Pump and method for pumping cryogenic liquids

Abstract

A pump for pumping cryogenic liquids includes a pump housing having a cylinder, in which a piston is slidably positioned. An intermediate fluid chamber for receiving an intermediate fluid is defined within the cylinder adjacent to a first end of the piston, and a fluid pumping chamber is defined within the cylinder adjacent to a second end of the piston. An intermediate fluid seal is attached to the piston and engages the cylinder. A pumping fluid seal is attached to the piston and configured to engage the cylinder, the pumping fluid seal being spaced apart from the intermediate fluid seal, thereby defining a differential pressure space within the cylinder between the intermediate fluid seal and the pumping fluid seal. A differential pressure vent valve is in fluid communication with the differential pressure space. A differential pressure switch senses the pressure within the differential pressure space and opens the differential pressure vent valve when the pressure within the differential pressure space reaches a predetermined pressure level.

Description

Technical Field

[0001] The present invention generally relates to pumps for cryogenic liquids, and more specifically, to cryogenic pumps that use intermediate fluids and reduce differential pressure on pump seals. Prior Technology

[0002] Cryogenic fluids, such as liquefied natural gas and hydrogen, are fluids with boiling points below -130°F / -90°C. Cryogenic fluids are becoming increasingly important as energy sources and also have many important industrial applications.

[0003] For example, with advancements in fuel cell technology and the use of hydrogen in home power generation, hydrogen is becoming increasingly important as an alternative clean energy source. Furthermore, the use of fuel cell technology, such as in fuel cell-powered vehicles, is growing.

[0004] Like other cryogenic fluids (such as liquefied natural gas), hydrogen is more efficient to transport and store in liquid form. Furthermore, there is a desire to store hydrogen at high density and to transport and use it with reduced volume and low cost to help establish practical hydrogen infrastructure. In addition, other cryogenic liquids often require pressurization for use, transportation, and efficient storage. Therefore, cryogenic pumps are a key component in the storage and transportation of cryogenic liquids.

[0005] Cryogenic pump seals (especially in high-pressure applications) are prone to leakage, which is detrimental to the performance of cryogenic pumps. Summary of the Invention

[0006] Several aspects of this subject matter may be implemented individually or together in the devices and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the individual use of these aspects or individual claims to these aspects or different combinations as set forth in the appended claims.

[0007] On one hand, a pump for pumping cryogenic liquids includes a pump housing defining a cylinder. A piston is slidably positioned within the cylinder such that an intermediate fluid chamber configured to receive an intermediate fluid is defined within the cylinder adjacent to a first end of the piston, and a fluid pumping chamber is defined within the cylinder adjacent to a second end of the piston. The fluid pumping chamber includes an inlet and an outlet. An intermediate fluid seal is attached to the piston and configured to engage the cylinder. A pumping fluid seal is also attached to the piston and configured to engage the cylinder. The pumping fluid seal is spaced apart from the intermediate fluid seal, thereby defining a differential pressure space within the cylinder between the intermediate fluid and the pumping fluid seal. A differential pressure vent valve is in fluid communication with the differential pressure space. A differential pressure switch is operatively connected to the differential pressure vent valve and configured to sense the pressure within the differential pressure space and open the differential pressure vent valve when the pressure within the differential pressure space reaches a predetermined pressure level.

[0008] On the other hand, a method for pumping cryogenic liquid includes the following steps: providing a pump having a piston, an intermediate fluid seal, and a pumping fluid seal slidably positioned within a cylinder and defining an intermediate fluid chamber and a fluid pumping chamber, thereby defining a differential pressure space between the intermediate and pumping fluid seals; actuating the piston by cyclically guiding intermediate fluid to the intermediate fluid chamber of the pump, such that the cryogenic liquid is received and pumped by the pumping fluid chamber of the pump; detecting the pressure of the differential pressure space; and discharging the differential pressure space when the detected pressure reaches a predetermined pressure level. Simple Explanation of the Diagram

