Abstract:
A manifold assembly and mineral extraction system including a multi-pressure flange is disclosed that includes a first set of fasteners in a first rectangular pattern for attachment in a first pressure rating and a second set of fasteners in a second rectangular pattern in which the first rectangular pattern is perpendicular to the second rectangular pattern. The second set of fasteners is selectively combinable with the first set of fasteners for attachment in a higher second pressure rating. The flange may include a recess to receive sealing component and a receptacle configured to receive a pipe fitting. Systems and methods including the multi-pressure flange are also disclosed.

Description:
BACKGROUND 
       [0001]    This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
         [0002]    Accumulators provide a supply of pressurized working fluid for the control and operation of subsea equipment, such as hydraulic actuators and motors. Typical subsea equipment may include, but is not limited to, blowout preventers that shut off the well bore to secure an oil or gas well from accidental discharges to the environment, valves for the control of flow of oil or gas to the surface or to other subsea locations, or hydraulically actuated connectors and similar devices. 
         [0003]    Accumulators are typically divided pressure vessels with a gas section and a useable hydraulic fluid section that operate on a common principle. The principle is to precharge the gas section with an inert, dry, ideal gas (e.g., nitrogen or helium), pressurized to a pressure at or slightly below the anticipated minimum pressure required to operate the subsea equipment. Hydraulic fluid will then be added (or “charged”) to the accumulator in the separate hydraulic fluid section, increasing the pressure of the pressurized gas and the hydraulic fluid to the maximum operating pressure of the control system. The precharge pressure determines the pressure of the very last trickle of fluid from the fluid side of the accumulator, and the charge pressure determines the pressure of the very first trickle of fluid from the fluid side of the accumulator. The discharged fluid between the first and last trickle will be at some pressure between the charge and precharge pressure, depending on the speed and volume of the discharge and the ambient temperature during the discharge event. The hydraulic fluid introduced into the accumulator is therefore stored at the maximum control system operating pressure until the accumulator is discharged for the purpose of doing hydraulic work. 
         [0004]    Accumulators generally come in three styles—the bladder type having a balloon type bladder to separate the gas from the fluid, the piston type having a piston sliding up and down a seal bore to separate the fluid from the gas, and the float type with a float providing a partial separation of the fluid from the gas and for closing a valve when the float approaches the bottom to prevent the escape of the precharging gas. A fourth type of accumulator is pressure compensated for water depth and adds the precharge pressure plus the ambient seawater pressure to the working fluid. 
         [0005]    The precharge gas can be said to act as a spring that is compressed when the gas section is at its lowest volume/greatest pressure and released when the gas section is at its greatest volume/lowest pressure. Accumulators are typically precharged on the surface in the absence of hydrostatic pressure and subsequently charged with hydraulic fluid on the seabed under full hydrostatic pressure. The surface precharge pressure is limited by the pressure containment and structural design limits of the accumulator vessel under surface ambient conditions. Yet, as accumulators are used in deeper water, the efficiency of conventional accumulators decreases as application of hydrostatic pressure causes the gas to compress, leaving a progressively smaller volume of gas to charge the hydraulic fluid. The gas section must consequently be designed such that the gas still provides enough power to operate the subsea equipment under hydrostatic pressure even as the hydraulic fluid approaches discharge and the gas section is at its greatest volume/lowest pressure. 
         [0006]    Typically, accumulators are arranged in banks located proximate the subsea equipment to be operated by the accumulators (e.g., blowout preventors). The accumulators within the bank are in fluid communication via a subsea fluid manifold which is connected to a common hydraulic source of hydraulic fluid. Conventional accumulator manifold systems are tack welded in place (i.e., connected to the accumulators in the accumulator bank). The accumulators are then removed from the accumulator bank and completed with final welds with full quality assurance and quality control testing taking place. After completing the final welding, the manifold is reinstalled in the accumulator bank and connected to a common hydraulic fluid supply source to recharge the hydraulic accumulators due to leakage or use. 
