EP0363247B1 - Apparatus for positioning and withdrawing a plasma arc torch in an installation working at such a pressure and temperature that a direct intervention is impossible - Google Patents

Description

The present invention relates generally to the use of plasma torches on installations, or apparatus operating under conditions of high temperature and pressure prohibiting any direct intervention for the setting or removal of the torch, and it relates more particularly to a device for handling a plasma torch with an arc not transferred to such an apparatus.

A method is known, described in French patent application FR-A-2,637,443 relating to a method and device for the placing and removing of a plasma torch on an apparatus operating under pressure and pressure conditions. temperature prohibiting direct intervention.

According to this process, a tight volume capable of varying is produced upstream of a valve closing a connection sleeve for the torch, and the pressure prevailing in this volume is balanced with that prevailing downstream of the valve, before opening this to post the nose of the torch.

Document GB-A-2,167,843 also discloses a device of the type defined in the preamble to the main claim in which a circular seal is inserted between the internal wall of the cuff and the nose of the torch which it surrounds , the nose of the torch being downstream of the valve and the fixed seal remaining in the upstream position in the active position of the torch.

The object of the present invention is to provide an embodiment of a device of the type described in this document for implementing the method described and represented in document FR-A-2,637,443 and which in particular makes it possible to produce a tight volume in the cuff without the torch nose stumbling on the closed valve.

It has for this purpose a device for the stationing in the active position of a plasma torch with arc not transferred to a cuff comprising a shut-off valve and connected to a device operating under high pressure and temperature conditions , without modification of these conditions, as well as its withdrawal, and of the type comprising at least one circular seal inserted between the internal wall of the cuff and the nose of the torch and surrounding the latter, characterized in that it comprises in combination means for balancing the pressures on either side of the valve and means for cooling the seal and characterized in that the dimensions of the device are such that the total length L1 of the cuff is equal to the length of the nose, L1 is greater than twice the distance L2 between the nose of the torch in the active position and the upstream plane of the valve and the distance L3 between the upstream plane of the seal and the nose of the tor che is less than L1 - L2.

According to another characteristic of the invention, the means for balancing the pressures on either side of the valve comprise a setting pipe communication bypassing the valve, and a tap interposed on this pipe.

According to one embodiment of the invention, said seal is mounted on the nose of the torch, in a peripheral groove.

According to a variant, said seal is mounted in a peripheral groove of a circular cradle fitted around the nose of the torch.

Advantageously, said cradle is formed of two parts joined axially and together delimiting said groove.

In another embodiment, said cradle is fitted into a groove formed in the external surface of the nose of the torch.

In another variant, said seal is arranged in a groove formed in the internal surface of the cuff.

Preferably said joint is a metal joint of C-shaped section or a self-elastic joint of U-shaped section.

In one example, the means for cooling the joint comprise a circuit for circulating a cooling fluid.

Advantageously, said circuit is that which cools the nose of the torch.

In another example, said circuit consists of a jacket surrounding the cuff at least at the joint.

The description which follows, with reference to the accompanying drawings by way of nonlimiting examples, will make it possible to understand clearly how the invention can be put into practice.

Figures 1, 2 and 3 are schematic sectional views showing the phases of the establishment of a plasma torch with non-transferred arc, in a first embodiment of the device according to the invention.

FIGS. 4 to 7 are partial sectional views of mounting variants of a joint according to the embodiment of FIGS. 1 to 3.

Figure 8 is a sectional view of another embodiment of the invention.

Referring to Figures 1 to 3, the reference 1 designates a nozzle of an apparatus, for example a blast furnace, on which a plasma torch 4 of the non-transferred arc type is used, having a nose 12 engaged in one end a cuff 3 fixed by its end opposite to the nozzle 1, and closed by a valve 5.

The cuff 3 comprises a flange 7 having a chamfer 8 adapted to cooperate with a frustoconical surface 9 for centering provided around the nose 12 of the torch 4.

A guide rod 10 is fixed on the collar 7 of the cuff and extends through a hole provided in a flange 11 of the torch in order to guide the latter towards the cuff 3.

An O-ring 2 is mounted on the nose 12, which it surrounds, in a manner which will be described in more detail below.

A pipe 6 connects the upstream side of the valve 5 to its downstream side, the side for introducing the torch into the cuff being considered as the upstream side as opposed to the end of the cuff on the nozzle side where the conditions prevail high operating pressure and temperature.

A tap 13 is interposed in the pipe 6 to control the communication of the upstream and downstream sides of the valve. Preferably the valve 13 is protected against overheating, for example by a coil 26 in which a coolant circulates.

FIG. 1 shows the torch 4 in position before it is set up and comes into action, the valve 5 being closed and subjected on its downstream face to the pressure of the device, the tap 13 being closed.

Figure 2 shows the nose 12 of the valve engaged in the cuff 3, the valve 13 and the valve 5 being always closed.

In this position the seal 2 is in sealing contact with the internal surface of the sleeve 3 and the nose 12 of the torch defines with the seal 2, the cuff 3 and the valve 5 a sealed volume which is variable as a function of the position of the nose 12.

The valve 13 is then opened in order to bring this volume upstream of the valve 5 to the same pressure as that prevailing downstream.

It then becomes possible to open the valve 5, the opening of which has hitherto been difficult due to the conditions of ΔP, and the torch is advanced into the position of use, as shown in FIG. 3.

