Patent Publication Number: US-11655809-B2

Title: Cryogenic pump flange

Description:
FIELD OF THE INVENTION 
     The present application relates to an arrangement for reducing the condensation of humidity around a flange for a cryogenic pump assembly, and the accumulation of frost and ice, and the freezing of a pump drive unit, that might otherwise be caused by flowing a cryogenic fluid through the flange. 
     BACKGROUND OF THE INVENTION 
     Gases can be stored at much higher densities when stored in liquefied form. Compared to a compressed gas stored in gaseous form, a gas can be stored at relatively low pressures if stored in liquefied form below or at its boiling point, such as below about −161.5° C. for a typical blend of natural gas. In this disclosure, “cryogenic” is used to describe fluids at such low temperatures and apparatus, such as a “cryogenic pump” that is designed to handle cryogenic fluids at cryogenic temperatures. 
     Cryogenic pumps are known for delivering a cryogenic fluid from a thermally insulated storage vessel. Such cryogenic pumps have what is referred to herein as a “cold end” which is immersed in the cryogenic fluid. Typically, cryogenic fluid is fed by gravity into a sump from which it is pumped, or the cold end can comprise a pump assembly that is disposed within the cryogen space defined by storage vessel itself. The drive unit for such a cryogenic pump is referred to herein as the “warm end” and it is usually located outside of the storage vessel to avoid introducing heat from the drive unit into the cold cryogen space defined by the storage vessel. The warm end is also typically located separated spaced apart and/or thermally insulated from the cold end and the delivery pipe exiting from the storage vessel to preventing freezing in the drive unit, especially when the drive unit is a hydraulic drive that uses hydraulic fluid pressure to actuate the cryogenic pump. 
     In vehicle applications there are often space constraints because of the limited space for mounting the fuel system, and accordingly, a more compact arrangement is preferred. Therefore, it is advantageous to mount the drive unit on, or close to, the flange that seals the opening through which the pump assembly is installed. In addition, it is desirable to reduce the number of heat transfer paths between the cryogen space and the surrounding environment, so it is preferred to have the delivery pipe, in addition to fill pipes and drain pipes, pass through the same flange. However, this can result in freezing of the hydraulic fluid in a hydraulic drive. 
     The delivery, fill and drain pipes are preferably welded to the flange to fluidly seal the interior of the storage vessel from the external environment. As the temperature of the flange decreases, due to cryogenic fluid, such as liquefied natural gas (LNG), passing through one or more of these pipes, the flange contracts putting stress on these weld joints, which can fatigue and compromise the fluid seal. 
     The applicant has designed and commercialized a different type of cryogenic pump which comprises a vaporizer integrated with the pump assembly, as disclosed by U.S. Pat. No. 7,607,898. With this arrangement, at the warm end there is no problem with mounting the drive unit on the same flange which the delivery pipe passes through because the vaporized fluid is warmer than the cryogenic fluid. 
     However, for systems that do not use a cryogenic pump integrated with a vaporizer, there is a need for a compact arrangement that allows for a warm end with a drive unit mounted on or close to the same flange that the delivery pipe passes through. 
     SUMMARY OF THE INVENTION 
     An improved flange for a pump comprises first and second faces and a passageway for cryogenic fluid flow extending from the first face to the second face, and at least one of (1) the passageway is for a pipe and comprises a first portion of a first diameter and a second portion of a second diameter that is greater than the first diameter, wherein when the pipe has an outer diameter that is smaller than the second diameter, a gap is formed between the pipe and the passageway where the pipe passes through the second portion; and (2) a first annular groove in one of the first face and the second face and extending around the passageway, wherein the first annular groove in cooperation with the passageway forms a bellows. 
     The pipe, which can be a fill pipe, a delivery pipe or a drain pipe, can be in contact with an inner wall of the first portion of the passageway. The pump can be a cryogenic pump for pumping a cryogenic fluid from a storage vessel to which the flange is mounted. 
     In preferred embodiments, the gap is annular. The passageway can be at an oblique angle to at least one of the first face and the second face. A first opening is formed by the intersection of the first portion of the passageway with the first face, and a second opening is formed by the intersection of the second portion of the passageway with the second face. It is preferable that the first opening is further away from a longitudinal axis of a mounting location for a drive unit, compared to the second opening. The second opening can be located within an area surrounded by a sleeve within which the pump is inserted when installed. 