[0009] Figure 1 is a process flow chart and schematic diagram illustrating an embodiment of the cryogenic pump of the present invention;

[0010] Figure 2 is a process flow and schematic diagram illustrating an alternative embodiment of a system including the cryogenic pump of the present invention;

[0011] Figure 3 illustrates an embodiment of the insulation system for the cryogenic pump that can be used in the systems of Figures 1 and 2. Implementation

[0012] It should be noted that although the embodiments shown and presented below are described in relation to pumping liquid hydrogen, the present invention can be used to pump other types of cryogenic liquids.

[0013] Figure 1 illustrates a system for pumping liquid hydrogen to a high pressure. By way of example only, the system can pump liquid hydrogen to approximately 1000 bar. The system includes a first cryogenic pump, generally designated 10, and a second cryogenic pump, generally designated 12. As will be described in more detail below, pumps 10 and 12 are driven by an intermediate fluid, such as propane, 1-butene, or other fluids known in the art. Although two cryogenic pumps are shown, the system may include a single cryogenic pump or more than two cryogenic pumps.

[0014] The embodiment in Figure 1 uses propane as an intermediate fluid to drive pumps 10 and 12. Propane can remain liquid at relatively warm temperatures (approximately -14°F) and therefore low pressures. Liquid hydrogen is approximately -415°F. As explained in more detail below, propane can be pumped to very high pressures (1000 bar = 14500 psi) using a fracturing pump. High-pressure propane drives the pistons of pumps 10 and 12 to pump liquid hydrogen to close to 1000 bar. The use of an intermediate fluid reduces sealing problems, and the differential pressure on the seals can be kept to a minimum. As a result, hydrogen seal leakage and friction (both detrimental to the overall performance of the hydrogen pump) can be reduced.

[0015] Fluids other than propane, including but not limited to 1-butene, may be used alternatively as intermediate fluids to drive pumps 10 and 12.

[0016] Referring to Figure 1, cryogenic pumps 10 and 12 are located in corresponding storage tanks 14 and 16, respectively. Storage tank 14 includes a liquid hydrogen inlet 18 through which liquid hydrogen flows into the tank, submerging the bottom of the housing 20 of pump 10. As a result, pump 10 is kept cooled by the liquid hydrogen, eliminating (or at least minimizing) vapor formation within pump 10 during pumping. Storage tank 14 also includes a liquid hydrogen outlet 22, allowing liquid hydrogen to be returned to the source to provide recirculation of liquid hydrogen through storage tank 14 (e.g., when the pump is idle and not in use). Storage tank 16 similarly has a pump housing 23, a liquid hydrogen inlet 24, and a liquid hydrogen outlet 26.

[0017] Pump housing 20 of pump 10 defines cylinder 32, within which piston 34 is slidably disposed. The piston includes an intermediate fluid or propane seal 36 and a pumping fluid or hydrogen seal 38. Similarly, pump housing 23 of pump 12 defines cylinder 42 containing piston 44. Pistons 34 and 44 of pumps 10 and 12 move between the bottom dead center position shown for pump 10 in Figure 1 and the top dead center position shown for pump 12 in Figure 1, respectively. When moving from bottom dead center to top dead center, the piston of each pump moves in the upward stroke or hydrogen intake direction indicated by arrow 46 of pump 12 in Figure 1, while when moving from top dead center to bottom dead center, it moves in the downward stroke or hydrogen discharge direction indicated by arrow 48 of pump 10 in Figure 1.

[0018] Piston 34 divides the cylinder 32 of pump 10 into a pumping chamber 52 and an intermediate fluid chamber 54. The pump inlet of pump 10 (indicated by arrow 56 in Figure 1) is formed in the pumping chamber 52, such that during the upward stroke of piston 34, liquid hydrogen from storage tank 14 enters the pumping chamber. During the downward stroke of piston 34, the liquid hydrogen in pumping chamber 52 exits the pumping chamber through pump discharge line 58. By way of example only, liquid hydrogen can exit pump 10 through pump discharge line 58 at a pressure of approximately 1000 bar, reaching a liquid hydrogen storage tank or process. Pump 12 has a similar structure and function.

