EP2662565B1 - Compression device for cryogenic jet fluid installations - Google Patents

Description

Disclosed is a piston compression device improved by more reliable and rapid detection of leaks that may occur around said piston. The invention further relates to an installation for working by jets of fluid at cryogenic temperature under high pressure, the operation of which is improved and made safer thanks to the use of a compression device according to the invention, which installation is suitable for and designed to perform surface treatment, stripping, cleaning, peeling or cutting of a material.

The surface treatment of coated or uncoated materials, in particular the stripping of paint, coating or the like, peeling or the like, in particular of concrete, the cutting of a material, etc. can be carried out by using jets cryogenic under very high pressure, as proposed by the documents US-A-7,310,955 and US-A-7,316,363 .

To do this, one or more jets of high pressure cryogenic fluid are typically used, generally liquid nitrogen, at a pressure of 300 to 5000 bars, typically between 1000 and 4000 bar, and at a cryogenic temperature of for example between - 100 and - 200 ° C, typically between -140 and -160 ° C, which are distributed by one or more nozzles which may or may not have a rotary movement or an oscillating movement.

A method of working by jets of high pressure cryogenic fluid, in particular a method of surface treatment, pickling, peeling, cleaning or cutting of a material is carried out by means of a working installation suitable for and designed to produce high pressure cryogenic fluid jets.

Usually, this type of work installation comprises means for supplying fluid, comprising in particular a reservoir for cryogenic fluid at low pressure, typically between 3 and 6 bar, for example nitrogen in the liquid state, and at at least one fluid supply duct, which supply means supply an internal heat exchanger and a first compression device capable of and designed to compress the cryogenic fluid to a first pressure typically ranging up to 1000 bar.

The cryogenic fluid compressed at the first pressure then supplies, via at least one other fluid supply conduit, a second compression device capable of and designed to compress the cryogenic fluid at the first pressure to a second pressure greater than the first pressure, said second pressure typically ranging up to 5000 bar, preferably up to 4000 bar.

The fluid compressed to the second pressure is then conveyed via a conveying line to an external heat exchanger where it undergoes cooling. This results in a fluid at a pressure typically greater than 300 bar and generally ranging up to 5000 bar, preferably up to 4000 bar, and at a cryogenic temperature of between -100 and - 200 ° C, typically between -140 ° C and -160 ° C, which is sent to a stripping tool or the like delivering one or more jets of cryogenic fluid.

Generally, the second compression device comprises a compression compartment in which the cryogenic fluid to be compressed is located. The fluid is compressed by a compression piston movable in translation in the compression compartment, which piston is arranged in a passage formed in a wall of said compartment.

In addition, sealing means, typically a seal, generally a seal formed of a plastic material with a metal band, are arranged around the piston, at the level of the passage formed in a wall of the compartment in which takes place the compression of the fluid. These sealing means are suitable for and designed to provide fluid sealing between the interior and the exterior of the compartment, the exterior of the compartment being generally at atmospheric pressure.

The seal of the second compression device is subjected to high thermal and mechanical stresses which eventually lead to wear, or even complete rupture, of the seal.

In fact, the back and forth translational movements of the piston taking place during the numerous compression cycles of the cryogenic fluid generate progressive wear of the seal by repeated friction of the piston against said seal.

In addition, the seal is subjected to repeated thermal cycles resulting from compression cycles. Indeed, when filling the cryogenic fluid in the compression compartment, the fluid is at cryogenic temperature, while after compression, the fluid has a temperature close to ambient temperature.

The wear of the seal progressively impairs its fluidic sealing performance. This results in fluid leaks at the passage formed in a wall of the compression compartment of the compression device, and therefore a loss in efficiency of said device, in particular a reduction in the pressure of the compressed fluid in the compression compartment.

When the second compression device is operating normally, the frequency of the translational movement of the piston is typically of the order of 25 strokes per minute, that is to say 25 piston round trips per minute.

When a significant drop in the pressure of the compressed fluid in the compression compartment occurs, for whatever reason, the machine continues to operate, i.e. to deliver the cryogenic fluid into the compression compartment and to compress it.

In order to bring the fluid pressure in the compression compartment back to the set pressure, i.e. the desired fluid compression pressure, the frequency of piston movement increases until the set pressure is again reached. This can occur during transient drops in the fluid pressure in the compression compartment or even when the machine is started up before the pressure is established, and makes it possible to regulate the pressure of the cryogenic fluid distributed by the work installation. .

The increase in the frequency of movement of the piston beyond a predetermined threshold value, typically beyond 28 strokes per minute, triggers a countdown of a predetermined duration, typically of the order of 10 seconds.

If the frequency of the movements of the piston falls below this threshold value again before the end of the typical duration of approximately 10 seconds, the working installation by jets of high pressure cryogenic fluid continues to operate and the countdown is stopped and reset.

If the frequency of piston movements remains abnormally high for too long a time, that is to say typically beyond 28 strokes per minute for a period of 10 consecutive seconds, this is the sign of a malfunction of the piston. second compression device. The shutdown of the working installation is then triggered automatically, which in particular results in stopping the translational movement of the piston and stopping the supply of fluid to the compression compartment.

