Abstract:
The hydraulic shuttle valve has two coaxial supply ports and a transverse function port to direct fluid coming from alternative control sources to a blow out preventor (BOP). The valve includes a moveable shuttle with opposing tapered metal sealing surfaces to alternatively engage opposing coaxial metal valve seats. The shuttle moves back and forth into alternative sealing engagement depending on which supply port has the highest fluid pressure. As the shuttle moves from engagement with one metal seat to engagement with another, there is low or no interflow from one supply port to the other, thus maximizing the amount of fluid directed to the function port. An obtuse metal point is formed on each metal valve seat which comes into contact with a respective outward tapered sealing surface on the shuttle. Repeated movement of the shuttle to and fro displaces a portion of the metal point into a recessed chamfer. This displacement of metal insures a good metal to metal seal between the shuttle and the metal valve seat. This displacement of metal is also known as “progressive coining.” 
     In alternative embodiments, the low interflow hydraulic shuttle valve with metal to metal seals can include three or more supply ports. In the alternative embodiments, a plurality of body sections each containing at least one supply port and a shuttle valve can be stacked one upon the other to achieve a multi-supply port configuration as required by the application. In the alternative embodiments, the metal to metal seals of the shuttle and the valve seats progressively coin to insure a good seal.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     This invention relates to valves, and more particularly to shuttle valves. The invention is an improvement upon shuttle valves of the type made and sold by applicant&#39;s assignee, Gilmore Valve Company, which is the owner of the other U.S. patents for improved shuttle valves including U.S. Pat. Nos. 3,533,431 and 4,253,481. 
     B. Description of the Prior Art 
     Shuttle valves have been used for many years to control the flow of gases as in U.S. Pat. Nos. 1,529,384 and 2,408,799. Other shuttle valves have been used to control the flow of liquids as in U.S. Pat. Nos. 1,686,310 and 1,795,386. 
     Shuttle valves used to control hydraulic fluid, particularly those used in underwater oil field equipment, must be designed taking into consideration working pressures, up to several thousand psi and flow rates of up to several hundred gpm. It is especially important that underwater shuttle valves used in connection with operation of subsea blowout preventers (BOPs) have a long trouble-free life because of their inaccessibility. The differential pressure on the shuttle often results in high momentum as it moves from one valve seat to another. When a shuttle contacts a valve seat, the repeated impact can break or crack the cage or cause it to be warped, and can otherwise disrupt proper valve operation. 
     One way to address the problem of shuttle impact is to lighten the shuttle and provide rubber cushions in the form of thick sealing elements as shown in U.S. Pat. No. 3,038,487. Yet another way of addressing shuttle impact is a hydraulic cushion as shown in U.S. Pat. No. 4,253,481 owned by applicant&#39;s assignee. The hydraulic cushion discussed above is similar to the action of a hydraulic cushioned slush pump valve as shown in U.S. Pat. Nos. 2,197,455 and 2,605,080. U.S. Pat. No. 2,654,564 discloses a metal to metal seat to take the axial load imposed on the shuttle and thereby to limit the pressure on the rubber seal ring so that the rubber is prevented from being overloaded, cut or extruded by the action of high pressure fluid. 
     The shuttle valve disclosed in U.S. Pat. No. 4,253,481 was sold for many years by Gilmore Valve Company for use with underwater oil field equipment. This prior art valve shuttle valve was limited to two inputs and was relatively expensive to manufacture. To overcome some of these limitations, Gilmore introduced the Mark I shuttle valve in 1997 as shown in FIG. 1 of the drawings. The Mark I relied upon two elastomeric o-rings mounted around the central flange of the shuttle to achieve a seal. The end portions of the shuttle were relatively thin and were prone to cracking because of shuttle impact. In addition, the o-rings were sometimes cut or blown off due to operational pressures and flow rates. 
