Heating element butt welding

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The butt welding (HS) after rules DVS applied 2207 Part. 1 It is used to connect plastic pipes made of semi-crystalline thermoplastic (e.g. polyethylene , polypropylene , polyvinylidene fluoride ) mainly in large dimensions (e.g. from 160 mm in diameter) and does not require any fittings or molded parts. The pipe ends are heated to the melting temperature and pressed together to create a connection.

A similar process is heating element socket welding , which is mainly used for smaller pipe dimensions. In contrast to heating element butt welding, sleeves are used here to connect the pipe ends, which are heated together with the pipe end before joining.

Welding process

DVS 2207-1 describes the exact workflow for the welding process. The welding cycle begins with the preparation of the surfaces to be joined and the insertion of the parts to be joined. After the mold halves have been closed, the parts to be joined are adjusted to the electrical heating element by melting them gently until they are completely in contact and can be heated well. If a sufficient melt layer has been created, the mold halves are quickly moved apart, the heating element moves out and the components are joined under pressure . This is followed by the cooling time , which must be waited for before the parts to be joined can be removed and reworked.

Advantages and disadvantages

The process produces a relatively high weld seam quality. The slow heating process, which is gentle on other processes, creates a thicker layer of melt. The cycle time is therefore quite long. Heating element welding is still known for its process reliability. Complex joining surfaces can be realized and small and large components can be welded.

application areas

The heated tool butt welding is u. a. used in gas and water supply. Here, plastic pipes with a diameter of OD 32 mm to OD 1200 mm are welded (OD = Outside Diameter). The DVS 2207-1 procedure is used by the certified welder according to the German Gas and Water Association DVGW GW 330. The GW 330 course is aimed at skilled workers from pipeline construction and supply companies, as well as at employees who can already demonstrate many years of professional experience in underground pipeline construction.

Pure DVS is used in container construction, ventilation construction, geothermal energy, in district heating supply and in the disposal sector. In DVS 2207-1, a further distinction is made according to DVS 2212-1 into subgroups (UG):

  • UG I-6.1 - I-6.2 - I-6.3 HS PE-HD ( polyethylene high density )
  • UG I-4.1 - I-4.2 HS PP-H; PP-R; PP-B ( polypropylene PP )
  • UG I-8 HS PVDF ( polyvinylidene fluoride PVDF )

Plastic welding license

The plastic welder with the license DVS 2207-1 with the corresponding subgroup is not allowed to weld in the public gas and water network. This is reserved for the plastic welder with the GW 330 license.

The extension test according to DVGW GW 330 must be carried out after one or three years in order to continue to be eligible for welding.

The extension test according to DVS 2207 must be carried out after one or two years in order to continue to be eligible for welding.

Sweat assessment

These HM connections are assessed in accordance with the DVS 2202 Part 1, assessment group I, II or III.

See also

literature

  • J. Wenner: Help for the production and assessment of heating element butt welds and electrofusion welds on thermoplastic pipe and pipeline parts . 2nd Edition. Dortmund 2012, ISBN 978-3-00-037602-3 (incl. Training DVD).

Web links

Individual evidence

  1. ↑ Pipeline system Fusiotherm® climatherm - pipeline systems made from Fusiolen® PP-R , p. 64f, aquatherm GmbH
  2. ↑ Pipeline system Fusiotherm® climatherm - pipeline systems made from Fusiolen® PP-R , p. 38ff, aquatherm GmbH
  3. ↑ a b Christian Bonten: Plastics technology introduction and basics. Hanser Verlag, 2014, ISBN 978-3-446-44093-7 .