         [0007]    One type of high pressure connection used in traditional accumulator manifolds is an autoclave style connection. While autoclave connections provide a higher pressure rating, they may restrict the hydraulic fluid flow from the accumulator. The autoclave connections may be difficult and time-consuming to install and assemble to a leak-free condition. Additionally, the tubing used with the autoclave connections may be more expensive than the tubing used with the conventional connections. 
         [0008]    An accumulator manifold that does not require welding and does not use autoclave connections is therefore desirable for simplicity, ease of installation, and economic efficiencies. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
           [0010]      FIG. 1  is a block diagram of a mineral extraction system in accordance with an embodiment of the present invention; 
           [0011]      FIG. 2  is a block diagram of a BOP and accumulator system in accordance with an embodiment of the present invention; 
           [0012]      FIG. 3  is a block diagram of an accumulator and dual pressure flange in accordance with an embodiment of the present invention; 
           [0013]      FIGS. 4A and 4B  are front and rear perspective views of the dual pressure flange of  FIG. 3  in accordance with an embodiment of the present invention; 
           [0014]      FIG. 5  is an exploded front perspective view of the dual pressure flange and a seal component that may be used with the dual pressure flange in accordance with an embodiment of the present invention; 
           [0015]      FIG. 6  a front perspective view of the assembled dual pressure flange and seal component in accordance with an embodiment of the present invention; 
           [0016]      FIG. 7  depicts a front view of the dual pressure flange in accordance with an embodiment of the present invention; 
           [0017]      FIG. 8  depicts a cross-section of the assembled dual pressure flange and seal component taken along line  7 - 7  of  FIG. 7  in accordance with an embodiment of the present invention; 
           [0018]      FIGS. 9A and 9B  depict a front and rear perspective view respectively of the dual pressure flange in a low pressure configuration in accordance with an embodiment of the present invention; 
           [0019]      FIG. 10  is a cross-sectional view of the dual pressure flange taken along line  7 - 7  of  FIG. 7  in accordance with an alternate embodiment of the present invention; 
           [0020]      FIG. 11  depicts a front view of the dual pressure flange in accordance with an alternate embodiment of the present invention; and 
           [0021]      FIG. 12  depicts a perspective view of an accumulator manifold including non-welded connections. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
         [0023]    When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
         [0024]      FIG. 1  is an illustration of an exemplary mineral extraction system  10 . The illustrated mineral extraction system  10  can be configured to extract various minerals and natural resources, including hydrocarbons (e.g., oil and/or natural gas), or configured to inject substances into the earth. In some embodiments, the mineral extraction system  10  is land-based (e.g., a surface system) or subsea (e.g., a subsea system). 
         [0025]    The system  10  typically includes multiple components that control and regulate activities and conditions associated with the well  14 . For example, the system  10  typically includes bodies, valves and seals that route produced minerals from the well  14 , provide for regulating pressure in the well  14 , and provide for the injection of chemicals into the well  14 . In the illustrated embodiment, the system  10  includes a production tree  22 , a tubing head  24 , a casing head  25 , and a hanger  26  (e.g., a tubing hanger or a casing hanger). The system  10  may include other devices that are coupled to the wellhead assembly  12 , and devices that are used to assemble and control various components of the wellhead assembly  12 . For example, in the illustrated embodiment, the system  10  includes a riser  28  coupled to a floating rig  36 . 
         [0026]    The production tree  22  generally includes a variety of flow paths (e.g., bores), valves, fittings, and controls for operating the well  14 . For instance, the production tree  22  may include a frame that is disposed about a tree body, a flow-loop, actuators, and valves. Further, the production tree  22  may provide fluid communication with the well  14 . For example, the production tree  22  includes a tree bore  32 . The production tree bore  32  provides for completion and workover procedures, such as the insertion of tools into the well  14 , the injection of various chemicals into the well  14 , and the like. Further, minerals extracted from the well  14 , such as oil and natural gas, may be regulated and routed via the production tree  22 . For instance, the production tree  12  may be coupled to a jumper or a flowline that is tied back to other components, such as a production manifold. Accordingly, produced minerals flow from the well  14  to the production manifold via the wellhead assembly  12  and/or the production tree  22  before being routed to shipping or storage facilities. A blowout preventer  31  may also be included during drilling or workover operations, either as a part of the production tree  22  or as a separate device. The blowout preventor  31  may consist of a variety of valves, fittings and controls to prevent oil, gas, or other fluid from exiting the well in the event of an unintentional release of pressure or an unanticipated overpressure condition. Two or more blowout preventors may be stacked together. 
