Assembly
Assembly
enough to withstand the force of the welding process. The pipe clamps can be used to make an oval pipe round (but they will also do the opposite). The tension must there fore not be either too high or too low. Welding itself is carried out as follows: 1. Check that the hot plate is up to temperature. 2. Clamp the pipes and use the trimmer on the ends. Stop the trimmer only when the pipes no longer contact the blade; this prevents "hooking". 3. Check that the pipe ends match precisely. If necessary clamp and trim again. 4. Press the pipe ends against the hot plate with a brief application of high pressure, then continue with application of very low pressure until a ridge of 1 mm has formed. 5. Quickly remove the hot plate and slowly increase the welding pressure (see the table on the machine for the welding pressure). 6. Hold the welding pressure steady and allow the weld to cool. 7. Remove the joint and inspect the weld. An irregular ridged seam should be rejected. Electrical spigot welding HDPE accessories are provided with spigot ends to allow butt and sleeve welding. The spigot ends are provided with low irregularities (ribbing) and the
welding sleeve has projections to allow their exact distance apart to be determined. This is particularly important with prefabrication. Welding equipment is required. Also required are: - A pipe cutter or a saw with teeth set wide. - Clean, lint-free cloths or white crepe paper (not printed). - Emery cloth, grit 40. - A scraper or knife for de-burring.
plastic layers together. However this is only possible if the HDPE surface is completely free from contamination. Pipes in storage develop an oxidised layer in production and storage which impedes welding. This must be removed before welding by cutting, scraping or abrasion, followed by cleaning. Furthermore the material must be free of moisture and must not move during and for a brief period after the welding. If these conditions are not met there will be adhesion but without fusion. The weld will be weaker and high loading or bending may later cause leaks. In order to achieve an even weld all round the pipe must be stress-free. Bent or oval pipes may require support. The components to be welded must be fixed with respect to one another, particularly when welding accessories and short sections of pipe. Preparation work Select the appropriate welding equip- ment. Check that the welding equipment is suitable for the diameter to be welded. The welding equipment must be protected from moisture and dirt. The voltage required is 220 Volts. In case of doubt the welding time can be checked. Full instructions for use should be provided with the welding equipment. Welding equipment, tools and pipework components must be in good condition. That means: - The welding equipment must be regularly inspected and the welding time must be correct. - The contact shoes on the welding cables must not be oxidised. - The contacts on the electro-weld sockets must be clean. - The pipe end to be welded must not be excessively oval. - The cloths used must be clean and lint free.
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3. Check that the pipe ends match precisely. If necessary clamp and trim again.
1. Check that the hot plate is up to temperature.
2. Clamp the pipes and use the trimmer on the ends. Stop the trimmer only when the pipes no longer contact the blade; this prevents "hooking".
- Felt tip pen or crayon. - Tape measure or ruler. - The electro-weld sleeve.
The HDPE electro-weld sleeve is provi- ded with 2 socket ends which can be welded in a single operation. The welding equipment sends current through the resistance wires in the electro-weld socket for a set period. Both electro-weld sockets are welded at the same time. The electro-weld socket has stops on the interior. In order to use the socket as a slide-on collar the stops can easily be remo- ved with a knife or screwdriver. The socket has two contact pins on the outside for connection of the welding equipment. There are also two wel- ding indicators which appear during and after the welding operation. These indicate that the welding temperature has been reached and that the welding pressure has been applied. They do not however give any indication of the quality of the weld. The quality of the weld is dependent on a great many other factors. See "Principles and Preparation". Principles of electro-welded sockets in HDPE During welding the surface of the interior of the socket and the exterior of the pipe are brought to a plastic state. Expansion of the pipe and shrinkage of the socket (the shrinkage is built in during manufacture) fuse the
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6. Hold the welding pressure steady and allow the weld to cool.
5. Quickly remove the hot plate and slow- ly increase the welding pressure (see the table on the machine for the wel- ding pressure).
4. Press the pipe ends against the hot plate by briefly applying a high pres- sure. Continue heating with very low pressure until an upstand of 1 mm has formed.
Before welding: A. The hot plate temperature should be 210° C. B. The hot plate must be clean and free of grease; clean as necessary with a clean cloth and alcohol. C. Ensure that the two pipe brackets and the two pipe supports are correctly aligned. This can be achieved by clamping 1 section of pipe in both clamps and both pipe supports. If necessary adjust the two pipe supports until they are correctly aligned with the pipe. D. Both pipe clamps must be adjusted so that they hold the pipe tightly enough to withstand the force of the welding process. The pipe clamps can be used to make an oval pipe round (but they will also do the opposite). The tension must therefore not be either too high or too low.
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7. Remove the joint and inspect the weld. An irregular weld seam should be rejected.
Most important data for hot plate welding of waste pipework:
warming up time
ridge height
welding pressure application time
cooling with welding force applied
(at very low pressure) (up to 160 mm)
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45 - 70 sec
1mm
5 -6 sec
6 - 10 min
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