1, welding preparation
The preparation for welding is mainly to check whether the condition of the welding machine meets the working requirements. For example, check whether the fasteners in various parts of the machine are loose or loose; check whether the electrical connection of the whole machine is correct and reliable; check whether the hydraulic oil in the hydraulic tank is sufficient; confirm that the power supply matches the requirements of the machine; whether the heating plate meets the requirements (Whether the coating is damaged); trial operation of milling cutters and oil pump switches, etc.
Then insert the slips with the same pipe specifications into the rack; set the temperature of the heating plate to the welding temperature (the welding temperature of the polyethylene pipe is 200~230 °C), and wipe the heating plate with soft paper or cloth alcohol before heating. Surface, but be careful not to scratch the PTFE release layer.
Welding shall be carried out in accordance with the parameters of the welding process card. When necessary, it should be appropriately adjusted according to changes in weather, ambient temperature, etc. The main steps are as follows.
(1) Clean the dirt on both ends with a clean cloth. Place the tubing in the rack slips so that the length of the ends is equivalent (should be as short as possible, usually 25 to 30 mm, if the milling and heating requirements are met). If necessary, the outside of the pipe rack is lifted with the support so that the pipe axis is at the same height as the centerline of the frame and then fastened with the slips.
(2) Insert the milling cutter, first turn on the power switch of the milling cutter, then slowly close the welded ends of the two pipes, and apply appropriate pressure until there are continuous chips at both ends, remove the pressure, wait a moment, then exit the activity. Rack, turn off the power to the milling cutter. The chip thickness should be 0.5~1.0mm, and the chip thickness can be adjusted by adjusting the height of the milling cutter.
(3) Take out the milling cutter, close the ends of the two tubes and check the alignment of the two ends. The displacement of the two ends of the pipe should not exceed 10% of the thickness of the pipe or the larger of 1mm. The pipe straightness and the tightness can be corrected to some extent. When the pipe is closed, there is no obvious gap between the two ends of the pipe. The maximum width cannot exceed: 0.3mm (DN< 225mm), 0.5mm (225mm<DN<400mm) or 1.0mm (DN>400mm). If the above requirements are not met, they should be milled again until the above requirements are met.
(4) Measure the drag force (the frictional resistance of the moving fixture), this pressure should be superimposed on the process parameter pressure to get the actual use pressure. Also check if the heater plate temperature has reached the set value.
(5) After the temperature of the heating plate reaches the set value, put it into the frame and apply the specified pressure until the minimum curl on both sides reaches the specified width, and the pressure is reduced to the specified value (just keep the tube end face and the heating plate in contact) , to absorb heat.
(6) After the time is reached, the movable frame is retracted, the heating plate is quickly taken out, and then the two pipe ends are closed. The switching time should be as short as possible and cannot exceed the specified value. After cooling to the specified time, the pressure is released, the slips are released, and the connected pipes are taken out.