PATENT ABSTRACT
A shuttle valve useful in connection with operation of underwater blowout preventers employs soft seals sealing an annulus between an inlet bore and the outer periphery of the shuttle to provide hydraulic function control from a high pressure low flow supply source such as a low volume positive displacement pump on a remotely operated vehicle without losing opposing inlet sealing and hydraulic fluid dump the opposing inlet during a return stroke of the pump.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/203,402, filed on Dec. 20, 2008, the disclosures of which are incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    1. Field of Disclosure 
         [0004]    This invention relates to valves, and more particularly to shuttle valves. 
         [0005]    2. Background 
         [0006]    Subsea wellheads are often relied upon during deep water exploration for oil and natural gas. Subsea drilling operations may experience a blow out, which is an uncontrolled flow of formation fluids into the drilling well. Blow outs are dangerous and costly. Blow outs can cause loss of life, pollution, damage to drilling equipment, and loss of well production. To prevent blowouts, blowout prevention (BOP) equipment is required. The subsea wellheads include a stack of BOPs. Annular BOPs are actuated on a routine basis to snub or otherwise control pressure during normal drilling operations. Other blow-out preventers, such as blind rams, pipe rams, kelly rams and shear rams will also be included in the stack on the subsea wellhead. When these types of rams are actuated, operations in the well cease in order to control pressure or some other anomaly. Blind rams, pipe rams, kelly rams and shear rams are periodically tested to make sure that they are operational. 
         [0007]    The well and BOP connect to the surface drilling vessel through a marine riser pipe, which connects to the BOP through a Lower Marine Riser Package (“LMRP”) that contains flow control devices to supply hydraulic fluids for the operation of the BOP. The LMRP and the BOP are commonly referred to collectively as simply the BOP. Many BOP functions are hydraulically controlled, with piping attached to the riser supplying hydraulic fluids and other well control fluids. Shuttle valves attached to each BOP, as in U.S. Pat. Nos. 4,253,481 and 6,257,268 have been used for many years to control the flow of hydraulic fluid. 
         [0008]    It is important that underwater shuttle valves used in connection with operation of subsea blowout preventers (BOPS) act properly because of the importance of their function and their inaccessibility. In emergency situations or during testing, it may be necessary to close the subsea BOPs using an alternate low flow circuit, a test pump, or in extreme situations a remotely operated vehicle (ROV). The ROV is an unmanned submarine with an on-board television camera so the ROV can be maneuvered by topside personnel on board a ship or platform. The ROV is equipped with a plug that stabs into a receptacle on the ROV docking station on the BOP stack. Tubing runs from the receptacle on the ROV docketing station to a biased shuttle valve. 
         [0009]    The ROV is maneuvered to stab into the receptacle on the ROV docking station. The ROV uses a hydraulic pump to inject hydraulic fluid at relatively high pressures (greater than 1,000 psi) and relatively low flow rates into the hose to the biased shuttle valve to close the BOPs. 
         [0010]    The Gilmore Valve Company pressure biased ROV shuttle valve with metal to metal seal as described in U.S. Pat. No. 6,256,268 is a current solution to allow a low flow (such as an ROV) to control a BOP Ram. Unfortunately this valve is very sensitive to reverse flow (one way flow), and in combination with the requirement of the metal to metal seal to stay rigidly seated not to leak, the valve will fail to provide BOP ram control from a low flow supply source like an ROV. 
         [0011]    The high pressures and low flow rates required by a ROV mandate use of a low volume positive displacement pump. These are similar to a bicycle pump. Stroking forward pushes the fluid thru an outlet check valve. When the stroke ends the flow stops and the outlet check valve closes. At this point the pump plunger is reversed back to the start position for another stroke and refilling of fluid into the stroking chamber from the pump inlet check valve. During the return stroke of the bike pump if the outlet check valve leaks ever so slightly, the line pressure on the outlet of the pump will decay because a small amount of fluid flowed back into the bike pump stroking chamber. 
         [0012]    This is the scenario where the Gilmore valve will get into a situation of the shuttle lifting off of the inlet seat and dumping fluid. This creates a vicious cycle with the function port never obtaining pressure to actuate a function. This is a disadvantage of a “one way” communication at the ROV inlet port. This is also a disadvantage in the “blocked” situation, when the ROV disconnects by closing a valve to block in the pressure on the ROV inlet port of the valve, as a small leak will make the valve “dump” all of the function pressure/fluid back through the opposing inlet port. Another problem is that the flow volume from the ROV pump is not high enough to over come the leak rate of the metal-to-metal seat attempting to close the opposing inlet port. This type of seat in practice will leak until there is a substantial hydraulic force (via pressure acting on the area of the seat) pushing it firmly closed enough to make metal-to-metal contact completely around the perimeter of the seat. Until this force is exceeded, the valve will leak. 
         [0013]    The valve exemplary embodiments herein described do not rely on a check valve (one-way communication) or metal to metal seat to maintain positive sealing and remain in control of the function pressure even when there is a decay in pressure or when closed when pressure is supplied to the function port and the ROV valve is blocked off. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic side sectional view of a first exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0015]      FIG. 2  is a schematic side sectional view of the exemplary embodiment of  FIG. 1 , showing a second shuttle position, providing flow 
           [0016]      FIG. 3  is a schematic side sectional view of a second exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0017]      FIG. 4  is a schematic side sectional view of the exemplary embodiment of  FIG. 3 , showing a second shuttle position, providing flow. 
           [0018]      FIG. 5  is a schematic side sectional view of a third exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0019]      FIG. 6  is a schematic side sectional view of the exemplary embodiment of  FIG. 5 , showing a second shuttle position, providing flow. 
           [0020]      FIG. 7  is a schematic side sectional view of the exemplary embodiment of  FIG. 5 , showing a third shuttle position, providing flow. 
           [0021]      FIG. 8  is a schematic side sectional view of a fourth exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0022]      FIG. 9  is a schematic side sectional view of the exemplary embodiment of  FIG. 8 , showing a second shuttle position, providing flow. 
           [0023]      FIG. 10  is a schematic side sectional view of the exemplary embodiment of  FIG. 8 , showing a third shuttle position, providing flow. 
           [0024]      FIG. 11  is a schematic side sectional view of a fifth exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0025]      FIG. 12  is a schematic side sectional view of the exemplary embodiment of  FIG. 11 , showing a second shuttle position, providing flow. 
           [0026]      FIG. 13  is a schematic side sectional view of the exemplary embodiment of  FIG. 11 , showing a third shuttle position, providing flow. 