[0019] Referring again to Figure 1, the annular differential pressure (“dP”) space 62 of pump 10 is defined between the sidewall of piston 34, the intermediate fluid seal, the pumping fluid seal, and the inner surface of pump housing 34. The annular dP space 62 is connected to a vent line 64 having a dP vent valve 66 controlled by a dP switch 68, which opens and closes based on the pressure difference between the pressure within the annular dP space and the intermediate fluid pressure within the intermediate fluid pump line 72.

[0020] The pressure in the annular dP space can be measured via vent line 64 (as shown in Figure 1) or via a dedicated connection between dP switch 68 and the annular dP space. Alternatively, the pressure of the intermediate fluid can be detected by dP switch 68 via a fluid connection to the intermediate fluid chamber 54 (instead of line 72). Pump 12 has a similar structure and function. dP switch 68 can be a pressure-sensing switch, or alternatively may include a pressure sensor or controller that senses the pressure, and a separate switch activated based on the pressure sensed by the sensor or controller.

[0021] The cryogenic pumps 10 and 12 in Figure 1 are driven by a drive system, such as an intermediate fluid circuit generally indicated by 80. The intermediate fluid circuit includes a cooling container 82 containing a refrigeration coil 84. The cooling container 82 can be refilled with propane via a line 86 and is also provided with a vent line 88 to accommodate the filling of liquid propane. As is known in the art, the vent line 88 may be equipped with a vent valve that automatically opens when the pressure inside the cooling container 82 reaches a predetermined level.

[0022] The refrigeration coil 84 receives refrigerant from the refrigeration system or other sources and cools the propane within the cooling container 82. The refrigeration system and coil 84 are preferably configured to cool the propane within the cooling container to a temperature corresponding to a pressure lower than that in the hydrogen storage tank 14 (or 16).

[0023] Liquid propane from cooling vessel 82 is pumped via one or more high-pressure intermediate fluid pumps 92 to cryogenic pump actuation valves 94a and 94b of pump 10 and pump actuation valves 96a and 96b of pump 12. By way of example only, the high-pressure pump 92 could be a fracturing pump that pumps propane to very high pressures, such as 1000 bar. Alternatively, alternative high-pressure pumps known in the art can be used.

[0024] Starting from the positions shown in Figure 1 (i.e., bottom dead center and top dead center) of pistons 34 and 44 of pumps 10 and 12, actuation valve 94a is closed and actuation valve 94b is opened. As a result, when piston 34 moves along its upward stroke or suction direction (opposite to arrow 48 in Figure 1), liquid propane in intermediate fluid chamber 54 is guided back to cooling container 82 via recirculation line 98 through valve 94b. Simultaneously, actuation valve 96a opens and actuation valve 96b closes, allowing pressurized propane from high-pressure intermediate fluid pump 92 to be supplied to intermediate fluid chamber 102 of cryogenic pump 12. As a result, piston 44 is driven along its downward stroke or hydrogen discharge direction (opposite to arrow 46 in Figure 1), thereby forcing / pumping liquid hydrogen in pump chamber 104 of pump 12 to reach liquid hydrogen storage or process via cryogenic pump discharge line 106. When piston 34 reaches top dead center and piston 44 reaches bottom dead center, actuation valves 94a and 96b open, while actuation valves 94b and 96a close, allowing pressurized liquid propane to be introduced from intermediate fluid pump 92 into intermediate fluid chamber 54 of pump 10. At the same time, liquid propane is driven from intermediate fluid chamber 102 of pump 12 to cooling container 82 via recirculation line 108.

