The present disclosure relates generally to devices and methods for filing a cryogenic tank and, more particularly, to a device and method that fills a cryogenic tank with cryogenic fluid while automatically maintaining a predetermined setpoint pressure in the cryogenic tank.
Cryogenic fluids, that is, fluids having a boiling point generally below −150° C. at atmospheric pressure, are used in a variety of applications, such as mobile and industrial applications. Cryogenic fluids are stored in insulated cryogenic tanks because of the low temperature requirements (˜−160° C.) and typically at lower pressures. Temperature and pressure regulation of cryogenic fluids in these tanks is extremely important.
Cryogenic tanks are typically filled from a mobile delivery unit that connects to the cryogenic tank.
The cryogenic tank 1 is filled by introducing cryogenic fluid from a delivery device at inlet 5 through delivery line 4. The valves 9 and 10 on tank lines 7 and 8 are manually adjusted in order to deliver the fluid to the tank through the desired pathway. The cryogenic tank can be top-filled (i.e. the incoming fluid is sprayed into the vapor space 2 of the tank) through line 7 by opening valve 9. The tank can also be bottom filled through line 8 by opening valve 10. The cryogenic fluid being transferred from the mobile delivery unit is usually subcooled to some degree. That is, the pressure of the fluid as it flows through the transfer lines is greater than the saturation pressure of the fluid. When the fluid is transferred in this subcooled manner it does not boil in the lines and is thus transferred efficiently. The utility of having one path to top-fill the tank and one to bottom-fill the tank is for pressure balancing. Top-filling cools the vapor space 2 of the tank and reduces the tank pressure, which allows the tank to be filled without venting. On the other hand, bottom-filling the tank (i.e. the incoming fluid pushed into the liquid space by a dip tube or bottom nozzle) causes the liquid level to rise acting like a piston and increasing tank pressure.
The above-described system requires manual adjustment of the fill valves and monitoring during the fill process to maintain a desired cryogenic tank pressure. Typically, the mobile delivery unit includes an automatic fill shut-off that will stop fluid delivery to the tank 1 when the tank is full. There is a chance that the automatic fill shut-off will stop fluid delivery when the shut-off senses a drastic change or spike in fluid pressure in delivery line 4. Such changes in pressure can results from sudden opening or closing of valves 9 and/or 10. Premature stopping of fluid delivery results in an incomplete filing of tank 1. Maintaining a desired cryogenic tank pressure during filling therefore requires operators with a high level of skill, training and experience.
There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.
In one aspect, a device for filling a cryogenic tank includes a body structure, a pressure comparison cylinder, a piston, an over-pressure member, a pressure regulator, and a slider tube. The body structure includes an inlet port for receiving fluid from a delivery tank, a first top-fill outlet port configured to connect to a top-fill line in communication with a cryogenic tank, a bottom-fill outlet port configured to connect to a bottom-fill line in communication with a cryogenic tank, and a slider tube cylinder. The cylinder housing is connected to the body structure and defines a pressure comparison cylinder having an upper volume and a lower volume. The lower volume is in fluid communication with a cryogenic tank. The piston is slidably positioned in the pressure comparison cylinder and a piston shaft connects the piston to the slider tube. The pressure regulator is in fluid communication with the upper volume of the pressure comparison cylinder and the slider tube cylinder. An over-pressure member is positioned in the upper volume of the pressure comparison cylinder, the piston contacting the over-pressure member as the piston slides upward in the pressure comparison cylinder. The slider tube is slidably positioned within the slider tube cylinder. The slider tube cylinder is configured to direct fluid to the top-fill line through the top-fill outlet port when a pressure in the lower volume exceeds a setpoint pressure and to direct fluid to the bottom-fill line through the bottom-fill outlet port when the pressure in the lower volume is below the setpoint pressure.
In another aspect, a device for filling a cryogenic tank includes a body structure, a pressure comparison cylinder, a piston, an over-pressure member, a pressure regulator, and a slider tube. The body structure includes an inlet port for receiving fluid from a delivery tank, a first top-fill outlet port configured to connect to a top-fill line in communication with a cryogenic tank, a bottom-fill outlet port configured to connect to a bottom-fill line in communication with a cryogenic tank, and a slider tube cylinder. The cylinder housing is connected to the body structure and defines a pressure comparison cylinder having an upper volume and a lower volume. The lower volume is in fluid communication with a cryogenic tank. The piston is slidably positioned in the pressure comparison cylinder and a piston shaft connects the piston to the slider tube. The pressure regulator is in fluid communication with the upper volume of the pressure comparison cylinder and the slider tube cylinder. The slider tube is slidably positioned within the slider tube cylinder. The slider tube cylinder including a top-fill opening configured to direct fluid through the top-fill outlet port and a bottom-fill opening configured to direct fluid through the bottom-fill. The slider tube also including one or more crevices in fluid communication with the top-fill opening.