           [0027]      FIG. 14  is a schematic side sectional view of a sixth exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0028]      FIG. 15  is a schematic side sectional view of an exemplary embodiment of  FIG. 14 , showing a second shuttle position, providing flow. 
           [0029]      FIG. 16  is a schematic side sectional view of a sixth exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0030]      FIG. 17  is a schematic side sectional view of the exemplary embodiment of  FIG. 16 , showing a second shuttle position, providing flow. 
           [0031]      FIG. 18  is a schematic side sectional view of an ROV valve exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0032]      FIG. 19  is a schematic side sectional view of the exemplary embodiment of  FIG. 18 , showing a second shuttle position, providing flow. 
           [0033]      FIG. 20  is a schematic side sectional view of the exemplary embodiment of  FIG. 18 , showing a third shuttle position, providing flow. 
           [0034]      FIG. 21  is a schematic top view of a shuttle valve of a type useful in an exemplary embodiment of the invention. 
           [0035]      FIG. 22  is a schematic cross sectional view in the direction along the lines B-B of  FIG. 21 . 
           [0036]      FIG. 23  is a schematic side sectional view of another ROV valve exemplary embodiment of the invention, showing a first shuttle position, blocking fluid flow. 
           [0037]      FIG. 24  is a schematic side sectional view of the exemplary embodiment of  FIG. 23 , showing a second shuttle position, providing flow 
           [0038]      FIG. 25  is a schematic side sectional view of the exemplary embodiment of  FIG. 23 , showing a third shuttle position, providing flow. 
           [0039]      FIG. 26  is a schematic side sectional view showing use of the ROV valve exemplary embodiment of  FIG. 23  coupled to a shuttle valve of the type shown in  FIG. 21 . 
           [0040]      FIG. 27  is a side sectional view showing the ROV exemplary embodiment of  FIG. 18  coupled in a gang of shuttle valves of the type shown in  FIG. 21 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0041]    In the following detailed description of exemplary embodiments, reference is made to the accompanying drawings, which form a part hereof and in which are shown by way of illustration examples of exemplary embodiments in which the invention may be practiced. In the drawings and descriptions, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Specific details described herein, including what is stated in the Abstract, are in every case a non-limiting description and exemplification of embodiments representing concrete ways in which the concepts of the invention may be practiced. This serves to teach one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner consistent with those concepts. Reference throughout this specification to “an exemplary embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one exemplary embodiment of the present invention. Thus, the appearances of the phrase “in an exemplary embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It will be seen that various changes and alternatives to the specific described embodiments and the details of those embodiments may be made within the scope of the invention. It will be appreciated that one or more of the elements depicted in the drawings can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Because many varying and different embodiments may be made within the scope of the inventive concepts herein described and in the exemplary embodiments herein detailed, it is to be understood that the details herein are to be interpreted as illustrative and not as limiting the invention to that which is illustrated and described herein. 
         [0042]    The various directions such as “upper,” “lower,” “back,” “front,” “transverse,” “perpendicular”, “vertical”, “horizontal,” “length,” “width,” “laterally” and so forth used in the detailed description of exemplary embodiments are made only for easier explanation in conjunction with the drawings. The components may be oriented differently while performing the same function and accomplishing the same result as the exemplary embodiments herein detailed embody the concepts of the invention, and such terminologies are not to be understood as limiting the concepts which the embodiments exemplify. 
         [0043]    As used herein, the use of the word “a” or “an” when used in conjunction with the term “comprising” (or the synonymous “having”) in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” In addition, as used herein, the phrase “connected to” means joined to or placed into communication with, either directly or through intermediate components. 
         [0044]    Referring to  FIG. 1 , in an exemplary embodiment, a shuttle valve  10  includes a body generically indicated by reference number  12 . Body  12  has an axial bore  14 , a first fluid flow inlet port  16  to bore  14 , a second fluid inlet port  18  to bore  14 , and a fluid pressure function outlet  20  from bore  14 . Outlet  20  is between inlet ports  16  and  18  and transverse to bore  14 . Interiorly of inlet ports  16  and  18  in bore  14  are chambers  1  and  2  respectively. Inlet port chambers  1  and  2 , as portions of bore  14 , are normally coaxial to bore  14 . Source fluid enters chambers  1  and  2  through inlet ports  16  and  18 . The term “inlet” is used in the sense of a fluid source passageway leading to one of inlet ports  16  or  18  exteriorly of ports  16  or  18 . A passageway leading to one of inlet ports  16  or  18  from exteriorly of ports  16  or  18  may be coaxial to the port to which it leads or may originate from a source conduit transverse to the port  16  or  18 . The term “outlet” is herein used in the sense of an outlet for flow from either chamber  1  or chamber  2  when fluid flow through one of inlet ports  16  or  18  exceeds fluid pressure at outlet  20 , as is the purposed use of outlet  20 , namely, to supply pressure to a function requiring pressure for operation in a downstream apparatus. However, outlet  20  may flow fluid through it back through inlet port  16  or  18  if pressure in outlet  20  exceeds pressure in one of inlet port  16  or inlet port  18  whichever one created pressure in the outlet port  20 . 
         [0045]    Bore  14  widens proximate outlet  20  to form shoulders  22  and  24  flanking outlet  20 . A shuttle, generally indicated by reference numeral  26 , is coaxial with body bore  14  and has a first cylindrical end portion  28  and a second cylindrical end portion  30 . First end portion  28  extends in the direction of first inlet port  16  and second end portion  30  extends in the direction opposite first end portion  28 , in the exemplary embodiment, in the direction of second inlet port  18 . Each end portion  28 ,  30  is coaxially slideably movable along the bore  14  under the force of fluid pressure from fluid entering either inlet port  16  or  18 . Shuttle  26  has a collar  32  between first and second end portions  28 ,  30 . Collar  32  has outer cylindrical surface  34  of diameter receivable within widened body bore  36  and greater than end portions  28 ,  30  and body bore  14 . Shuttle  26  slideably moves from one shoulder to the other shoulder under the pressure of fluid in one of the inlet ports  16 ,  18  exceeding pressure in the other one of the inlet ports  16 ,  18 . When collar  32  engages shoulder  22  on the side of first inlet port  16  of body bore  14 , collar  32  does not engage shoulder  24  on the side of second inlet port  18  of bore  14 , and when collar  32  engages shoulder  24  on the side of the second inlet port  18  of body bore  14 , collar  32  does not engage shoulder  22  on the side of first inlet port  16  of bore  14 . 