         [0027]    In the illustrated embodiment, the production tree  22  is landed on the tubing head  24 . The tubing head  24  includes a tubing head bore  34 . The tubing head bore  34  sealably connects (e.g., enables fluid communication between) the tree bore  32  and the well  16 . Thus, the tubing head bore  34  may provide access to the well bore  20  for various completion and workover procedures. For example, components can be run down to the wellhead assembly  12  and disposed in the tubing spool bore  34  to seal-off the well bore  20 , to inject chemicals down-hole, to suspend tools down-hole, to retrieve tools downhole, and the like. 
         [0028]    The blowout preventor  31  may be hydraulically operated and may close the wellhead assembly  12  or seal off various components of the wellhead assembly  12 . To enable hydraulic operation of the blowout preventor  31 , the blowout preventor  31  may be coupled to a source of hydraulic pressure, e.g., pressurized hydraulic fluid.  FIG. 2  is a block diagram of the blowout preventor  31  and an accumulator bank  36  in accordance with an embodiment of the present invention. The accumulator bank  36  may include one or more accumulators  38 . The accumulator bank  36  may house the accumulators  38 , providing easier installation and operation of the accumulators  38 . In some embodiments, a group of accumulators  38  may also be referred to as a “module” or a “rack.” A control valve  40  may also be included to control the blowout preventor  31  and the accumulator bank  36 . The control valve  40  may also include a vent  42 . The blowout preventor  31  may include an open port  43  and a close port  44 . The accumulators  38  may provide pressurized hydraulic fluid to either the open port  43  or close port  44 , as determined by the control valve  40 , to open or close the blowout preventor  31 . 
         [0029]    The accumulators  38  output pressurized hydraulic fluid to the blowout preventor  31 . Thus, the accumulators  38  may be referred to as having a gas end  39  and a liquid end  41 . As shown in  FIG. 2 , the liquid end  41  may be coupled to the control valve  40  and to a hydraulic conduit. The accumulators  38  provide pressurized hydraulic fluid to the blowout preventor  31  to enable operation of the blowout preventor via hydraulic pressure. In some embodiments, the blowout preventor  31  (i.e., blowout preventor stack) may include anywhere from about 10 to over 100 accumulators, depending on size, rack configurations, blowout preventor size, rated water depth, the number of hydraulic circuits, and other factors. 
         [0030]    Once the blowout preventor  31  is coupled to the wellhead assembly  12 , the accumulators  36  may provide charging of the blowout preventor  31  with the hydraulic fluid from a liquid end  41  of the accumulator. In some embodiments, the working hydraulic pressure of the control system for the blowout preventor  31  may be about 5,000 psi. However, in a subsea installation, the precharge pressure of the gas may be higher than the maximum system pressure to overcome the subsea hydrostatic pressure (approximately 0.5 psi/ft of water depth) and the minimum system pressure required to operate the blowout preventor  31 . In such an embodiment, the gas end  39  of the accumulators  38  is typically capable of a higher rated pressure than the liquid end  41 . According to industry standards, the pressure rating of each accumulator  38  may be determined as the pressure rating of its lowest rated connection. Thus, if a specific pressure rating is desired, the lowest rated end connection must be selected to achieve the desired pressure rating. 
         [0031]    While conventional accumulators may be rated from about 5,000 psi to about 6,000 psi (e.g., the pressure rating for the accumulator matches the pressure rating of the gas end  39 ), deeper subsea wellhead assemblies may include higher pressures. The present disclose provides a manifold  104  comprising one or more multi-pressure (e.g., dual pressure) flanges capable of supporting pressure ratings for high pressure subsea installations (e.g., at least about 15,000 psi) and pressure ratings for low pressure installations (e.g., at least about 6,000 psi). As used herein, the terms “high pressure” and “low pressure” are relative terms used to refer to a relationship between two pressures. 