     An improved flange assembly for a pump comprises a process fluid pipe and a flange. The flange comprises a first face, a second face and a passageway for cryogenic fluid flow extending from the first face to the second face, and at least one of (1) the passageway is for the process fluid pipe and comprises a first portion of a first diameter and a second portion of a second diameter that is greater than the first diameter, wherein when the process fluid pipe has an outer diameter that is smaller than the second diameter, a gap is formed between the process fluid pipe and the passageway where the process fluid pipe passes through the second portion; and (2) a first annular groove in one of the first face and the second face and extending around the passageway, wherein the first annular groove in cooperation with the passageway forms a bellows. 
     In a preferred embodiment, the flange comprises a bore extending from the first face to the second face and having a diameter equal to the second diameter. The flange assembly further comprises an annulus having an inner diameter equal to the first diameter. The passageway is formed by inserting the annulus into the bore. 
     The process fluid pipe can be welded to the flange. In a preferred embodiment the flange is disc shaped, but other shapes are possible in other embodiments. The passageway can be at an oblique angle to at least one of the first face and the second face. A first opening is formed by the intersection of the first portion of the passageway with the first face, and a second opening is formed by the intersection of the second portion of the passageway with the second face. In a preferred embodiment the first opening is further away from a longitudinal axis of the flange compared to the second opening. 
     An improved multi-functional flange for (a) attaching to a corresponding flange on storage vessel, (b) for supporting a pump assembly, and (c) for mounting a hydraulic drive unit, comprises a first face, a second face and a passageway for cryogenic fluid flow extending from the first face to the second face, and at least one of (1) the passageway is for a pipe and comprises a first portion of a first diameter and a second portion of a second diameter that is greater than the first diameter, wherein when the pipe has an outer diameter that is smaller than the second diameter, a gap is formed between the pipe and the passageway where the pipe passes through the second portion; and (2) a first annular groove in one of the first face and the second face and extending around the passageway, wherein the first annular groove in cooperation with the passageway forms a bellows. 
     The pipe can be in contact with an inner wall of the first portion of the passageway. In a preferred embodiment, the multi-functional flange comprises at least one hydraulic fluid passageway in fluid communication with the hydraulic drive unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a cryogenic pump. 
         FIG.  2    is a cross-sectional partial view of a double-walled cryogenic vessel with the pump of  FIG.  1    inserted into a sleeve. 
         FIG.  3    is a simplified cross-sectional view of a warm end assembly of the pump of  FIG.  1    comprising a flange assembly and a flange according to a first embodiment. 
         FIG.  4    is a cross-sectional view of the flange of  FIG.  3   . 
         FIG.  5    is a cross-sectional view of a flange of the pump of  FIG.  1    according to a second embodiment. 
         FIG.  6    is an exploded view of the flange of  FIG.  4   . 
         FIGS.  7  and  8    are schematic views of an annulus of the flange of  FIG.  4   . 
         FIG.  9    is a cross-sectional view of the annulus of  FIG.  8    taken along line  8 - 8 ′. 
         FIG.  10    is a cross-sectional view of a flange assembly of the pump of  FIG.  1    comprising a flange according to a third embodiment. 
         FIG.  11    is a cross-sectional view of the flange of  FIG.  10   . 
         FIG.  12    is a cross-sectional view of a flange of the pump of  FIG.  1    according to a fourth embodiment. 
         FIG.  13    is a cross-sectional view of a flange assembly of the pump of  FIG.  1    comprising a flange according to a fifth embodiment. 
