WO2017203547A1

WO2017203547A1 - Gas distribution device, for reverse protection of welding joints and related method

Info

Publication number: WO2017203547A1
Application number: PCT/IT2017/000102
Authority: WO
Inventors: Massimiliano TACCONELLI; Stefano Rossi
Original assignee: Walter Tosto S.P.A.
Priority date: 2016-05-24
Filing date: 2017-05-22
Publication date: 2017-11-30
Also published as: ITUA20163735A1

Abstract

The present invention concerns a gas distribution device (1) for reverse protection of welding joints, in which said joint to be welded is provided between two flaps forming a first surface to be welded and a second surface opposite to said first surface, said device (1) comprising a longitudinal support (2), intended to be applied to said second surface, so as to define with it a protection volume, for the introduction of an inert gas, wherein said support (2) has mechanical properties of flexibility, so as to be bendable in any direction, and of elasticity, so as to reacquire the initial shape due to a mechanical stress. The present invention also concerns a welding method by means of the gas distribution device (1) for reverse protection of welding joints.

Description

Gas distribution device, for reverse protection of welding joints and related welding method

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The present invention relates to a gas distribution device, for reverse protection of welding joints and related welding method.

More specifically, the invention concerns a gas distribution device for protecting the flaps or edges of the root welding, namely in which the protection is applied to the surface of the flaps to be welded opposite to the surface on which the actual welding is performed, studied and realized in particular to protect said welding, even when the welding joint to be made is particularly inaccessible and/or the welded flaps have a variable geometry with an irregular profile (i.e. curved or double-curved, both in section and length).

In the following, the description will be directed to welding joints in the oil or nuclear industry, but it is clear that the same should not be considered limited to this specific use.

Every time an electric arc welding on a joint accessible only from one side has to be made, there is the need to keep inert the opposite side of the welding, in order to limit the effects of the oxidation, inclusion and other possible impacts not acceptable from a qualitative point of view.

Various techniques exist to guarantee the inert conditions required for a qualitative welding. Among these, the use of supports, generally made of steel, is known, so that they have the same shape of the welding joint to be made, in such a way as they are then placed on the surface opposite to that on which the welding joint will be made, so as to realize a sort of isolated room, filled with inert gases, such as argon, helium or similar mixtures.

In this way, by carrying out the welding, welding sparks, sparks and the like cannot propagate on the opposite side of the welding joint. Inert gases, in general, also provide high quality and safety welding.

A technical problem of the welding systems according to the prior art is that, for each welding joint to be made, a specific protective support having exactly the same joint geometry has to be provided. Once the welding is carried out and the joint is made, generally the protective supports, except for rare cases, cannot be reused.

In addition, if the volume at least partially individuated by the surface formed by the two edges of the joint to be welded on the face opposite to the welding, were irregular, due to irregularities (for example, the section of a tube can vary considerably along its longitudinal development), then it would be problematic to secure the metal support to the surface to be welded. This implies an additional limit to the adaptation of the prior art systems to the realization of different types of welding joints.

In light of the above, it is object of the present invention to propose a gas distribution device for inverted protection of a welding, which may be adapted to the different needs and geometries of the welding joints to be realized.

It is also object of the present invention to propose a device which allows reusing the support used to carry out a welding of other joints.

Another object of the invention is to propose a welding method by means of the device according to the invention.

It is therefore specific object of the present invention a gas distribution device for reverse protection of welding joints, in which said joint to be welded is provided between two flaps forming a first surface to be welded and a second surface opposite to said first surface, said device comprising a longitudinal support, intended to be applied to said second surface, so as to define with it a protection volume, for the introduction of an inert gas, characterized in that said support has mechanical properties of flexibility, so as to be bendable in any direction, and of elasticity, so as to reacquire the initial shape due to a mechanical stress.

Always according to the invention, said device could have a "U"- shaped cross section, having edges intended to be arranged in contact with said second surface, so as to define with it said protection volume, for the introduction of said inert gas.

Still according to the invention, on said edges of said support, a seat is obtained and said device could comprise a gasket arranged on said seat.

Advantageously according to the invention, said support could be made of inert and high temperature resistant plastic polymers.

Further according to the invention, said support could have a groove on each of the side surfaces and said device could comprise at least one pair of guides, engageable with said grooves, having a shape suitable to follow the shape of the welding joint provided on said first surface to be welded.

