Refer to PE Pipes, the connection method of different pipe diameters is different because we need consider its features and applications. Following we will introduce the general provisions and the connection methods of different pipe diameters.
- Before the connection of polyethylene water supply pipeline, the pipes, pipe fittings and pipeline accessories shall be checked according to the design requirements, and the appearance quality inspection shall be carried out on the construction site. They can be used only if they meet the requirements of national standards and regulations.
- Hot melt connection or mechanical connection shall be adopted for the connection of pipes, pipe fittings and pipe accessories. Pipes with nominal outer diameter greater than or equal to 110mm shall not be connected by manual hot melt socket, and polyethylene pipes and fittings shall not be connected and adhered by thread.
- Polyethylene pipes of different SDR pressure grade series shall not be connected by hot-melt butt joint; The connection between polyethylene water supply pipe and metal pipe or metal pipe accessories shall be connected by flange or steel plastic transition joint. Hot melt socket connection can be adopted for pipes with nominal outer diameter less than or equal to 90mm.
- Corresponding special tools shall be used for various pipe connections. Open flame heating is strictly prohibited during connection.
- Pipes, pipe fittings and pipe accessories with the same grade and pressure grade should be used for pipe connection. The connection of pipes and pipe accessories of different brands shall be tested and determined that the connection quality can be guaranteed before connection.
- When polyethylene pipes and fittings are connected with metal pipes and pipe accessories, when steel plastic spraying or nodular cast iron transition fittings are used, the pressure grade of the transition fittings shall not be lower than the nominal pressure of the pipe.
- When hot-melt connection is carried out in cold climate (- below 5 ° C) or windy environment, protective measures shall be taken or the process parameters of hot-melt welding machines and tools shall be adjusted. In rainy, foggy or windy weather in winter, the construction shall be carried out in a rain canopy that can avoid wind and rain.
- When the temperature difference between the storage place of pipes, pipe fittings and pipe accessories and the construction site is large, polyethylene pipes, pipe fittings and pipe accessories shall be placed on the construction site for a period of time before connection to make their temperature close to the temperature of the construction site.
- During pipe connection, special knife or pipe cutting tool shall be used for pipe cutting, and the cutting section shall be flat, smooth and free of burrs, and shall be perpendicular to the pipe axis.
- After the pipe is connected, the appearance quality of the joint shall be checked in time. Unqualified products must be reworked.
Hot Melt Socket Installation(DN20 ~DN63mm)
- Cut the pipe with pipe shear according to the installation needs; Generally, chamfering shall be carried out outside the pipe end, the angle shall not be less than 30 °, and the groove length of the pipe surface shall not be greater than 4mm.
- Measure the socket length of pipe fittings, mark the insertion depth at the pipe insertion end, and wipe the dirt on the pipe, the surface to be connected of pipe fittings and the heating surface of hot-melt socket connection tools with clean cotton cloth.
- Heat the fuser within the range of 220 + 5 "C. the welding operation can be carried out only after the fuser indicator is in the insulation state when the red light is displayed.
- Heat the outer surface of the pipe and the inner surface of the pipe with the hot-melt socket heating tool at the same time. After heating, the connector shall be quickly separated from the socket connection heating tool, and check the melting uniformity and damage of the heating surface of the connector. Then, insert the pipe into the socket of the pipe fitting with uniform external force to the marked position of the pipe insertion length, so that the socket end forms a uniform flange. Natural cooling (release your hand after the socket is in place for a moment, and do not twist during heating, socket and cooling).
- After the completion of construction, the pipe can be sealed and put into use only after passing the pressure test and acceptance.
- For hot melt socket connection of pipes with nominal outer diameter greater than or equal to 63mm, hot melt socket connection of mechanical device shall be adopted, and two corresponding parts to be connected shall be straightened to make them on the same axis. For hot-melt connection of pipes with nominal outer diameter less than 63mm, manual hot-melt socket connection can be adopted with the cooperation of rounding tools.
Hot Melt Butt Joint Installation (DN75 ~ DN200mm)
- Place the two PE pipes to be installed and connected on the fixture of the hot melt at the same time (the fixture can replace the clamping tile according to the pipe diameter to be installed), and the other end of each pipe is supported by a special bracket to align with the same horizontal plane as the connecting end. A spacing of about 5cm shall be reserved between pipes or pipe fittings.
