate, welding pipes, connecting pipes and checking quality.

1. Preparation

Before welding, the PE pipe needs to be inspected in detail to ensure that its quality and size meet the requirements and there is no damage and deformation. Use a special cutting tool to cut the PE pipe into the required length and clean the pipe end to ensure that there are no impurities and oil on the surface.

2. Heating the hot plate

Heat the hot plate to an appropriate temperature, usually between 220°C and 240°C. The choice of temperature needs to be adjusted according to the material and specifications of the PE pipe to avoid too high or too low temperature resulting in poor welding effect. The heating plate should be able to evenly heat the pipe end face to ensure the quality of welding.

3. Welding pipes

Put the ends of the two PE pipes on the heated hot plate, maintain a certain pressure (generally 0.2MPa to 0.4MPa), and wait for a while until the pipe ends melt. The length of the melting time depends on the wall thickness of the PE pipe, generally following the formula of wall thickness multiplied by 10 seconds. During the welding process, the heating plate should be kept in close contact with the pipe end face to ensure uniform heat transfer.

4. Connecting pipes

After the pipe ends are melted, quickly connect the two pipes together and maintain a certain pressure until the molten material cools and solidifies. This process needs to be quick and accurate to ensure the quality of the welding. During the connection process, avoid the misalignment of the pipe end faces and the generation of bubbles.

5. Check the quality

After the welding is completed, use tools to check the quality of the welding parts to ensure that there are no problems such as bubbles, cracks and water leaks. If necessary, a pressure test can be performed to verify the integrity of the connection. Quality inspection is an important part of ensuring the quality of hot-melt welding and must be strictly enforced.

Electric heat welding method

The electric heat welding method is a method of heating the connection part of the PE pipe and the pipe fittings by an electric heat welding head to melt and connect them together. This method is suitable for occasions where the welding temperature and time need to be precisely controlled, such as PE pipes with smaller diameters and connection points in complex pipe network layouts.

1. Preparation work

It is also necessary to inspect and cut the PE pipe to ensure that the pipe end is clean and free of impurities. Use special tools to install the electric hot melt head on the pipe end face, ensuring close contact with the pipe.

2. Heating the electric hot melt head

Heat the electric hot melt head to an appropriate temperature, generally between 220°C and 240°C. The temperature control needs to be precise to avoid damage to the PE pipe. The heating of the electric hot melt head should be uniform to ensure that the pipe end face can be completely melted.

3. Welding the pipe fittings

Insert the electric hot melt head into the pipe end of the PE pipe, maintain a certain pressure and time to melt the pipe end. Then, insert the pipe fitting into the melted pipe end, continue to heat and maintain pressure until the molten material cools and solidifies. During the welding process, pay close attention to the heating of the electric hot melt head to ensure that the pipe end face can be completely melted and connected together.

4. Cooling and solidification

After inserting the pipe fitting, continue to maintain a certain pressure and time until the molten material is completely cooled and solidified. This process requires patience to ensure the quality of welding. During the cooling and solidification process, avoid applying additional external force to the pipe to avoid affecting the welding effect.

Precautions for hot-melt welding

When performing hot-melt welding of PE pipes, in addition to following the above steps, you also need to pay attention to the following points:

1. Temperature control

During the welding process, the heating temperature must be strictly controlled to avoid poor welding results due to excessively high or low temperatures. Too high a temperature will cause oxidation and degradation of the PE pipe material, affecting the connection strength; too low a temperature will not allow the plastic molecules to fully fuse.

2. Pressure control

During the welding process, a certain pressure needs to be maintained to ensure that the molten material is fully in contact and solidified. Insufficient pressure will cause gaps in the welded part, affecting the sealing performance.

3. Time control

The heating and holding time needs to be adjusted according to the wall thickness and material of the PE pipe. Too long a time will cause the material to melt excessively, affecting the connection strength; too short a time will not allow the plastic molecules to fully fuse.

4. Quality inspection

After the welding is completed, the welded part must be carefully inspected to ensure that there are no problems such as bubbles, cracks, and water leaks. If necessary, a pressure test can be performed to verify the integrity of the connection.

5. Safe operation

During the welding process, pay attention to safe operation to avoid burns and other accidents. Operators should wear appropriate protective equipment, such as heat-resistant gloves and protective glasses.

6. Environmental requirements

The welding operation should be carried out in a clean and tidy environment to avoid dust and impurities. At the same time, the operation area should be well ventilated to avoid harmful gases from harming operators.

Application scenarios of hot melt welding

Hot melt welding has a wide range of application scenarios in urban water supply and drainage systems. For large-diameter PE pipes, hot melt butt welding has become the preferred connection method due to its high connection strength and good sealing. For small-diameter PE pipes, electric heat welding is more suitable for use at connection points in complex pipe network layouts due to its simple operation and high precision. In addition, in emergency repairs or small-scale renovation projects, hot melt welding can respond quickly and reduce construction costs.

Advantages and challenges of hot melt welding

Hot melt welding has significant advantages in urban water supply and drainage systems, such as high connection strength, good sealing, and strong adaptability. However, hot melt welding also faces some challenges, such as precise control of temperature, pressure and time, as well as operator skill requirements. In order to ensure the quality of hot melt welding, it is necessary to adopt advanced welding equipment and processes, strengthen the training and management of operators, and improve the construction level.

Hot melt welding of PE pipes in urban water supply and drainage systems is an efficient and reliable connection method with broad application prospects. By strictly controlling the heating temperature, pressure and time, strengthening quality inspection and safe operation, the quality of hot melt welding can be ensured and the operating efficiency and safety of the entire water supply and drainage system can be improved. In the future, with the continuous advancement of technology and continuous optimization of processes, hot melt welding will play a more important role in urban water supply and drainage systems.