An embodiment of the filing device of the disclosure provides a piston that compares a target setpoint pressure with the pressure of the tank being filled with cryogenic fluid and selectively diverts a flow stream to a top-fill and/or a bottom-fill pathway, or portions of flow to each pathway, based on the comparison, thus reducing or eliminating the need for monitoring and manually diverting the flow stream while operating the filling device to deliver cryogenic fluid to the tank.
As an example only, the body structure 18 may be tube-shaped. The body structure includes an inlet port 15 for receiving fluid from a delivery tank (such as the tank of a mobile delivery unit) or an alternative delivery device or system. The body structure also includes a top-fill outlet port 12a that leads to a top-fill line 12 in communication with a cryogenic tank being filled and a bottom-fill outlet port 13a that leads to a bottom-fill line 13 in communication with the cryogenic tank. The body structure 18 defines a slider tube cylinder 19 that slidably receives a slider tube 29. The slider tube 29 is able to slide up and down freely inside the slider tube cylinder 19.
Although specific detail is not shown in the figures, both the inlet and outlet ports can feature a number of specific fittings. For instance, each port may comprise a removable and reusable seal. Each port may also include a valve or vent. The inlet port 15 is connected to a delivery tank or other delivery device during filling, such as by a flexible hose or insulated piping.
The cylinder housing 22 defines a pressure comparison cylinder that slidably receives the piston 21. The piston 21 is able to slide up and down freely inside the pressure comparison cylinder. The pressure comparison cylinder includes two separate volume cavities: an upper volume 23 and a lower volume 27. The upper volume 23 is maintained at a predetermined setpoint pressure by the pressure regulator 24, as will be explained below.
An over-pressure member 32 is located in the pressure comparison cylinder. In the illustrated embodiment, the over-pressure member 32 is located in the upper volume or cavity 23 of the pressure comparison cylinder. In one alternative, for example, the over-pressure member 32 is above the piston 21 and between the piston 21 and the upper wall 34 of the pressure comparison cylinder. The over-pressure member 32 may be any suitable biasing member that biases or pushes the piston 21 away from the upper wall 34 until the upward force on piston 21 overcomes the force(s) of the over-pressure member 32 (i.e. when the device goes into “over-pressure”). In the illustrated embodiment, the over-pressure member 32 is a coil spring having a plurality of coils. Optionally, but not necessarily, the bottom end of the coil spring may include a finger 36 (shown in broken line) that protrudes downward from the coil spring and comes into contact with the piston 21 (
The coiled spring has a preload and a spring constant that are tuned with a range of tank pressures. The preload is selected so that the piston pushes up against the spring but cannot displace it until there is enough pressure in the bottom chamber. Once there is enough pressure below the piston, a low spring constant allows the piston to move rapidly upward to generate a rapid flow change which will trigger the delivery vehicle to terminate the fill. Thus, as force within the headspace of the tank increases, the preload of the coiled spring holds the piston 21 in place until the pressure in lower volume 27 becomes greater than the preload of the coiled spring and the device goes into over-pressure. The piston 21 then compresses the coiled spring against the upper wall 34 of the pressure comparison cylinder (
In alternative embodiments, the over-pressure member 32 may be any other suitable biasing member, such as any suitable type spring, bladder, elastic members, etc. that assists in the piston 21 rapidly moving to its top-most position.
The lower volume 27 is in fluid communication with the headspace of the cryogenic tank being filled via pressure sensing line 28 and therefore is maintained at the cryogenic tank pressure. The piston 21 preferably includes a seal between the piston 21 and the interior surface of the wall of the pressure comparison cylinder defined by cylinder housing 22 eliminating any type of communication or gas exchange between the upper volume 23 and the lower volume 27.
A piston shaft 30 is connected to the head of piston 21 and the slider tube 29. The piston shaft 30 also preferably includes a seal preventing exchange of fluid between the pressure comparison cylinder defined by cylinder housing 22 and the slider tube cylinder 19 of body structure 18.
As noted previously, pressure regulator 24, which is preferably a relieving pressure regulator, is used to maintain the pressure in upper volume 23 of the cylinder housing 22 at a generally constant setpoint pressure. Suitable pressure regulators are well known in the art and may include at least a valve that opens based on the pressure setting or setpoint to permit fluid to either enter the upper volume 23 (if the pressure within the upper volume is below the setpoint) or exit the upper volume (if the pressure within the upper volume is above the setpoint). The pressure regulator 24 is connected to the upper volume 23 of the pressure comparison cylinder and the slider tube cylinder 19/inlet port 15 through communication lines 25 and 26/26a, respectively. As shown in
Piston 21 will move downward when the cryogenic tank pressure (which equals the pressure within lower volume 27) is below the setpoint pressure of regulator 24 and will move upward when cryogenic tank pressure exceeds the setpoint of regulator 24. In the latter instance, excess pressure caused by the displacement of piston 21 upwards is vented from the upper volume 23 to the atmosphere by pressure regulator 24 (via line 25), keeping upper volume 23 generally at constant setpoint pressure. When the pressure within the lower volume 27 (i.e. the cryogenic tank pressure) of the pressure comparison cylinder drops below the setpoint pressure, and thus the pressure within the upper volume 23, piston 21 will lower. As this occurs, the regulator 24 opens and pressurized fluid from the upper portion of slider tube cylinder 19 travels through lines 26 and 25 into the upper volume 23 so that the setpoint pressure may be maintained. When the setpoint pressure is reached within the upper volume 23, and downwards movement of piston 21 ceases, the regulator 24 closes.