[0025] The cycle repeats, causing cryogenic pumps 10 and 12 to be driven by an intermediate fluid supplied to the pumps in a circulated manner, while liquid hydrogen is pumped at high pressure in a circulated manner through pump discharge lines 58 and 106 during the downstroke / discharge stroke of pumps 10 and 12. While this is happening, during the upstroke / suction stroke of pumps 10 and 12, the intermediate fluid / propane is circulated back to the cooling vessel 82 through recirculation lines 98 and 108.

[0026] The high-pressure recirculation valve 112 is also in fluid communication with the outlet of the intermediate fluid pump 92. When the piston in each of the cryogenic pumps 10 and 12 descends to its lowest point / reaches bottom dead center, the high-pressure recirculation valve 112 temporarily opens to prevent system overpressure when the corresponding piston shifts to the upward stroke / suction direction. When valve 112 is open, propane flow from the intermediate fluid pump 92 that is not directed to the actuation valve is directed back to the cooling container 82 via the recirculation line 108 (although a dedicated return line may be used).

[0027] The propane flow pressure is set by actuation valves 94a, 94b, 96a and 96b, and determined by the pressure required to force the pistons of pumps 10 and 12 to reach a hydrogen pressure of 1000 bar in order to pump liquid hydrogen to storage or process.

[0028] Alternative drive systems known in the prior art can be used to replace the intermediate fluid circuit 80 of Figure 1 to drive cryogenic pumps 10 and 12 using intermediate fluid.

[0029] Optional proximity switches 114 and 116 can be used in conjunction with piston position levers 115 and 117 to indicate the position of pistons 34 and 44 of cryogenic pumps 10 and 12. These switches can be used to control the rate of intermediate fluid flow and the speed of the piston, and to ensure that the piston can be lowered to its lowest point in the cylinder without damage, thereby minimizing clearance volume in the pump.

[0030] Intermediate fluid seals 36 and 122, as well as pumping fluid seals 38 and 124, typically keep the annular dP space 62 of pump 10 and the annular dP space 132 of pump 20 free of hydrogen and propane.

[0031] The dP switch 68 of pump 10 and the dP switch 118 of pump 12 are configured to prevent the propane intermediate fluid from leaking into the liquid hydrogen and to prevent the liquid hydrogen from leaking into the propane intermediate fluid, and in all cases to reduce the differential pressure on the intermediate fluid seals 36, 122 and the pumping fluid seals 38, 124, preferably to a minimum.

[0032] In the embodiment of Figure 1, the pressure settings of the dP switches 68 and 118 for each cryogenic pump 10 and 12 are slightly lower than the intermediate fluid pressure (measured via intermediate fluid pump lines 72 and 126) to prevent leakage of the intermediate fluid into the hydrogen product during the downstroke (arrow 48), where the intermediate fluid pressure must be higher than the hydrogen storage tank pressure. This pressure setting for each dP switch also prevents hydrogen from leaking into the intermediate fluid during the upstroke (arrow 46), where the hydrogen storage tank pressure must be higher than the intermediate fluid pressure.

[0033] During operation, referring to the cryogenic pump 10 in Figure 1, during the piston downstroke completed by pump 10, the propane pressure must be higher than the pressure in the hydrogen storage tank (to drive piston 34 and pump hydrogen). Propane may therefore leak into the annular dP space 62 through the intermediate fluid seal 36. The dP switch 68 controls the vent valve 66 such that the pressure in the annular dP space 62 is slightly lower than the intermediate fluid / propane pressure, which will also be lower than the pressure at which hydrogen is pumped from storage tank 14 and pumping chamber 52. As a result, if the pressure in the annular dP space 62 rises to just below the propane pressure in the intermediate fluid chamber 54 (and line 72), the propane leaking into the annular dP space 62 will be driven out of the open dP vent valve 66 instead of entering the liquid hydrogen through seal 38. The propane leaving the open dP vent valve 66 can be vented or recycled for use, for example, in the intermediate fluid loop 80.