         FIG.  14    is a cross-sectional view of the flange of  FIG.  13   . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) 
     Referring to  FIG.  1   , there is shown cryogenic pump  10  comprising warm end assembly  20  and cold end assembly  30 . Process fluid pipe  40 , also known as a delivery pipe, delivers cryogenic fluid pumped from cold end assembly  30  through flange  50  in warm end assembly  20 . Pipe  40  connects with external piping (not shown) that delivers the cryogenic fluid to another cryogenic vessel (when the system is transferring cryogenic fluid, for example when filling a vehicle fuel tank) or to an external vaporizer (when the cryogenic fluid is to be used by an end user in gaseous form, for example when the cryogenic fluid is natural gas that is used to fuel an internal combustion engine for powering a vehicle). With reference to both  FIGS.  1  and  3   , a compact arrangement is shown for a hydraulic drive unit that is mounted adjacent to flange  50  with hydraulic fluid passageways  60  and  70  for delivering hydraulic fluid into and out of cylinder  75  in a manner that is well known for causing piston  80  to produce reciprocating motion. Fittings  90  and  100  connect passageways  60  and  70  to external hydraulic conduits (not shown). 
     Referring now to  FIGS.  3  and  4   , passageway  110  is provided in flange  50 , extending from opening  125  in face  65  to opening  135  in face  85 . Passageway  110  comprises first portion  120  and second portion  130  which in this embodiment are cylindrical bores. The diameter of first portion  120  is less than the diameter of second portion  130 . When process fluid pipe  40  is assembled into passageway  110  it is in contact with inner wall  145  of first portion  120 , but gap  140  exists between the pipe and inner wall  150  of second portion  130 . In other embodiments there can be a finite space between pipe  40  and first portion  120  of passageway  110  at least around a portion of the external surface of the pipe. Gap  140  is an annular gap in the present example. Process fluid pipe  40  is secured to flange  50  by weld  160 . Depending upon application requirements, it is possible in other embodiments that a mechanical arrangement or an adhesive can secure pipe  40  to flange  50 , or other known techniques can be employed. 
     The thermal resistance between process fluid pipe  40  and flange  50  is increased by gap  140  since the contact area between the pipe and the flange is reduced. Normally both pipe  40  and flange  50  are made from metal, which is a better conductor of heat than air occupying gap  140 . The gap decreases cooling effect on flange  50  caused by the flow of cryogenic fluid through pipe  40 , thereby reducing the likelihood of the hydraulic fluid freezing and reducing condensation of humidity and frost/ice build-up around warm end assembly  20 . 
     Passageway  110  is at an oblique angle to both faces  65  and  85 , such that opening  125  is further from longitudinal axis  15  than opening  135 . Referring now to  FIG.  2   , when cryogenic pump  10  is installed in storage vessel  25  the majority of its length is preferably housed in sleeve  35  as shown in  FIG.  2   , so that opening  135  is located within the sleeve, where it is not exposed directly to the cryogen space. Storage vessel  25  is a double-walled vessel comprising outer wall  26  and inner wall  27 . In preferred embodiments vacuum space  45  provides additional thermal insulation between sleeve  35  and cryogen space  55 . The oblique angle of passageway  110  has the advantage of locating the contact area between pipe  40  and inner wall  145  of passageway  110  further from hydraulic fluid in passageways  60  and  70  and in cylinder  75 . This has the effect of increasing the thermal resistance of the heat path between hydraulic fluid and cryogenic fluid in pipe  40 . In other embodiments opening  125  can be located the same distance from axis  15  or closer compared to opening  135 . In a preferred embodiment, process fluid pipe  40  is secured to flange  50  by weld  160  such that gaseous fuel vapor between sleeve  35  and pump  10  does not escape to the external environment. It is preferred that pipe  40  is welded to flange  50  at opening  125 , compared to opening  135  which would tend to increase heat transfer between pipe  40  and cylinder  75  and passageway  70 . 
     Referring now to  FIGS.  5 - 9   , there is shown a second embodiment wherein like parts to the previous embodiment and all other embodiments have like reference numerals and may not be discussed in detail, if at all. Flange  52  comprises a bore  200  that extends from face  65  to face  85 . An annulus  210  generally in the form of a hollow cylindrical tube is inserted into bore  200  thereby forming passageway  110  and first and second portions  120  and  130 . Annulus  210  can be secured to flange  52  in a variety of ways. As non-limiting examples, annulus  210  can be press or interference fit into bore  200 , slip fit into the bore and secured by an adhesive or by welding, by a combination of these techniques, or by other known techniques to mechanically secure parts together. 