         [0046]    In the exemplary embodiment depicted in  FIG. 1 , a first seal  38 , suitably a Teflon O-ring seal, is fixed in seal groove  40  on the outer periphery  42  of first end portion  28  of shuttle  26 , for sealing an annulus  44  between that outer periphery  42  and the inner periphery  46  of body bore  14  on the first inlet port side of bore  14  when collar  32  engages shoulder  22  on the side of first inlet port  16  of body bore  14 . A second seal  48 , suitably a Teflon O-ring seal or a Poly-seal, is fixed by seal groove  50  on outer periphery  52  of shuttle second end portion  30  and inner periphery  54  of bore  14  on the side of second inlet port  18 , for sealing an annulus  56  between outer periphery  52  of the shuttle second end portion  30  and inner periphery  54  when collar  32  engages shoulder  24  on the side of second inlet port  18  of bore  14 . First and second end portions  28 ,  30  each extend a distance from collar  32  relative to the placement of seals  38  and  48  sufficient that (i) when collar  32  engages shoulder  22  on the side of first inlet port  16  of bore  14 , annulus  56  is not sealed, (ii) when collar  32  engages shoulder  24  on the side of second inlet port  18  of bore  14 , annulus  44  not sealed, and (iii) when collar  32  does not engage and is distally spaced from both shoulder  22  and  24 , both annulus  44  and annulus  56  are sealed.  FIG. 1  depicts valve  10  in condition (iii) where collar  32  does not engage and is distally spaced from both shoulders  22  and  24 , and both annulus  44  and annulus  56  are sealed. This position of the shuttle in valve  10  herein is sometimes is called a mid-stroke position. 
         [0047]    In the exemplary embodiment of  FIG. 1 , end portions  28 ,  30  of shuttle  26  have a central bore  60 ,  65  respectively, and in each central bore have at least one passage connecting the central bore to periphery  42 ,  52  of shuttle  26 . In the exemplary embodiment, a plurality of fluid passages  61 ,  62 ,  63 ,  64  (and suitably two others not seen in this view) radiate from bore  60  and a plurality of passages  66 ,  67 ,  68  and  69  (and suitably two others not seen in this view) radiate from central bore  65 . Seal  38  is fixed on end portion  28  between collar  32  and the passages  61 ,  62 ,  63  and  64  radiating from central bore  60 . Seal  48  is fixed on end portion  30  between collar  32  and the passages  66 ,  67 ,  68  and  69  radiating from central bore  65 . 
         [0048]    Referring to  FIG. 2 , when collar  32  engages shoulder  22  on the side of first inlet port  16  of bore  14 , annulus  56  is not sealed and fluid flows through bore  65  thence through passages  66 ,  67 ,  68 , and  69  (and two others not seen) into widened bore  14  to and out outlet  20 . Or if pressure in fluid pressure function outlet  20  exceeds pressure in inlet port  18 , fluid flows from outlet  20  through passages  66 - 69  (and two others not seen) through bore  65  into inlet port  18  of bore  14 . 
         [0049]    Conversely to  FIG. 2 , when collar  32  engages shoulder  24  on the side of second inlet port  18  of bore  14 , annulus  44  is not sealed, and fluid flows through bore  60  thence through passages  61 ,  62 ,  63 , and  64  (and two others not seen) into widened bore  14  to and out outlet  20 . Or if pressure in fluid pressure function outlet  20  exceeds pressure in inlet port  16 , fluid flows from outlet  20  through passages  61 - 64  (and two others not seen) through bore  60  into inlet port  16  of bore  14 . 
         [0050]    As shown in  FIG. 1 , when collar  32  does not engage either shoulder  22  or  24  and both annulus  44  and annulus  56  are sealed, fluid cannot escape through either bore  60  or  65  into their respective passages to widened bore  14  to and out outlet  20 , and vice versa, fluid cannot escape from outlet  20  through the respective passages of bores  60  and  65  into either chamber  1  and inlet port  16  or chamber  2  and inlet port  18  of bore  14 . 
         [0051]    Referring now to  FIG. 3 , another exemplary embodiment is depicted, in  FIG. 3  also in mid-stroke position. As in the exemplary embodiment of  FIG. 1 , a shuttle valve  10  includes a body generically indicated by reference number  12 . Body  12  has an axial bore  14 , a first fluid flow inlet port  16  to bore  14 , a second fluid inlet port  18  to bore  14 , and a fluid pressure function outlet  20  from bore  14 . Outlet  20  is between inlet ports  16  and  18  and transverse to bore  14 . In  FIG. 1 , inlet ports  16  and  18  are segments of bore  14 . 
         [0052]    Bore  14  widens proximate outlet  20  to form shoulders  22  and  24  flanking outlet  20 . Cylindrical sectors  70 ,  71  (as depicted), or alternatively an entirely circumferential groove or a plurality of grooves or other forms of fluid passage reliefs  70 ,  71  is or are formed in shoulders  22  and  24  adjacent bore  14 . 
         [0053]    In the exemplary embodiment of  FIG. 3 , as in the exemplary embodiment depicted in  FIG. 1 , shuttle  26 , coaxial with body bore  14 , has a first cylindrical end portion  28  and a second cylindrical end portion  30 . First end portion  28  extends in the direction of first inlet port  16  and second end portion  30  extends in the direction opposite first end portion  28 , in the exemplary embodiment, in the direction of second inlet port  18 . Each end portion  28 , is coaxially slideably movable along the bore  14  under the force of fluid pressure from fluid entering either inlet port  16  or  18 . Shuttle  26  has a collar  32  between first and second end portions  28 ,  30 . Collar  32  has outer cylindrical surface  34  of diameter receivable within widened body bore  36  and greater than end portions  28 ,  30  and body bore  14 . Shuttle  26  slideably moves from one shoulder to the other shoulder under the pressure of fluid in one of the inlet ports  16 ,  18  exceeding pressure in the other one of the inlet ports  16 ,  18 . When collar  32  engages shoulder  22  on the side of first inlet port  16  of body bore  14 , collar  32  does not engage shoulder  24  on the side of second inlet port  18  of bore  14 , and when collar  32  engages shoulder  24  on the side of the second inlet port  18  of body bore  14 , collar  32  does not engage shoulder  22  on the side of first inlet port  16  of bore  14 . 
