The PERT tube is a heat-resistant polyethylene PERT tube, which is a kind of medium-density polyethylene produced by a special molecular design and synthesis process. It uses a method of copolymerizing ethylene and octene.
PERT tube using two hot-melt processes: a, hot melt socket welding process; b, hot melt butt welding process.
a, PERT hot melt socket welding process, this process in the hot melt socket pert tube, should pay attention to two points:
1. Hot melter temperature control at 250-260°C
2. PERT pipe, fittings stay in the die when soaking time should be short, the speed should be faster when the pipe and pipe pull out again when the pipe fittings should be quickly inserted into the socket. The normal operation flow is to adjust the machine to 255°C, and prepare the pert pipe fittings to be hot-melted. When the temperature of the hot-melt machine reaches the set temperature, the left-hand pipe takes the pipe and the right-hand pipe balances and exerts equalization to the right and left hands until the left and right hands feel the same time. When the pipe fittings have reached the depth of the socket, the pipe fittings are quickly pulled out of the die, and the pipe is quickly inserted into the pipe for a certain period of time until the temperature cools.
b, hot-melt docking process: This process is used for large-caliber PERT tubes. The installation of PERT tubes is divided into four steps:
1. Fix the parts to be docked and fix the PERT pipes and parts to be welded on the fixture of the welding machine. The line of the fixed pipe and parts should be on the same level, and the walls should be overlapped to avoid staggering.
2, milling PERT pipe end face before milling a clean cotton cloth to clean the inside and outside of the pipe within 100mm, and then fixed the milling cutter to promote the milling part of the end of the pipe. There are two problems to be noticed here. One is that the force should be slowly evacuated before the stop and the end of the tube should be smooth (suddenly retracting the milling cutter will leave the shell at the end of the tube). The second is to prevent secondary pollution of the tube end before heating.
3. Hot-melt butt welding Before the heating plate melts the mating surface, it is necessary to check the condition of the counterpart again. If there is visible gap, the phenomenon of misalignment should be corrected by adjusting the fastening nut. The hot-melt butt welding machine heating plate is first preheated to 210-220°C, and then the end of the PERT tube is melted, and the melting time is generally a wall thickness × 10 seconds. It should be noted here that the number of the temperature of the heating plate can only be used as a reference, and the number of indications of the heating plate may sometimes differ from the actual temperature and the quality of the plate. The design requirements of the hot melt are mainly to see that the curling of the tube end is not less than 1/10 of the wall thickness of the pipe. It is considered to be up to the standard if the two ends are completely fused together.
4, welding face the surface of the two hot melt surface (PERT tube and pert tube or PERT tube and PERT tube) have reached the requirements of welding, quickly remove the heating plate, and force the two ends into one. After the force is applied, the lock must be locked immediately to maintain a constant butt pressure at the interface until the interface temperature drops to ambient temperature. Then the pressure is released and the fixing device is removed. Note that the pipe cannot be moved during the cooling process. No external force can act on the tube. 5. After the machine is fixed, the appearance of the fusion joint is checked. The height and width of the counterfusion ring should be uniform and beautiful. The height is 2 to 4mm, and the width is 4 to 8mm.