Abstract:
A high pressure separator/accumulator that uses dual bellows is provided. The dual bellows are not mechanically linked but rather operationally coupled through a fluid medium. The high pressure separators includes a housing defining a first internal space. The housing is in fluid communication with a first fluid system and a second fluid system. A first bellows is coupled to the interior of the separator and defines a space with a variable volume. The space is in fluid communication with the first fluid system. A second bellows is coupled to the interior of the separator, generally opposed to the first bellows, and defines a space with a variable volume. The space is in fluid communication with the second fluid system. The two fluid systems, however, are isolated from each other by the separator. The housing is charged with a fluid medium that transmits force between the first and second bellows.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     BACKGROUND 
       [0001]    Fluid systems are ubiquitous in many industrial markets. Often these systems have pressures and/or temperatures that vary. One device useful in offsetting the expansion and contraction of fluid systems are metallic bellows accumulators. The metallic bellows accumulators allow fluid to ingress or egress to maintain a system pressure, especially in systems that experience temperature changes. For example, as temperature rises, the density of most fluids decreases causing the fluid volume to expand at a given pressure, which is generally known as Boyle&#39;s law. When temperature falls, the density of most fluids increases causing the fluid volume to contract at a given pressure. The bellows accumulators all systems to expand and contract when temperature changes occur in a closed fluid system. 
         [0002]    A cross sectional view of a prior art accumulator  100  is shown in  FIGS. 1A and 1B . In  FIG. 1A , the accumulator  100  is shown in the expanded state  102 . The accumulator  100  in this construction has a housing  104  or outer shell defining a first space  106  and a bellows  108  have an end plate  109  defining a second space  110 . The first space  106  is at a desired pressure and temperature. The first space  106  may be in fluid communication with a first fluid port  112  that regulates the pressure and/or temperature of the first space  106 . The bellows  108  may be, for example, a welded bellows in which a number of individually formed diaphragms  114  are welded to each other along welds  116  or a formed bellows where a cylindrical tube is cold formed into a bellows. The housing  104  may be unnecessary in situations where the first space  106  is maintained at atmospheric pressures and temperatures. The second space  110  is in fluid communication with a system through a second fluid port  118 . The second space  110  is generally filled with the fluid (gas or liquid). In the expanded state, as shown, the pressure of the second space  110  is greater than the pressure of the first space  106  causing the expansion of bellows  108 . As can be appreciated, either of the first fluid port  112  or the second fluid port  118  can be in fluid communication with the fluid system or the regulated pressure source. 
         [0003]    As shown in  FIG. 1B , the accumulator  100  is shown in the compressed state  120 . In this state, the bellows  108  is compressed, which reduces the volume of the second space  110  and increases the volume of the first space  106 , which may have the effect of decreasing the pressure of the first space  106  if first space  106  is not in communication with a pressure regulation system as described above. 
         [0004]    As the pressures in the first and second space  106 ,  110  change, the bellows  108  moves from a more expanded state to a more compressed state. The maximum pressure differentials occur at the compressed state  120  and the fully expanded state  102 . 
         [0005]    The bellows  108  is capable of withstanding very high pressure differentials in the compressed state  120  as the stacked bellows support each other through contact and limit the amount of deflection. The bellows  108  in the expanded state, however, are susceptible to failure. In particular, the thin metal of the bellows and the welds limit the maximum differential pressures the bellows  108  can withstand in the fully extended state as the individual diaphragms  114  do not provide significant support to adjacent diaphragms. 
         [0006]    High pressure bellows separators, however, are desirable despite the maximum differential pressures that the bellows can withstand. Thus, a need exists in the industry for a high pressure bellows separator that can withstand significant differential pressures in the expanded state. Thus, against this background, an improved high pressure bellows separator is desirable. 
       SUMMARY 
       [0007]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary, and the foregoing Background, is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. 
         [0008]    The technology described herein provides, among other things, a high pressure separator/accumulator that uses dual bellows. The dual bellows are not mechanically linked but rather operationally coupled through a fluid medium. In particular, the high pressure separators in certain aspects has a housing defining a first internal space. The housing is in fluid communication with a first fluid system and a second fluid system. A first bellows is coupled to the interior of the separator and defines a space with a variable volume. The space is in fluid communication with the first fluid system. A second bellows is coupled to the interior of the separator, generally opposed to the first bellows, and defines a space with a variable volume. The space is in fluid communication with the second fluid system. The two fluid systems, however, are isolated from each other by the separator. The housing is charged with a fluid medium that transmits force between the first and second bellows. 
         [0009]    These and other aspects of the present system and method will be apparent after consideration of the Detailed Description and Figures herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0011]      FIG. 1A  consists of a cross sectional view of a metallic bellows accumulator consistent with the prior art in an expanded state. 
           [0012]      FIG. 1B  consists of the cross sectional view of the metallic bellows accumulator of  FIG. 1A  in a compressed state. 
           [0013]      FIG. 2  consists of a partial cross sectional view of a dual metallic bellows accumulator consistent with the technology of the present application. 
           [0014]      FIG. 3  consists of the partial cross sectional view of the dual metallic bellows accumulator of  FIG. 2 . 
           [0015]      FIG. 4  consists of the partial cross sectional view of the dual metallic bellows accumulator of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The technology of the present application will now be described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the technology of the present application. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense. 
         [0017]    The technology of the present application is described with specific reference to dual bellows separator usable in fluid systems where high differential pressures may make conventional bellows unacceptable. However, the technology of the present application would be useful in any separator application as the reduced pressure differential demands when the bellows are fully expanded provide decreased wear and fatigue on the bellows, which may increase life and decrease maintenance. Moreover, the technology of the present application will be described with relation to exemplary embodiments. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary. 
