RU2810859C1 - Method of socket welding of polymer pipes at low air temperatures - Google Patents

Abstract

FIELD: welding of polymer pipes.

SUBSTANCE: invention can be used for socket welding of polyethylene pipes at ambient temperatures lower than those provided for in regulatory documents. Before welding, a separate heating device is installed on the pipes and fittings at the site of the future welded joint. A separate heating device consists of a flexible material such as silicone, equipped with a temperature sensor, controller and power wires. A certain voltage is applied to the heating device and the internal and external walls of the pipes and fittings are preheated. Next, a certain free cooling time is maintained (a process pause) to level the temperature field in the welding area. During the process pause, part of the heating device is removed from the inner walls of the parts being welded. Part of the device on the outer walls of the fitting remains in place. The welding process is then started through the socket terminals using a standard welding machine. After welding, a separate heating device maintains the cooling rate of the welded joint, as at permissible ambient temperatures.

EFFECT: dynamics of the temperature field in the heat-affected zone during welding and cooling of the welded joint at any low temperatures is forcibly maintained close to the temperature field during welding in a regulated temperature range, taking into account the ambient temperature.

1 cl, 3 dwg

Description

Field to which the invention relates

The invention relates to welding of polymer pipes and can be used for sleeve welding of polymer pipes at low ambient temperatures.

State of the art

A known technical solution (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 p.), in which, with a wider interval ambient temperatures than from minus 15 °C to plus 45 °C, welding work is recommended to be performed in rooms (shelters) that ensure compliance with the specified temperature range (clause 6.48). The disadvantage of this method is that it is labor intensive and takes a lot of time to build the structure and to achieve the regulated air temperature inside the structure and at the ends of the polymer pipes being welded.

The closest is the technical solution (2. Pat. 2450202. Method of sleeve welding of polymer pipes. Published 05/10/2012, Bulletin No. 13), in which during the welding process at low air temperatures (below minus 15 ºС) the method of preheating the thermal zone is used influence of the welded joint of the coupling (fitting) and pipe by supplying voltage to the embedded heater of the fitting with a separate power source, and after welding, cooling of the welded joint is carried out under a layer of thermal insulation. Heating is carried out until the temperature of the melting zone is reached from the regulated temperature range, and the reading of the temperature sensor of the welding machine, based on which welding is performed, is maintained equal to the heating temperature of the heat-affected zone of the welded joint. The disadvantage of the technical solution is the need to use an additional powerful power source and thermal insulation of various thicknesses and sizes for different ambient temperatures and pipe sizes, and also that it is necessary to artificially maintain the temperature for the standard temperature sensor of the welding machine equal to the value of the temperature heated in the heat-affected zone of the welded joint and use of thermal insulation when cooling a welded joint.

Disclosure of the invention

The objective of the present invention is to simplify the welding of polymer pipes at ambient temperatures below the regulated ones.

The technical result achieved when solving the problem is that at any low temperatures and coupling diameters, along with a standard welding machine, a separate heating device is used, consisting of a non-freezing material such as silicone, a temperature sensor and a controller. A separate heating device preheats the welded parts before welding and maintains the cooling rate of the welded joint at the corresponding cooling rate at a regulated ambient temperature.

Essential features characterizing the invention.

Restrictive: welding is carried out by installing and securing the ends of the pipes to be welded in the clamps of the centering device with simultaneous seating of the part (coupling/fitting) with an embedded heater, connecting the part with an embedded heater to the welding machine, and starting the welding process.

Distinctive: when socket welding of polymer pipes at air temperatures below the regulated ones, before assembling the joint, a separate heating device is installed on the fitting and the welded ends of the pipes. A separate heating device is controlled by a microcontroller, which contains a program that allows preheating throughout the entire area from the inner and outer walls of the welded coupling and pipes in the melting area and leveling until the temperature reaches the permissible range for welding, as well as adjusting the required cooling rate of the welded joint after welding Since the mode of the welding process depends, in addition to the barcode data of the part, also on the ambient temperature, to start the welding process, the temperature value of the heat-affected zone of the welded joint before welding is set for the temperature sensor of the welding machine.

Brief description of drawings

In fig. Figure 1 shows a welded coupling joint with a separate heating device installed before welding. In fig. Figure 2 shows a separate heating device during welding. In fig. 3 shows a separate heating device. 1 - polymer pipes; 2 - coupling with embedded heater; 3 - embedded heater; 4 - separate heating device; 5 - temperature sensor; 6 - terminals of the embedded heater; 7 - indicator; 8 - heating device controller; 9 - power wires for the heating device; 10 - temperature sensor wire.

Carrying out the invention

The method is carried out as follows. Before welding at low ambient temperatures, the pipes to be welded 1 and the coupling 2 are assembled. The assembly includes such activities as: cleaning and scraping of contaminants, installation and fastening of the ends of the pipes to be welded and the coupling with an embedded heater 3 in the clamps of the centering device and connection to the welding machine couplings through terminals 6. Before assembly, a separate heating device 4 with a temperature sensor 5 and power wires 9 is installed on the coupling and pipe ends. Using a smartphone with a special mobile application connected via radio communication with the heating device controller, the coupling barcode is read to calculate preheating parameters and controlled cooling. After calculating the parameters, preheating of the welded parts with a heating device begins. The pipes and couplings being welded are heated from all sides, i.e. from internal and external walls. After the end of preheating, time is maintained (technological pause) to achieve a more uniform temperature in the area of fusion of the coupling and pipes. During a process pause, a separate heating device is removed from the ends of the pipes and the inner wall of the fitting. The heating device remains on the outer wall of the fitting. The welded joint is being assembled. Then, the bar code is scanned with the reading pencil of the welding machine and welding is started, while the temperature sensor is in an environment where the temperature is maintained at a temperature value within the permissible range. Next, the welding machine performs a standard weld, while a separate heating device remains wrapped over the welded joint. After welding, the cooling process is controlled by a separate heating device to maintain the specified cooling rate. The parameters for preheating, technological pause and polymer cooling are pre-set into the heating device program in the form of formulas in which the variables are data from the barcodes of the fittings and the ambient air temperature.

Claims (1)

A method of sleeve welding of polymer pipes, which consists in the fact that at low air temperatures welding is carried out as at regulated temperatures by applying a certain voltage for preheating from the internal and external walls of the welded parts before welding and controlled cooling of the welded joint after welding, characterized in that a separate heating device is used, consisting of a flexible material such as silicone, equipped with a temperature sensor, controller and power wires, which allows maintaining the required temperature in the welded joint area.

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