EP2662565A1 - Compression device for cryogenic jet fluid installations - Google Patents

Abstract

The device has a set of compartments (8) including a peripheral wall that is attached to one of the set of compartments. A passage is arranged between the set of compartments. A compression piston (5) is arranged in the passage. A detection unit (11) detects a flow of fluid i.e. liquid nitrogen. A micro switch includes two electric poles. A strip (12) is actionable under the effect of pressure by the flow of fluid on the strip so that the strip ensures or interrupts an electrical contact between the poles when the flow of fluid escapes by an exhaust opening (9). An independent claim is also included for a work installation.

Description

An improved piston compression device is provided by a more reliable and rapid detection of leaks that may occur around said piston. The invention further relates to a working installation by high-pressure cryogenic fluid jet whose operation is improved and made safer by the use of a compression device according to the invention, which installation is suitable for and designed to perform surface treatment, stripping, cleaning, scraping or cutting of a material.

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

For this purpose, one or more jets of cryogenic fluid under high pressure, usually liquid nitrogen, are typically used at a pressure of 300 to 5000 bar, 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 animated or not of a rotary movement or an oscillation movement.

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

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

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

The fluid compressed at the second pressure is then conveyed via a conveyor 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. C and -160 ° C, which is sent to a pickling 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. Compression of the fluid is performed by a compression piston movable in translation in the compression compartment, which piston is arranged in a passage in a wall of said compartment.

In addition, sealing means, typically a gasket, generally a seal formed of a plastic material with a metal strapping, are arranged around the piston, at the passage formed in a wall of the compartment in which is the compression of the fluid. These sealing means are adapted to and designed to ensure a fluidic seal between the inside and the outside of the compartment, the outside of the compartment being generally at atmospheric pressure.

The seal of the second compression device is subjected to high thermal and mechanical stresses which cause a term wear, or even complete failure, of the seal.

Indeed, the movements in translation back and forth of the piston occurring during the many compression cycles of the cryogenic fluid generate a 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, during the filling of the cryogenic fluid in the compression compartment, the fluid is at cryogenic temperature, while after compression, the fluid has a temperature close to room temperature.

The wear of the seal progressively alters its fluidic sealing performance. It follows leakage of fluid at the passageway arranged in a wall of the compression compartment of the compression device, and therefore a loss of efficiency of said device, in particular a decrease in the pressure of 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, i.e., round trips of the piston per minute.

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

In order to reduce the fluid pressure in the compression chamber 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 before the pressure is established, and can regulate the pressure of the cryogenic fluid dispensed by the installation of work .

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

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

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

However, the process described above is also triggered during wear or rupture of the seal, these phenomena also producing a decrease in the fluid pressure in the compression compartment. In this case, the frequency of the movements of the piston remains abnormally high for the duration of typically 10 seconds and the working installation continues to function at the end of said period.

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

These pieces of joints become very hard because of the cryogenic temperatures prevailing in the compression compartment. It follows an increased risk of breakage of components of the compression device, including the piston which is generally formed of a relatively fragile material, such as ceramic.

The breakage of the piston then requires a long and costly intervention, which negatively impacts the productivity of the installation, and this more important than if it had been necessary to proceed simply to change the worn seal.

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

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

In particular, an object of the invention is to provide a working installation by jets of cryogenic fluid under high pressure whose operation is improved and made safer than in the prior art.

The solution of the invention is then 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 a portion of the first and second compartments and sealing means arranged around the piston at the passage so as to ensure, under normal conditions of use, a fluidic seal between said first and second compartments, the second compartment further comprising at least one exhaust port provided in the peripheral wall of the second compartment and fluid flow detecting means arranged at the exhaust port for detecting a flow of escaping fluid the second compartment through the exhaust port and resulting from a flow of fluid passing from the first compartment to the second compartment through the passage in the event of fluidic leakage between the first and second compartments, characterized in that the means for detecting a fluid flow comprise a microswitch comprising at least two poles and a tongue actuatable under the effect of a pressure exerted by a fluid flow on said tongue so that the tongue ensures or interrupts an electrical contact between said electric poles when a flow of fluid escapes through the exhaust port.

• 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.