However, the process described above is also triggered when the seal is worn or broken, these phenomena themselves also producing a decrease in the fluid pressure in the compression compartment. In this case, the frequency of movements of the piston remains abnormally high during the period of typically 10 seconds and the working installation does not cease to operate until the end of said period.

It follows that, during the period of typically 10 seconds, the installation is still supplied with cryogenic fluid and the piston continues its translational movement through the seal at high frequency, that is to say - typically say more than 28 strokes per minute. The movement of the piston through the worn seal then causes the detachment of pieces of seals, in particular in the compression compartment.

These pieces of gaskets become very hard due to the cryogenic temperatures prevailing in the compression compartment. This results in an increased risk of breakage of constituent elements of the compression device, in particular of the piston which is generally formed of a relatively fragile material, such as ceramic.

Breaking the piston then requires a long and expensive intervention, which has a negative impact on the productivity of the installation, and this to a greater extent than if it had been necessary to simply change the worn seal.

Different solutions have been proposed for detecting seal wear during operation of a piston compression device, but none is ideal because of either too great complexity, excessive bulk or response time. insufficient to prevent piston breakage. As such, we can cite the documents WO-A-2007/009278 , US-A-4128831 , WO-A-2007/000189 , EP-A-0950815 , US-A-2012/097026 , US-A-3914752 , and US-A-3887196 .

The problem to be solved is therefore to provide a compression device, in particular a cryogenic fluid compression device, which is improved in such a way as to greatly minimize, or even eliminate, the aforementioned problems, and which is also complex to implement. reduced implementation and improved efficiency compared to the solutions of the prior art.

In particular, one aim of the invention is to provide a working installation by jets of fluid at cryogenic temperature under high pressure, the operation of which is improved and made safer than in the prior art.

The solution then comprises a compression device comprising a first compartment, a second compartment comprising a peripheral wall secured to the first compartment, a passage being arranged between the first and second compartments, a piston arranged in the passage and movable in translation in at least one part of the first and second compartments and of the sealing means arranged around the piston at the level of the passage so as to ensure, under normal conditions of use, a fluid seal between said first and second compartments, the second compartment further comprising at the at least one exhaust port arranged in the peripheral wall of the second compartment and means for detecting a flow of fluid arranged at the level of the exhaust port so as to detect a flow of fluid escaping from the second compartment through the exhaust port and resulting from a flow of fluid passing from the first compartment to the second xth compartment by the passage in the event of a fluidic sealing defect between the first and second compartments, characterized in that the means for detecting a flow of fluid comprise a microswitch comprising at least two electrical poles and a tab that can be actuated under the effect of a pressure exerted by a flow of fluid on said tab so that the tab provides or interrupts electrical contact between said electrical poles when a flow of fluid escapes through the exhaust port.

The invention is defined by claim 1.

• la languette (12) est apte à se déplacer sous l'effet d'une pression exercée par un flux de fluide (20) sur ladite languette (12) entre aux moins deux positions comprenant :
  • une position ouverte lorsqu'un flux de fluide (20) nul ou quasi-nul s'échappe du deuxième compartiment (8) par l'orifice d'échappement (9), les pôles électriques du micro-rupteur (11) n'étant pas en contact électrique, et
  • une position fermée lorsqu'un flux de fluide (20) s'échappe du deuxième compartiment (8) par l'orifice d'échappement (9), les pôles électriques du micro-rupteur (11) étant mis en contact électrique par la languette (12).
• la languette (12) est apte à se déplacer sous l'effet d'une pression exercée par un flux de fluide (20) sur ladite languette (12) entre aux moins deux positions comprenant :
  • une position ouverte lorsqu'un flux de fluide (20) s'échappe du deuxième compartiment (8) par l'orifice d'échappement (9), les pôles électriques du micro-rupteur (11) n'étant pas en contact électrique, et
  • une position fermée lorsqu'un flux de fluide (20) nul ou quasi-nul s'échappe du deuxième compartiment (8) par l'orifice d'échappement (9), les pôles électriques du micro-rupteur (11) étant mis en contact électrique par la languette (12).
• les moyens de détection d'un flux de fluide sont aptes à et conçus pour détecter un flux de fluide s'échappant du deuxième compartiment par l'orifice dont la pression, le débit ou la vitesse au niveau des moyens de détection sont respectivement supérieurs à un seuil de détection en pression, un seuil de détection en débit ou un seuil de détection en vitesse prédéterminés.
• les moyens de détection d'un flux de fluide produisent un signal électrique d'alarme lorsqu'un flux de fluide s'échappant du deuxième compartiment par l'orifice est détecté.
• le dispositif est relié fluidiquement à des moyens d'alimentation en fluide dont la mise en marche et/ou l'arrêt sont contrôlés par une première commande, ledit dispositif étant en outre relié électriquement à une deuxième commande contrôlant la mise en mouvement et l'arrêt du piston et les moyens de détection d'un flux de fluide étant reliés électriquement à la première et à la deuxième commandes de manière à ce qu'une pression exercée par un flux de fluide sur ladite languette de manière à assurer ou interrompre le contact électrique entre les pôles électriques du micro-rupteur déclenche l'arrêt du mouvement de translation du piston et l'arrêt de l'alimentation en fluide.