Preferably according to the invention, said support could have internally a base and said device could comprise a metal sheet for the protection from the overheating generated by the welding, arranged on, or parallel to said base.

Always according to the invention, said support could comprise at least one duct on at least one of the front and/or rear end, for feeding one or more flows of inert gas into said protective volume.

Still according to the invention, said device could comprise a perforated grid arranged within said support and in output or in correspondence of said ducts.

Advantageously according to the invention, said support could have an internal longitudinal seats, in which said perforated grid is insertable.

Further according to the invention, said lifting means could be of the mechanical, and/or pneumatic and/or electromechanical type and are placed below said support, said lifting means being adapted to exert a vertical push on said support.

Always according to the invention, said lifting means could comprise an air chamber inflatable by suitable inflation members.

Still according to the invention, said lifting means could comprise mechanic jacks, hydraulic jacks or spring devices.

It is further object of the present invention a welding method by means of the gas distribution device for reverse protection of welding joints, as defined above, characterized in that it comprises the following steps: (A) positioning the distribution device on said second surface, so as to define with it a protection volume, to be filled with an inert gas; (B) activating said lifting means so as to adhere said gasket of said distribution device with said second surface; (C) introducing an inert gas through at least one of said ducts into said protective volume; and (D) performing the welding on said first surface, opposite to said second surface.

Always according to the invention, said method could comprise the following steps: (E) draining the inert gas from said protection volume, through at least one of said ducts of said support; (F) deactivating said lifting means; and removing said distribution device.

Still according to the invention, said step (B) could provide the inflating said air chamber and/or the activation of said jack.

Advantageously according to the invention, said step (F) could provide the deflation of said air chamber and/or the deactivation of said jack.

The present invention will be now described, for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the figures of the enclosed drawings, wherein:

figure 1 shows an overview of a gas distribution device for reverse protection of welding joints according to the invention;

figure 2 shows a detail of the protection device according to figure 1 ;

figure 3 shows a cross-sectional view of the protective device according to figure 1 ;

figure 4 shows the inert gas inlet mouth of the device according to the invention;

figures 5 and 6 show details of the inside of the device according to the invention;

figure 7 shows a lifting mechanical member;

figure 8 shows a sectional view of a pipe, which the protection device according to the present invention is applied to; and

figure 9 shows a sectional view showing the application to a joint of the protection device according to the present invention.

In the various figures, similar parts will be indicated by the same reference numbers. Referring to figures 1-6, a gas distribution device 1 for reverse protection of welding joints according to the present invention is provided.

The distribution device 1 essentially comprises a support 2, a gasket 3, fixed to said support 2, and possibly lifting means 4 of said support 2.

The support 2 has a longitudinal structure, with a "U"-shaped cross section. Said support 2 is made of flexible and high temperature resistant material, having elastoplastic properties and in particular flexibility mechanical properties, so as to be self-adaptive, i.e. that can be curved in any direction, and elastic, so as to recover the initial shape following a stress, so that it can be adapted to the surface to be protected and to the shape of the welding joint to be realized.

For example, said support 2 can be made of plastic inert and high temperature resistant polymers, such as quartz-loaded and thermotreacted PTFE.

The support 2 at the upper ends has edges 22, on which a respective seat 22' is formed, which the operation will be further explained in the following.

Said support 2, when the distribution device 1 is applied to the walls to be welded, in the terms better described in the following, forms with them a volume or protective chamber V.

Within said support 2, which will form a sealing on the walls surrounding the joint to be welded, the inert gas needed to protect the flaps for the welding joint can be introduced and circulated. Said support 2 has internally a base 21 , on or parallel to which a plate 21' is provided, suitable to provide an additional protection against the overheating generated by the welding, when it is made under special conditions.

Said support 2 comprises at the front and rear ends a duct 23 for introducing one or two (or more) inert gas streams into the protection volume V individuated by said support 2 and the surfaces to be welded. The use of one or more ducts 23 is constrained by the amount of gas to be injected. If only one duct 23 is used, the other can be used as a drain to prevent excessive gas overpressure in the protection volume V, which is damaging for a proper welding.

A gas distribution structure, typically a perforated grid 24, can be inserted at the outlet of the gas ducts 23, to prevent turbulence within the protection volume V, necessary to break the laminar flow of gas from the external duct (not shown in the figure) coupled to the conduit 23. For the same reason, it is possible to install such distribution system 24 on the whole support 2. In particular, the support 2 has inner longitudinal seats 25, in which the perforated grid 24 is insertable.