         [0018]    With reference now to  FIGS. 2-3 , a partial cross-sectional view of an accumulator  200  is provided. The cross section is taken along a center line  201  of the accumulator showing only ½ of cross section of the accumulator  200  for convenience. The accumulator  200  has a housing  202  with a system side  204  and a pressure control side  206 . The accumulator  200  has a first port  208  on the system side  204  placing the accumulator  200  in fluid communication with fluid system, not shown for convenience, but generally known in the art. The accumulator  200  has a second port  210  on the pressure control side  206 , which may be in fluid communication with a regulated pressure source. The accumulator may initially be provided with the first and second fluid ports capped or sealed. For example, if the accumulator  200  was designed to inject fluid into a fluid system, the first and second ports may be sealed with a rupture disk of the like (not specifically shown). This allows the accumulator  200  to be charge with a fluid, installed into a system, and a motive force to be applied to one of the fluid ports. 
         [0019]    The accumulator  200  has a first bellows  212  and a second bellows  214 . In this exemplary embodiment, the bellows  212 ,  214  may comprise edge-welded metal bellows constructed from stainless steel, nickel alloys, titanium, titanium alloys, or the like. The first bellows  212  has a first proximal end  216  and a first distal end  218 . The first proximal end is coupled to the housing  202  on the system side  204  of the accumulator  200 . The first distal end terminates at a plate  220 , which may be referred to as a piston. The first bellows  212  defines a first space  222  in fluid communication with the first port  208  and the fluid system such that the first space  222  is at approximately the same pressure as the fluid system, which is identified as P2. The second bellows  214  has a second proximal end  224  and a second distal end  226 . The second proximal end  224  is coupled to the housing  202  on the pressure control side  206  of the accumulator  200 . The second distal end  226  terminates at a plate  228 , which also may be referred to as a piston. The second bellows  214  defines a second space  230  in fluid communication with the second port  210  and the regulated pressure source such that the second space  230  is at approximately the same pressure as the regulated pressure source, which is identified as P2. 
         [0020]    The housing  202  of the accumulator  200  defines a third space  232  internal to the housing, but external of the first and second bellows  212 ,  214 . The third space  232  is charged with a fluid F to a predetermined pressure, which is identified as P3. The fluid F may be a low thermal expansion liquid, such as, for example, silicone gel, hydraulic fluid, or the like. 
         [0021]    With specific reference now to  FIG. 2 , the accumulator  200  is shown in a state of equilibrium  212 . In other words, the pressure control and the fluid system pressures are approximately equal, which means P1≈P2≈P3. At or approximately at equilibrium, the bellows  212 ,  214  expand to their free length, shown by L1, L2. The plates  220 ,  220  are separated by the fluid F and a distance L3, which may be minimized for efficiency. Notably, while first bellows  212  and second bellows  214  are operably coupled by the fluid F, they are not mechanically linked. The free lengths L1 and L2 generally relate to the spring rates as they equalize. 
         [0022]    With reference now to  FIG. 3 , the accumulator  200  is shown where P1&lt;P2. As can be shown, in this case, the first bellows  212  expands such that L2′&gt;L2. Correspondingly, the second bellows  214  collapses such that L1′&lt;L1. Notably, the distance L3 between plates  220 ,  228  should remain approximately the same. The pressure differential between the fluid system and the regulated pressure source can be very great in this construction because the collapsed second bellows  214  can withstand a high differential pressure between spaces  230  and  232 . While the second bellows  214  may experience a high differential pressure, the first bellows  212  is still at a relatively constant pressure such that the pressure P2≈P3 such that in the expanded state, the first bellows  212  does not experience a similarly high differential pressure. 
         [0023]    With reference now to  FIG. 4 , the accumulator  200  is shown where P2&lt;P1. As can be shown, in this case, the first bellows  212  collapses such that L2″&lt;L2. Correspondingly, the second bellows  214  expands such that L1″&gt;L1. Similarly to the above, the distance L3 between plates  220 ,  228  should remain approximately the same. The pressure differential between the fluid system and the regulated pressure source can be very great in this construction because the collapsed first bellows  212  can withstand a high differential pressure between spaces  222  and  232 . While the first bellows  212  may experience a high differential pressure, the second bellows  214  is still at a relatively constant pressure such that the pressure P1≈P3 such that in the expanded state, the second bellows  214  does not experience a similarly high differential pressure. 
         [0024]    The accumulator  200  allows for systems where either the fluid system pressures are high and the regulated pressure source is low or the fluid system pressures are low and the regulated pressure source is high. Such fluid systems may include applications where hazardous fluids are involved. 
         [0025]    In one exemplary application, the accumulator  200  may be useful to refuel satellites. Generally, moving a fluid, such as rocket fuel, from a storage, such as an accumulator, to the tanks of a satellite requires a motive force. In most applications, the motive force is a pump. However, most pumps use elastomer seals. Rocket fuel, however, is generally not compatible with most elastomers making most pumps unsatisfactory. The accumulator  200  solves this problem by providing a separation between the regulated pressure source, which may be in fluid communication with a pump discharge and the fluid system, which may be in fluid communication with the tanks. To facilitate, for example, a refueling operation, the accumulator  200  may have the first or second space  222 ,  230  charged with fuel. The metallic bellows contains the fuel and isolates the fuel from the pump. Other applications for accumulator  200  are of course possible in, for example, hydrocarbon fluid systems such as with pipelines and oil wells and derricks. 
         [0026]    Although the technology has been described in language that is specific to certain structures and materials, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and materials described. Rather, the specific aspects are described as forms of implementing the claimed invention. Because many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, etc. used in the specification (other than the claims) are understood as modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should at least be construed in light of the number of recited significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).