RU2757742C2 - Fitting assembly method - Google Patents

Abstract

FIELD: pipeline transport.

SUBSTANCE: fitting assembly method refers to pipeline transport and pipe fittings made of pipes of different materials; it is intended for tapping gas pipelines without lowering the pressure. An integral fitting connection consists of a polyethylene pipe, a formed bell, a steel pipe with round profile thread, a threaded flange and a coupling mounted on the outer surface of the polyethylene pipe covering a working part of the steel pipe, while a working part of the polyethylene pipe is made in the form of a bell. The latter is connected to the working part of the pipe of the steel fitting by heating the polyethylene pipe with the bell and the steel part of the fitting and then winding the working part of the bell of the polyethylene pipe on the thread on the working part of the steel fitting. The fitting is assembled using a device that combines a mechanism for obtaining thread with mandrels designed to preserve internal and external dimensions of a heated polyethylene pipe. Fitting with a permanent connection is obtained that can withstand effects of dynamic loads, shocks, vibrations and torsion.

EFFECT: invention makes it possible to increase the degree of reliability of the tightness of the polyethylene - steel fitting connection.

1 cl, 2 dwg

Description

The invention "A method for assembling a fitting and a device" relates to pipeline transport and pipe fittings from pipes of different materials and is intended for the manufacture of a fitting for tapping gas pipelines without lowering the pressure in polyethylene pipelines.

The known "Method of permanent connection of polyethylene-steel pipes and permanent connection of pipes" (RU, patent 2127394, cl. F16L 13/007, F16L 47/00 published on 03/10/1999), which consists in the fact that before assembling the connection, the working part of the steel pipe and the coupling is heated, the connection is carried out by installing the working part of the polyethylene pipe on the working part of the steel pipe and the resulting connection is cooled in water, while a bell is pre-formed on the working part of the polyethylene pipe, and the coupling is pressed onto the bell after connecting the pipes, the length of the coupling exceeds the length of the working part of the pipes , while the coupling is installed in such a way that its ends protrude beyond the working part of the pipe, and polyethylene with a linear expansion coefficient equal to the linear expansion coefficient of the polyethylene pipe is used as the coupling material.

The disadvantage of this method is the impossibility of making a fitting for the production of tie-ins without reducing the pressure in the network, since it is impossible to ensure the necessary alignment of the pipe parts of the product, in addition, the one-piece connection made by the proposed method is not sufficiently stable to work under dynamic loads, vibration and torsion.

The technical objective of the invention is to eliminate the disadvantages inherent in the previous methods of assembling a tie-in fitting with a permanent connection and a transition from steel to polyethylene, while it is required to provide equal cross-sections at the pipe junction necessary for the passage of the cutting tool, to create a connection that is resistant to dynamic loads, vibration and torsion, the necessary force of pressing the polyethylene pipe to the steel pipe, which should increase the degree of reliability of the tightness of the polyethylene-steel connection and the strengthening of the connection due to the overlap of the working section of the connection by the coupling. In addition, it is necessary to ensure the required dimensional accuracy and alignment of the pipe parts of the joint. The task is achieved by the fact that before assembly, the connection of the working part of the steel pipe and the coupling is heated, the connection is carried out by installing the working part of the polyethylene pipe on the working part of the steel pipe and the resulting connection is cooled, while a bell is pre-formed on the working part of the polyethylene pipe, and the coupling is pressed onto the socket after connecting the pipes, the length of the coupling exceeds the length of the working part of the pipes, while the coupling is installed in such a way that its ends protrude beyond the working part of the pipe, and as the material of the coupling, polyethylene is used with a coefficient of linear expansion equal to the coefficient of linear expansion of a polyethylene pipe, which differs the fact that the socket of the polyethylene pipe is cooled after molding in air, a steel flange is made and a threaded hole is made in it for seating the plug, on the working part of the steel pipe of the fitting, the thread of the round profile is cut, the flange and the steel pipe of the fitting are connected by welding, providing the necessary alignment, the working part of the socket of the polyethylene pipe is connected to the thread on the working part of the steel pipe by heating the polyethylene pipe with the socket and the steel part of the pipe, followed by screwing the working part of the socket onto the thread of the working part of the steel pipe, after the assembly is completed, the connection is cooled in air, while a stop is installed on the steel pipe of the fitting to prevent excessive movement of the coupling when it is pressed onto the socket of the polyethylene pipe.