[0034] Conversely, regarding the cryogenic pump 12, during the piston upstroke completed by pump 12, the hydrogen pressure in the pumping chamber 104 of pump 12 will be higher than the intermediate fluid pressure in the intermediate fluid chamber 102 (and line 126). As a result, hydrogen may leak into the annular dP space 132 through the pumping fluid seal 124. As in the case of pump 10, dP switch 118 will control dP vent valve 136 such that the pressure in the annular dP space 132 is slightly lower than the intermediate fluid / propane pressure. As a result, if the pressure in the annular dP space 122 rises to a level just below the propane pressure in the intermediate fluid chamber 102 (and line 126), the hydrogen leaking into the annular dP space 132 will be driven out of the open dP vent valve 136 instead of entering the propane intermediate fluid through seal 122. The hydrogen leaving the open dP vent valve 136 can be vented or recovered for use, for example, in systems supplying hydrogen to tanks 14 and 16.

[0035] During the upward stroke phase of pump 10, pump 10 operates as described above for pump 12, and during the downward stroke phase of pump 12, pump 12 operates as described above for pump 10. As liquid hydrogen is pumped, pumps 10 and 12 cycle through each phase.

[0036] As shown in Figure 2, one or more optional supplementary seals 202 and 204 can be used to separate leaked intermediate fluid from leaked hydrogen between the intermediate fluid seal 236 and pumping fluid seal 238 of the cryogenic pump 210 and the intermediate fluid seal 222 and pumping fluid seal 224 of the pump 212. As shown in Figure 2, supplementary seals 202 and 204 divide the annular dP spaces of pumps 210 and 212 into intermediate fluid annular dP spaces 242 and 244 and pumping fluid dP spaces 246 and 248. Each dP annular space of each pump 210 and 212, or both dP annular spaces of each pump, can be equipped with the dP switch and dP vent valve device described above with reference to Figure 1.

[0037] Figure 2 also illustrates an embodiment of a dedicated dP switch and dP valve. More specifically, as previously described, the cryogenic pump 210 includes an intermediate fluid annular dP space 242 and a pumping fluid dP space 246. An intermediate fluid dP vent valve 252 is in fluid communication with the intermediate fluid annular dP space 242. The intermediate fluid dP vent valve 252 is controlled by an intermediate fluid dP switch 254, which opens and closes based on the pressure difference between the pressure within the intermediate fluid annular dP space 242 and the pressure within the intermediate fluid pump line 256. The cryogenic pump 212 has a similar arrangement.

[0038] Similarly, the pumping fluid dP vent valve 262 is in fluid communication with the pumping fluid annular dP space 246. The pumping fluid dP vent valve 262 is controlled by a pumping fluid dP switch 264, which opens and closes based on the pressure difference between the pressure within the pumping fluid annular dP space 246 and the pressure within the intermediate fluid pump line 256. The cryogenic pump 212 has a similar arrangement.

[0039] As in the embodiment of Figure 1, the dP switches 254 and 264 of Figure 2 (and the corresponding dP switch for pump 212) are set slightly lower than the intermediate fluid pressure (measured via intermediate fluid pump line 256) to prevent leakage of the intermediate fluid into the hydrogen product during the downstroke (indicated by arrow 248 of pump 210), where the intermediate fluid pressure must be higher than the hydrogen storage pressure. This pressure setting for each dP switch also prevents hydrogen leakage into the intermediate fluid during the upstroke (indicated by arrow 256 of pump 212), where the hydrogen storage tank pressure must be higher than the intermediate fluid pressure.

[0040] The cryogenic pumps 10 and 12 of Figure 1, or the cryogenic pumps 210 and 212 of Figure 2, can be insulated as shown in the insulation embodiment of Figure 3. As shown in pump 10, a reservoir sleeve 302 is formed around a reservoir 14, thereby providing a vacuum space 304. Furthermore, a pump sleeve 306 is disposed around a pump housing 20, thereby forming a vacuum space 308. Vacuum spaces 304 and 308 can be connected by a neck sleeve 312. The neck sleeve 312 can be used to suspend the pump sleeve within the reservoir and define a vacuum space open relative to vacuum spaces 304 and 308. The neck sleeve 312 can also surround the structure for suspending the pump housing 20 within the reservoir and the piston position rod 115 (Figure 1). Pump 12 has similar insulation.