Moreover, according to the embodiment considered, the invention may include one or more of the following features:

• the tongue (12) is able to move under the effect of a pressure exerted by a fluid flow (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 electric 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 tongue (12).
• the tongue (12) is able to move under the effect of a pressure exerted by a fluid flow (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 electric poles of the microswitch (11) being electrical contact by the tongue (12).
• the means for detecting a fluid flow are adapted to and designed to detect a flow of fluid escaping from the second compartment through the orifice whose pressure, flow rate or velocity at the level of the detection means are respectively greater than a pressure detection threshold, a flow detection threshold or a predetermined 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 whose start and / or stop are controlled by a first control, said device being further 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 second controls so that a pressure exerted by a fluid flow on said tongue so as to ensure or interrupt the contact electrical connection between the electric poles of the micro-switch triggers the stop of the translational movement of the piston and the stopping of the supply of fluid.

According to another aspect, the invention also relates to a working installation using at least one cryogenic fluid jet under high pressure comprising at least one nozzle for dispensing a fluid jet, means for supplying fluid , whose start and stop 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 central compressor and heat exchanger cooperating with the feed means fluid for supplying the at least one nozzle for dispensing a fluid jet 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 electric poles and a tongue that can be actuated under the effect a pressure exerted by a flow of fluid on said tongue so that the tongue ensures or interrupts an electrical contact between said electric poles when a flow of fluid escapes from the first compartment to the second compartment and triggers the stopping the translation movement of the piston and stopping the supply of fluid.

Preferably, the fluid dispensed 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 perform a surface treatment, stripping, cleaning, scraping 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 schematically a compression device comprising a piston respectively in the retracted position and in the extended position,
• the Figures 3a and 3b schematize a compression device according to one embodiment of the invention, and
• the Figure 4 schematizes a working installation by jets of cryogenic fluid comprising a compression device according to the invention.

As we see 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 is carried out the compressing said fluid 20.

The first and second compartments 7, 8 may be two pieces assembled mechanically, for example by threading as illustrated on the 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 passage 16 so as to ensure, under normal conditions of use, a fluidic 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 of polymer material, a ring of polymer material and a ring of metallic material.

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

The sealing means 4 provide a fluidic seal between the compartments 7, 8 and also serves to guide the piston 5, which piston 5 is movable in translation in at least a portion of the first and second compartments 7, 8 and means of 4. It is specified that the compression piston 5 is generally moved 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 merged. More precisely, the piston 5 is able to move between at least two positions: a retracted position (shown schematically 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 schematically in FIG. Figure 2 ) according to which the piston 5 is translated towards the first compartment 7 with respect to its retracted position.

The second compartment 8 further comprises at least one exhaust port 9 arranged in the peripheral wall 1 of the second compartment 8. The orifice 9 is opening and fluidly communicates the interior, i.e., the internal volume, of the second compartment 8, 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 moved by a hydraulic piston 5a, the free volume of the compartment 8 varies depending on 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, the outside air to the second compartment 8 is sucked through the orifice 9.

In operation, the compression device compresses a fluid 20 in the first compartment 7 when the piston 5 translates towards the first compartment 7 until it is in its extended position.

As already explained, in case of wear of the sealing means 4, in particular of the seal, fluid leaks 20 occur and cause the passage of a flow of fluid 20 from the first compartment 7 to the second compartment 8. The displacement of the piston through the worn seal causes the detachment of pieces of joints that become very hard because of the cryogenic temperatures prevailing in the compression compartment. It follows an increased risk of breakage of the piston 5, as well as the stop ring 3, the retaining ring 6, or even the first compartment 7 itself.

To remedy this, the present invention proposes to arrange means 11 for detecting a fluid flow at the exhaust orifice 9 so as to detect a fluid flow escaping from the second compartment 8 by orifice 9, as illustrated by the 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, it is meant any device for detecting a 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 fluid flow 20 are adapted to 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 fluid leakage fault between the first and second compartments 7, 8.

Preferably, the fluid 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 towards the outside of the compartment 8, in the direction of means 11 for detecting a fluid flow.

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

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

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

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

The pressure, flow rate or speed values of these predetermined detection thresholds will be adjusted according to the characteristics of the compression device of the invention, in particular the pressure prevailing in the first compartment 7, the number of orifices 9 arranged on the second compartment 8. Typically, the values of these detection thresholds may be predetermined empirically, during routine tests conducted under different conditions of use of the compression device of the invention, for example different pressure values 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 velocity are respectively greater than the pressure, flow or velocity variations resulting from the low air flow. generated by the movement of the hydraulic piston 5a.

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

According to the invention, and as illustrated on the Figures 3a and 3b , the means 11 for detecting a fluid flow 20 comprise a device of the micro-switch type. By microswitch means a device comprising at least two electric poles and a tongue 12 actuable under the effect of a pressure exerted by a fluid flow 20 on said tongue 12.

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

Advantageously, a microswitch micro-switch type miniature lever or lever brand Cherry and marketed under the DG13-B3LA reference can be used.