         [0054]    In the exemplary embodiment of  FIG. 3 , a first seal  72 , suitably a Teflon O-ring seal, is fixed in seal groove  73  on the inner periphery  46  of first inlet port  16 , for sealing annulus  44  between that inner periphery  46  and the outer periphery  42  of end portion  28  of shuttle  26  when collar  32  engages shoulder  22  on the side of first inlet port  16  of body bore  14 . A second seal  74 , suitably a Teflon O-ring seal, is fixed by seal groove  75  on the inner periphery  54  of second inlet port  18 , for sealing annulus  56  between that inner periphery  54  and the outer periphery  52  of end portion  30  of shuttle  26  when collar  32  engages shoulder  24  on the side of second inlet port  18  of body bore  14 . First and second end portions  28 ,  30  each extend a distance from collar  32  relative to the placement of seals  72  and  74  sufficient that (i) when collar  32  engages shoulder  22  on the side of first inlet port  16  of bore  14 , annulus  56  is not sealed and fluid flows through fluid passage  71  to outlet  20 , (ii) when collar  32  engages shoulder  24  on the side of second inlet port  18  of bore  14 , annulus  44  is not sealed, and fluid flows through fluid passage  70  to outlet  20 , and (iii) when collar  32  does not engage and is distally spaced from both shoulder  22  and  24 , both annulus  44  and annulus  56  are sealed, and fluid does not flow either from inlet port  16  through fluid passage  70  or from inlet port  18  through or passage  71  to outlet  20 , or vice versa, fluid cannot escape from outlet  20  through the respective passages of  70  or  71  into inlet port  16  or inlet port  18  of bore  14 . 
         [0055]      FIG. 4  depicts fluid flow when collar  32  engages shoulder  22  on the side of first inlet port  16  of bore  14 , so annulus  56  is not sealed, and fluid flows through fluid passageway  71  to outlet  20 . 
         [0056]    The exemplary embodiment of  FIG. 1  places seals on both ends portion of shuttle  26  with fluid passages formed more distally from the shuttle collar than the seals, such that when an end portion containing the passages moves past the seal toward the opposite inlet port, fluid flows both through the annulus portion that is past the seals in the direction of the opposite inlet port and through the passages, flow through the passages exceeding flow through the annulus owing to the larger cross sectional flow area through the passages. The exemplary embodiment of  FIG. 3  places seals on the bore and provides passages in the bore such that when an end portion moves past the seal toward the opposite inlet port, fluid flows both through the annulus portion that is past the seals in the direction of the opposite inlet port and through the passages in the wall of the bore, flow through the passages exceeding flow through the annulus owing to the larger cross sectional flow area through the passages. An alternative exemplary embodiment provides a combination of the flow solutions of exemplary embodiments of  FIG. 1  and  FIG. 3 . For example, not shown, a valve  10  could provide seal  38  and bore  60  and passages  61 - 64  (and two not seen) on end portion  28  of shuttle  26 , as in  FIG. 1 , and could provide seal  74  on end portion  30  and passage  71  in bore  14  as in  FIG. 3 . 
         [0057]    Referring to  FIG. 5 , a variation of the exemplary embodiment of  FIG. 1  is depicted, which body  12  is formed of plural pieces  11 ,  13  sealingly fastened together. Body piece  11  with axial bore  14  matingly accepts male body piece flange  13 . The male piece flange  13  including male portion  15  has a central bore  17  that is concentric and coaxial with bore  14  of body piece  11 , reducing body bore  14  to a smaller diameter. So reduced, central bore  17  is considered a body bore. Central bore  17  provides the body bore surface on which the first end portion  28  of shuttle  26  axially slideably moves. Male portion  15  forms a terminal shoulder  23  providing the same function as shoulder  22  of the exemplary embodiment of  FIG. 1 . Fasteners  19 - 1 ,  19 - 2 ,  19 - 3 , and  19 - 4  (fasteners  19 - 1  and  19 - 2  are not seen in the longitudinal section view of  FIG. 5 ) fasten male piece flange  13  to body piece  11 . O-ring seal  21 , suitably a buna O-ring seal, provides a seal between female body piece  11  and male body piece flange  13 . The other parts of the valve of  FIG. 2  are the same as and are corresponding numbered as described for  FIG. 1 . As in  FIG. 1 , shuttle  26  is shown in mid-stroke. The exemplary embodiment of  FIG. 5  provides the shuttle valve functions as does the exemplary embodiment of  FIG. 1 , and similarly seals both annulus  44  and annulus  56  and the passages through shuttle bores  60  and  65  when collar  32  does not engage either shoulder  24  or  23 . 
         [0058]      FIG. 6  is the same exemplary embodiment as depicted in  FIG. 5  but in  FIG. 6  shuttle  26  is shown in the position where collar  32  engages shoulder  23  on the first inlet port side  16  of bore  17  with seal  38  sealing annulus  44  while annulus  54  around shuttle end portion  30  and shuttle bore  65  and passages  66 - 69  (and two not seen) are not sealed, allowing fluid flow from inlet port  18  to outlet  20 . 
         [0059]      FIG. 7  is the same exemplary embodiment as depicted in  FIG. 5  but in  FIG. 7  shuttle  26  is shown in the position where collar  32  engages shoulder  24  on the second inlet port side  18  of bore  14  with seal  48  sealing annulus  56  while annulus  44  around shuttle end portion  28  and shuttle bore  60  and passages  61 - 64  (and two not seen) are not sealed, allowing fluid flow from inlet port  16  to outlet  20 . 
         [0060]      FIG. 8  depicts another exemplary embodiment using the same shuttle configuration as in the exemplary embodiment of  FIG. 1  except the shuttle is carried in a valve body  80  that forms outlet  20 , first inlet port  16  is in a first adapter  82  that threadingly engages valve body  80 , as at  81 ,  83 , in valve body bore  14  and second inlet port  18  is in a second adapter  84  that threadingly engages valve body  10 , as at  85 ,  87 , in valve body bore  14 . Inlet ports  16  and  18  of respective adapters  82 ,  84  are located on opposite sides of transverse outlet  20  of valve body  80  and form a spaced reduced bore  17  concentric and coaxial to body bore  14 . So reduced, central bore  17  is considered a body bore. O-ring seal  86 , suitably a buna O-ring seal, provides a seal between valve body piece  80  and adapter  82 . O-ring seal  88 , also suitably a buna O-ring seal, provides a seal between valve body piece  80  and adapter  84 . The other parts of the valve of  FIG. 8  are the same as and are corresponding numbered as described for  FIG. 1 .  FIG. 8  depicts valve in mid-stroke, where collar  32  does not engage either shoulder  22  or  24  and both annulus  44  and annulus  56  are sealed. 
         [0061]      FIG. 9  is the same exemplary embodiment as depicted in  FIG. 8  but in  FIG. 9  shuttle  26  is shown in the position where collar  32  engages shoulder  22  on the first inlet port side  16  of bore  17  with seal  38  sealing annulus  44  while annulus  56  around shuttle end portion  30  and shuttle bore  65  and passages  66 - 69  (and two not seen) are not sealed, allowing fluid flow from inlet port  18  to outlet  20 . 
