The present disclosure relates generally to cryogenic pumps and, more particularly, to an insulating arrangement for a cryogenic pump.
Some applications require the handling, and more particularly the pumping, of cryogenic liquids. For example, heavy machines like locomotives or large mining trucks may have engines that use more than one fuel. The engine may be a dual fuel engine system, in which a gaseous fuel, such as compressed natural gas, is injected into a cylinder at high pressure while combustion in the cylinder from a diesel pilot is already underway. With such engines, the gaseous fuel is stored in a liquid state at a low pressure, such as atmospheric pressure, and at low, cryogenic temperatures in a storage tank in order to achieve a higher storage density. However, the use of such a cryogenic fuel requires the use of specialized equipment, including a cryogenic tank for storing the liquefied natural gas (“LNG”) fuel and a cryogenic pump for withdrawing and pressurizing the liquefied natural gas fuel.
The cryogenic pumps used in these types of applications may be configured with a cold end and a warm end. The cold end is generally the end at which fluid is pumped and, as such, comes into contact with the cryogenic fluid. The warm end of the cryogenic pump generally contains many of the pump driving elements and may be exposed to atmospheric temperatures. Heat transfer from the warm end of the pump to the cold end can adversely impact the efficiency of a cryogenic pump. Accordingly, arrangements have been developed that insulate the warm end of the pump from the cold end. Such insulating arrangements also help prevent excessive heat transfer from the warm end of the pump allowing less expensive conventional materials to be used at the warm end while materials rated for cryogenic service may be used at the cold end.
U.S. Pat. No. 4,576,557 (“the '557 patent”) discloses one example of an insulating arrangement for thermally insulating a pumping section of a cryogenic pump from the driving section of the pump. More specifically, the '557 patent discloses surrounding the entire pumping section of the pump with an insulation space that is bounded on its sides by plates and is filled with a low conductivity material, such as perlite.
The arrangement disclosed in the '557 patent as well as other similar arrangements using low thermal conductivity materials to insulate the cold and warm ends of a cryogenic pump from each other suffer from several drawbacks. For example, such materials are often not robust enough in terms of their mechanical properties for use in many pumping applications. Additionally, such materials can be relatively expensive.
In one aspect, the present disclosure describes a cryogenic pump configured for pressurizing a cryogenic fluid. The cryogenic pump includes a warm end portion adapted to not contact cryogenic fluid during operation of the pump and including one or more driving components. The cryogenic pump also includes a cold end portion adapted to contact cryogenic fluid during operation of the pump and including a pump inlet and a pump outlet. An insulating arrangement including an insulator plate is arranged between the warm end portion and the cold end portion and defines a first air gap between the cold end portion and the insulator plate.
In another aspect, the present disclosure describes a cryogenic pump configured for pressurizing a cryogenic fluid. The cryogenic pump includes a warm end portion adapted to not contact cryogenic fluid during operation of the pump. The warm end portion including a shaft and a load plate for driving movement of a plurality of pushrods, at least a portion of the plurality of pushrods being contained in a pushrod housing. The cryogenic pump includes a cold end portion adapted to contact cryogenic fluid during operation of the pump and including a pump inlet and a manifold defining a pump outlet. An insulating arrangement including an insulator plate is arranged between the pushrod housing and the manifold and defines a first air gap between the cold end portion and the insulator plate and a second air gap between the insulator plate and the warm end portion.
In yet another aspect, the present disclosure describes an insulating arrangement for a cryogenic pump configured for pressurizing a cryogenic fluid, the cryogenic pump including a warm end portion adapted to not contact cryogenic fluid during operation of the pump and including one or more driving components and a cold end portion adapted to contact cryogenic fluid during operation of the pump and including a pump inlet and a pump outlet. The insulating arrangement includes an insulator plate arrangeable between the warm end portion and the cold end portion so as to define a first air gap between the cold end portion and the insulator plate and a second air gap between the insulator plate and the warm end portion.
