Welded PFA pipes and fittings with DN10, 20, 25, 50 (1/4, 3/4, 1, 2) specifications for chemical pipelines are welded by special PFA welding machine. The connection with equipment is usually flanged.
Such pipes are generally used from receiving devices to receiving tanks of chemicals to supplying devices.
(1) The system consists of a receiving device on the outer wall of the chemical room, a receiving tank, a supply device and a chemical supply pipeline in the chemical room. See Figure 8-10. A. Chemicals receiving device is set in the chemical room, and a receiving window is set on the outside wall to receive chemicals directly from the outdoor chemical tanker and inject them into the drug storage tank; B. Standardized chemical receiving tank in the air shower room is placed on the underground basis of the chemical room to store chemicals; C. Chemicals supplying device is placed in the chemical room to supply chemicals to the use equipment; D. Chemical supply pipeline, from receiving device to chemical storage tank, and then from chemical storage tank to chemical supply device. It consists of an outer sleeve and an inner tube, both of which are transparent PVC tubes. The inner tube consists of a welded PFA tube and a PFA elbow.
(2) Installation of sequential receiving device, receiving tank and supplying device in place-one frame fabrication and installation-one inner pipe welding, outer casing bonding, double air shower chamber-one inner pipe elbow welding-one outer casing elbow welding-one inner tube pressure testing-one outer casing pressure testing-one cleaning test operation equipment installation in place must meet the design requirements and relevant standards and specifications, and the equipment in place. After acceptance, the piping work can be carried out. When the inner pipe is welded, the outer sleeve is almost installed synchronously. When the inner pipe is connected with the straight pipe, the outer sleeve is also sleeved outside the inner pipe. Reserve only at the elbow for temporary non-installation. The direct pipe connection of the outer casing is a direct two-way bonding, and the specific requirements are as described above. The elbow of the outer sleeve is R:1.5D of the finished socket elbow. After welding the elbow of the inner sleeve, the elbow of the outer sleeve is symmetrically cut into two halves, and then the elbow of the inner sleeve of the button is bonded with both ends of the outer sleeve. The hot air welding torch and the PVC welding rod are used to weld the split seam, and the method is the same as that of the ordinary PVC plastic hot air welding. Before welding straight pipe, elbow and flange of inner pipe, the two ports to be welded are fixed in the fixture of welding equipment. A double-sided heating plate is set in the gap between the two ends. When heating, the heating plate does not contact with the end face of the pipe, and the two ends reach the melting temperature through thermal radiation. This operation is controlled by the operator visually, to judge whether the end face has melted or not, when the melting process is completed. When appropriate, remove the heating plate immediately. Quickly make the two ends contact and exert certain pressure to make the pipe end melt flow. It can form mixing and welding. When cooled, the original contact surface disappears. At the same time, the two ends are combined and the weld seam remains unchanged.
The main points for attention in welding are as follows. A. Welding places should be clean, dry and well ventilated (harmful gases are produced when heated). B. Do not contaminate any side of the heating plate because it touches the end of the tube during heating. Avoid touching the end of the tube. C. The special cutter with ratchet wheel should be used to cut the pipe. D. During welding, the interface should not be dislocated. E. Keep the PFA tube clean all the time. Pipeline and equipment connection, generally using flange connection, flange and pipe welding connection, as mentioned above, pipe flange and equipment interface flange connection method is the same as common flange connection method.
