RU2119114C1 - Method of manufacture of insulating insert - Google Patents

Abstract

FIELD: mechanical engineering manufacture of pipe joints used as members of cathodic protection against electrochemical corrosion. SUBSTANCE: monoblock tubular billet for tips is placed in winding device; load-bearing bush made from reinforced plastic material is formed on outer surface of billet. Tips and circular clearance between them are obtained after dismantling the tubular billet from winding device by machining, for example. EFFECT: low cost of manufacture. 2 cl, 2 dwg

Description

 The invention relates to mechanical engineering and can be used in the manufacture of pipe joints, which are elements of cathodic protection against electrochemical corrosion of pipelines, both general and special purposes, especially when underground laying them.

 A known method of manufacturing an electrically insulating insert (see French patent N 2109371, class F 16 L 17/00, 1970), consisting in the manufacture of two symmetrical flanges with nozzles for welding into the pipeline and circumferential holes for the bolts with subsequent placement of a sealing gasket between them rings of electrically insulating material, such as rubber.

 This method has a number of significant drawbacks, namely: a low value of volumetric electrical resistance, associated with a limitation of the thickness of the insulating ring, and therefore, reduced dielectric strength during breakdown, high cost associated with the use of expensive metal forgings.

 There is also known a method of manufacturing an insulating insert (see UK patent acc. Application N 1286480, 1968), including the manufacture of two metal endings with bead thickenings at the ends, followed by their coaxial connection with the placement of a ring of electrically insulating material, such as rubber, between them, and coverage of the endings with a sleeve having an internal protrusion, with the latter resting in the shoulder of one of the endings. In this case, the opposite end of the female sleeve is connected to the shoulder of the second ending by welding. This method can significantly reduce the cost of the manufactured sleeve, because eliminates the need for expensive rolled products and allows the production of bead thickenings from rolled steel.

 There is also a known method of manufacturing an electrically insulating insert (see British Patent Application No. 1347419, 1971), which includes manufacturing two metal tips with outer collars, installing the tips coaxially on a shaft with a clearance, installing the shaft in a winding device, filling the gap with an electrically insulating material, laying on the outer surface of the endings of the power sleeve from the layers of the reinforcing filler impregnated with a polymer binder, curing the binder, dismantling the endings and the power sleeve from the shaft.

 At the same time, a significant increase in the electrical resistance of the sleeve is achieved by increasing the length of the insulating ring, but the cost rises, since it is assumed that an expensive exact shaft is used to ensure the ends of the alignment and place them in the winding device. In addition, the method includes two labor-intensive operations: mounting the tips on the shaft and dismantling the finished insert from it.

 The technical result of the claimed method of manufacturing an electrically insulating sleeve is to reduce the cost and increase the accuracy of the bushings.

 The essence of the claimed invention lies in the fact that in the known method of manufacturing an electrically insulating insert, comprising obtaining two metal endings, the formation of an annular gap between their adjacent ends, the placement of the endings in the winding device, the formation on the outer surfaces of the ends of the power sleeve made of reinforced plastic and dismantling from the winding device , a monoblock tubular billet of the endings is installed in the winding device, on the outer surface of which The power sleeve is made of reinforced plastic, and the workpieces and the annular gap between them are obtained after dismantling the tubular workpiece from the winding device, for example, by machining.

 In addition, the annular gap between the tips is filled with a dielectric material, for example fiberglass.

 Obtaining the blanks of the endings in the form of a monoblock pipe eliminates the use of an expensive shaft and place them directly in the winding device, providing a high degree of alignment of the endings.

 Placing the one-piece tubular billet of the endings directly in the winding device and forming on its outer surface a power sleeve made of reinforced plastic eliminates the labor-intensive operations of assembling the endings and their dismantling from the shaft.

 Obtaining the endings and the annular gap between them by machining after the formation of the power sleeve and dismantling from the winding device allows you to provide the required accuracy of the position of the outer ends of the insert, which facilitates its installation in the pipeline.

 Filling the annular gap between the tips with a dielectric material, for example fiberglass, provides protection for the power sleeve made of reinforced plastic, and also allows to reduce the hydro- or gas-dynamic losses of the flow of the transported medium.