     In order to overcome some of the limitations of the Mark I, Gilmore developed a retrofit design known as the Mark II which was introduced in 1998 as shown in FIG. 2 of the drawings. The Mark II design included an increased thickness of the end portions or cage, a decrease in hole size, larger o-rings which were stretched around the shuttle and a pair of plastic teflon bearings to center the shuttle and reduce vibration as it traveled back and forth. The Mark II eliminated many of the problems of the Mark I; however, at the highest operational flow rates, o-rings were still lost. The present invention is designed for operation at 5,000 psi; the ½ inch model is designed for an 80 gpm flow rate, the 1 inch model is designed for a 250 gpm flow rate and the 1½ inch model, is designed for a 350 gpm flow rate. 
     In an effort to overcome the limitations of the Mark I and Mark II, applicant has developed an improved design which is the subject of the present invention. In order to overcome some of the problems associated with elastomeric seals, the present invention has eliminated such seals and now relies upon a metal to metal seal. In addition, the shuttle of the present invention has been hardened by nitriding. The metal to metal seal of the present invention is progressively coined because of repeated contact between opposing tapered sealing surfaces surrounding a central flange on the shuttle and opposing metal valve seats. 
     The present invention includes alternative embodiments having a modular design that allows the components to be stacked one upon the other to receive more than two inputs. Another stackable, multi-input valve is disclosed in U.S. Pat. No. 4,467,825. This design uses a plurality of spool valve members to direct a superior fluid input signal to the outlet. 
     The present invention is less expensive to manufacture than prior shuttle valves sold by Gilmore Valve Company as disclosed in U.S. Pat. No. 4,253,481. Alternative embodiments of the present invention allow the shuttle valve to receive 3 or more inputs which was not possible with the shuttle valve disclosed in U.S. Pat. No. 4,253,481. In addition, the present invention overcomes the limitations of the Mark I and Mark II discussed above. 
     SUMMARY OF THE INVENTION 
     The preferred embodiment of the present invention includes two coaxial inlets or supply ports and a single transverse outlet or function port. A metal valve seat surrounds each of the coaxial opposing supply ports. An elongate shuttle is coaxial with the metal valve seats and the supply ports. The shuttle valve moves from one valve seat to the other in response to differential fluid pressure. The shuttle includes a central circumferential flange with opposing tapered sealing surfaces that alternatively engage the metal valve seats around the supply ports. Each metal valve seat has a chamfer which forms an obtuse metal point. As the shuttle moves back and forth into alternative engagement with the metal valve seats, the opposing tapered sealing surfaces strike the obtuse points and displaces a portion of the metal into each respective chamfer. This displacement occurs repeatedly as the shuttle strikes the obtuse points. This displacement of metal from the obtuse point into the chamfer insures a good metal to metal seal between the valve seats and the tapered sealing surfaces on the flange of the shuttle. This phenomena is also known as “progressive coining.” 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above-identified features, advantages, and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiment thereof which is illustrated in the appended drawings. 
     It is noted, however, that the appended drawings illustrate only a typical embodiment of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. Reference the appending drawings, wherein: 
     FIG. 1 is a section view of the Mark I shuttle valve, a prior art design, sold by Gilmore Valve Company. 
     FIG. 2 is a section view of the Mark II shuttle valve, a prior art design, sold by Gilmore Valve Company. 
     FIG. 3 is a perspective view of the low interflow hydraulic shuttle valve of the present invention with two supply ports. 
     FIG. 4 is a top view of the shuttle valve shown in FIG.  3 . 
     FIG. 5 is an end view of the shuttle valve of FIG. 3 along the line  5 — 5 . 
     FIG. 6 is a section view of the shuttle valve of FIG. 3 with the shuttle in engagement with the valve seat of the second supply port allowing fluid flow from the first supply port to the function port. 
     FIG. 7 is a section view of the shuttle valve of FIG. 6, except the shuttle has moved to the mid-point of travel which is a low or no flow position. 