[0041] Several aspects of this subject matter may be implemented individually or together in the methods, apparatus, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the individual use of these aspects or individual claims to these aspects or different combinations as set forth in the appended claims.

[0042] While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications can be made thereto without departing from the spirit of the invention, the scope of which is defined by the appended claims.

[0043] 10, 210: Cryogenic pumps 12, 212: Second cryogenic pump 14, 16: Hydrogen storage tanks 18, 24: Hydrogen liquid inlet 20, 23: Pump casing 22, 26: Liquid hydrogen outlet 32, 42: Cylinder block 34, 44: Pistons 36, 122, 236, 222: Propane seals 38, 124, 238, 224: Hydrogen gas sealing components 46, 48: Arrows 52, 104: Pumping chamber 54, 102: Intermediate fluid chamber 56: Pump inlet 58, 106: Discharge pipelines 62, 132, 242, 244: Circular differential pressure ("dP") space 64, 88: Ventilation ducts 66, 136, 252, 262dP: Ventilation valve 68, 118, 254, 264 dP: Switch 72, 86, 98, 108, 126, 256: Pipelines 80: Fluid Circuit 82: Cooling container 84: Refrigeration coil 92: High-pressure pump 94a, 94b, 96a, 96b: Actuation valves 112: Reflow valve 114, 116: Switches 115, 117: Piston position rod 202, 204: Supplementary seals 246, 248: Pumped fluid dP space 302: Storage tank sleeve 304, 308: Vacuum space 306: Pump sleeve 312: Neck Glove

[0044]

Claims

1. A pump for pumping cryogenic liquids, comprising: a. Pump housing, which defines the cylinder; b. A piston slidably positioned within a cylinder such that an intermediate fluid chamber configured to receive intermediate fluid is defined within the cylinder adjacent to a first end of the piston, and a fluid pumping chamber is defined within the cylinder adjacent to a second end of the piston, the fluid pumping chamber including an inlet and an outlet; c. An intermediate fluid seal attached to the piston and configured to engage the cylinder. d. A pumping fluid seal attached to a piston and configured to engage a cylinder, the pumping fluid seal being spaced apart from an intermediate fluid seal such that a differential pressure space is defined within the cylinder between the intermediate fluid seal and the pumping fluid seal; e. A differential pressure vent valve in fluid communication with the differential pressure space; f. A differential pressure switch operably connected to the differential pressure vent valve and configured to sense the pressure within the differential pressure space and the pressure within the intermediate fluid chamber, compare the sensed pressures within the differential pressure space with those within the intermediate fluid chamber, and open the differential pressure vent valve when the pressure within the differential pressure space reaches a predetermined pressure level, the predetermined pressure level being lower than the intermediate fluid pressure within the intermediate fluid chamber.

2. The pump according to claim 1 further includes a reservoir, a portion of the pump housing located within the reservoir, the reservoir being configured to receive and immerse the portion of the pump housing in a cryogenic liquid, and to supply the cryogenic liquid to the inlet of the pumping chamber for pumping.

3. The pump according to claim 1 further includes a supplementary seal attached to the piston between the intermediate fluid seal and the pumping fluid seal, such that the differential pressure space is divided into an intermediate fluid differential pressure space and a pumping fluid differential pressure space.