Furthermore, according to the embodiment considered, the invention may comprise one or more of the following characteristics:

• the tongue (12) is able to move under the effect of a pressure exerted by a flow of fluid (20) on said tongue (12) between at least two positions comprising:
  • an open position when a zero or almost zero fluid flow (20) escapes from the second compartment (8) through the exhaust port (9), the electrical poles of the microswitch (11) not being not in electrical contact, and
  • a closed position when a flow of fluid (20) escapes from the second compartment (8) through the exhaust port (9), the electrical poles of the microswitch (11) being brought into electrical contact by the tab (12).
• the tongue (12) is able to move under the effect of a pressure exerted by a flow of fluid (20) on said tongue (12) between at least two positions comprising:
  • an open position when a flow of fluid (20) escapes from the second compartment (8) through the exhaust port (9), the electrical poles of the microswitch (11) not being in electrical contact, and
  • a closed position when a zero or almost zero fluid flow (20) escapes from the second compartment (8) through the exhaust port (9), the electrical poles of the microswitch (11) being put in electrical contact via the tab (12).
• the means for detecting a flow of fluid are suitable for and designed to detect a flow of fluid escaping from the second compartment through the orifice, the pressure, flow rate or speed of which at the level of the detection means are respectively greater than a predetermined pressure detection threshold, a flow rate detection threshold or a speed detection threshold.
• the means for detecting a flow of fluid produce an electrical alarm signal when a flow of fluid escaping from the second compartment through the orifice is detected.
• the device is fluidly connected to fluid supply means, the starting and / or stopping of which are controlled by a first control, said device also being electrically connected to a second control controlling the setting in motion and the stopping the piston and the means for detecting a flow of fluid being electrically connected to the first and to the second controls so that a pressure exerted by a flow of fluid on said tongue so as to ensure or interrupt the contact between the electrical poles of the micro-switch triggers the stopping of the translational movement of the piston and the stopping of the fluid supply.

According to another aspect, the invention also relates to a work installation implementing at least one jet of fluid at cryogenic temperature under high pressure comprising at least one nozzle for dispensing a jet of fluid, means for supplying fluid. , the starting and stopping of which are controlled by a first control, at least one compression unit supplied with fluid by the supply means and an external heat exchanger, the compression unit comprising at least a first and a second compression devices, which second compression device comprises a first and a second compartment, a piston, a second control controlling the setting in motion and / or stopping of the piston and an internal heat exchanger, the at least one compression unit and heat exchanger cooperating with the means for supplying fluid for supplying the at least one nozzle for distributing a jet of fluid, characterized in that the second compression device is according to one of the preceding claims.

Preferably, the second compression device comprises means for detecting a flow of fluid electrically connected to the first and second controls, said detection means comprising a microswitch comprising at least two electrical poles and a tab which can be actuated under the effect. a pressure exerted by a flow of fluid on said tab so that the tab provides or interrupts electrical contact between said electrical poles when a flow of fluid escapes from the first compartment to the second compartment and triggers the stopping the translational movement of the piston and stopping the fluid supply.

Preferably, the fluid distributed by the working installation according to the invention is at a pressure between 300 and 5000 bar, preferably between 1000 and 4000 bar, and at a temperature between -100 ° C and -200 ° C, preferably between -140 ° C and - 160 ° C.

Advantageously, the installation according to the invention is suitable for and designed to carry out a surface treatment, pickling, cleaning, peeling or cutting of a material.

• les Figures 1 et 2 schématisent un dispositif de compression comprenant un piston respectivement en position rentrée et en position sortie,
• les Figures 3a et 3b schématisent un dispositif de compression selon un mode de réalisation de l'invention, et
• la Figure 4 schématise une installation de travail par jets de fluide cryogénique comprenant un dispositif de compression selon l'invention.

The invention will now be better understood thanks to the following detailed description given with reference to the appended figures, among which:

• the Figures 1 and 2 show schematically a compression device comprising a piston respectively in the retracted position and in the extended position,
• the Figures 3a and 3b show schematically a compression device according to one embodiment of the invention, and
• the Figure 4 shows schematically a working installation using cryogenic fluid jets comprising a compression device according to the invention.

As seen on the Figure 1 , a piston compression device generally comprises a first compartment 7 secured to a second compartment 8, a first compartment 7 being the compression compartment, that is to say the compartment supplied with fluid 20 and in which the compression of said fluid 20.

The first and second compartments 7, 8 can be two parts assembled mechanically, for example by threading as illustrated on the figure. Figure 2 , or by any other means of assembly.

Preferably, the first and second compartments 7, 8 are parts of revolution each comprising a recess and of cylindrical shape, and arranged coaxially. Advantageously, the material used for the manufacture of the first and second compartments 7, 8 is type 316 stainless steel.

A passage 16 is arranged between the first and second compartments 7, 8 and a compression piston 5 is arranged in the passage 16.