         [0062]      FIG. 10  is the same exemplary embodiment as depicted in  FIG. 8  but in  FIG. 10  shuttle  26  is shown in the position where collar  32  engages shoulder  24  on the second inlet port side  18  of bore  17  with seal  48  sealing annulus  56  while annulus  44  around shuttle end portion  28  and shuttle bore  60  and passages  61 - 64  (and two not seen) are not sealed, allowing fluid flow from inlet port  16  to outlet  20 . 
         [0063]      FIG. 11  depicts another exemplary embodiment generally indicated by reference number  100 . In the exemplary embodiment of  FIG. 11 , the male portion  15  of body piece flange  13  in the exemplary embodiment of  FIGS. 5-7  is replaced by an adapter  115  that has an axial bore  117  coaxial to bore  14  and inlet port  16 . Referring to  FIG. 11  in detail, a shuttle valve  100  comprises a body piece  111  and a flange  113 . Body piece  111  has an axial bore  114 , second fluid flow inlet port  118  to bore  114 , and a fluid pressure function outlet  120  from bore  114 . Outlet  120  is between inlet ports  116 ,  118  and is transverse to bore  114 . Body bore  114  widens proximate outlet  120  on the second inlet port  118  side of outlet  120  to form a shoulder  124 , and on the side of outlet port distal to the inlet port  118  widens as at  105  to receive adapter  115 . Body bore  114  further widens past  105  in the direction opposite inlet port  118  to form recess  103 . Adapter  115  is received in widened bore  114 . Adapter  115  has opposite first and second ends  101 ,  122 . First end  101  has a flange  104  on its periphery engaging recess  103 . An axial bore  117  runs between ends  101 ,  122  coaxially to bore  114 . Flange  113  has a bore  102  coaxial with adapter axial bore  117 . The margin between bore  102  and adapter bore  117  defines inlet port  116  in adapter first end  101  coaxial with body bore  114 . 
         [0064]    Flange  113  is sealingly fastened to body  111  by fasteners  119 - 1 ,  119 - 2 ,  119 - 3  and  119 - 4  (fasteners  119 - 1  and  119 - 2  are not seen in the longitudinal section view of  FIG. 11 ). A seal  121 , suitably a buna O-ring seal, in recess  103 , engages and seals flange  104  of first end  101  of adapter  115  to body pieces  111  and  113 . Adapter second end  122  provides a shoulder on the first inlet port side  116  of outlet  120 . 
         [0065]    A shuttle  126  coaxial with body bore  114  and adapter bore  117  has first and second cylindrical end portions, respectively  128 ,  130 . Shuttle first end portion  128  extends in the direction of the first inlet port  116 , and is coaxially slideably movable along adapter bore  117 . Shuttle second end portion  130  extends in the direction opposite first end portion  128  and is coaxially slideably moveable along body bore  114 . A collar  132  between first end portion  128  and second end portion  130  of shuttle  126  has an outer cylindrical surface  134  of diameter receivable within the widened body bore as at  105  and has a greater diameter than the end portions  128 ,  130  of shuttle  126 , adapter bore  117  and body bore  114  in which end portions  128 ,  130  respectively slideably move. Shuttle  126  may move from one shoulder to the other shoulder, such that when collar  132  engages first inlet port side shoulder  122 , collar  132  does not engage second inlet port side shoulder  124 , and when collar  132  engages second inlet port side shoulder  124 , collar  132  does not engage first inlet port side shoulder  122 . In the exemplary embodiment depicted in  FIG. 11 , a first seal  138 , suitably a Teflon O-ring seal, is fixed located in seal groove  140  on the outer periphery  142  of first end portion  128  of shuttle  126  for sealing an annulus  144  between that outer periphery  142  and the inner periphery  146  of adapter bore  117  on first inlet port  116  side of bore  117  when collar  132  engages first inlet port side shoulder  122 . A second seal  148 , suitably a Teflon O-ring seal, is fixed by seal groove  150  on outer periphery  152  of shuttle second end portion  130  and inner periphery  154  of bore  117  on second inlet port  118  side, for sealing an annulus  156  between outer periphery  152  of the shuttle second end portion  130  and inner periphery  154  when collar  132  engages second inlet port side shoulder  124 . First and second end portions  128 ,  130  each extend a sufficient distance from collar  132  relative to the placement of seals  138  and  148  that (i) when collar  132  engages first inlet port side shoulder  122 , annulus  156  is not sealed, (ii) when collar  132  engages second inlet port side shoulder  124 , annulus  144  is not sealed, and (iii) when collar  132  does not engage and is distally spaced from both shoulder  122  and  124 , both annulus  144  and annulus  156  are sealed.  FIG. 11  depicts valve  100  in mid-stroke, where collar  132  does not engage either shoulder  122  or  124  and both annulus  144  and annulus  156  are sealed. 
         [0066]    In the exemplary embodiment of  FIG. 11 , end portions  128 ,  130  of shuttle  126  have a central bore  160 ,  165  respectively, and in each central bore have at least one passage connecting the central bore to periphery  142  or  152  of shuttle  126 . In the exemplary embodiment, a plurality of fluid passages  161 ,  162 ,  163 ,  164  (and suitably two others not seen in this view) radiate from bore  160  and a plurality of passages  166 ,  167 ,  168  and  169  (and suitably two others not seen in this view) radiate from central bore  165 . Seal  138  is fixed on end portion  128  between collar  132  and the passages  161 ,  162 ,  163  and  164  radiating from central bore  160 . Seal  148  is fixed on end portion  130  between collar  132  and the passages  166 ,  167 ,  168  and  169  radiating from central bore  165 . 
         [0067]    Referring to  FIG. 12 , when collar  132  engages shoulder  122  on the side of first inlet port  116  of bore  117 , annulus  156  is not sealed and fluid flows through bore  165  thence through passages  166 ,  167 ,  168 , and  169  (and two others not seen) into widened bore  114  to and out outlet  120 . Or if pressure in fluid pressure function outlet  120  exceeds pressure in inlet port  118 , fluid flows from outlet  120  through passages  166 - 169  (and two others not seen) through bore  165  into inlet port  118  of bore  114 . 
         [0068]    In  FIG. 13 , conversely to  FIG. 12 , when collar  132  engages shoulder  124  on the side of second inlet port  118  of bore  114 , as depicted in  FIG. 13 , annulus  144  is not sealed, and fluid flows through bore  160  thence through passages  161 ,  162 ,  163 , and  164  (and two others not seen) into widened bore  114  to and out outlet  120 . Or if pressure in fluid pressure function outlet  120  exceeds pressure in inlet port  116 , fluid flows from outlet  120  through passages  161 - 164  (and two others not seen) through bore  160  into inlet port  116  of bore  114 . 
