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2020 №11 (02) DOI of Article
10.37434/tpwj2020.11.03
2020 №11 (04)

The Paton Welding Journal 2020 #11
TPWJ, 2020, #11, 12-17 pages

Quality and operational characteristics of welded joints of pipes of different-type polyethylenes

Authors
M.O. Kovalchuk, M.V. Iurzhenko, V.L. Demchenko, M.G. Korab and R.V. Kolisnyk
E.O. Paton Electric Welding Institute of the NAS of Ukraine 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

Abstract
Polyethylene raw materials used for production of polyethylene pipes are constantly being improved. At the beginning of the construction of plastic pipelines, the so-called low pressure polyethylene, currently known as PE-63 grade was used. Subsequently, new, more advanced types of raw materials, which represent a copolymer of polyethylene with hexane, were developed. Today, almost all pressure pipes are made of PE-80 and PE-100 grades of polyethylenes. However, during the repair and reconstruction of plastic pipelines, there is an urgent problem of joining pipes of PE-63, which have been operated for a long time, with new pipes made of polyethylenes of grades PE-80 and PE-100. In the paper, complex investigations of thermophysical properties of technical polyethylenes were carried out and significant differences were revealed, which should be taken into account during the repair of polymer pipelines. Experimental welding of pipe specimens from both single- as well as different-type polyethylenes was carried out. Morphological and mechanical studies of welded joints of polyethylene pipes of grades PE-63, PE-80, and PE-100 were performed. According to the results of investigations, the influence of their thermophysical properties and parameters of the welding process on the morphological structure and quality of welded joints of different-type polyethylenes was determined. Mathematical modeling of temperature fields during butt welding was carried out. A two-zone heating tool for butt welding of pipes with an outer diameter of up to 110 mm of different-type polyethylenes of pipe grades PE-63 and PE-80, PE-100 using a heated tool was designed and created. In order to test an experimental specimen of a two-zone heating tool, a series of experiments were carried out, which showed an improvement in the strength characteristics of the produced welded joints. 8 Ref., 4 Tables, 10 Figures.
Keywords: polyethylene raw material of different types, polyethylene pipes, welded joints

Received 13.10.2020

References

1. Kimelblat, V.I., Volkov, I.V., Glukhov, V.V. (2020) Optimization of resistance butt welding. Accounting for the properties of polymers. Polimernye Truby, 28(2), 32–36 [in Russian].
2. Komarov, G.V. (2015) Composition and properties of polymer materials affecting their weldability. Polimernye Materialy, 9, 44‒48 [in Russian].
3. GOST 16338‒85: Low-pressure polyethylene. Specifications [in Russian].
4. GOST R 50838–95: Polyethylene pipes for gas pipelines. Specifications [in Russian].
5. DSTU B V. 2.7-73–98: Polyethylene pipes for the supply of gaseous fuel. Specifications [in Ukrainian].
6. DSTU B V.2.7-151:2008: Polyethylene pipes for the supply of cold water. Specifications [in Ukrainian].
7. DBN V. 2.5–41:2009: Gas pipelines from polyethylene pipes. Design. Construction [in Ukrainian].
8. DSTU EN12814–2:2018: Testing of welded joints of thermoplastics semi-finished products. Pt 2: Tensile test [in Ukrainian].

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