         [0032]      FIG. 3  depicts a block diagram of a multi-pressure flange  50  and an accumulator  38  which can be used with the manifold  104  presently disclosed. In the following discussion, the flange  50  is generally described as a dual-pressure flange  50 . However, various embodiments of the flange  50  may be a tri-pressure flange, a quad-pressure flange, or some other multi-pressure flange. The accumulator  38  includes a gas end  52  and a liquid connection  54 . The accumulator  38  may be precharged with gas. For example, the accumulators  38  of a bank  36  may each be precharged with gas on the surface before installation, such as via a valve  56 . The liquid connection  54  may be connected to the blowout preventor  31  (or other hydraulic component) of a wellhead assembly  12  via a pipe  58 . 
         [0033]    The accumulator  38  may include a plurality of chambers, such chambers  60  and  62 , for receiving gases and fluids. For example, in one embodiment the chamber  60  may be precharged with gas through the valve  56 , and may output pressurized hydraulic liquid from the chamber  62  through the connection  54 . 
         [0034]    The gas end  52  and liquid connection  54  may be separated by an energy storage and transfer device  64 . In some embodiments, the energy storage and transfer device  64  may be a piston, an elastomeric bladder, or any other suitable device or combination thereof. The energy storage and transfer device  64  may isolate the chambers of the accumulator  38 , such as isolating chamber  60  from  62 . The energy transfer and storage device  64  transfers energy (such as from the pressurized gas from the chamber  60 ) and controls flow of the hydraulic fluid in and out of the accumulator through the connection  54 . 
         [0035]    As described above, in certain installations, it may be desirable to have a specific pressure rating for the gas end  52  and/or the connection  54 . The dual pressure flange  50  may couple to the connection  54  of the accumulator  38  to provide the desired pressure rating and allow connection of the liquid line  58 . For example, as described further below, the dual pressure flange  50  provides connection and sealing capability to enable use in a deep water subsea installation of the accumulator  38 , such as for pressure ratings of at least about 10,000 psi. Further, the dual pressure flange  50  provides connection and sealing capability to enable use in conventional subsea installations, such as for pressure ratings of at least about 6,000 psi. 
         [0036]      FIGS. 4A and 4B  depict a front perspective view and a rear perspective view respectively of the dual pressure flange  50  in accordance with an embodiment of the present invention. As shown in  FIG. 4A , the dual pressure flange  50  includes eight fasteners, such as attaching bolts  68 , arranged in two rectangular four-bolt patterns, as described further below. In some embodiments, the fasteners may be threaded to enable coupling to the connection  54  of the accumulator  38 . As shown in  FIG. 4B , the bolts  68  are removed from the flange  50  to illustrate a plurality of holes  69  (e.g., threaded receptacles) that receive the bolts  68 . The holes  69  are also arranged in two rectangular four-hole patterns, as described further below. 
         [0037]    The dual pressure flange  50  also includes a receptacle  70  configured to receive a sealing mechanism, such as the seal component described in  FIG. 5 . Additionally, the dual pressure flange  50  includes a threaded connection  72  that may receive a fitting, pipe, or other component to transport fluid through the flange  50  into and out of the accumulator  38 . For example, in one embodiment, the threaded connection  72  may include National Pipe Thread (NPT) threads. The flange  50  may comprise or consist essentially of steel or any other suitable alloy. In one embodiment, the flange  50  may consist essentially of type  316  stainless steel. 
         [0038]      FIG. 5  depicts a perspective view of a sealing component, such as a seal sub  74 , and the dual pressure flange  50  in accordance with an embodiment of the present invention. The seal sub  74  may be used to aid in sealing the dual pressure flange  50  when installed on the accumulator  38 . The seal sub  74  may include a first seal  76  configured to seal against the flange  50  (such as by against the walls of the receptacle  70 ) and a second seal  78  configured to seal against the connection  54  on the accumulator  38  when the sub seal  74  is installed. In some embodiments, the first seal  76  and second seal  78  may comprise o-rings. The seal sub  74  includes a hole  80  through which gas or fluid may flow though the flange  50  and into and out of the accumulator  38 . Additionally, the threaded connection  72  and hole  80  may provide increased flow capacity over conventional “autoclave” connections, resulting in lower response times for the blowout preventor  31 . 