         [0069]      FIGS. 14 and 15  depict another exemplary embodiment.  FIG. 14  shows this exemplary embodiment in mid-stroke position of the shuttle and  FIG. 15  shows the shuttle disposed against a shoulder. This exemplary embodiment uses two adapters  215 - 1  and  215 - 2  to support the shuttle  26  described for the exemplary embodiments of  FIGS. 1 ,  5 ,  8  and  11 , rather than one adapter as in the exemplary embodiment of  FIG. 11 . The two adapters  215 - 1  and  215 - 2  are identical so the description of one, referred to as  215 , will be understood as applying to both. Referring to  FIG. 14  in detail, a shuttle valve  200  comprises a body piece  211  with an axial bore  214  to which two inlet flanges  213 - 1  and  213 - 2  and one outlet flange  213 - 3  are sealingly fastened by respectively by fasteners  219 - 1 ,  219 - 2 ,  219 - 3  and  219 - 4  (fasteners  219 - 1  and  219 - 2  are not seen in the longitudinal section view of  FIG. 14 ),  219 - 5 ,  219 - 6 ,  219 - 7 ,  219 - 8  (fasteners  219 - 5  and  219 - 6  are not seen in the longitudinal section view of FIG.  14 ) and  219 - 9 ,  219 - 10 ,  219 - 11 , and  219 - 12  (fasteners  219 - 9  and  219 - 10  are not seen in the longitudinal section view of  FIG. 14 ). Flanges  213 - 1  and  213 - 2  have inlet bores, respectively  202 - 1  and  202 - 2  coaxial to body bore  214 . Bore  214  receives adapter  215 . Adapter  215  has opposite first and second ends  201 ,  202 . An axial bore  217  runs between ends  201 ,  202  coaxially to bore  214  and inlet bores  202 - 1  and  202 - 2 , respectively, of flanges  213 - 1  and  213 - 2 . The margin between adapter bore  217  at end  201  of adapter  215 - 1  and flange bore  202 - 1  defines first inlet port  216 . The margin between adapter bore  217  at end  201  of adapter  215 - 2  and bore  202 - 2  defines second inlet port  218 . First inlet port  216  is coaxial with bore  214 , as is second inlet port  218 . Body  211  has a fluid pressure function outlet bore  220  between inlet ports  216 ,  218  transverse to bore  214 . Flange  213 - 3  has a bore  206  coaxially aligned with transverse bore  220  (alternatively, it could be aligned at an offset or could be a 90 degree flange). Adapter bore  217  widens at the end  202  distal from inlets  202 - 1  and  202 - 2  to form a shoulder. In adapter  215 - 1 , the shoulder is identified by reference numeral  222 . In adapter  215 - 2 , the shoulder is identified by reference numeral  224 . Bore  214  widens proximate inlets  202  and  206  to form recess  203 . Adapter  215  first end  201  has a flange  204  on its periphery engaging recess  203 . A seal  221 , suitably a buna O-ring seal, in recess  203 , engages and seals flange  204  of first end  201  of adapter  215  to body piece  211  and flanges  213 - 1  and  213 - 2 . 
         [0070]    A shuttle  226  coaxial with body bore  214  and adapter bore  217  has first and second cylindrical end portions, respectively  228 ,  230 . Shuttle  226  first end portion  228  extends in the direction of the first inlet port  216 , and is coaxially slideably movable along adapter bore  217 . Shuttle second end portion  230  extends in the direction opposite first end portion  228  and is also coaxially slideably moveable along adapter bore  217 . A collar  232  between first end portion  228  and second end portion  230  of shuttle  226  has an outer cylindrical surface  234  of diameter receivable within the widened adapter bore as at  202  and has a greater diameter than the end portions  228 ,  230  of shuttle  226  and adapter bore  217  in which end portions  228 ,  230  respectively slideably move. Shuttle  226  may move from one shoulder to the other shoulder, such that when collar  232  engages first inlet port side shoulder  222 , collar  232  does not engage second inlet port side shoulder  224 , and when collar  232  engages second inlet port side shoulder  224 , collar  232  does not engage first inlet port side shoulder  222 . In the exemplary embodiment depicted in  FIG. 14  a first seal  238 , suitably a Teflon O-ring seal, is fixed located in seal groove  240  on the outer periphery  242  of first end portion  228  of shuttle  26  for sealing an annulus  244  between that outer periphery  242  and the inner periphery  246  of adapter bore  217  on first inlet port  216  side of bore  217  when collar  132  engages first inlet port side shoulder  222 . A second seal  248 , suitably a Teflon O-ring seal, is fixed by seal groove  250  on outer periphery  252  of shuttle second end portion  230  and inner periphery  254  of adapter bore  117  on second inlet port  218  side, for sealing an annulus  256  between outer periphery  252  of the shuttle second end portion  230  and inner periphery  254  when collar  232  engages second inlet port side shoulder  224 . First and second end portions  228 ,  230  each extend a sufficient distance from collar  232  relative to the placement of seals  238  and  248  that (i) when collar  232  engages first inlet port side shoulder  222 , annulus  256  is not sealed, (ii) when collar  232  engages second inlet port side shoulder  224 , annulus  244  is not sealed, and (iii) when collar  232  does not engage and is distally spaced from both shoulder  222  and  224 , both annulus  244  and annulus  256  are sealed.  FIG. 14  depicts valve  200  in mid-stroke, where collar  232  does not engage either shoulder  222  or  224  and both annulus  244  and annulus  256  are sealed. 
         [0071]    In the exemplary embodiment of  FIG. 14 , end portions  228 ,  230  of shuttle  226  have a central bore  260 ,  265  respectively, and in each central bore have at least one passage connecting the central bore to periphery  252  or  242  of shuttle  226 . In the exemplary embodiment, a plurality of fluid passages  261 ,  262 ,  263 ,  264  (and suitably two others not seen in this view) radiate from bore  260  and a plurality of passages  266 ,  267 ,  268  and  269  (and suitably two others not seen in this view) radiate from central bore  265 . Seal  238  is fixed on end portion  228  between collar  232  and the passages  261 ,  262 ,  263  and  264  radiating from central bore  260 . Seal  248  is fixed on end portion  230  between collar  232  and the passages  266 ,  267 ,  268  and  269  radiating from central bore  265 . 
         [0072]    Referring to  FIG. 15 , when collar  232  engages shoulder  224  on the side of second inlet port  218  of adapter bore  217 , annulus  244  is not sealed, and fluid flows through bore  260  thence through passages  261 ,  262 ,  263 , and  264  (and two others not seen) into widened bore  214  to and out outlet  220 . Or if pressure in fluid pressure function outlet  220  exceeds pressure in inlet port  216 , fluid flows from outlet  220  through passages  261 - 264  (and two others not seen) through bore  261  into inlet port  216  of bore  214 . 
