1, welding preparation
Welding preparation is mainly to check whether the condition of the welding machine meets the working requirements. Check whether the fasteners on each part of the machine are loose or loose; check whether the electrical circuit connection of the whole machine is correct and reliable; check whether the hydraulic oil in the hydraulic tank is sufficient; confirm the match between the power supply and the input requirements of the machine; if the heating plate meets the requirements (whether the coating is damaged); trial operation of milling cutters, oil pump switches, etc.
Then install the slip with the same pipe size into the rack; set the temperature of the hot plate to the welding temperature (the welding temperature of the polyethylene pipe is 200~230°C). Before heating, wipe the hot plate with soft paper or alcohol. The surface, but be careful not to scratch the PTFE anti-stick layer.
2, welding
Welding shall be performed in accordance with the parameters of the welding process card. When necessary, appropriate adjustments should be made according to changes in the weather, ambient temperature, etc. The main steps are as follows.
(1) Use a clean cloth to remove dirt from both ends. Place the tube in the rack slip so that the length of both ends protrudes (it should be as short as possible to meet the requirements of milling and heating, usually 25~30mm). If necessary, the parts other than the tube rack are lifted with support so that the axis of the tube is at the same height as the centerline of the rack and then fastened with slips.
(2) Insert the milling cutter, first open the power switch of the milling cutter, then slowly close the welding end of the two tubes and apply proper pressure until there are continuous chips on both ends, remove the pressure, wait for a moment, and then exit the activity Frame, turn off the cutter power. The chip thickness should be 0.5~1.0mm, and the chip thickness can be adjusted by adjusting the height of the milling insert. See below.
(3) Take out the milling cutter, close both ends and check the alignment. The amount of misalignment between the ends of the pipe should not exceed 10% of the thickness of the pipe or 1mm of the pipe. Adjustment of the straightness of the pipe and tightness of the slips can be corrected to a certain degree; there is no obvious gap between the two ends of the pipe when closing. The maximum width cannot exceed: 0.3mm (DN<225mm), 0.5mm (225mm400mm). If it does not meet the above requirements, it should be milled again until it meets the above requirements.
(4) Measure the drag force (frictional resistance of the moving jig). This pressure should be added to the process parameter pressure to get the actual working pressure. And check whether the heating plate temperature reaches the set value.
(5) After the temperature of the heating plate reaches the set value, it is placed in the frame and the specified pressure is applied until the minimum crimping on both sides reaches the specified width. When the pressure reaches the specified value, the pressure is reduced to the specified value (so that the end face of the tube is kept in contact with the heating plate) Heat absorption.
(6) After the time is up, retract the movable frame, quickly remove the heating plate, and then close the two pipe ends. The switching time should be as short as possible and cannot exceed the specified value. After cooling to the prescribed time, the pressure is relieved, the slip is released, and the connected pipe is taken out.
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