Sealing means 4 are arranged around the piston 5 at the level of the passage 16 so as to ensure, under normal conditions of use, a fluid seal between said first and second compartments 7, 8.

Preferably, the sealing means 4 comprise a seal. Typically the seal is formed of 3 parts consisting of a lip seal made of polymer material, a ring made of polymer material and a ring made of metallic material.

In addition, the sealing means 4 comprise a stop ring 3 and a retaining ring 6 arranged at the level of the passage 16, around the piston 5, so as to hold the seal in position. Preferably, the rings 3 and 6 are formed of a metallic material. Advantageously, the ring 3 is formed of bronze and the ring 6 of 316 stainless steel.

The sealing means 4 provide fluid tightness between the compartments 7, 8 and also makes it possible to guide the piston 5, which piston 5 is movable in translation in at least part of the first and second compartments 7, 8 and of the means of sealing 4. It being specified that the compression piston 5 is generally driven by a hydraulic piston 5a arranged in the second compartment 8. The piston 5 is generally formed of a material of the ceramic type.

The piston 5 is able to move in axial translation along the axes of symmetry of the first and second compartments 7, 8, which axes are preferably coincident. More precisely, the piston 5 is able to move between at least two positions: a retracted position (shown diagrammatically in Figure 1 ) according to which the major part of the piston 5 is arranged in the second compartment 8 and an extended position (shown diagrammatically in Figure 2 ) according to which the piston 5 is translated in the direction of the first compartment 7 relative to its retracted position.

The second compartment 8 further comprises at least one exhaust orifice 9 arranged in the peripheral wall 1 of the second compartment 8. The orifice 9 opens out. and places the interior, ie the internal volume, of the second compartment 8 in fluid communication with the exterior of said compartment. Preferably, the pressure prevailing inside the second compartment 8 is of the order of atmospheric pressure.

The piston 5 being driven by a hydraulic piston 5a, the free volume of the compartment 8 varies as a function of the compression cycle. In other words, when the piston 5 compresses the cryogenic fluid, the free volume of the compartment 8 decreases and air is discharged through the at least one orifice 9. Conversely, when the piston 5 returns to the retracted position, from the air outside the second compartment 8 is sucked in through orifice 9.

In operation, the compression device ensures the compression of a fluid 20 located in the first compartment 7 when the piston 5 performs a translational movement in the direction of the first compartment 7, until it is in its extended position.

As already explained, in the event of wear of the sealing means 4, in particular of the seal, fluid leaks 20 occur and cause a flow of fluid 20 to pass from the first compartment 7 to the second compartment. 8. Movement of the piston through the worn seal results in the detachment of pieces of seals which become very hard due to the cryogenic temperatures in the compression compartment. This results in an increased risk of breakage of the piston 5, as well as of the stop ring 3, of the retaining ring 6, or even of the first compartment 7 itself.

To remedy this, the present invention proposes to arrange means 11 for detecting a flow of fluid at the level of the exhaust port 9 so as to detect a flow of fluid 20 escaping from the second compartment 8 through port 9, as illustrated by Figures 3a and 3b which schematize a preferred embodiment of the present invention.

It should be noted that by means 11 for detecting a flow of fluid, is meant any device for detecting the flow of fluid making it possible to detect a flow of fluid escaping from the second compartment 8 through the orifice 9.

According to the invention, the means 11 for detecting a flow of fluid 20 are capable of and designed to detect a flow of fluid escaping from the second compartment 8 through the exhaust port 9 and resulting from a flow of fluid 20 passing from the first compartment 7 to the second compartment 8 through the passage 16, in the event of a fluidic sealing defect between the first and second compartments 7, 8.

Preferably, the fluid 20 escaping through the orifice 9 is in the gaseous state.

Typically, a flow of fluid 20 passing from the first compartment 7 to the second compartment 8 generates a flow of fluid 20 escaping from the orifice 9, and circulating from the inside of the compartment 8 to the outside of the compartment 8, in the direction of means 11 for detecting a flow of fluid.

The lowest pressure value, the lowest flow rate value or the lowest measurable fluid speed value determine the sensitivity of the detection means 11.

Note that the movement of the piston 5 carried out in the direction of the compartment 7 during the compression of the fluid 20 can cause the escape of a slight flow of air from the compartment 8 through the orifice 9. In fact, when the compression piston 5 compresses the cryogenic fluid, the volume of compartment 8 left free by hydraulic piston 5a decreases and air is discharged through orifice 9.

Advantageously, the sensitivity of the detection means 11 is adjusted so that the lowest pressure value, the lowest flow rate value or the lowest measurable fluid speed value is respectively greater than a pressure detection threshold, a threshold speed detection or a predetermined speed detection threshold.

In other words, the detection means 11 are preferably capable of and designed to detect a flow of fluid 20 whose pressure, flow rate or speed at the level of the detection means 11 is greater than a pressure detection threshold, a threshold of flow detection or a predetermined speed detection threshold.

The pressure, flow or speed values of these predetermined detection thresholds will be adjusted as a function of the characteristics of the compression device of the invention, in particular of the pressure prevailing in the first compartment 7, of the number of orifices 9 arranged on the second compartment 8. Typically, the values of these detection thresholds can be predetermined empirically, during routine tests carried out under different conditions of use of the compression device of the invention, for example different values of pressure prevailing. in the first compartment 7, different numbers of orifices 9 arranged on the second compartment 8, ...