- The dirt on the connecting surface of pipes and pipe fittings and the dirt on the heating surface of hot-melt butt joint connecting tools shall be wiped with clean cotton cloth, and the connecting surface shall be milled to make it perpendicular to the axis. Ensure that the contact surfaces of two pipe ends can be fully matched.
- Raise the temperature of the electric heating plate to 220 + 5 "C. after the heating of the hot melt is completed (the heating state indicator light shows green), it can be used only when the indicator light shows red and is in the insulation state. Place the electric heating plate between the end faces of the two pipes, operate the welding machine to make the end faces of the two pipes fully contact with the electric heating plate for heating at the same time, and pressurize it to 2MPa. When there is about 5mm flanging at the pipe joint, the heating is completed.
- Remove the heating plate, operate the pressurizing device and maintain the pressure for 5 minutes to fully connect the end faces of the two melted pipes and lock the pressurizing device (to prevent rebound). During pressure maintaining and cooling, do not move the connector or apply any external force on the connector.
- Keep a certain cooling time for about 10 ~ 15 minutes, release it, and the operation is completed; Natural cooling can be adopted, and air cooling can also be adopted if conditions permit, but water cooling is strictly prohibited.
Hot Melt Butt Joint Installation (DN200 ~ DN630mm)
- Place the welding machine in order, connect the oil pipe, heating, oil pump and planer lines, and finally connect the power supply before switching on. At this time, pay attention to whether the generator is connected to the zero line to avoid damaging the electrical device of the welding machine and debugging the oil cylinder. If it does not work, it is necessary to switch off and replace two live wires.
- Pay attention to safety when lifting PE pipe onto the welding machine Φ During 450 welding machine, both ends of the pipe must be exposed about 7 ~ 18cm from the clip, which is in use Φ During 630 welding machine, the two ends of the pipe must be exposed about 10 ~ 12cm from the clip. After the oil cylinder is fully opened, the planer can be put in. After the clip is compressed, the height of the two pipe interfaces shall be aligned neatly, and the allowable deviation of dislocation is 5% of the pipe wall thickness. After the pipe is planed, wipe the dirt and wet water on the pipe material, the connecting surface of the pipe fitting and the heating surface of the ironing plate with clean cotton yarn cloth.
- Welding can be started only after the hot plate is heated to about 220 ± 5C. During welding, the pressure relief valve shall be opened to relieve the pressure. For large-diameter pipes, the pressure can be relieved to 2 ~ 3 MPa to maintain the pressure. After the melting pressure of the pipes drops by 1 MPa, DN200 ~ dn400 pipes only need to be pressurized once, DN500 ~ dn630 pipes need to be pressurized 2 ~ 3 times. During pressurization, the pressure relief valve shall be opened to avoid completely pushing the melted section away, After pressurization, continue to use 2 ~ 3Mpa pressure maintaining mode and other pressure reducing methods. When the pipe melting flanging is 7 ~ 10mm, close the pressure relief valve tightly. The locking pressure of the pipe below dn400 is about 5MPa, and the locking pressure of the pipe above DN500 is about 6Mpa. Quickly close the interface, and a perfect flanging can be obtained at this time. In the whole heating process, it takes about 10 minutes for pipes below dn400 and 12 ~ 15 minutes for pipes above DN500.
- Pipe cooling time: it takes about 15 ~ 20 minutes for pipes below dn400; It takes about 20 ~ 25 minutes for pipes above DN500. The above are reference data. It is best to have a long cooling time. The specific parameters and cooling time shall be adjusted appropriately according to seasonal changes. According to the temperature, the natural temperature in summer and autumn is high, and the cooling time is the longest value. In winter and spring, the natural temperature is low, and the cooling time is the minimum value.
- Pipe welding staff should have a serious and responsible working attitude. Any minor mistake may lead to construction accidents. Grasping every detail during construction can completely eliminate the occurrence of accidents.
Hot melt butt joint shall also meet the following requirements:
- The connecting ends of the connecting pieces at both ends shall extend a certain length, and the two corresponding pieces to be connected shall be straightened to make them on the same axis. The misalignment shall not be greater than 5% of the pipe wall thickness.
- After heating, the parts to be connected shall be quickly separated from the heating tool, and the melting uniformity and damage of the heating surface of the parts to be connected shall be checked. Then, use uniform external force to make the connecting surface fully contact and flanging to form a flange, and the shape and size of the flange are uniform without pores, bubbles and cracks; There are smooth and symmetrical outer flanging along the circumference of the pipe joint at the joint, and the depth of the lowest part of the outer flanging shall not be lower than the outer surface of the pipe joint.