RU2457449C1 - Method of testing polymer tube weld ring joint - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: weld seam durability is determined. Test machine clamps draw-apart speed makes 20-50 mm/min. Specimens of ring weld joints with flaws made before welding are tested. Area of flaws makes half the welded area.

EFFECT: qualitative determination of weld joint durability.

2 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of testing a sleeve welded joint of polymer pipes and can be used to determine the strength of the welded joint of polymer pipes produced under various welding conditions and conditions.

State of the art

A technical solution is known (1. Design and construction of gas pipelines from polyethylene pipes and reconstruction of worn-out gas pipelines SP 42-103-2003. - Official publication. - M .: ZAO POLIMERGAZ, 2004. - 84 pp.), In which, for the purpose of determining the quality of the coupling welded joint, the prepared sample segment is installed between the crimp plates of the press. Then, the crimping plates are brought together until the distance between them is reduced to twice the pipe wall thickness. After removing the load, the sample is removed from the press and visually inspected, determining the presence of separation of the pipe from the coupling. For each sample, the percentage of separation is determined. The disadvantage of this technical solution is that it does not determine the strength of the welded joint along the seam in quantitative terms.

The closest is the technical solution (2. ISO 13954: 97 Plastics pipes and fittings - Peel decohesion test ibr polyethylene electrofusion assemblies), in which the couplings of welded joints are stretched on a tensile testing machine, fixing the main pipe material on one side and the electrofusion on the other. The disadvantage of this method is that the method is applicable for joints with a nominal external diameter greater than or equal to 90 mm, and, as a rule, failure occurs not by weld, but by pipe material. With a small thickness of the pipe wall, the destruction does not occur in the fusion zone, but in the region of the main pipe material, or in the region of the coupling material. If the sample is destroyed by the pipe material, it is considered that the welded joint is stronger than the pipe material, so that the strength of the welded joint is determined qualitatively.

Disclosure of invention

The task of the invention is the development of a simple method for determining the strength of the coupling welded joint in quantitative terms.

The technical result obtained by the implementation of the invention is to determine the strength of the coupling welded joint in the welding zone.

The essential features characterizing the invention.

Restrictive: tests are carried out at a speed of separation of the clamps of the testing machine (20 ÷ 50) mm / min. During the test, the breaking stress at break of the weld is determined.

Distinctive: before welding, a defect is applied to the place of the future weld, which prevents complete welding of surfaces over the entire area. The defect is applied in such a way that its width is half the width of the weld seam, regardless of the location of the defective (non-welded) surface.

It is known that before assembly and welding, the ends of the pipes are thoroughly cleaned and wiped of all contaminants. After cleaning the ends, mechanical cleaning (scrubbing) is performed. This operation is due to the fact that an oxide layer forms on the surface of the pipes being welded, which negatively affects the quality of the welded joint. To ensure good quality of the welded joint, a clean surface of the welded parts is required.

Brief Description of the Drawings

Figure 1 shows the option of applying the defect to the welding area of the polymer pipe with the width of the test sample 10 mm Figure 2 shows samples of the sleeve welded joint of polymer pipes for testing for delamination with different positions of the defective area on the test sample (heating coil not shown).

The implementation of the invention

The method is as follows. Before socket welding, cleaning and scraping of contaminants of the surfaces to be welded, installation and fastening of the ends of the polymer pipes to be welded in the clamps of the centering device are performed. Before fitting the coupling on the prepared ends of the polymer pipes 1 with a diameter of d (Fig. 1), a quick-drying substance, such as a dye pen, is applied, so that in the manufacture of the test sample, the width of the applied substance 2 is equal to the width of the actually welded area of the test sample (Fig. 2). Next, the current leads from the welding machine are connected to the terminals of the coupling. The reading code of the welding machine reads the bar code and starts welding. After starting, welding of the connected parts takes place automatically. After 24 hours, samples are prepared for delamination tests, so that the width of the applied defect is equal to half the width of the sample. The test is carried out at a speed of separation of the clamps of the testing machine (20 ÷ 50) mm / min.

Example. Before conducting socket welding, according to SP 42-103-2003, the oxide layer is removed from the ends of the PE100 SDR11 63 × 5.8 polyethylene pipes to be welded, after which a felt-tip dye (defect) is applied on them with strips of 5 mm wide and a length l greater than half the height (width) of the coupling h (figure 1). Further, the ends of the pipes 1, excluding turns; inserted into the coupling, and welding is performed. 24 hours after welding, samples 5 are prepared with an opening for loading 4 in the coupling 3. The width of the samples ready for testing is 10 mm. Moreover, regardless of where the defective section 2 will be located, its width will be 5 mm, i.e. half of the welded area will be defective. Then, delamination tests are carried out at a speed of separation of the clamps of the testing machine (20 ÷ 50) mm / min. Since, due to the previously applied defect, the welding zone occupies half the area of the sample, the delamination occurs precisely along the fusion zone.

Thus, the collapse of the coupling weld occurs in the welding zone, which allows you to determine the strength of the weld produced in a particular mode.

Claims (1)

A method of testing a sleeve welded joint of polymer pipes to determine the strength of the weld at a sliding speed of the clamps of the testing machine 20 ÷ 50 mm / min, characterized in that samples of sleeve welded joints with defects previously applied before welding, the area of which is half the welded area, are tested.

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