The slider tube cylinder 29 is configured to direct a greater portion of fluid from a flow stream entering inlet port 15 of the device to a cryogenic tank top-fill line 12 through top-fill port 12a (to decrease the cryogenic tank pressure) when a pressure in the lower volume 27 of the pressure comparison cylinder exceeds a pressure setpoint and to direct fluid to a cryogenic tank bottom-fill line 13 through the bottom-fill outlet port 13a (to increase the cryogenic tank pressure) when the pressure in the lower volume 27 is below a pressure setpoint. The slider tube 29 has at least two slots, holes, or other openings 20a, 20b that direct flow of the cryogenic fluid from the inlet 15 to the top-fill outlet port 12a and/or the bottom-fill outlet port 13a, depending on the position of the slider tube 29. Although one slot is shown on each side of the slider tube, the slider tube may include more than two slots/holes. The holes or slots 20a, 20b may be any shape. They may be circular, rectangular, or any other known shape. Slot 20a may be a top-fill opening that comes into communication with top-fill port 12a. Slot 20b may be a bottom-fill opening that comes into communication with bottom-fill port 13a.
Referring to
Although, slots 20a and 20b are shown on opposite sides of the slider tube 29, they may be positioned elsewhere on the slider tube and in a different orientation relative to one another. In one alternative, the slots 20a and 20b may be located in the slider tube 29 or have a configuration such there is fluid flow through both top-fill port 12a and bottom-fill port 13a. As the slider tube 29 moves to gradually close the flow of fluid to one of ports 12a and 13a, flow to the other ports 12a or 13a is gradually opened. Thus, there is a point wherein there is simultaneous flow of fluid out of ports 12a and 13a. Alternatively, the slots 20a and 20b may be located in the slider tube 29 or have a configuration such fluid flows out of only one of the top-fill port 12a or bottom-fill port 13a. The movement of the slider tube 29 closes the flow of fluid to one of ports 12a and 13a before opening fluid flow to the other one of the ports 12a or 13a
A design element that may be exploited by the fact that the fill pressure (pressure of the fluid entering through inlet port 15) always exceeds tank pressure is the relationship between the cross-sectional area of piston shaft 30 and the weight of the piston-shaft-slider tube assembly. If the pressure drop from the body structure 18 to the cryogenic tank during normal fill operations is known, the weight of the piston-shaft-slider tube assembly may be selected to match the excess upward force on piston 21. Ideally, there is no net force on the piston-shaft slider tube assembly when cryogenic tank pressure exactly equals the setpoint pressure (the pressures in lower volume 27 and upper volume 23, respectively). The downward force on the piston 21=the force of gravity on the piston-shaft-slider tube assembly+(pressure in the upper volume 23×cross sectional area of the pressure comparison cylinder). The upward force on the piston 21=the pressure in lower volume 27×(the cross sectional area of pressure comparison cylinder−the cross-sectional area of piston shaft 30)+(the pressure in body structure 18×the cross-sectional area of the piston shaft 30).
The weight of the piston-shaft-slider tube assembly is ideally equal to the pressure drop from body structure 18 to the cryogenic tank multiplied by the cross-sectional area of shaft 30. However, it is not necessary (or possible) to have this tuned exactly because the pressure drop from the body structure 18 to the tank depends on the fill rate, which may vary slightly from one mobile delivery vehicle to another depending on vehicle capabilities.
The filling device 16 of
As illustrated in
With reference to
Referring to
Referring to
Turning to
As mentioned above, slider tube 29, optionally, incudes one or more crevices 48 in communication with slot 20a. Referring to
As described with reference to
In the device of
In the device of
While the preferred embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the disclosure, the scope of which is defined by the following claims.
This application claims the benefit of U.S. Provisional Patent Application No. 63/479,293, filed Jan. 10, 2023, and is a continuation-in-part of U.S. patent application Ser. No. 17/524,458, filed Nov. 11, 2021, which claims the benefit of U.S. Provisional Application No. 63/112,803, filed Nov. 12, 2020, the contents of each of which are hereby incorporated by reference.
Number | Date | Country | |
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63479293 | Jan 2023 | US | |
63112803 | Nov 2020 | US |
Number | Date | Country | |
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Parent | 17524458 | Nov 2021 | US |
Child | 18328884 | US |