According to one embodiment of the invention, illustrated on the Figures 3a and 3b , the microswitch 11 is arranged at the orifice 9 so that the tongue 12 provides electrical contact between said electric poles when a flow of fluid 20, preferably nitrogen, escapes through the exhaust port 9 and presses on the tongue 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 specifically, the tongue 12 is able to move under the effect of a pressure exerted by a fluid flow 20 on said tongue 12 between at least two positions comprising:

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

Preferably, the second compartment 8 of the compression device of the invention advantageously comprises means 11 for detecting a flow of fluid 20, electrically powered, said means being adapted to and designed to produce an electric 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, notably stopping the translation movement of the piston 5 and stopping the supply of fluid 20 the second compression compartment 8.

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

According to an alternative embodiment of the invention, not shown, the microswitch 11 is arranged at the orifice 9 so that the tongue 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 tongue 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 specifically, the tongue 12 is able to move under the effect of a pressure exerted by a fluid flow 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 a pressure on the tongue 12, the electrical contact between the electric poles of the microswitch 11 being interrupted because of of the displacement of the tongue 12,
• a closed position when a zero or almost zero fluid flow escapes from the second compartment 8 through the exhaust port 9, the tab 12 ensuring electrical contact between the electric poles of the microswitch 11.

Preferably, the interruption of the electrical contact between the electric 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 whose start or stop are controlled by a first command. In addition, the setting in translation movement or the stopping of the piston 5 is controlled by a second command. The means 11 for detecting a fluid flow 20 are then electrically connected to the first and second controls by at least one electrical cable 13, thus forming a closed electrical 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 above, the pressure sensing thresholds of the microswitch are advantageously chosen so that the microswitch is adapted to and designed to detect only a fluid stream 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 contact or interrupt the electrical poles of the microswitch. .

To do this, the microswitch is advantageously characterized by a trigger threshold opening or closing non-zero electrical contact, said otherwise by a minimum force necessary to actuate the tab 12 non-zero. 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 electric poles of the microswitch each form the terminals of an electrical circuit which is open. in normal operation of the compression device, and which can be closed by displacement of the tongue 12 under the effect of a flow of fluid escaping through the orifice 9.

Alternatively, the electrical poles of the micro-breaker each form the terminals of an electric circuit which is closed during normal operation of the compression device, and which can be opened by displacement of the tongue 12 under the effect of a flow. of fluid escaping through the orifice 9.

The tongue 12 thus serves as a switch. The invention therefore has the advantage of requiring no other electrical alarm trigger device that the tab 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 fluid stream 20 through the orifice 9 triggers in a simple and fast manner 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 in an automatic and rapid manner, and thus to greatly limit, or even eliminate, the aforementioned risks of breakage of components of the compression device, in particular the piston 5.

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

Depending on the case, one or more exhaust ports 9 may 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 fluid flow detection means 11 according to the invention. When only a portion of the orifices 9 is provided with means 11 according to the invention, the orifices which are not provided with means 11 may be plugged, so as to increase the flow of fluid escaping from one or orifices provided with means 11, or left free.

In any case, the device of the invention is preferably adapted to and designed to compress a fluid 20 in the first compartment 7 in the liquid state, the fluid 20 passing from the first compartment 7 to the second compartment 8 and 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 holding member 10 of the means 11 for detecting a fluid flow 20 at the orifice 9.

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

The holding piece 10 may for example be fixed on the outer 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 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 towards 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, as long as it comprises at least one fluid compression device, for example an ultra high pressure water jet (UHP) working installation. .

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

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

In addition, the device of the invention offers the advantage of being adapted to and designed to trigger the stopping of the movement of the piston and / or the supply of fluid of the compression compartment almost instantaneously after the detection of a sealing defect of the sealing means 4, and much faster 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 to limit production costs. The device of the invention is also particularly advantageous when the presence of an operator near the work facility is to be avoided, as is the case for certain applications of the nuclear or chemical industries.

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

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

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

The fluid conveying 20 between the various elements of the installation is done via fluid supply ducts, or pipes, preferably insulated. The start and / or stop of the supply means 41 are controlled by a first command.

The supply means 41 feed fluid 20 to a compression unit 42 by 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 fed by the fluid circulating in the conduit 45 at low pressure, that is to say at a pressure of approximately 3 to 6 bar, and at a pressure of temperature of about -180 ° C. This first compression device allows a first pressure of the fluid 20, typically greater than 200 bar and preferably up to 1000 bar.

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

This results in a 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 feed line 47 to a pickling tool or nozzle 44 or the like delivering one or more UHP fluid jets. in general several jets, preferably jets of liquid nitrogen.