     FIG. 8 is a section view of the shuttle valve of FIG. 6, except the shuttle has moved into engagement with the valve seat of the first supply port allowing fluid flow from the second supply port to the function port. 
     FIG. 9 is an enlarged view of a portion of the metal valve seat and a portion of the shuttle before any coining has occurred. 
     FIG. 10 is an enlarged view of a portion of the metal valve seat and a portion of the shuttle after coining has occurred and sealing engagement has been established. 
     FIG. 11 is a section view of an alternative embodiment of the present invention with three supply ports. 
     FIG. 12 is an alternative embodiment of the present invention with four supply ports. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Subsea wellheads are often relied upon during deep water exploration for oil and natural gas. The subsea wellhead includes 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. 
     The control pod is a capsule attached to the lower marine riser package until (LMRP) which extends from the subsea wellhead. The accumulators (tanks with air space in the tops) are mounted on the LMR. At least one shuttle valve of the present invention may be attached to each BOP on the subsea wellhead. Fluid flows from the accumulators through valves on the control pod through the shuttle valve of the present invention, to activate the BOPs. 
     FIG. 1 is a section view of the Mark I shuttle valve, a prior art design sold by Gilmore Valve Company. The shuttle valve  10 , has a first inlet or supply port  12 , a coaxial second inlet or supply port  14  and a transverse outlet or function port  16 . The supply ports  12  and  14  are in fluid communication with the accumulators and the function port  16  is in fluid communication with the BOP on the subsea wellhead. The shuttle valve  10  mounts via a bracket  18  to a BOP. The shuttle  20  includes a central circumferential flange  22  which is located between a first o-ring groove  24  and a second o-ring groove  26 . A first o-ring  28  is positioned in the first o-ring groove  24 . A second o-ring  30  is positioned in the second o-ring groove  26 . 
     The shuttle  20  has elongate end portions or cages  32  and  34 . The first end portion  32  includes a central bore  36  which is perforated by apertures  38 ,  40 ,  42  and fourth aperture not shown in the drawing. These apertures allow fluid to flow from the first supply port  12  through the bore  36 , through the apertures  38 ,  40  and  42  through a passageway  43  in the body  54  and out through the function port  16 . The other end portion or cage  34  has a bore  44  and apertures  46 ,  48 ,  50  and a fourth aperture not shown. 
     The first supply port  12  is formed by an adapter  52  which threadably engages the body  54 . The second supply port  14  is formed by an adapter  56  which also threadably engages the body  54 . The first supply port  12  and the second supply port  14  are located on opposite sides of the body  54  and are coaxial. The adapter  52  further defines a tubular valve seat  58  which engages and seals with the o-ring  28  on the shuttle  20 . The other adapter  56  likewise defines a tubular valve seat  60  which engages and seals with the o-ring  30  as shown in this figure. During operation of this prior art shuttle valve, o-rings were sometimes cut or lost and the end portions or cages were cracked due to shuttle impact. 
     FIG. 2 is a section view of the Mark II shuttle valve, a prior art design sold by Gilmore Valve Company. The Mark II was developed as a retrofit design to overcome some of the limitations in the Mark I. In this embodiment, the shuttle  20  was redesigned with deeper o-ring grooves  27  and  31  and larger o-rings  63  and  65 . In addition, the diameter of the bores  36  and  44  was diminished, thereby thickening the wall of the end portions or cages  32  and  34 . The diameter of the holes was decreased thus necessitating more holes to accommodate the same volume of fluid flow. End portion  32  was redesigned with six holes  66 ,  68 ,  70 ,  72  and two other holes not shown in the drawing. Likewise, end portion or cage  34  was redesigned with six holes  74 ,  76 ,  78 ,  80  and two other holes not shown. (The Mark I only had four holes.) In order to reduce valve impact and vibration, a circumferential channel  82  was formed in end portion  32  to receive a plastic teflon bearing  84 . Likewise, a circumferential channel  86  was formed around end portion  34  to receive another plastic teflon bearing  88 . These improvements in the design overcame many of the limitations of the prior art shown in FIG. 1; however, at the highest flow rates, o-rings were still being lost. Further improvements were needed. 