Said support 2 also has grooves 26 obtained on the side surface of the support 2, intended to engage with respective guides (not shown in the figure) having a shape suitable to follow the shape of the edges of the flaps, on which the welding joint can be made. In this way, the guides can be inserted into grooves 26, so as to position said support 2 at the edges of said flaps.

The gasket 3 is arranged on said seats 21' of the edges of said support 2 and it is intended to adhere to the surface of the welded flaps, opposite to that on which the joint to be welded is provided, in particular near the edges to be welded, so as to individuate the above-mentioned protection volume V.

This allows to obtain an efficient edge adhesion and prevents the inert gas dispersion on the sides of the support 2.

Said gasket 3 is sufficiently elastic to provide a good adherence and seal with the contact surface and, at the same time, it is high temperatures resistant.

In addition, the gasket 3 is flame-retardant and inert, so as not to contaminate the joint to be welded due to overheating of the material.

The lifting means 4 of said device may be of mechanical, pneumatic or electromechanical type. Said lifting means 4 are positioned below said support 2 to exert a vertical thrust on said support 2 so as to adapt it to the possible curvature of the surface of the flaps to be welded, opposite to that on which the welding joint is to be made, by pressing said gasket 3 against said surface.

In the embodiment shown in figures 1-6, said lifting means are pneumatic, comprising an inflatable air chamber 41 with appropriate inflating members (not shown). In a second embodiment, shown in figure 7, said lifting means 4 may comprise mechanical lifting members, such as jacks 42.

According to further embodiments, said lifting system 4 can be made of spring or piston systems.

The operation of the gas distribution device 1 for reverse protection of welding joints described above is as follows.

Referring to figure 8, a pipe T (called pipeline) or the like, having a curved shape, is shown. Said pipe T has an outer surface or first surface S¹, on which there is provided a slot or an opening formed by two flaps, between which the welding joint must be made, and an inner surface S", within the pipe T or second surface. Said inner surface S" is opposite to said outer surface S' of said pipe T.

In order to weld said joint on the outer surface S' of said pipe T, the distribution device 1 is preliminarily positioned within the pipe T itself. As it is flexible, the support 2 can easily follow the shape and the curvature of the pipe T.

Subsequently, the air chamber 41 is inflated with appropriate inflation means (not shown in the figures), so that the device 1 fills the inner volume of the pipe T with its own bulk and the gasket 3 can adhere with the internal surface S" of the pipe T, opposite, as said, to the outer surface S', on which there is the joint to be welded. Also it has to be considered that the inner surface S" of said pipe T may also have its own curvature and said gasket is adapted to allow the proper adaptation of said support 2 to said inner surface S".

Once the device 1 is positioned in correspondence of the welding joint (which is, as said, on the outer surface S' of the pipe T) and the gasket 3 adheres with the internal surface S" of the pipe T, the inert gas can be introduced through a duct 23 within the protection volume V formed by said support 2 and the inner surface of said pipe T.

The gas is uniformly distributed also by means of said perforated grid 24, along the entire protection volume V formed by said support 2 and the inner surface of the pipe T, which said distribution device 1 adheres to. it is thus possible to carry out the welding by realizing the welding joint, possibly by providing material or metal for its realization. During this last step, any welding sprays or sparks will be contained by said distribution device 1.

After the welding is carried out, it is sufficient to drain away the inert gas from said protection volume V by means of suitable valves (not shown in the figure), through one of said ducts 23 at the ends of said support 2, deflate the air chamber 41 and remove the distribution device 1 from the pipe T.

Said distribution device 1 can be used for a further welding, for example of another section of the pipe T, possibly with a different shape or curvature.

Referring now to figure 9, the application of the distribution device 1 to an internal surface S" is observed, opposite to the outer surface (not shown in the figure), on which there is the joint to be welded. In this case, said inner surface S" is that of a reservoir or container in general, having internally irregular surfaces.

Once the protective device 1 is positioned, possibly by guides (not shown in the figure) engaged in said grooves 26, by inflating the air chamber 26, the latter rests and fits said inner surface irregularities I, by adhering the gasket 3 to said inner surface S" near the edges of the flaps, on which the welding has to be made on the opposite face of said inner surface S".