         [0073]    Although not depicted, it will be appreciated from the preceding descriptions of other exemplary embodiments, that when collar  232  engages shoulder  222  on the side of first inlet port  216  of adapter bore  217 , annulus  256  is not sealed and fluid flows through bore  265  thence through passages  266 ,  267 ,  268 , and  269  (and two others not seen) into widened bore  214  to and out outlet  220 . Or if pressure in fluid pressure function outlet  220  exceeds pressure in inlet port  218 , fluid flows from outlet  220  through passages  266 - 269  (and two others not seen) through bore  265  into inlet port  218  of adapter bore  217 . 
         [0074]      FIGS. 16 and 17  depict another exemplary embodiment, valve  300 , using two adapters,  FIG. 16  showing the shuttle in mid-stroke and  FIG. 17  showing the shuttle at end-stroke. Like numbers as used in the dual adapter exemplary embodiment of  FIGS. 14 and 15  will be used for constancy of description, the like numbered parts acting as they do in the exemplary embodiments of  FIGS. 14 and 15 . Differing from the exemplary embodiment in  FIGS. 14 and 15  are the shuttle and the adapters in this exemplary embodiment, carrying a 300 numbering series, which is carried forward into descriptions in following exemplary embodiments.  FIGS. 16 and 17  do not depict structure that is present in adapters  315  and reference is made to  FIGS. 18-22  for a description of the adapter flow passages hidden in  FIGS. 16 and 17 . Shuttle  326  drilled, tapped and internally threaded as at  307  on end portions  328  and  330  is coaxially slidably moveable on adapter bore  317  of adapters  315 - 1  and  315 - 2  as in the exemplary embodiment of  FIGS. 14 and 14 , but in this exemplary embodiment, seal  338  is fixed in seal recess  340  on the inner periphery of the adapter bore  317 . The two adapters  315 - 1  and  315 - 2  are identical so the description of one, referred to as  315 , will be understood as applying to both. Referring to  FIG. 16  in detail, a shuttle valve  300  comprises a body piece  211  with an axial bore  214  to which to two inlet flanges  213 - 1  and  213 - 2  and one outlet flange  213 - 3  are sealingly fastened respectively by fasteners  219 - 1 ,  219 - 2 ,  219 - 3  and  219 - 4  (fasteners  219 - 1  and  219 - 2  are not seen in the longitudinal section view of  FIG. 14 ),  219 - 5 ,  219 - 6 ,  219 - 7 ,  219 - 8  (fasteners  219 - 5  and  219 - 6  are not seen in the longitudinal section view of FIG.  14 ) and  219 - 9 ,  219 - 10 ,  219 - 11 , and  219 - 12  (fasteners  219 - 9  and  219 - 10  are not seen in the longitudinal section view of  FIG. 14 ). Flanges  213 - 1  and  213 - 2  have inlet bores, respectively  202 - 1  and  202 - 2  coaxial to body bore  214 . Body bore  214  receives adapter  315 . Adapter  315  has opposite first and second ends  301 ,  302 . An axial bore  317  runs between ends  301 ,  302  coaxially to bore  214  and inlet bores  202 - 1  and  202 - 2 , respectively, of flanges  213 - 1  and  213 - 2 . The margin between adapter bore  317  at end  301  of adapter  215 - 1  and flange bore  202 - 1  defines first inlet port  316 . The margin between adapter bore  317  at end  301  of adapter  315 - 2  and bore  202 - 2  defines second inlet port  318 . First inlet port  316  is coaxial with bore  214 , as is second inlet port  318 . Body  211  has a fluid pressure function outlet bore  220  between inlet ports  316 ,  318  transverse to bore  214 . Flange  213 - 3  has a bore  206  coaxially aligned with transverse bore  220 . Adapter bore  317  widens at the end  302  distal from inlets  202 - 1  and  202 - 2  to form a shoulder. In adapter  315 - 1 , the shoulder is identified by reference numeral  322 . In adapter  315 - 2 , the shoulder is identified by reference numeral  324 . Bore  214  widens proximate inlets  202 - 1  and  202 - 2  to form recess  203 . Adapter first end  301  has a flange  304  on its periphery engaging recess  203 . A seal  221 , suitably a buna O-ring seal, in recess  203 , engages and seals flange  304  of first end  301  of adapter  315  to body piece  211  and flanges  213 - 1  and  213 - 2 . 
         [0075]    A shuttle  326  coaxial with body bore  214  and adapter bore  317  has first and second cylindrical end portions, respectively  328 ,  330 . Shuttle  326  first end portion  328  extends in the direction of the first inlet port  316 , and is coaxially slideably movable along adapter bore  317 . Shuttle second end portion  330  extends in the direction opposite first end portion  328  and is also coaxially slideably moveable along adapter bore  317 . A collar  332  between first end portion  328  and second end portion  330  of shuttle  326  has an outer cylindrical surface  334  of diameter receivable within the widened adapter bore as at  302  and has a greater diameter than the end portions  328 ,  330  of shuttle  326  and adapter bore  317  in which end portions  328 ,  330  respectively slideably move. Shuttle  326  may move from one shoulder to the other shoulder, such that when collar  332  engages first inlet port side shoulder  322 , collar  332  does not engage second inlet port side shoulder  324 , and when collar  332  engages second inlet port side shoulder  324 , collar  332  does not engage first inlet port side shoulder  322 . In the exemplary embodiment depicted in  FIGS. 16 and 17 , a first seal  338 , suitably a Teflon O-ring seal, is fixed located in seal groove  340  on the inner periphery  346  of adapter bore  317  retained by retainer ring  309  for sealing an annulus  344  between outer periphery  342  of end portion  328  of shuttle  326  and the inner periphery  346  of adapter bore  317  on first inlet port  316  side of bore  317  when collar  332  engages first inlet port side shoulder  322 . A second seal  348 , suitably a Teflon O-ring seal, is fixed by seal groove  350  on inner periphery  352  of adapter bore  317  retained by retainer ring  308  for sealing an annulus  356  between outer periphery  354  of end portion  330  of shuttle  326  and the inner periphery  354  of adapter bore  317  on second inlet port  318  side of bore  317  when collar  332  engages second inlet port side shoulder  324 . First and second end portions  328 ,  330  each extend a sufficient distance from collar  332  relative to the placement of seals  338  and  348  that (i) when collar  332  engages first inlet port side shoulder  322 , annulus  356  is not sealed, (ii) when collar  332  engages second inlet port side shoulder  224 , annulus  344  is not sealed, and (iii) when collar  332  does not engage and is distally spaced from both shoulder  322  and  324 , both annulus  344  and annulus  356  are sealed.  FIG. 16  depicts valve  300  in mid-stroke, where collar  332  does not engage either shoulder  322  or  324  and both annulus  344  and annulus  356  are sealed. 