         [0039]      FIG. 6  depicts a rear perspective view of the assembled dual pressure flange  50  and the seal sub  74  in accordance with an embodiment of the present invention. As shown in  FIG. 6 , the seal sub  74  inserts into the receptacle  70  such that the first seal  76  engages the walls of the receptacle  70 . The second seal  78  remains outside the receptacle  70  to provide sealing against a connection when the flange  50  installed. The seal sub  74  “floats” between the flange  50  and the connection  54  of the accumulator  38 . For repair or replacement, the seal sub  74  may be removed from the flange  50 . 
         [0040]      FIG. 7  depicts a front view of the dual pressure flange in accordance with an embodiment of the present invention. As seen more clearly in  FIG. 7 , when assembled, the threaded connection  72  of the flange  50  and the hole  80  of the seal sub  74  align to allow insertion of a pipe fitting, or other component to allow fluid or gas flow in and out of the accumulator  38 . As described above, the dual pressure flange  50  includes eight attaching bolts  68  arranged in two rectangular four-bolt patterns. The rectangular patterns may be displaced at 90° to each other. For example, as shown in  FIG. 7 , a first group  82  of four bolts may be arranged in a first rectangular pattern  84 , and a second group  86  of four bolts may be arranged in a second rectangular pattern  88 . As described further below, when using the dual pressure flange  50  in a low-pressure configuration (e.g., at least about 6,000 psi) such that only four bolts are used to secure the flange to a connection of an accumulator, the two rectangular patterns  84  and  88  allow easier orientation of the flange  50  during installation onto a connection. For example, when installing with four bolts, either one of the two rectangular patterns  84  and  88  may be aligned with the respective mating surface for the flange  50 . As shown in  FIG. 7 , the first group  82  of four bolts and the second group  86  of four bolts are not uniformly spaced between the first rectangular pattern  84  and the second rectangular pattern  88 . 
         [0041]      FIG. 8  is a cross-sectional view of the dual pressure flange  50  taken along line  7 - 7  of  FIG. 7  in accordance with an embodiment of the present invention. As illustrated in  FIG. 8 , the flange  50  receives the seal sub  74  such that the seal sub  74  (and the included seals  76  and  78 ) provides an enhanced sealing mechanism against the connection of the accumulator (as opposed to the sealing provided by a face seal of the flange  50 ). Additionally, because of the positioning of the seal sub, i.e., “floating” in the flange  50  and the connection  54  of the accumulator  38 , the integrity of the seal between the flange  50  and the connection  54  is not dependent on the makeup torque on the attaching bolts  68  when installing the flange  50 . Further, use of the seal sub  74  may eliminate machining requirements for the face of the flange  50 . However, in a low pressure configuration, as described below in  FIGS. 9A and 9B , the seal sub  74  may be omitted from the installed flange  50 . 
         [0042]      FIGS. 9A and 9B  depict a front and rear perspective view respectively of the dual pressure flange  50  in a low pressure configuration in accordance with an embodiment of the present invention. In a low pressure configuration, the flange  50  may include four attaching bolts  90  arranged in one of the rectangular patterns  84  or  88 . The four attaching bolts  90  may be used to secure the flange as a low pressure (e.g., at least about 6,000 psi) connection. 
         [0043]    In other embodiments, eight attaching bolts may remain in the flange  50  in the low pressure configuration, so that the flange  50  may be more easily oriented during installation to ensure that one of the two rectangular patterns  84  or  88  of the bolts  90  couple with the low pressure connection on the accumulator  38 . Advantageously, the low pressure configuration of the dual pressure flange  50  allows the flange  50  to function as a conventional Society of Automotive Engineers (SAE) Code  62  flange. In this configuration, the flange  50  may be usable with any equipment configured to use or connect via an SAE Code  62  flange. In such an embodiment, the dual pressure flange  50  may be used with or without the seal sub  74 . In some embodiments, the sealing function may be provided by a face seal of the flange  50  sealing against the connection  54 . However, in contrast to the embodiments discussed above, use of face seal makes the sealing capability of the flange  50  sensitive to the makeup torque on the bolts  90  when installing the flange, and may also make the flange  50  susceptible to pressure induced face flange separation. A face seal may also be used in a high pressure flange configuration that uses eight bolts in both rectangular patterns  84  and  88  to couple the flange  50 . 