     FIG. 3 is a perspective view of the present invention, which is a low interflow hydraulic shuttle valve, generally identified by the numeral  100 . The shuttle valve  100  includes a body  102  which is supported by a bracket  104 . The valve  100  includes a first adapter  106  and a second adapter  108  coaxially aligned on opposite sides of the body  102 . The first adapter  106  forms an inlet or supply port  110  and the second adapter  108  forms a second inlet or supply port  112 . Each supply port  110  and  112  is connected to a separate hose or piping, not shown in the drawings. The body  102  forms a transverse outlet or function port  114 . The function port  114  is connected to a hose or piping, not shown, in the drawing. Fluid enters the valve  100  either through the first supply port  110  or the second supply port  112  and exits the valve  100  through the function port  114 . 
     FIG. 4 is a top view of the valve  100  of FIG.  3 . The bracket  104  includes a first aperture  116  and a second aperture  118  for mounting purposes. Looking down into the function port  114 , the shuttle  120  is shown in a right-hand position shutting off any fluid flow from the second supply port  112 . 
     FIG. 5 is an in view of the valve  100  and the bracket  104  along the line  5 — 5  of FIG.  3 . The second supply port  112  is formed by the second adapter  108 . 
     FIG. 6 is a section view of the present invention with the shuttle  120  in the right hand position sealing off fluid flow from the second supply port  112 . In this view, fluid can flow from the first supply port  110  through a passageway  111  in the body  102  and out the function port  114  as shown by the flow arrows in the drawing. The first adapter  106  threadably engages an aperture  122  in the body  102 . An o-ring  124  seals the adapter  106  to the body  102 . The second adapter  108  includes a recess  126  to engage the bracket  104 . The second adapter  108  threadably engages an aperture  128  in the body  102 . An o-ring  130  seals the adapter  108  to the body  102 . The adapter  106  includes a metal valve seat  132  and the second adapter  108  includes an opposing coaxial metal valve seat  134 . The shuttle  120  includes a centrally located circumferential flange  136  which has opposing tapered sealing surfaces  138  and  140 . As shown in this drawing, sealing surface  140  is in sealing engagement with the metal valve seat  134  blocking any fluid flow from the second supply port  112 . 
     The shuttle  120  is hardened by nitriding which causes the metal to darken. Applicant currently fabricates its shuttle  120  from 17-A P H Stainless Steel. After machining the shuttle  120  is nitrided by Houston Unlimited, Inc. of Houston, Tex. Other hardening processes, such as conventional heat treating may also be suitable depending on the application. Nitriding, like heat treating, is widely available from other vendors on a national basis. 
     FIGS. 6,  7  and  8  show a section view of the preferred embodiment of the present invention with the shuttle  120  in three different operational positions. In FIG. 6, the shuttle  120  is shown in the right hand position in sealing engagement with the metal valve seat  134  of second supply port  112 . This allows fluid to flow from the first supply port  110  through the bore  146  and apertures  148 ,  150 ,  152  and  156  through the passageway  111  of valve  100  to the function port  114 . In FIG. 7 the shuttle  120  has disengaged with the valve seat  134  of the second supply port  112  and is shown at the mid point of its travel where there is little or no interflow from the first supply port  110  or the second supply port  112  into the passageway  111  or the function port  114 . In FIG. 8 the shuttle  120  has moved into the left hand position in sealing engagement with the valve seat  132  of the first supply port  110 . As shown by the flow arrows in FIG. 8, fluid can now pass through the second supply port  112  through the passageway  111  of valve  100  and out the function port  114  as indicated by the flow arrows in the drawing. 