Preferably, the sensitivity of the detection means 11 is adjusted so that the predetermined detection thresholds in pressure, flow rate or fluid speed are respectively greater than the variations in pressure, flow rate or speed resulting from the low air flow. generated by the movement of the hydraulic piston 5a.

In other words, the detection means 11 are preferably suitable for and designed to detect only a flow of fluid 20 whose pressure, flow or speed at the level of the detection means 11 is greater than the pressure, flow or speed. the slight flow of air escaping through the orifice 9 during the movement of the hydraulic piston 5a in the second compartment 8, in the direction of the first compartment 7.

According to the invention, and as illustrated in the Figures 3a and 3b , the means 11 for detecting a flow of fluid 20 comprise a device of the microswitch type. The term micro-switch is understood to mean a device comprising at least two electrical poles and a tab 12 which can be actuated under the effect of pressure exerted by a flow of fluid 20 on said tab 12.

The choice of the characteristics of the microswitch, in particular the lift of the tongue 12 and the distance separating the points of contact of the tongue with the electrical poles of the microswitch, makes it possible to adjust the sensitivity of the microswitch.

Advantageously, a miniature micro-switch with tongue or lever type Cherry and sold under the reference DG13-B3LA can be used.

According to one embodiment of the invention, illustrated in the Figures 3a and 3b , the microswitch 11 is arranged at the level of the orifice 9 so that the tongue 12 provides electrical contact between said electrical poles when a flow of fluid 20, preferably nitrogen, escapes through the exhaust port 9 and presses on the tab 12.

• une position ouverte (schématisée sur la Figure 3a) lorsqu'un flux de fluide 20 nul ou quasi-nul s'échappe du deuxième compartiment 8 par l'orifice d'échappement 9, la pression exercée sur la languette 12 n'étant pas suffisante pour mettre les pôles électriques du micro-rupteur 11 en contact électrique, et
• une position fermée (schématisée sur la Figure 3b) lorsqu'un flux de fluide 20 s'échappe du deuxième compartiment 8 par l'orifice d'échappement 9 et exerce une pression sur la languette 12, les pôles électriques du micro-rupteur 11 étant mis en contact électrique par la languette 12.

More precisely, the tongue 12 is able to move under the effect of a pressure exerted by a flow of fluid 20 on said tongue 12 between at least two positions comprising:

• an open position (shown schematically on the Figure 3a ) when a zero or almost zero fluid flow 20 escapes from the second compartment 8 through the exhaust port 9, the pressure exerted on the tab 12 is not sufficient to put the electrical poles of the microswitch 11 in electrical contact, and
• a closed position (shown schematically on the Figure 3b ) when a flow of fluid 20 escapes from the second compartment 8 through the exhaust port 9 and exerts pressure on the tab 12, the electrical poles of the microswitch 11 being brought into electrical contact by the tab 12.

Preferably, the second compartment 8 of the compression device of the invention advantageously comprises means 11 for detecting a flow of fluid 20, supplied electrically, said means being capable of and designed to produce an electrical alarm signal when a flow of fluid 20 escaping from the second compartment 8 through the orifice 9 is detected.

Preferably, the electrical signal produced by the means 11 makes it possible to trigger the stopping of the operation of the compression device of the invention, in particular the stopping of the translational movement of the piston 5 and the stopping of the supply of fluid 20. of the second compression compartment 8.

Advantageously, the device of the invention is fluidly connected to fluid supply means 20, the starting or stopping of which is controlled by a first control. In addition, the translational movement or stopping of the piston 5 is controlled by a second command. The means 11 for detecting a flow of fluid 20 are then electrically connected to the first and second controls by at least one electrical cable 13 so that the electrical alarm signal produced when a flow of fluid escapes from the second compartment 8 through the orifice 9 triggers the stopping of the translational movement of the piston 5 and the stopping of the fluid supply 20.

According to an alternative embodiment of the invention, not illustrated, the microswitch 11 is arranged at the level of the orifice 9 so that the tab 12 interrupts an electrical contact initially established between said electrical poles when a flow of fluid 20, preferably nitrogen, escapes through the exhaust port 9 and presses on the tab 12.

• une position ouverte lorsqu'un flux de fluide 20 s'échappe du deuxième compartiment 8 par l'orifice d'échappement 9 et exerce une pression sur la languette 12, le contact électrique entre les pôles électriques du micro-rupteur 11 étant interrompu du fait du déplacement de la languette 12,
• une position fermée lorsqu'un flux de fluide 20 nul ou quasi-nul s'échappe du deuxième compartiment 8 par l'orifice d'échappement 9, la languette 12 assurant un contact électrique entre les pôles électriques du micro-rupteur 11.

