EP0628723B1 - Self-cooling integrated pump for cryogenic liquid - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to a self-cooled cryogenic liquid pump intended to be removably integrated into a cryogenic liquid reservoir and allowing either the transfer of this liquid at moderate pressure, or the production of gas under high pressures. Nitrogen, argon, oxygen, hydrogen and liquid helium are the products most particularly concerned by such a device.

PRIOR ART

Conventionally, the liquid pumps used in a cryogenic environment, whether of the centrifugal or piston type, are placed outside the source of liquid. This results in many drawbacks, the main one being the need to pre-cool the pump before starting it. Indeed, it must take place according to complex cycles which naturally cause, during their implementation, a lack of availability of this pump. In addition, in these devices of the prior art, only a use based on liquid nitrogen is really common. For example, there are no high pressure pumps operating from liquid helium and it is therefore necessary to compress this liquid in gaseous form to allow its use, which is particularly disadvantageous in energy as in investment, c is to say ultimately in cost. A similar problem arises with the use of liquid hydrogen.

Patent document WO 84/02969 has attempted to provide a solution to these problems by proposing to immerse the pump in the cryogenic liquid (in this case liquid nitrogen). However, such a pump has proved to be particularly fragile, in particular at the level of its shaft line, limiting the necessary reliability that can be expected from such a device.

Another solution is taught by French patent FR 771 813 which discloses a pump integrated into a tank of liquefied gas at low pressure. However, this pump being integral with the tank, it is of course not possible to ensure its removal in service, which is particularly troublesome when a malfunction of the pump is observed. In addition, since this pump does not ensure perfect control of the pressure, gas returns through the outlet, and not only through the purge duct, are entirely possible. Last but not least, as the pump is not at liquid temperature, the temperature difference between its cold interior and its warm exterior has the effect of causing thermal shock detrimental to its operation.

DESCRIPTION OF THE INVENTION

The present invention aims to overcome the aforementioned drawbacks and to provide a removable and self-cooled cryogenic liquid pump which can be used with any type of cryogenic liquid and in particular hydrogen and liquid helium. Another object of the invention is to provide a pump of simple and reliable structure which allows perfect control of the pressure, making it particularly adaptable to different operating conditions.

These aims are achieved by a cryogenic liquid pump provided with a pump body and actuated by a motor assembly and integrated into a cryogenic liquid tank, characterized in that said removable pump body can slide in a well and be selectively activated. communication with the reservoir, a first valve allowing, in the open position, a transfer of the liquid from the reservoir to the pump body before its evacuation in liquid or gaseous form through an outlet orifice and a second valve allowing, in the position of opening, the establishment of a cold gas flow from the gaseous sky of this tank towards a rear end of the pump body from which it is evacuated towards the outside by a purge / purge orifice. The purge / sweep orifice is provided at the outlet with a device for adjusting the cold gas flow leaving the pump body.

The adjustment device makes it possible to regulate the cold gas flow discharged to the outside which may result, for example, from additional calories due to friction losses from the pump.

According to a first embodiment, the first and second valves are put in the open position, during installation and fixing of the pump body in the well, by a double stopper fixed to a front end of this pump body and acting on each of these valves to cause their lifting.

According to a second embodiment, the second valve is placed in the open position, during installation and fixing of the pump body in the well, by a stopper fixed to a front end of the pump body and causing it to be lifted. , the first valve being placed in the open position by a control device external to the pump body.

Advantageously, this pump comprises sealing devices placed respectively between the well and the pump body and between the well and the exterior.

In a first variant applicable to one or other of the preceding embodiments, the pump body is coupled to a sealed motor, the assembly formed by these two elements being isolated from the outside by a sealed connection connecting them in solidarity. In a second variant, the pump body is coupled to a motor with submerged rotor, the stator being separated from the rotor by a sealed jacket secured to the pump body.

For each of these variants, the watertight partition formed by the connection or the jacket has a bleed orifice.

This separation of the stator and the submerged rotor is advantageous when the fluid used is incompatible (for example corrosive) with the materials used in the stator. In the extreme, by using a fully sealed motor, it becomes possible to use known and reliable components, thereby reducing the cost of the pump.

When the cryogenic liquid pump is intended to be mounted on a double-walled tank, the pump body is preferably mounted on the internal wall of the tank, a sealed connection connecting the external wall of the tank to the side wall of the well and making it possible to leave the space between walls at the pressure of the vacuum to which it was subjected before integrating the pump.

Depending on the use and the performance required, the pump according to the invention will be, without this list being limiting, of the centrifugal, axial or piston type.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue en coupe d'une pompe liquide cryogénique à piston pourvue d'un moteur étanche,
• la figure 2 est une vue en coupe d'une pompe liquide cryogénique centrifuge pourvue d'un moteur étanche,
• la figure 3 est une vue en coupe d'une pompe liquide cryogénique centrifuge pourvue d'un moteur semi-immergé, et
• les figures 4 à 6 montrent des exemples de disposition de pompes selon l'invention au niveau de réservoirs cryogéniques de différentes formes.