4. The pump according to claim 3, wherein, The differential pressure vent valve includes an intermediate fluid vent valve in fluid communication with the intermediate fluid differential pressure space and a pumping fluid vent valve in fluid communication with the pumping fluid differential pressure space. The differential pressure switch includes an intermediate fluid differential pressure switch operably connected to the intermediate fluid differential pressure vent valve and a pumping fluid differential pressure switch operably connected to the pumping fluid differential pressure vent valve. The intermediate differential pressure switch is configured to sense the pressure in the intermediate fluid differential pressure space and open the intermediate fluid differential pressure vent valve when the pressure in the intermediate fluid differential pressure space reaches a first predetermined pressure level. The pumping fluid differential pressure switch is configured to sense the pressure in the pumping fluid differential pressure space and open the pumping fluid differential pressure vent valve when the pressure in the pumping fluid differential pressure space reaches a second predetermined pressure level.

5. The pump according to claim 4, wherein, The first and second predetermined pressure levels are lower than the intermediate fluid pressure in the intermediate fluid chamber.

6. The pump according to claim 1, wherein, The predetermined pressure level is lower than the intermediate fluid pressure in the intermediate fluid chamber.

7. The pump according to claim 1, wherein, The differential pressure space is an annular space.

8. The pump according to claim 1 further includes a drive system for cyclically supplying intermediate fluid to the intermediate fluid chamber, such that the piston is actuated to pump cryogenic liquid from the pumping chamber.

9. The pump according to claim 8, wherein, The drive system includes: i) an intermediate fluid container configured to contain a supply of intermediate fluid; ii) a high-pressure pump configured to receive and pump intermediate fluid from the intermediate fluid container; iii) a first actuating valve configured to receive intermediate fluid from the high-pressure pump when in an open configuration; and iv) a second actuating valve configured to receive intermediate fluid from the intermediate fluid chamber of the pump cylinder and guide the intermediate fluid to the intermediate fluid container when in an open configuration.

10. The pump according to claim 9, wherein, The drive system also includes a high-pressure reflow valve configured to direct intermediate fluid flow from the high-pressure pump to the intermediate fluid container when in an open configuration.

11. The pump according to claim 9, wherein, The intermediate fluid container includes a cooling coil configured to cool the intermediate fluid supply within the intermediate fluid container.

12. The pump according to claim 1 further includes a proximity switch operatively connected to the piston and configured to allow detection of the piston's position.

13. The pump according to claim 1, wherein, The cryogenic liquid is a hydrogen liquid.

14. The pump according to claim 1, wherein, The intermediate fluid is propane.

15. The pump according to claim 1, wherein, The intermediate fluid is 1-butene.

16. The pump according to claim 1, further comprising: g. A reservoir, a portion of the pump housing located within the reservoir, the reservoir being configured to receive and immerse the portion of the pump housing in a cryogenic liquid and to supply the cryogenic liquid to the inlet of the pumping chamber for pumping; h. A reservoir sleeve surrounding the reservoir, thereby defining a reservoir insulation space between them; i. A pump sleeve surrounding the pump housing, thereby defining a pump insulation space between them.

17. A method for pumping a cryogenic liquid, comprising the steps of: a. providing a pump having a piston slidably positioned within a cylinder and defining an intermediate fluid chamber and a fluid pumping chamber, an intermediate fluid seal and a pumping fluid seal, thereby defining a differential pressure space between the intermediate and pumping fluid seals; b. actuating the piston by cyclically guiding intermediate fluid to the intermediate fluid chamber of the pump, such that the cryogenic liquid is received and pumped by the fluid pumping chamber of the pump; c. detecting the pressure of the differential pressure space; d. venting the differential pressure space when the detected pressure reaches a predetermined pressure level.

18. The method according to claim 17, wherein, The predetermined pressure level is a pressure lower than the intermediate fluid pressure in the intermediate fluid chamber.

19. The method according to claim 17 further includes the step of cooling the pump in a storage tank using a cryogenic liquid.

20. The method according to claim 17, wherein, The cryogenic liquid is liquid hydrogen.

21. The method according to claim 17, wherein, The intermediate fluid is propane.

22. The method according to claim 17, wherein, The intermediate fluid is 1-butene.

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