         [0044]    The flange  50  may be coupled to a family of different components to achieve different pressure ratings. For example, the low pressure configuration, e.g., using four bolts of the flange  50 , may be used to couple the flange  50  to a first component to achieve a first pressure rating. Similarly, a higher pressure configuration, e.g., using eight bolts of the flange  50 , may be used to couple the flange  50  to a second component to achieve a second pressure rating. 
         [0045]      FIG. 10  is a cross-sectional view of the dual pressure flange  50  taken along line  7 - 7  of  FIG. 7  in accordance with an alternate embodiment of the present invention. In the embodiment depicts in  FIG. 10 , the dual pressure flange  50  may be designed and manufactured without a cavity for the seal sub  74 . Instead, the dual pressure flange  50  may include an integral seal sub nose  92 . The integral seal sub nose  92  may include an external groove  94  configured to receive a seal, such as an o-ring. The integral seal sub nose  92  is configured to penetrate the seal sub sealing counterbore and may eliminate a potential leak path between the inner diameter of the flange  50  and the outer diameter of the seal sub  74 . Further, the integral seal sub nose  92  may eliminate the “floating” capability of the seal, e.g., o-ring, disposed in the external groove  94 . 
         [0046]      FIG. 11  depicts a front view of the dual pressure flange in accordance with an alternate embodiment of the present invention. The embodiment depicts in  FIG. 11  includes additional bolt patterns, e.g., a first cross pattern  96  and a second cross pattern  98 , that may be used in sealing the flange  50 . The first cross pattern may include four bolts  100 , wherein each pair of the four bolts  100  includes two bolts radially across from each other, as shown in  FIG. 11 . Similarly, the second cross pattern  98  may include four bolts  102 , wherein each pair of the four bolts  102  also includes two bolts radially across from each other. When installing the flange  50  in either a four-bolt or eight-bolt, any combination of first rectangular pattern  84 , second rectangular pattern  88 , first cross pattern  96 , and second cross pattern  98  may be used to achieve a desired pressure rating and withstand the exerted pressure loads. 
         [0047]      FIG. 12  depicts an accumulator manifold  104  including a dual pressure flange  106  as disclosed in  FIG. 4A  above. Alternative dual pressure flange embodiments as disclosed in  FIGS. 5-11  can also be incorporated into the manifold. 
         [0048]    The accumulator manifold  104  is coupled to a common hydraulic source (not shown) and provides fluid communication to the accumulators  38  arranged on the accumulator manifold  104 . The accumulator manifold  104  comprises a frame  108  composed of pipe segments  110 . The pipe segments  110  are coupled to spools  112  disposed along the frame  108 . The spools  112  comprise upper, lower and lateral surfaces. The connection between each pipe segment  110  and each spool  112  is established via a dual pressure flange  106 . 
         [0049]    As illustrated, each spool  112  is coupled to two pipe segments  110  on its lateral surfaces and one pipe segment  110  on its upper surface. The pipe segments  110  extending from the spool  112  lateral surfaces are in fluid communication with adjacent spools. The pipe segments  110  extending from the spool  112  upper surface are in fluid communication with accumulators  38  positioned above the respective spools  112 . The accumulators  38  are coupled to the spools  112  by way of the dual pressure flanges  106 . In alternative embodiments, a spool  112  may comprise one or more pipe segment  110  connections on any of its upper, lower and/or side surfaces. 
         [0050]    Accumulator manifold  104  does not require welding and does not use autoclave connections and is desirable for simplicity, ease of installation, and economic efficiencies. 
         [0051]    While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.