More precisely, the tongue 12 is able to move under the effect of a pressure exerted by a flow of fluid 20 on said tongue 12 between at least two positions comprising:

• an open position when a flow of fluid 20 escapes from the second compartment 8 through the exhaust port 9 and exerts pressure on the tab 12, the electrical contact between the electrical poles of the microswitch 11 being interrupted due to the displacement of the tongue 12,
• a closed position when a zero or almost zero fluid flow 20 escapes from the second compartment 8 through the exhaust port 9, the tab 12 providing electrical contact between the electrical poles of the microswitch 11.

Preferably, the interruption of the electrical contact between the electrical poles of the microswitch 11 makes it possible to trigger the stopping of the operation of the compression device of the invention, in particular the stopping of the translational movement of the piston 5 and the stopping of the fluid supply 20 of the second compression compartment 8.

Advantageously, the device of the invention is fluidly connected to fluid supply means 20, the starting or stopping of which is controlled by a first control. In addition, the translational movement or stopping of the piston 5 is controlled by a second command. The means 11 for detecting a flow of fluid 20 are then electrically connected to the first and second controls by at least one electric cable 13, thus forming a closed electric circuit. The pressure exerted on the tongue 12 of the microswitch when a flow of fluid escapes from the second compartment 8 through the orifice 9 then opens the circuit and triggers the stopping of the translational movement of the piston 5 and the stopping of the 'fluid supply 20.

As explained previously, the pressure detection thresholds of the microswitch are advantageously chosen so that the microswitch is capable of and designed to detect only a flow of fluid 20 exerting a pressure at the level of the means 11 greater than that exerted by the slight air flow resulting from the movement of the hydraulic piston 5a in the second compartment 8.

In other words, the slight air flow resulting from the movement of the hydraulic piston 5a in the second compartment 8 does not exert sufficient pressure for the tongue 12, as the case may be, to bring into contact or interrupt the electrical poles of the microswitch. .

To do this, the microswitch is advantageously characterized by a non-zero electrical contact opening or closing tripping threshold, in other words by a minimum force necessary to actuate the non-zero tongue 12. Preferably, this threshold or this force is at least 0.1 N, more preferably at least 0.4 N, typically of the order of 0.44 N.

It is then understood that by using a microswitch according to the invention, the electrical poles of the microswitch each form the terminals of an electric circuit which is open. in normal operation of the compression device, and which can be closed by moving the tab 12 under the effect of a flow of fluid escaping through the orifice 9.

Alternatively, the electrical poles of the microswitch each form the terminals of an electrical circuit which is closed in normal operation of the compression device, and which can be opened by displacement of the tab 12 under the effect of a flow. of fluid escaping through port 9.

The tab 12 thus acts as a switch. The invention therefore has the advantage of not requiring any other electrical alarm triggering device than the tongue of the microswitch itself, nor any intermediate mechanical device.

In this way, the detection of a leak occurring at the level of the sealing means 4 and generating the escape of a flow of fluid 20 through the orifice 9 simply and quickly triggers the stopping of the compression device. , in particular stopping the movement of the piston through the sealing means 4 and stopping the supply of the first compartment 7 with fluid 20.

This makes it possible to stop the compression device automatically and quickly, and therefore to greatly limit, or even eliminate, the aforementioned risks of breakage of constituent elements of the compression device, in particular of the piston 5.

In the context of the invention, the device of the invention is suitable for and designed to compress a fluid 20 in the second compartment 8 by translation of the piston 5 in the direction of the second compartment 8, the initial pressure of fluid 20 being between 200 and 1500 bar and the pressure of the compressed fluid being between 300 and 5000 bar, preferably up to 4000 bar.

Depending on the case, one or more exhaust orifices 9 can be arranged in the peripheral wall 1 of the second compartment 8. Preferably, these orifices 9 have diameters of between 9 and 10 mm, more preferably of the order of 9.7. mm.

In the case of several orifices 9, all or part of the orifices 9 may be provided with means 11 for detecting the flow of fluid in accordance with the invention. When only part of the orifices 9 is provided with means 11 according to the invention, the orifice (s) which are not provided with means 11 may be blocked, so as to increase the flow of fluid 20 escaping from one or more orifices provided with means 11, or else left free.

In all cases, the device of the invention is preferably suitable for and designed to compress a fluid 20 located in the first compartment 7 in the liquid state, the fluid 20 passing from the first compartment 7 to the second compartment 8 and s' escaping from the second compartment 8 through the orifice 9 being in the gaseous state.

In a particular embodiment of the invention, visible on the Figures 3a and 3b , the compression device of the invention further comprises at least one part 10 for holding the means 11 for detecting a flow of fluid 20 at the level of the orifice 9.

The retaining part 10 comprises an axial recess 15 extending through axis A in which the means 11 for detecting a flow of fluid 20 are arranged, the retaining part 10 being positioned against the peripheral wall 1 of the second compartment 8 so that the axis A of the axial recess 15 is substantially aligned with the center of the exhaust port 9.

The retaining part 10 can for example be fixed to the external surface of the peripheral wall 1 by means of at least one screw 14.

In this way, the axial recess 15 constitutes a fluid conduit extending the orifice 9 to channel a flow of fluid 20 escaping from the second compartment 8 through the orifice 9, and thus improve the sensitivity of the detection means 11.