Subsequently, as in the previous case, inserting the inert gas and allowing the welding to be made on the joint, always opposite to that in which the device 1 adheres, is possible.

Again draining the inert gas from one of said ducts 23 and deflate said air chamber 41 to pull out the distribution device 1 will then be sufficient.

In addition to the above-mentioned applications, device 1 according to the present invention can also be used as a protection of a chamber, i.e. the protection volume V, during adjacent operations that can pollute/dirt/oxidize the surface to be protected.

Furthermore, device 1 according to the present invention can also be used as a guide for brushing or mechanical abrasion of root wormhole operations.

An advantage of the present invention is to allow both the reuse of the support and the fact that the protective device can adapt to different configurations and geometries of the joint to be welded.

The present invention has been described for illustrative but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be introduced by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.

Claims

1. Gas distribution device (1) for reverse protection of welding joints, in which said joint to be welded is provided between two flaps forming a first surface (S') to be welded and a second surface (S") opposite to said first surface (S'), said device (1) comprising

a longitudinal support (2), intended to be applied to said second surface (S"), so as to define with it a protection volume (V), for the introduction of an inert gas,

characterized in that said support (2) has mechanical properties of flexibility, so as to be bendable in any direction, and of elasticity, so as to reacquire the initial shape due to a mechanical stress.

2. Device (1) according to claim 1 , characterized in that it has a "IP- shaped cross section, having edges (22) intended to be arranged in contact with said second surface (S"), so as to define with it said protection volume (V), for the introduction of said inert gas.

3. Device (1) according to the preceding claim, characterized in that on said edges (22) of said support (2) a seat (22') is obtained and

in that it comprises a gasket (3) arranged on said seat (22').

4. Device (1) according to anyone of the preceding claims, characterized in that said support (2) is made of inert and high temperature resistant plastic polymers.

5. Device (1) according to anyone of the preceding claims, characterized

in that said support (2) has a groove (26) on each of the side surfaces and

in that it comprises at least one pair of guides, engageable with said grooves (26), having a shape suitable to follow the shape of the welding joint provided on said first surface (S') to be welded.

6. Device (1) according to anyone of the preceding claims, characterized

in that said support (2) has internally a base (21) and

in that it comprises a metal sheet (21 ') for the protection from the overheating generated by the welding, arranged on, or parallel to said base (21).

7. Device (1) according to anyone of the preceding claims, characterized in that said support (2) comprises at least one duct (23) on at least one of the front and/or rear end, for feeding one or more flows of inert gas into said protective volume (V).

8. Device (1) according to the preceding claim, characterized in that it comprises a perforated grid (24) arranged within said support (2) and in output or in correspondence of said ducts (23).

9. Device (1) according to the preceding claim, characterized in that said support (2) has internal longitudinal seats (25), in which said perforated grid (24) is insertable.

10. Device (1) according to anyone of the preceding claims, characterized in that said lifting means (4) are of the mechanical, and/or pneumatic and/or electromechanical type and are placed below said support (2), said lifting means (4) being adapted to exert a vertical push on said support (2).

11. Device (1) according to the preceding claim, characterized in that said lifting means (4) comprise an air chamber (41) inflatable by suitable inflation members.

12. Device (1) according to anyone of claims 10 or 11 , characterized in that said lifting means (4) comprise jacks (42).

13. Welding method by means of the gas distribution device (1) for reverse protection of welding joints, as defined in anyone of claims 1-12, characterized in that it comprises the following steps:

(A) positioning the distribution device (1) on said second surface (S"), so as to define with it a protection volume (V), to be filled with an inert gas;

(B) activating said lifting means (4) so as to adhere said gasket (3) of said distribution device (1) with said second surface (S");

(C) introducing an inert gas through at least one of said ducts (23) into said protective volume (V); and

(D) performing the welding on said first surface (S'), opposite to said second surface (S").

14. Method according to the preceding claim, characterized in that it further comprises the following steps:

(E) draining the inert gas from said protection volume (V), through at least one of said ducts (23) of said support (2);

(F) deactivating said lifting means (4); and

(G) removing said distribution device (1).

15. Method according to anyone of claims 13 or 14, characterized in that said step (B) provides the inflating said air chamber (41) and/or the activation of said jack (42).

16. Method according to anyone of claims 14-15, characterized in that said step (F) provides the deflation of said air chamber (41) and/or the deactivation of said jack (42).