     FIG. 7 is a section view of the shuttle valve  100  with the shuttle  120  at its mid point of travel between valve seat  134  and valve seat  132 . The shuttle  120  has a first end portion or cage  142  that includes a central bore  146  and a total of six apertures  148 ,  150 ,  152 ,  156  and two others not shown. The other end portion or cage  158  includes a bore  160  that is coaxial with the bore  146  and a total of six apertures  162 ,  164 ,  166 ,  168  and two others not shown. 
     FIG. 8 is a section view of the shuttle valve  100  with the shuttle  120  in sealing engagement with the metal valve seat  132  so that fluid can not flow from the first supply port  110  to the function port  114 . In FIG. 8, fluid flows from the second supply port  112  through the central bore  160  of the end portion or cage  158  through the apertures  162 ,  164 ,  166  and  168  into a central passageway  111  in the body  102  and out the shuttle valve  100  through the function port  114  as shown by the flow arrows in the drawing. 
     Due to differential pressure, the shuttle  120  will travel from the right hand position as shown in FIG. 6 to the mid-point position shown in FIG. 7 to the left hand position shown in FIG.  8 . This movement of the shuttle  120  from right hand position to the left hand position, occurs quickly and creates impact forces on the shuttle  120  and the valve seats  132  and  134 . Cracking of the end portions or cages was one of the problems in the prior art design shown in FIG.  1 . The cracking problem has been overcome through the use of holes with a smaller diameter thus allowing more structural metal in the cage between the holes and a smaller diameter bore  146  and  160  thus allowing a thicker cage wall  172  and  174  when contrasted with the prior art design of FIG.  1 . These dimensions vary with each size valve. Applicant has found that a six hole design with holes having a diameter of 0.328 inches and a cage wall thickness of 0.113 inches works well for a 1 inch valve. However, a shuttle with a different number or size of holes and a different cage wall thickness is within the scope of this invention provided that it does not result in cracks due to valve impact or otherwise damage the valve  100 . 
     FIG. 9 is an enlarged section view of a portion of the shuttle  120  and a portion of the adapter  108 . FIG. 9 shows the sealing surfaces after the valve  100  has been manufactured but before any coining has occurred. FIG. 10 shows the sealing surfaces after coining has occurred. In FIG. 9 the shuttle  120  includes a circumferential external flange  136  with opposing outwardly tapered metal sealing surfaces  138  and  140 . Applicant believes that a taper of approximately 8 degrees is optimum for this application. However, other tapers are within the scope of this invention so long as they will create a coining effect on the metal valve seats  132  and  134  of the adapters  106  and  108 . Other tapers may be suitable for other applications possibly in the range of 5 to 15 degrees. The only requirement for the angle of taper is to achieve coining and therefore sealing with the metal valve seats  132  and  134 . 
     The adapter  108  includes a chamfer  176  recessed behind the metal valve seat  134  to thereby create an obtuse metal point  180  that will contact the tapered metal sealing surface  140  on the flange  136  of the shuttle  120 . FIG. 9 shows the metal valve seat  134  and the metal sealing surface  140  on the shuttle  120  before any coining has occurred. Applicant uses a chamfer with a 15 degree angle and a 0.0070″ radius. However, the exact size and depth of the chamfer are not particularly critical because this is merely a recess or space into which displaced metal will move due to progressive coining. A stepped back shoulder or other recess would be sufficient to achieve the goals of this invention, provided that there is room to receive the displaced metal from the point  180  such that it does not interfere with movement of the shuttle  120 . When adapter  106  is first manufactured it likewise has a chamfer  177  recessed behind the metal valve seat  132  to thereby create an obtuse metal point  181  that will contact the tapered metal sealing surface  138  on the flange  136  of the shuttle  120 . The point  181  is progressively coined in the same fashion as the point  180  by the impact of the shuttle  120 . 