The essence of the invention is illustrated by drawings: FIG. 1 shows an assembled fitting with a polyethylene-steel connection; in fig. 2 shows the assembly process of the permanent connection.

List of assemblies and parts with digital designation:

1 - polyethylene pipe;

2 - bell;

3 - working part of the socket;

4 - clutch;

5 - steel pipe;

6 - the working part of the steel pipe;

7 - flange;

8 - stop for moving the clutch.

IMPLEMENTATION OF THE FITTING ASSEMBLY METHOD

The pipes are connected by the proposed method as follows. Before assembling the connection, a socket 2 is formed from the working part of the polyethylene pipe 1.

For this, the working part 3 of the polyethylene pipe 1 is kept in glycerin at a temperature from 125 ° C to 135 °. Exposure time 15 min. The heated part intended for the device of the socket 2 of the pipe 1 is pressed onto a mandrel, held under load and, together with the mandrel, cooled in air.

The steel part of the fitting is pre-made in compliance with the required dimensional accuracy, the alignment of the parts to be connected and the tightness of the connection between the flange 7 and the steel pipe 6. A round profile thread is cut on the working part of the steel pipe 5. Since round threads of general purpose, due to smooth transitions in the contour, have a relatively low concentration of stresses. Therefore, they are used for parts subject to dynamic loads, shocks and vibrations. A round thread in comparison with a thrust one has increased strength due to the absence of sharp corners on the turns, ease of screwing due to the large angle of the helix rise, it takes shock loads well, and is distinguished by a relatively high wear resistance.

The assembled unit 2 is heated in an oven to t = 300 ° C before joining. They are removed from the oven, installed with a flange 7, for example, on the working table of a vertical drilling machine, centered and attached to the working table using fasteners, and prepared for connection.

Simultaneously with node 2, node 1 - a polyethylene pipe 1 with a formed bell 2 is placed in a container with glycerin, kept at a temperature of 125 ° C to 135 ° C for 15 minutes. At the end of heating, remove node 1 from the container and connect node 1 to node 2 by screwing the working part of the socket 3 of the polyethylene pipe 1 of node 1 onto the working part of the steel pipe 5 of node 2. After complete cooling in air, the fasteners on the machine table are removed. At the end of the manufacture of the connection, they begin to install the coupling 4. On the steel pipe 6, set the stop for moving the coupling 8. The coupling 4 is heated in glycerin, installed on the polyethylene bell 2 and pressed, while the coupling 4 is installed on the bell 2 so that its surface overlaps the ends of the bell 2 polyethylene pipe 1 and the section of the steel pipe 6 emerging from the joint due to the fact that its length exceeds the length of the working part of the steel pipe 5, and the working part of the bell 3. Such installation of the coupling 4 provides reinforcement of the polyethylene bell and prevents damage from the cut (end) steel pipe under deformation and bending. The finished compound is left to cool in air. After cooling, remove the stop 8. After that, the product is inspected, the deformed ends are cut off if necessary.

Claims (1)

A method for assembling a fitting, which consists in the fact that before assembling the joint, the working part of the steel pipe and the coupling are heated, the connection is carried out by installing the working part of the polyethylene pipe on the working part of the steel pipe and the resulting connection is cooled, while a bell is pre-formed on the working part of the polyethylene pipe, and the coupling is pressed onto the socket after connecting the pipes, the length of the coupling exceeds the length of the working part of the pipes, while the coupling is installed in such a way that its ends protrude beyond the working part of the pipe, and polyethylene with a linear expansion coefficient equal to the linear expansion coefficient of polyethylene is used as the coupling material pipes, characterized in that the socket of the polyethylene pipe is cooled after molding in air, a steel flange is made and a threaded hole is made in it for seating a plug, a thread of a round profile is cut on the working part of the steel pipe of the fitting, the flange and the steel pipe of the fitting are connected by welding, providing In order to achieve the necessary alignment, the working part of the socket of the polyethylene pipe is connected to the thread on the working part of the steel pipe by heating the polyethylene pipe with the socket and the steel part of the pipe, followed by screwing the working part of the socket onto the thread of the working part of the steel pipe, after the assembly is completed, the connection is cooled in air, when At the same time, a stop is installed on the steel pipe of the fitting to prevent excessive movement of the coupling when it is pressed onto the socket of the polyethylene pipe.

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