This disclosure generally relates to a cryogenic pump 10 and, more particularly, to an insulation arrangement separating a warm end portion 12 of the pump from a cold end portion 14 of the pump. With reference to
With reference to
With reference to the cross-sectional view of
As further shown in
A plurality of tappets 32 may be arranged immediately beneath with an upper end of each tappet in contact with the load plate 28. Only a single tappet 32 is visible in the cross-section of
A lower end of each tappet 32 may engage a corresponding upper pushrod 34 that, in turn, engages at its lower end a corresponding lower push rod 36. In the cross-sectional view of
Referring to
The reservoir 48 may include an outer vacuum jacket 52 that has an opening 54 at its lower end to allow for cryogenic fluid, e.g. LNG, to enter into the reservoir 48. The reservoir 48 may further house a plurality of barrels 56 each of which defines an inlet for the cryogenic pump 10. According to one embodiment, at least a portion of the barrel 56 may be submerged in cryogenic fluid contained in the reservoir 48. Generally, as discussed further below, each barrel 56 corresponds to a respective one of the tappet and pushrod combinations. Thus, while three barrels 56 are visible in the cross-sectional view of
Each lower pushrod 36 may extend downward through a corresponding passage through the manifold 46 and into a corresponding one of the barrels 56 where it engages with a plunger 60 arranged in the barrel 56 to form a pumping element. With this arrangement, movement of the lower pushrod 36 (as driven by the load plate 28 through the corresponding tappet 32 and upper pushrod 34) can drive movement of the plunger 60. Movement of the plunger 60, in turn, draws the cryogenic fluid into the barrel 56 and pressurizes it. The pressurized cryogenic fluid may then be directed into the manifold 46 which defines the outlet for the pressurized fluid from the cryogenic pump 10.
To help limit the transfer of heat from the warm end portion 12 of the cryogenic pump 10 to the cold end portion 14, the cryogenic pump 10 may include an insulating arrangement 62 arranged between the warm and cold end portions 12, 14 of the cryogenic pump 10. More particularly, as shown for example in
As shown in
The insulator plate 64 may be arranged and the pushrod housing 22 may be configured so as to define a second air gap 76 between the cold and warm end portions 14, 12 of the cryogenic pump 10. In particular, the second air gap 76 may be formed by the lower cavity 42 of the pushrod housing 22 which would be cut off from the cold end portion 14 of the cryogenic pump 10 by the insulator plate 64. In such a case, the upper second side 68 of the insulator plate 64 may define a lower bound of the second air gap 76 while the upper bound is defined by the transverse section 38 of the pushrod housing 22. This second air gap 76 may provide a further barrier to heat transfer between the warm and cold end portions 12, 14 of the cryogenic pump 10. In the illustrated embodiment, the second upper side 68 of the insulator plate 64 is substantially flat, however it will be appreciated that other configurations may be used so long as the second air gap 76 is formed between the insulator plate 64 and the pushrod housing 22.
The insulator plate 64 may be mounted in the cryogenic pump 10 with an outer portion of the insulator plate sandwiched between the pushrod housing 22 and the manifold 46. In particular, as shown in
The recessed center portion 72 in the lower first side 66 of the insulating plate 64 may include raised seal supports 78 extending around each of a plurality of openings 80 extending through the insulating plate 64 between the first and second sides. The plurality of openings 80 may be arranged in an annular pattern radially inward of the raised outer portion 70 and be configured to have extending therethrough a respective one of the lower pushrods 36 as shown in
The provision of the first and second air gaps 73, 76 between the warm and cold end portions 12, 14 of the cryogenic pump 10 may allow the insulator plate 64 to be constructed of a more conventional, more thermally conductive material. Air has a relatively low thermal conductivity, particularly in comparison to many solid materials. As such, with the insulating arrangement of the present disclosure, materials that are considered relatively thermally conductive may be used for the insulator plate 64. For example, according to one embodiment, the insulator plate 64 may be made of stainless steel. Other metal materials also could be used such as carbon steels, aluminum and other relatively low-cost metals. An advantage of using such materials is that while they may have a relatively high thermal conductivity, they have a relatively low thermal expansion as compared to conventional insulating materials. Moreover, materials such as stainless steel and other metals may have superior strength and toughness as compared to conventional insulating materials.
The insulating arrangement 62 of the present disclosure may be applicable to any type of cryogenic pumps having separate cold and warm end portions. Moreover, the cryogenic pump 10 may be used in any application requiring the pumping of a cryogenic fluid. For example, the cryogenic pump 10 of the present disclosure has particular applicability to the pumping of LNG at high pressures in fuel delivery systems for vehicles such as locomotives and large mining trucks.
As noted above, the insulating arrangement 62 of the present disclosure allows for the use of relatively low cost materials with relatively higher thermal conductivities, such as stainless steel, for the insulator plate. This may allow for a significant cost savings over expensive low thermal conductivity materials such as yttria stabilized zirconia and titanium. These lower cost materials also may be much easier to machine than conventional insulating materials. Moreover, as compared to relatively expensive low thermal conductivity materials, the use of a material such as stainless steel provides the insulator plate with better mechanical properties such as lower thermal expansion and greater strength and toughness. This can allow the insulator plate to better withstand the significant thermal gradients and high mechanical stresses found in a cryogenic pump application without cracking or other failures as compared to conventional insulating materials.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
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