RU206794U1 - EXPANSION HEAD FOR CALIBRATING LARGE DIAMETER PIPES - Google Patents

Abstract

The utility model relates to the production of longitudinal welded pipes of large diameter. The state of the art contains the design of a hydromechanical expander - shown in Fig. 1. The axial force is created by a hydraulic cylinder (item 2) fixed on the frame (item 3), the rod of which (item 4) is connected to a wedge pyramid, along the edges of which sliders slide (item 7) resting on the housing of the pipe expansion the head (pos. 5) connected to the rod (pos. 6), the sliders move together with the punches (pos. 10) and the wedges of the pyramid (pos. 9) fixed on them. The "weak" element of the expansion head is the contact between the slide and the pyramid ... Each face has a guiding T-groove - shown in FIG. 2, which forms additional surfaces, the wear of which can lead to seizure. The technical problem of eliminating T-shaped slots is solved as follows: the central pyramid (pos. 1 in Fig. 3) is located between two end discs (pos. 2), fixed on the discs guide rods (pos. 3) parallel to the faces of the pyramid and passing through the holes in the sliders (pos. 4).

Description

The utility model relates to the field of metal forming, in particular, to the production of longitudinal welded large diameter pipes. It is also possible to use it in chemical and petroleum engineering for the calibration of round shells of welded vessels for various purposes.

Shaping processes, including welding, used in the manufacture of large diameter longitudinal welded pipes, regardless of the forming method - UOE, JCOE, three-roll forming - do not provide an ideal cylindrical shape of the pipe. It is characteristic that each individual operation, starting with the machining of flat sheet edges (and even earlier for UOE and JCOE processes, from the welding of technological strips), "contributes" to the distortion of the pipe geometry. In this case, deviations from the cylindrical shape resulting from the performance of each operation never compensate each other, but only add up. This is due to a number of factors that cannot be taken into account: the scatter of the mechanical properties of the original sheet (both within the same batch / melt and over the sheet area), insufficient tool park, the current state of the equipment, tool wear, etc. Taking this into account, with all production methods longitudinal welded pipes of large diameter - from 457 to 1625 mm (18 ÷ 64 inches) in diameter, the final shaping operation is the sizing of the pipe along the entire length. The most commonly used method of such calibration is the step-by-step expansion of the pipe using a hydromechanical expander.

The current state of the art contains a generally accepted and highly rational design and principle of operation of a hydromechanical expander. FIG. 1 shows the required elements of a hydromechanical tube expander. Axial force, then converted into radial, is created by a hydraulic power cylinder (item 2), fixed on a rigid frame (item 3). The rod of the hydraulic power cylinder (pos. 4), located inside the rod (pos. 6), is rigidly connected to the wedge pyramid, along the edges of which sliders slide (pos. 7) during movement. The sliders themselves in the axial direction remain stationary, resting on the body of the expansion head (item 5), connected to the rod (item 6), and are movable in the radial direction due to radial sliding relative to the body and end ring (item 8). The sliders are brought into working movement together with punches fixed on them (pos. 10), which, in fact, carry out the distribution (expansion) of the pipe (pos. 1), by the wedges of the pyramid (pos. 9). It is characteristic that the distribution (working stroke) is carried out by the reverse pulling movement of the rod. Otherwise, axial bending of the rod is possible, which is quite possible, since its length is large enough and amounts to the sum of the maximum length of the pipes being processed and the overall length of the expansion head. Three additional mandatory elements of the expander design: retractable stand (pos. 11), designed to prevent bending of the rod and stem under the action of gravity in the "idle" position, when the inner surface of the pipe does not come into contact with the support roller of the head (pos. 12) - this is the second optional element and the stem guides (key 13) to prevent stem bending by adding the stem and stem bending resistance. Differences in the design of large diameter pipe expanders from different developers relate mainly to devices designed for feeding and positioning the pipe.

When further considering the possible options for the design of the expander, one should take into account the conventional conventional division of the expander into main nodes. It is customary to highlight:

The expander pipe head is a replaceable unit, the support dimensions of which depend on the pipe diameter. Typically, one expansion head is designed to expand a fairly narrow range of pipe diameters. The pipe expansion head consists of: a body (pos. 5 of Fig. 1), a pyramid (pos. 9) with 10 ÷ 12 faces (hereinafter, a variant with a 10-sided pyramid is considered); corresponding to the number of faces of the pyramid of sliders (pos. 7.), each of which has a replaceable punch (pos. 10); the radius of the surface and the length of the working part of which depend on the diameter and thickness of the pipe wall, as well as the end ring (pos. 8).