 The method is illustrated by drawings, where in FIG. 1 tubular billet endings of an insulating insert in a winding device; in FIG. 2 - insulating insert with an annular gap; in FIG. 3 - insulating insert with an annular gap filled with a dielectric material.

 The method is as follows. The tubular monoblock blank 1 (Fig. 1) of the endings 2, 3 (Fig. 2) with external thickenings 4, 5 is installed in the winding device 6 and laid on the outer surface of the blank 1 of the power sleeve 7 by winding the annular layers 8 of reinforced plastic filling the space between the thickenings 4, 5, laying the longitudinal layers 9 and winding the annular layers 10 of reinforced plastic to form the outer surfaces of the sleeve 7. Then, the tubular billet 1 is dismantled from the winding device 6, placed in a thermoele an insulating oven (not shown) and produce the plastic solidification by a known mode.

 After curing the plastic, the tubular tip 1 is placed in a turning cup (not shown in the drawing), its external ends 11, 12 are machined and the workpiece 1 is cut, forming an annular gap 13.

 The annular gap 13 can be filled with dielectric material 14 (Fig. 3), for example, cold cured fiberglass.

An example of a specific implementation. An electrically insulating insert was made for a transport gas pipeline with the following characteristics:
Conditional through diameter, mm - 700
Conditional operational pressure, MPa - 7.0
Outer diameter mm - 800
Electrical resistance, MΩ - 10.0
Operating temperature, ^o C - -50 ... + 100
We prepared a blank of 1 endings 2, 3 from a pipe 12X12H10T TU 14-3-1109-82, having machined the outer surface and welded thickenings 4, 5 from a rolled bar from steel 20 GOST 1050-88. The obtained preform 1 was installed in a KU 421 winding machine and the ring layers were wound from a rope РВМН10 GOST 17139-79, impregnated with a binder ETFM TU 92-932-2-211-88, then longitudinal layers 9 were manually laid from the same material and the ring layers were wound 10. After that, the workpiece was removed from the winding machine, placed in an ARP16 furnace and cured the plastic according to the regime:
raising the temperature to 90 ^o C for 1 h;
holding at 95 ^o C for 4 hours;
raising the temperature to 125 ^o C for 1 h;
holding at 130 ^o C for 5 hours;
raising the temperature to 160 ^o C for 1 h;
holding at 165 ^o C for 10 hours;
cooling to 70 ^o C for at least 6 hours;
cooling to 40 ^o C free.

After cooling the workpiece 1, it was installed in a KZH-16122F2 lathe and the ends 11 were machined, a groove 13 was cut through a width of 80 mm, then it was filled with fiberglass T-10-80 GOST 19170-73 impregnated with an epoxy binder of cold curing of the following composition, wt. h:
Compound KDA-1, TU6-69-13802-70 - 100
Hardener PEPA-1, TU6-02-594-85 - 10
and kept at room temperature for 24 hours. After that, the insert in a special device was checked for strength and tightness with a hydraulic pressure of 9.0 MPa, no damage and leaks were found.

 The cost of the manufactured insert was 11.2 million rubles.

 An insert was also made according to the prototype method, its cost was 13.1 million rubles, while the cost of the shaft for assembling the endings was 140 million rubles. (in prices as of October 1, 1995).

 The implementation of the proposed method allows to reduce the cost of the inserts by eliminating the operation of assembling the endings and dismantling the inserts from the shaft, as well as eliminating the need for the use and manufacture of the shaft, as such.

 In addition, the inventive method facilitates the installation of the insert into the pipeline through the use of a single monoblock tubular billet endings.

Claims (2)

 1. A method of manufacturing an insulating insert, including obtaining two metal endings, the formation of an annular gap between their adjacent ends, the placement of the endings in the winding device, the formation on the outer surfaces of the endings of the power sleeve made of reinforced plastic and dismantling from the winding device, characterized in that in the winding device establish a one-piece tubular billet of endings, on the outer surface of which a power sleeve of reinforced plastic is formed and the endings and the annular gap between them are obtained after dismantling the tubular workpiece from the winding device, for example, by machining.  2. The method according to claim 1, characterized in that the annular gap between the tips is filled with a dielectric material, for example fiberglass.

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