In the context of the present invention, the second compression device is a piston compression device as schematized on the Figures 3a and 3b comprising a first and a second compartment 7, 8 and a piston 5 mu 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 by 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 a 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 the second control and allowing, in the event of the escape of a fluid flow 20 of the second compartment 8 to the second compartment 8 of the compression device 43, to trigger the stop of the translational movement of the piston 5 and the stoppage of the fluid supply 20. The means 11 for detecting a flow of fluid 20 can also be electrically connected to an emergency stop command of the installation to cut off the general power supply of the installation, which has the effect of stopping in particular the translational movement of the piston 5 and the power supply. 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 at cryogenic temperature under high pressure, preferably one or more jets of liquid nitrogen, for performing a surface treatment, stripping, cleaning, scraping or cutting of a material by means of an installation according to the invention.

Claims (10)

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 arranged between the first and second compartments (7, 8) , a piston (5) arranged in the passage (16) and movable in translation in at least a portion of the first and second compartments (7, 8) and sealing means (4) arranged around the piston (5) at the the passage (16) so as to ensure, under normal conditions of use, a fluidic seal between said first and second compartments (7, 8), the second compartment (8) further comprising at least one exhaust port ( 9) arranged in the peripheral wall (1) of the second compartment (8) and means (11) for detecting a flow of fluid arranged at the exhaust port (9) so as to detect a flow of fluid (20) 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 fluid leakage fault between the first and second compartments (7, 8), characterized in that the means (11) for detecting a fluid flow comprise a microswitch comprising at least two electric poles and a tongue (12) operable under the effect of a pressure exerted by a fluid flow (20) on said tongue (12) so that the tongue (12) ensures or interrupts an electrical contact between said electric poles when a fluid flow (20) s escapes through the exhaust port (9). Device according to claim 1, characterized in that the tongue (12) is able to move under the effect of a pressure exerted by a fluid flow (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) does not being not in electrical contact, and - a closed position when a fluid flow (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 tongue (12). Device according to claim 1, characterized in that the tongue (12) is able to move under the effect of a pressure exerted by a fluid flow (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) via the exhaust port (9), the electric 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 in electrical contact by the tongue (12). Device according to one of the preceding claims, characterized in that the means (11) for detecting a fluid flow (20) are adapted to and designed to detect a fluid flow (20) escaping from the second compartment ( 8) through the orifice (9) whose pressure, flow rate or velocity at the detection means (11) are greater than a pressure detection threshold, a flow detection threshold or a detection threshold respectively. predetermined speed. Device according to one of the preceding claims, characterized in that the means (11) for detecting a fluid flow (20) produce an electric alarm signal when a fluid flow (20) escaping from the second compartment (8) through the orifice (9) is detected. Device according to one of the preceding claims, characterized in that it is fluidly connected to fluid supply means (41) whose start and / or stop are controlled by a first command, said device being further electrically connected to a second control controlling the setting in motion and stopping of the piston (5) and the means (11) for detecting a flow of fluid (20) being electrically connected to the first and to the second controls so that a pressure exerted by a fluid flow (20) on said tongue (12) so as to ensure or interrupt the contact electrical connection between the electric poles of the micro-switch triggers the stopping of the translational movement of the piston (5) and the stopping of the supply of fluid (20). Working installation employing at least one cryogenic high pressure fluid jet (20) comprising at least one nozzle (44) for dispensing a fluid jet (20), feed means (41) for fluid (20), whose start and stop 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 setting in motion and / or stopping of the piston 5 and an internal heat exchanger, the at least one compression unit (42) and heat exchanger (43) cooperating with the fluid supply means (20) for feeding the at least one dispensing nozzle (44) a fluid jet (20) characterized in that the second compression device is according to one of the preceding claims. Installation according to claim 7, characterized in that the second compression device comprises means (11) for detecting a fluid flow (20) electrically connected to the first and second controls, said detection means (11) comprising a microphone switch comprising at least two electric poles and a tongue (12) operable under the effect of a pressure exerted by a fluid flow (20) on said tongue (12) so that the tongue (12) ensures or interrupts an electrical contact between said electric poles when a flow of fluid (20) escapes from the first compartment (7) to the second compartment (8) and triggers the stop of the translational movement of the piston (5) and the stopping the fluid supply (20). Installation according to one of claims 7 or 8, characterized in that the fluid (20) 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. Plant according to one of claims 7 to 9, characterized in that it is suitable for and designed for surface treatment, stripping, cleaning, scraping or cutting of a material.

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