Other characteristics and advantages of the present invention will emerge more clearly from the following description, given by way of non-limiting illustration, with reference to the appended drawings, in which:

• FIG. 1 is a sectional view of a cryogenic liquid piston pump provided with a sealed motor,
• FIG. 2 is a sectional view of a centrifugal cryogenic liquid pump provided with a sealed motor,
• FIG. 3 is a sectional view of a centrifugal cryogenic liquid pump provided with a semi-submerged motor, and
• Figures 4 to 6 show examples of arrangement of pumps according to the invention in cryogenic tanks of different shapes.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Figure 1 illustrates a first embodiment of a cryogenic liquid pump according to the invention. The cryogenic pump described with reference to this figure is a high pressure piston pump intended for the production of gas and driven by a sealed electric motor. Obviously, the invention is not limited to this single type of pump and an axial, centrifugal pump (see for example Figures 2 and 3) or of any other type can be similarly implemented. Similarly, the use of an electric motor is not compulsory and all types of motor can be envisaged such as hydraulic, pneumatic or even thermal motors without omitting gas turbines for example.

The pump according to the invention comprises a pump body 10 which can be installed by sliding in a well 12, a first end 18 of which is rigidly fixed, for example by welding, to a wall 14 of a reservoir 16 containing a cryogenic liquid. This first end of the well is closed by a valve device 20, the opening of which, bringing the reservoir into communication with the well, is caused, during the installation of the pump body in the well, by the action of 'A double cleat 22 acting on the seat of the valve device. The valve device comprises a first valve 24, the lifting of which by the double stopper causes the cryogenic liquid to pass through the pump body and a second valve 26, the lifting of which by this same stopper allows the overhead gas communication of this tank with the rear part 28 of the pump body, this communication being made possible by the presence of a tube 30 passing through the reservoir between the valve, point of withdrawal of the liquid, and the overhead gas. The free end of the well 12 is terminated by an external flange 32 on which is fixed, by a screw / washer assembly, a first end 36 of the pump body, an opposite end 38 of this pump body being in contact with The reservoir. A seal 40 placed at this second end 38 and whose crushing pressure is fixed by the screw / washer assembly 34, seals between the well and the pump body and limits the differential expansions between these two elements. . Flange seals 76 ensure, during a partial withdrawal of the pump, a seal between the side wall of the well and the outside.

The piston pump body is actuated by an oblique turntable assembly 42 driven by a shaft 44 itself connected to a sealed electric motor 46 by means of a coupling 48. The motor 46 is mechanically decoupled by force of the pump by a support structure 50 (which can advantageously be fixed to the wall of the tank) ensuring centering of the motor by an axis 52. A deformable tight connection 54 ensures sealing (a seal 56 being kept pressed against the end 36 of the pump body by fixings 58) and the isolation of the entire device according to the invention from the outside.

The fluid is evacuated by an outlet pipe 60 connected to the rear end (in the direction of introduction of the pump) 36 of the pump body. An adjustment device 62 is placed at the outlet of a purge / sweep orifice 64 opening on the side wall of the well 12 and on the inside of the pump body 10, substantially at the free end 32 of the well. Likewise, a second bleed orifice 68 is present at the level of the deformable tight connection 54.

Advantageously, the reservoir 16 can be provided with a second wall 70, a second deformable link 72 then connecting it to the side wall of the well 12 in a sealed manner, the space 74 between the two walls of this reservoir being at the pressure of the empty.

The operation of the pump according to the invention is as follows. It is recalled that the installation of the pump body in the well causes the latter to communicate with the tank and in particular the connection of the gaseous sky of the tank, which is by nature in overpressure relative to the outside (any tank closed cryogenic increases in pressure), with the rear part of the pump body. The opening of the adjustment device then allows the establishment of a cold gas flow to the outside which will naturally cool the entire pump body by compensating for the thermal inputs of the device and therefore allow a immediate start of the pump. Once it is started and in operation, the excess calories due in particular to friction losses in the pump body will also be evacuated by the purge / sweep orifice, the adjustment device then having a larger opening to allow the evacuation of those extra calories. Obviously, the outlet line must be thermally compatible with the fluid used, a thermally insulated or vacuum-insulated outlet line may for example be necessary.

In the event of a pump malfunction, it can be easily removed and replaced. Indeed, the separation of the pump body from the well, the motor having previously been also separated from its support, allows its sliding in the well (the pump being in principle mounted in a vertical position) and correspondingly the closure of the valve device which causes the liquid supply to the pump to be cut off as well as the establishment of the cold gas flow, the seal between the well and the exterior however remaining ensured due to the presence of the flange seals. During this extraction, care will have been taken to introduce through the purge / sweeping orifice 64 a gas of determined composition to protect against any air intake, this sweeping being maintained during the installation and the connection of a new pump.

Thus, the installation of this pump is possible very quickly and the internal assembly of the pump being conditioned, via the orifice 68, with the same fluid as that with which it will have to operate, any risk of pollution by the ambient air is eliminated and the complex and once essential sanitation operations are consequently avoided.

By this possibility of rapid replacement, the cryogenic pump according to the invention offers exceptional qualities of availability which reinforce its ability to instant start made possible by the withdrawal of cold gas inside the cryogenic liquid tank.