     Referring now to  FIGS.  10  and  11   , there is shown a third embodiment of flange  53 . Pipe  41  is welded to face  85 , and is employed to communicate a cryogenic fluid through flange  53 , which depending on the type of pipe (fill pipe, delivery pipe or drain pipe) can flow in either direction. Passageway  111  is similar to passageway  110  in  FIG.  4   , except that portion  120  of passageway  111  extends from face  85  and portion  130  extends from face  65 . Annular groove  155  extends around passageway  111 , which in cooperation with the passageway forms a bellows to redirect thermal contractions of flange  53  in a direction that is not constrained, thereby reducing stress on weld  160 . Annular portion  56  allows for axially contraction (in the direction of the axis of passageway  111 ) and flexion when flange  50  thermally contracts. Pipe  41  is normally not anchored within storage vessel  25 , and is free to move, such that when a thermal gradient exists between the pipe and flange  53  along portion  56 , the portion can contract along the axial direction of passageway  111 . The thermal resistance between pipe  41  and flange  53  is also increased by annular groove  155 , compared to when annular groove  155  is not employed, due to the narrowing of the metal conduction path from the pipe to the flange. Water vapour can condense and freeze (and/or desublimate) in annular space  165 , formed by bore  150  and pipe  41 , due to the cold temperatures of the cryogenic fluid in the pipe. Annular space  165  can be filled with a low thermal conductivity material that can contract at a predetermined rate comparable to the rate of temperature change, to displace moisture. Non-limiting examples of such materials comprise glass fiber reinforced plastic, a composite material, and a PTFE foam. Alternatively, the opening into annular space  165  can be sealed at surface  65  to prevent the accumulation of moisture in the space. In general, portion  120  of the passageway can extend from either face  65  or  85 , as long as the relative spatial relationship between portion  120  and annular groove  155  is maintained, that is the annular groove extends from the opposite face as portion  120 . 
     Referring now to  FIG.  12    a fourth embodiment of flange  54  is shown where passageway  111  and annular groove  155  are formed by placing insert  58  in bore  175 , which extends from face  85  to face  65  of the flange. Insert  58  is connected to bore  175  by annular groove weld  161 , or alternatively the insert can be epoxied to, threaded into or press-fit into the bore. By using insert  58  the length of annular portion  56  can be increased, which allows for an increased range of axial contraction and flexion when flange  54  thermally contracts, thereby reducing the stress on weld joints between the pipe and the flange. The increased length of annular portion  56  also increases the thermal resistance between the pipe and the flange. In alternative embodiments, flange  55  can be formed as illustrated in  FIG.  12    as an integrated component, for example machined from a unitary metal block. 
     Referring now to  FIGS.  13  and  14   , a fifth embodiment of flange  55  is shown. Pipes  42  and  44  are welded to face  65  and  85  by welds  162  and  164  respectively, and are employed to communicate a cryogenic fluid to and from flange  55 , which depending on the type of pipe (fill pipe, delivery pipe or drain pipe) can flow in either direction through a passageway defined by bore  300 . In other embodiments pipes  42  and  44  can be one pipe that extends through bore  300  in flange  55 . Annular groove  155  around bore  300  extends into flange  55  from face  65 , in the illustrated embodiment. Annular groove  310  extends from face  85  into the flange and around both annular groove  155  and bore  300 . Annular grooves  155  and  300  in cooperation with bore  300  form a bellows to redirect thermal contractions of flange  50  in a direction that is not constrained, thereby reducing stress on welds  162  and  164 . Annular portions  56  and  57  allow for axially contraction (in the direction of the axis of passageway  111 ) and flexion when flange  50  thermally contracts. In other embodiments, additional annular grooves can be employed, around bore  300 , alternating between face  65  and  85 , to increase the size of the bellows formed by these grooves, thereby increasing the flexion of the flange during thermal contractions. Annular groove  155 , and any other annular grooves that are externally facing with respect to storage vessel  25  (seen in  FIG.  2   ), can be filled with a low thermal conductivity material (such as epoxy), or sealed at the opening, to displace moisture therein thereby reducing the likelihood of frost and/or ice forming in the groove(s). 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.