         [0076]      FIGS. 18-20  schematically depict an exemplary embodiment of an ROV valve  400 . The exemplary embodiment of  FIGS. 18-20  employs the two adapter shuttle valve exemplary embodiment of  FIGS. 16-17 , and that description is incorporated hereat by reference for brevity. In the exemplary embodiment of  FIGS. 18-20 , end portions  330  and  328  of shuttle  320  are sealed by a seal on the inner periphery of the body bore and the body has at least one passage in fluid communication with the body bore between said seal and the shoulder proximate the seal as described in connection with  FIGS. 16-17 . 
         [0077]    Shuttle valve  400  further comprises an elongate tubular housing  410  having first and second end portions  412  and  414 , a central bore  416 , a spring seat  418  formed in central bore  416  distal from first end portion  412  of housing  410 . Second end portion  414  of the housing  410  is sealingly fastened respectively by fasteners  219 - 1 ,  219 - 2 ,  219 - 3  and  219 - 4  (fasteners  219 - 1  and  219 - 2  are not seen in the longitudinal section view of  FIG. 18 ) to valve body  211  adjacent first inlet port  316  of valve body  211  with the housing central bore  416  coaxial with body bore  214  and adapter bore  317  and in fluid communication with adapter bore  317 . Housing  410  includes an inlet  420  in first end portion  412  of housing  410  in fluid communication with central bore  416 . An elongate stem  422  passes through housing  410  and connects on one end  424  to the first end portion  328  of shuttle  326  at threaded tap  307 . The other end of stem  422  comprises a spring retainer  428  of diameter allowing stem  422  to coaxially moveably slide in central bore  416  of housing  410  and to allow fluid to flow from housing inlet  420  into central bore  416 . An aperture  432 ,  433  may be provided in stem  422  to aid passage of fluid from inlet  420  into central bore  416 , A spring  430  surrounds a portion of stem  422  and is positioned in elongate tubular housing  410  on spring seat  418  and in contact with spring retainer  428 . Spring  430  urges the stem toward housing inlet  420  in response to reduction of fluid pressure in housing inlet  420  or in response to fluid pressure in a portion of the adapter bore  317  and relatedly in body bore  214  in fluid communication with function outlet  220  higher than fluid pressure in housing inlet  420 . 
         [0078]    In operation, fluid flow from an ROV will start moving shuttle  326  from a position as depicted in  FIG. 19  when shuttle collar is against shoulder  322  as filling pressure from fluid passing from inlet  420  through center bore presses against the inlet end  328  of shuttle  326  and passes through adapter  315 - 1  inlet port  316  and thence through internal grooves within adapter  315 - 1  (see the description in reference to  FIGS. 20-21  for further information on this internal structure of adapter  315 - 1 ). At mid-stroke, as depicted in  FIG. 18 , both inlet ports  316  and  318  are closed. Both ends of the shuttle are sealed with soft seals. Then, as pressure within adapter  315 - 1  exceeds pressure from inlet  315 - 2 , shuttle  326 , as depicted in  FIG. 20 , will be pressed against shoulder  324  on adapter  315 - 2  closing off inlet port  318 . ROV fluid will fill function outlet and increase pressure until full operating pressure is obtained at the function. At this point the ROV can be blocked out and pressure will be maintained on the function. If there is any slight leakage from the function or the ROV block valve, shuttle  326  will remain seated and inlet port  318  will remain closed. When venting the function, the ROV has complete control of the function pressure as long as the pressure is maintained above the set pressure of the ROV spring (150-300 psi, for example). 
         [0079]    Referring to  FIGS. 21 and 22 , depicted is a shuttle valve of the type disclosed in U.S. Pat. No. 4,253,481, the content of which is incorporated by reference as if set forth herein verbatim. A shuttle valve  500  includes a tubular body  502  having two coaxial inlet ports  504 ,  506  at its ends and a transverse outlet port  508  at its side. Internally threaded connector rings  509 ,  510 ,  511  are secured over each port by cap screws  512 ,  513 ,  514 ,  515 ,  516  and  517 . Two adapter cages  518 ,  519  having an external radial flange  520 ,  521  are telescopically disposed within each inlet port  504 ,  506 , with its flange clamped between the adjacent connector ring  510 ,  511  and an outwardly facing shoulder  522 ,  523  (not seen) in body  500 . O-rings  524 ,  525 ,  526  seal the three connector rings  509 ,  510 ,  511  and the two cages  518 ,  519  to the body. Each cage is axially grooved, providing flow passages  530 ,  531 ,  532 ,  533 . The ribs left between the grooves provide guide bearings  534 ,  535 ,  536 ,  537 . The inner ends of the ribs form stop shoulders  548 . A shuttle in the form of a cylindrical plug  540  tapered at each end  542 ,  544  is axially slideably disposed inside body  500  within cages  518 ,  519  supported and guided by the rib bearings alternately to engage the stops of one or the other of the cages  518 ,  519  according to whether the pressure on one end of the shuttle or the other is higher. A collar  546  around the middle of the shuttle provides a piston. 
         [0080]    Referring now to  FIGS. 23-25 , an exemplary embodiment of an ROV valve  600  is depicted assembled with the components of the shuttle valve  200  described in connection with the exemplary embodiment of  FIG. 14  and the elongate tubular housing  510  structure described for valve  500 . The descriptions of  FIG. 14 ,  FIG. 18  and  FIGS. 21 ,  22  are incorporated using the reference numerals for identifications of the components. In valve  600  at least one of end portions  328  and  330  of shuttle  326  has a central bore and at least one fluid passage connecting said bore to the periphery of the shuttle, and the seals are fixed on the end portion  328  and  330  between collar  332  and the passage. 
         [0081]    Referring now to  FIGS. 26 and 27 , an exemplary embodiment of an ROV valve  400  of  FIG. 18  is coupled to shuttle valves of the type shown in  FIG. 21  to provide three or more supply ports for redundancy. 
         [0082]    The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all modifications, enhancements, and other embodiments that fall within the true scope of the present invention, which to the maximum extent allowed by law, is to be determined by the broadest permissible interpretation of the following claims and their equivalents, unrestricted or limited by the foregoing detailed descriptions of exemplary embodiments of the invention.