FIG. 2 illustrates a second embodiment of a cryogenic liquid pump according to the invention. The pump described here is a centrifugal pump with a sealed electric motor. The elements common with the pump of Figure 1 have the same references. Thus the tank 16 with double wall 14 and 70; the motor 46, its coupling 48, its support 50 and its sealed connection 54 with the pump body; the fasteners 34 and 58 between the end of the pump body 36 and respectively the collar 32 of the well and this sealed connection 54; the fluid and purge outlets 60 and 62, 64; finally, in the presence of a double-walled tank, the sealed connection 72 with the well 12.

The body of the centrifugal pump 10 is connected to a valve body 100 comprising a seat 110 whose opening is controlled by a control assembly 120 and the turbine 130 ensures the pumping of the liquid as soon as this seat is opened. A stopper 220 placed on the valve body causes, when the pump is put in place, the opening of a valve 260 for placing the gas headspace in communication with the rear of the pump body. A filter 200 is placed at the inlet of the valve body at the level of the reservoir 16.

The operation of this pump is almost identical to the previous one (subject of course to the operating conditions: at low pressure for this centrifugal liquid transfer pump or at medium and high pressure for the previous piston pump) with the exception of liquid transfer from tank to the pump, the departure of which can, in this embodiment, be controlled by means of the control assembly 120. As previously, the cooling of the device is immediate, the installation of the pump in the well having the effect of open the valve 260 and therefore cause the establishment of a cold gas flow in this pump.

FIG. 3 is an alternative embodiment of a liquid cryogenic pump of FIG. 2 in which the control motor 400 of the pump is of the semi-submerged type with a rotor 460 subjected to the action of cold gases coming from the tank and a stator 470 isolated from these by a gap 480 secured to the pump body by the fixings 58. As before, a purge member 68 is present but placed on the jacket 480. It can be noted that this configuration is especially interesting when the rotor materials are compatible with the nature of the gas present in the pump body.

FIGS. 4 to 6 schematically show examples of the arrangement of the pump according to the invention at the level of cryogenic liquid tanks of different shapes. Each however has a filling / emptying line 150 and a degassing line 160. Of course, there is the well 12 (the pump and the motor have not been shown) as well as the tube 30 for collecting cold gas in the gaseous sky of the reservoir. The well is advantageously placed at the base of the tank and the degassing line at its top. Preferably, the filling line is also placed at the base of the tank. It should be noted that the simplicity of the external structure of the invention allows it to be adapted to all types of tanks: horizontal, vertical or spherical for example.

Claims (9)

1. Cryogenic liquid pump provided with a pump body and driven by a motor assembly and integrated in a cryogenic liquid tank, characterized in that said pump body is removable (10) and can be put selectively in communication with the tank (16) by sliding in a well (12), a first non-retum valve (24, 110) making it possible when in the open position to transfer liquid from the tank to the pump body prior to evacuation thereof in the form of a liquid or a gas via an outlet orifice (60), and a second non-return valve (26, 260) making it possible, when in the open position, to establish a flow of cold gas from the gas overhead of the tank towards a rear end (28) of the pump body from which it is exhausted to the outside via a sweeping/venting orifice (64).
2. Cryogenic liquid pump according to claim 1, characterized in that the sweeping/venting orifice (64) is provided at its outlet with a device (62) for adjusting the flow rate of cold gas leaving the pump body (10).
3. Cryogenic liquid pump according to claim 1 or claim 2, characterized in that the first and second non-return valves (24, 26) are put in the open position during installation and fastening of the pump body in the well by means of a double-headed driver (22) fixed at a front end (38) of said pump body and acting on each of said non-return valves in order to cause them to open.
4. Cryogenic liquid pump according to claim 1 or claim 2, characterized in that the second non-retum valve (260) is put into the open position while the pump body is being installed and fastened in the well by means of a driver (220) fixed to a front end of the pump body that causes the non-retum valve to open, and in that the first non-retum valve (110) is put into the open position by a control device (120) external to the pump body.
5. Cryogenic liquid pump according to any one of claims 1 to 4, characterized in that it includes sealing devices (40, 76) placed respectively between the well and the pump body, and between the well and the outside.
6. Cryogenic liquid pump according to any one of claims 1 to 5, characterized in that the pump body is coupled to a sealed motor (46) the assembly constituted by said two elements being isolated from the outside by a sealed link (54) that connects them together.
7. Cryogenic liquid pump according to any one of claims 1 to 6, characterized in that the pump body is coupled to a motor (400) having an immersed rotor, the stator (470) being separated from the rotor (460) by a sealed jacket (480) secured to the pump body.
8. Cryogenic liquid pump according to claim 6 or claim 7, characterized in that the sealed partition (54, 480) includes a venting orifice.
9. Cryogenic liquid pump according to any one of claims 1 to 8, integrated in a double-walled tank (16), and characterized in that the pump body (10) is mounted on the inside wall (14) of the tank, a sealed link (72) connecting the outside wall (70) of the tank to the side wall of the well and making it possible to leave the space (74) between the walls at the vacuum pressure to which it is subjected prior to installing the pump.

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