• si L1 est la longueur totale de la manchette 3 et est égal à la longueur du nez 12,
• si L2 est la distance entre le nez 12 de la torche en position active et le plan amont de la vanne 5,
• si L3 est la distance entre le plan amont du joint et le nez 12,

on doit avoir L1 > L2 afin que le joint soit situé en amont de la vanne lorsque la torche est en position active, et L3 < L1 - L2 afin de réaliser un volume étanche dans la manchette sans que le nez 12 bute sur la vanne 5 fermée (figures 2 et 3), et enfin L1 > L2 x 2.We see, considering Figures 2 and 3 that the device can only operate on condition of respecting certain dimensional requirements, which are as follows:

• if L1 is the total length of the cuff 3 and is equal to the length of the nose 12,
• if L2 is the distance between the nose 12 of the torch in the active position and the upstream plane of the valve 5,
• if L3 is the distance between the upstream plane of the joint and the nose 12,

we must have L1> L2 so that the seal is located upstream of the valve when the torch is in the active position, and L3 <L1 - L2 in order to achieve a tight volume in the cuff without the nose 12 coming up against the valve 5 closed (Figures 2 and 3), and finally L1> L2 x 2.

We will now describe in more detail different possible arrangements for mounting the seal 2 on the nose 12 of the torch, with reference to Figures 4 to 7 in which the identical parts are designated by the same references.

Following the example of the partial view of FIG. 4, the reference 3 designates the wall of the cuff, and the reference 12 designates the nose of the torch as a whole.

The nose 12 is formed in two parts 14, 15 upstream and downstream respectively adjusted together for example by means of threads 16 and which are shaped so as to form between them a peripheral groove 17 forming a housing for the seal 2.

As known per se, the nose 12 internally comprises a cooling circuit in which a cooling fluid circulated designated by the reference 18 and the sealing of this circuit is ensured by a seal 19 between the parts 14 and 15.

Advantageously, the seal 2 is made of metal, of section in C. Thanks to this arrangement, the seal 2 is effectively cooled by the cooling circuit of the nose of the torch.

According to the example of the partial view of FIG. 5, the arrangement is identical to that of FIG. 4, with the exception of the seal 20, which is of the so-called self-elastic type of U-section having a metal core and an elastomer coating and the wings of which are in contact with the parts between which it seals.

Following the example of Figure 6, the seal 2 is disposed in a housing 17 delimited by two annular elements 24, 25 fixed around the nose 12 by any suitable means, thus leaving a gap between the nose of the torch and the cuff. This arrangement also ensures good heat transfer between the nose and the seal, and therefore good cooling of the latter.

The arrangement of FIG. 7 is similar to the previous one, but the elements 24, 25 supporting the seal 2 are mounted in a groove 27 delimited between the parts 14 and 15 of the nose 12.

This arrangement provides the elements 24 and 25 with a larger contact surface with the nose 12, further improving the heat transfer.

FIG. 8 shows a variant in which the seal 22 is mounted in a groove 21 formed in the internal surface of the cuff 33.

In this example, the seal 22 must be cooled through the cuff by means of a jacket 23 surrounding the latter and in which a cooling fluid is circulated.

Although this device also allows the implementation of the above process, maintenance or Changing the seal is difficult and requires changing the cuff to cool the seal. For these reasons, the solutions of the examples according to FIGS. 1 to 7 are preferable because of the ease of access to the seal, which allows its rapid replacement, each time the torch is used if desired.

Claims (10)

1. Arrangement for putting into its position of use a plasma torch on the non-transferred arc type in a sleeve comprising a closing shutter and attached to apparatus which operates in elevated pressure and temperature conditions, without modification of these conditions, as well as its withdrawal, of the type comprising at least one circular sealing joint (2, 20, 22), interposed between the internal wall of the sleeve (3, 33) and the tip (12) of the torch (4) and surrounding the latter, characterised in that it comprises means (6, 13) for balancing the pressures on the one side and the other of the shutter (5) and means (18, 23) for cooling the joint, and in that the dimensions of the arrangement are such that the total length L1 of the sleeve (13) is equal to the length of the tip (12), L1 is greater than the twice the distance L2 between the tip (12) of the torch in its operative position and the plane upstream of the shutter (5) and the distance L3 between the plane upstream of the seal and the tip (12) of the torch is less than L1 - L2.
2. Arrangement according to claim 1, characterised in that the said means for balancing the pressures on one side and the other of the shutter comprise a communicating pipe (6) by-passing the shutter (5) and a valve (13) introduced in this pipe and interconnecting the side upstream of the shutter (5) with that downstream.
3. Arrangement according to claim 1, characterised in that the said seal (2, 20) is mounted on the tip (12) of the torch (4) in a peripheral groove (17).
4. Arrangement according to claim 3, characterised in that the said seal (2) is mounted in a peripheral groove (17) in a circular cradle (24, 25) mounted around the tip (12) of the torch (4).
5. Arrangement according to claim 4, characterised in that the said cradle is formed of two parts (24, 25) joined axially and defining between them the said groove (17).
6. Arrangement according to claim 5, characterised in that the said cradle (24, 25) is mounted in a groove (27) provided in the external surface of the tip (12) of the torch (4).
7. Arrangement according to claim 1, characterised in that the said seal (22) is disposed in a groove (21) provided in the internal surface of the sleeve (3).
8. Arrangement according to any one of claims 2 to 6, characterised in that the said seal is a metallic seal (2) of C-section or a self-elastic seal (20) of U-section.
9. Arrangement according to any one of claims 2 to 6, characterised in that the means for cooling the seal (2, 20) comprise a circuit (18) for circulating a cooling fluid which is that which provides cooling of the tip (12) of the torch.
10. Arrangement according to claim 7, characterised in that the means for cooling the seal (22) comprise a jacket (23) around the sleeve (3) and through which a cooling fluid is circulated.

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