Preferably, the detection means 11 arranged in the axial recess 15 do not hermetically seal said axial recess 15 and allow the passage of a flow of fluid to the outside of the second compartment 8. In this way, it There is no risk of overpressure in the second compartment 8 during the passage of a flow of fluid 20 from the first compartment 7 to the second compartment 8.

The device of the invention can be used in any type of industrial installation, provided that the latter comprises at least one fluid compression device, for example an Ultra High Pressure (UHP) water jet working installation. .

However, the invention is particularly advantageous in the context of a compression device suitable for and designed to serve as a compression device in a working installation using cryogenic fluid jets.

In fact, the device of the invention makes it possible to greatly limit the aforementioned problems linked in particular to cryogenic temperatures and to the high pressures of the fluid 20 prevailing in the first compartment 7.

In addition, the device of the invention offers the advantage of being able to and designed to trigger the stopping of the movement of the piston and / or the supply of fluid to the compression compartment almost instantaneously after the detection of a lack of sealing of the sealing means 4, and in a much faster manner than with the delay time of the order of 10 seconds used in the prior art.

Finally, the presence of an operator near the controls of the compression device is no longer essential, which is a considerable advantage for limiting production costs. The device of the invention is also particularly advantageous when the presence of an operator near the work installation is to be avoided, as is the case for certain applications in the nuclear or chemical industries.

Thus, according to another aspect, the invention also relates to a working installation implementing at least one jet of fluid 20 at cryogenic temperature under high pressure, preferably the fluid 20 is nitrogen.

FIG. 4 shows schematically the architecture of a working installation for implementing a method of pickling, surface treatment or the like by jets of cryogenic liquid, in particular of liquid nitrogen, in particular a method of working by jets of water. 'liquid nitrogen.

As can be seen, such an installation comprises means 41 for supplying fluid 20. The supply means 41 typically comprise a fluid reservoir 20, preferably a large capacity storage reservoir, such as a truck tank or a tank. storage capacity of several thousand liters. In general, the fluid 20, preferably nitrogen, is stored in the liquid state at cryogenic temperature.

The fluid 20 is conveyed between the different elements of the installation via fluid supply conduits, or pipes, preferably insulated. The starting and / or stopping of the supply means 41 are controlled by a first command.

The supply means 41 supply fluid 20 to a compression unit 42 via at least one conduit 45 for supplying fluid. The compression unit 42 comprises at least two compression stages as well as an internal heat exchanger 43.

Typically, the compression unit 42 comprises a first compression device which is supplied by the fluid 20 circulating in the duct 45 at low pressure, that is to say at a pressure of about 3 to 6 bar, and at a temperature of approximately -180 ° C. This first compression device allows the fluid 20 to be brought to a first pressure, typically greater than 200 bar and preferably ranging up to 1000 bar.

The fluid 20 at cryogenic temperature at the first pressure is conveyed to a second compression device in which it is again compressed to a second pressure typically ranging up to 4000 bars. The fluid 20 compressed at the second pressure is then conveyed via a conveying line 46 to the external heat exchanger 43 where it is cooled with liquid nitrogen at atmospheric pressure (at 48).

This results in a 20 UHP fluid, at a pressure typically greater than 300 bar and generally up to 5000 bar, preferably up to 4000 bar, and at a cryogenic temperature between -100 and -200 ° C, typically lower at -140 ° C, typically between -140 ° C and -160 ° C, which is sent, via a supply line 47, to a pickling tool or nozzle 44 or the like delivering one or more jets of 20 UHP fluid , generally several jets, preferably liquid nitrogen jets.

In the context of the present invention, the second compression device is a piston compression device as shown schematically on the figure. Figures 3a and 3b comprising a first and a second compartment 7, 8 and a piston 5 driven by a hydraulic piston 5a. The first compartment 7, which is the one in which the compression takes place at the second pressure, is supplied with the fluid 20 at cryogenic temperature and at the first pressure.

In addition, the installation of the invention comprises a second control which controls the setting in motion and the stopping of the piston 5 in at least part of the first and second compartments 7, 8.

According to the invention, the second compression device comprises means 11 for detecting a flow of fluid 20 electrically connected to the first and to the second control and allowing, in the event of the escape of a flow of fluid 20 from the second compartment 8 to the second compartment 8 of the compression device 43, to trigger the stopping of the translational movement of the piston 5 and the stopping of the supply of fluid 20. The means 11 for detecting a flow of fluid 20 can also be electrically connected to an emergency stop control of the installation making it possible to cut off the general electrical supply of the installation, which has the effect of stopping in particular the translational movement of the piston 5 and the power in fluid 20.

The main application of the present invention is a working method implementing a working installation according to the invention by means of one or more jets of fluid 20 at cryogenic temperature under high pressure, preferably one or more jets of liquid nitrogen, for carrying out a surface treatment, pickling, cleaning, peeling or cutting of a material by means of an installation according to the invention.