The "weakest" element of the expansion head design is the contact between the slider and the pyramid. By itself, this contact works under rather harsh conditions: the normal force transmitted to the pipe metal through the punch is large, especially with pipe wall thicknesses of more than 20 mm, as a result, the friction force is also high, despite the lubricant being continuously supplied to the contact zone. In addition, in most cases, each edge has an undercut guide groove (T-groove) - shown in FIG. 2, which, firstly, reduces the contact area, and secondly, forms additional wear surfaces. These grooves perform the following functions: prevention of axial movements of the sliders; fixing the relative position of the faces of the pyramid and sliders in the radial direction, including sliders located in the lower semicircle. The presence of these slots should be considered a mandatory element of the expander design, as well as the reason for a number of shortcomings of the equipment under consideration. In particular, a large number of contact surfaces subject to wear at different rates - normal contact surfaces (item 14 in Fig. 2), side planes (item 15) and reverse surfaces (item 16) - makes the structure practically unrepairable. Moreover, all of these surfaces affect the performance of the head. In particular, wear, or scuffing on normal contact surfaces, can lead to seizure and destruction of the pyramid-stem connection. No less dangerous is the wear of the side surfaces - the presence of an increased and uneven length of contact of the gap between the side surfaces of the groove of the pyramid and the protrusion of the slider, as in the case described above, can lead to jamming of the contact due to the skew of the slider as a result of its rotation around the radial axis. The least pronounced wear of the reverse contact surfaces during operation can also lead to seizure. In general, the entire structure of a pipe expansion head with T-shaped slots requires regular maintenance in terms of monitoring the condition and cleaning of sliding surfaces with timely grinding of the resulting scratches, replacing anti-friction inserts, checking the tightening of bolted (screw) connections, etc. There are known ways to minimize damage caused by wear of sliding pipe expansion head connections. In particular, the patent of the Russian Federation No. 2 615 671 (B21D 39/20 (2006.01) B21D 41/02 (2006.01)), publ. 12/20/2016, where a number of measures are proposed for expanding pipes with a diameter of less than 20 (508 mm) inches, aimed at increasing the transmitted force and reducing the possibility of destruction of the connection between the stem and the pyramid. In particular, there it is proposed to make a rod (in the terminology, pleasant in the patent - a barbell) monolithic with a pyramid (in the terminology, pleasant in the patent, a wedge) - this option is capable of preventing the rod from being pulled off the pyramid in case of jamming, while the pipe receives seizures incompatible with requirements for the quality of pipes. There, the concept of a wedge tip is introduced, which is an additional connection that does not weaken the structure, the separation of which does not lead to destruction, and a number of additional measures and design options. This solution, as mentioned above, does not exclude the possibility of jamming and only minimizes possible damage. Also known RF patent No. 2 667 946 (B21D 3/14 (2006.01) B21D 41/02 (2006.01)), publ. 09/25/2018, where the use of interchangeable surface elements of the working part of the pyramid (in the terminology of the patent - a cone) - inserts is proposed in various versions of material design and hardness ratios of sliding surfaces. In this case, rather massive liners are attached to the faces of the pyramid using screw connections. The disadvantages of this solution are obvious: the use of screw connections, evenly spaced over the entire area of the pyramid faces, will significantly weaken the pyramid, which is the main element of the head design, due to the large number of threaded holes. In addition, the screws will shear / crush. And the main drawback is that the soft replaceable liners will only protect the surfaces of normal contact, and the side and back planes (pos. 15 and 16 in Fig. 2) will be subject to wear at the same rate.

Considering all of the above, the technical problem is formulated as follows: to develop a design of a pipe expansion head for expanding large-diameter pipes on sliding wedge pairs without the use of T-shaped guide slots. The goals achieved in this way will be to eliminate jamming of wedge pairs as a result of misalignment, to ensure the maintainability of the pyramid, and to generally increase the reliability of the mechanism as a whole.

This technical problem can be solved by using external guiding devices. In this case, the general arrangement and operating principle of the expander shown in FIG. 1 do not change. The central pyramid (pos. 17 in Fig. 3) is located between two end discs (pos. 18 in Fig. 3), having diameters exceeding the diameter of the circle described around the bases, but less than the minimum inner diameter of the expanded pipes (this limitation applies mainly to the larger grounds). On the edge discs, guide rods are fixed (pos. 3 in Fig. 3), parallel to the faces of the pyramid and passing through the holes in the sliders (pos. 4 in Fig. 3) through antifriction bushings (not shown in Fig. 3), made of softer material, than guide rods. The ends of the sliders are in contact and have radially sliding connections with the end rings - front (pos. 5 in Fig. 3) and rear (pos. 6 in Fig. 3). The latter is rigidly connected to the body (pos. 7), which, in turn, is connected to the rod (pos. 8) and has a hole in the center through which the stem (pos. 9) passes. In the embodiment under consideration, the expander generally works similarly to the above-described analogs: the rod carries out a reverse stroke, moving a pyramid with end discs and guide rods relative to the stationary body. The wedges (edges) of the pyramid move the sliders in the radial direction, and the axial immobility of the sliders is provided by a system of guide rods and end rings. With a straight stroke, the rod returns the sliders to their original position. This variant of the design of the expansion head is less compact than the traditional scheme with T-shaped slots, but it allows to ensure the maintainability of the pyramid, together with the reduction in the cost of its manufacturing technology, eliminates jamming, and also transfers part of the wear, which is inevitable in the case of sliding joints, to easily replaceable and cheap guide elements. rods and anti-friction bushings. The design of the sliders can provide, by analogy with the bushings of the guide rods, anti-friction bushings in contact with the faces of the pyramid. It should be borne in mind that pipe expansion heads in all versions have a system of holes, channels and grooves for supplying lubricant to rubbing surfaces.

Claims (1)

Expansion head for calibrating large diameter pipes, adapted for use with a hydromechanical pipe expander, containing 10 wedges combined into a truncated pyramid, a body with a support roller, 10 sliders, end rings adjacent to the end planes of the sliders, and a system of channels, holes and grooves to ensure the supply of lubricant on the sliding surface of the pipe expansion head, while the sliders are made with the possibility of performing radial movements by means of the axial movement of the wedges under the action of the hydraulic cylinder of the expander and are equipped with punches and replaceable antifriction liners installed on the plane of contact of the sliders with the wedges, characterized in that it is equipped with external guide rods and end discs adjacent to the bases of said truncated pyramid formed by wedges, while the sliders are made with holes and are fixed in the axial direction to prevent their axial movements A set of external guide rods, which are fixed on the end discs, are located parallel to the edges of the truncated pyramid and pass through the holes in the sliders, in which replaceable antifriction bushings are installed.

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