Claims (10)

1. Compression device comprising a first compartment (7), a second compartment (8) comprising a peripheral wall (1) secured to the first compartment (7), a passage (16) being created between the first and second compartments (7, 8), a piston (5) arranged in the passage (16) and able to move translationally in at least part of the first and second compartments (7, 8) and sealing means (4) arranged around the piston (5) at the level of the passage (16) so as to ensure, under normal conditions of use, a fluid-tight seal between the said first and second compartments (7, 8), the second compartment (8) further comprising at least one exhaust orifice (9) created in the peripheral wall (1) of the second compartment (8) and fluid flow detection means (11) arranged at the exhaust orifice (9) so as to detect a flow of fluid (20) escaping from the second compartment (8) via the exhaust orifice (9) and resulting from a flow of fluid (20) passing from the first compartment (7) to the second compartment (8) via the passage (16) in the event of a loss of fluid tightness between the first and second compartments (7, 8), characterized in that the fluid flow detection means (11) comprise a microswitch comprising at least two electric poles and a blade (12) able to be brought into contact with the said electric poles at respective contact points of the blade, the said blade being able to be actuated under the effect of a pressure applied by a flow of fluid (20) to the said blade (12) in such a way that the blade (12) makes or breaks electrical contact between the said electric poles when a flow of fluid (20) is escaping via the exhaust orifice (9).
2. Device according to Claim 1, characterized in that the blade (12) is able to move under the effect of a pressure applied by a flow of fluid (20) to the said blade (12) between at least two positions comprising:

   - an open position when a zero or near-zero flow of fluid (20) is escaping from the second compartment (8) via the exhaust orifice (9), the electric poles of the microswitch (11) not being in electrical contact, and

   - a closed position when a flow of fluid (20) is escaping from the second compartment (8) via the exhaust orifice (9), the electric poles of the microswitch (11) being brought into electrical contact via the blade (12).
3. Device according to Claim 1, characterized in that the blade (12) is able to move under the effect of a pressure applied by a flow of fluid (20) to the said blade (12) between at least two positions comprising:

   - an open position when a flow of fluid (20) is escaping from the second compartment (8) via the exhaust orifice (9), the electric poles of the microswitch (11) not being in electrical contact, and

   - a closed position when a zero or near-zero flow of fluid (20) is escaping from the second compartment (8) via the exhaust orifice (9), the electric poles of the microswitch (11) being brought into electrical contact via the blade (12).
4. Device according to one of the preceding claims, characterized in that the means (11) for detecting a flow of fluid (20) are able and designed to detect a flow of fluid (20) escaping from the second compartment (8) via the orifice (9) in which the pressure, the flow rate or the velocity at the detection means (11) are respectively higher than a predetermined pressure detection threshold, a predetermined flow rate detection threshold or a predetermined velocity detection threshold.
5. Device according to one of the preceding claims, characterized in that the means (11) for detecting a flow of fluid (20) produce an electrical alarm signal when a flow of fluid (20) escaping from the second compartment (8) via the orifice (9) is detected.
6. Device according to one of the preceding claims, characterized in that it is fluidically connected to means (41) for supplying fluid (20), the switching on and/or off of which are controlled by a first control, the said device also being electrically connected to a second control that controls the starting and stopping of the piston (5) and the means (11) for detecting a flow of fluid (20) being electrically connected to the first and the second controls in such a way that a pressure applied by a flow of fluid (20) to the said blade (12) so as to make or break the electrical contact between the electric poles of the microswitch triggers the stopping of the translational movement of the piston (5) and the switching-off of the supply of fluid (20).
7. Working installation employing at least one jet of fluid (20) at cryogenic temperature and under high pressure, comprising at least one nozzle (44) for distributing a jet of fluid (20), means (41) for supplying fluid (20), the switching on and off of which are controlled by a first control, at least one compression unit (42) supplied with fluid (20) by the supply means (41) and an external heat exchanger (43), the compression unit (42) comprising at least a first and a second compression device, which second compression device comprises a first and a second compartment (7, 8), a piston (5), a second control controlling the starting and/or stopping of the piston (5) and an internal heat exchanger, the at least one compression unit (42) and heat exchanger (43) collaborating with the means for supplying fluid (20) to supply the at least one nozzle (44) for distributing a jet of fluid (20), characterized in that the second compression device is a device according to one of the preceding claims.
8. Installation according to Claim 7, characterized in that the second compression device comprises means (11) for detecting a flow of fluid (20), which means are electrically connected to the first and second controls, the said detection means (11) comprising a microswitch comprising at least two electric poles and a blade (12) that can be actuated under the effect of a pressure applied by a flow of fluid (20) to the said blade (12) so that the blade (12) makes or breaks electrical contact between the said electric poles when a flow of fluid (20) is escaping from the first compartment (7) towards the second compartment (8) and triggers the stopping of the translational movement of the piston (5) and the switching-off of the supply of fluid (20).
9. Installation according to one of Claims 7 and 8, characterized in that the fluid (20) is at a pressure comprised between 300 and 5000 bar, preferably comprised between 1000 and 4000 bar, and at a temperature comprised between -100°C and -200°C, preferably comprised between -140°C and -160°C.
10. Installation according to one of Claims 7 to 9, characterized in that it is able and designed to perform a surface treatment, a blasting, a cleaning, a descaling or a cutting of a material.

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