     FIG. 10 is an enlarged section view of a portion of the shuttle  120  and a portion of the second adapter  108  after coining has occurred. As the tapered metal sealing surface  140  of the shuttle  120  impacts the point  180  of the metal valve seat  134 , a portion of the metal in the point  180  is displaced into the chamfer  176 . This displaced metal is identified by the numeral  182 . A metal to metal seal is therefore achieved between the metal valve seat  134  and the outwardly tapered metal sealing surface  140  of the flange  136  on the shuttle  120 . 
     Likewise, the outwardly tapered metal sealing surface  138  will impact point  181  on the metal valve seat  132  and will displace a portion of the metal  183  into the chamfer, thus creating a metal to metal seal between the metal valve seat  132  and the outwardly tapered sealing surface  138  on the flange  136  of shuttle  120 . 
     FIG. 11 is a section view of an alternative embodiment of a low interflow hydraulic shuttle valve with three supply ports. (The embodiment in FIG. 3 has two supply ports.) The shuttle valve  200  includes a first body portion  202  and a second body portion  204  that are held together by a plurality of bolts  206  and  208  and a plurality of nuts  210 ,  212 ,  214  and  216  that mechanically grip the two body sections  202  and  204  thus joining them together into an integral assembly. An alignment pin  220  fits into a bore  222  of the body  202  and a coaxial bore  224  of the body  204 . A zig-zagged interconnecting passageway  226  is formed in the body  202  and is in fluid communication with a second zig-zag passageway  227  in the body  204 . A connector  228  is positioned in a bore  230  of the body  202  and another coaxial bore  232  in the body  226 . The connector  228  has a first seal  234  and a second seal  236  to prevent fluid from leaking from the zig-zagged passageways  226  and  227 . The connector  228  also helps align the body portions  202  and  204 . 
     A first supply port  236  is formed in the body  202  and is in fluid communication with the passageway  226 . A second supply port  238  is formed in a first adapter  240 . The adapter  240  threadably engages the body  202 . The adapter  240  is sealed against the body  202  by an o-ring  242 . A metal valve seat  244  is formed on one end of the adapter  240 . A second metal valve seat  246  is formed in the body  202  and is coaxial with valve seat  244 . A shuttle  248  moves from sealing engagement with the metal valve seat  244  of the adapter  240  to alternative sealing engagement with the valve seat  246  of the body  202 . 
     A third supply port  250  is formed in another adapter  252 . The adapter  252  threadably engages the body  204  and is sealed by an o-ring  254 . A mounting bracket  105  is positioned between the body  204  and the adapter  252 . The adapter  252  includes a metal valve seat  256 . An opposing metal valve seat  258  is formed in the body  204  and is coaxial with valve seat  244 . A shuttle  260  travels back and forth into alternative sealing engagement with the metal valve seat  256  and the metal valve seat  258  depending on differential fluid pressure in the third supply port  250  and the passageway  227 . A function port  270  is formed in the body  204  and connects to the BOP, not shown. 
     A first supply line, not shown in the drawing, connects to the first supply port  236 , a second supply line, not shown in the drawing, connects to the second supply port  238  and a third supply line, not shown in the drawing, connects to the third supply port  250 . If the pressure into the first supply port  236  is greater than the fluid pressure in the second supply port  238  or the third supply port  250 , the shuttle  248  and the shuttle  260  will be urged into sealing engagement with the metal valve seats  244  and  256  as shown in FIG.  11 . This allows fluid to flow from the first supply port  236  through the zig-zagged passageways  226  and  227  and out the function port  260  to the BOP, not shown. 
     If fluid pressure in the second supply port  238  is greater than fluid pressure in the first supply port or the third supply port, the shuttle  248  will unseat and move into sealing engagement with the metal valve seat  246  of the body  202 . This will allow fluid to flow from the second supply port  238  through the zig-zagged passageways  226  and  227  and out the function port  270  to the BOP, not shown. If, in the alternative, fluid pressure in the third supply port  250  is greater than fluid pressure in the first supply port  236  or the second supply port  238 , then the shuttle  260  will disengage from the metal valve seat  256  and engage the metal valve seat  258  of the body  204 . This allows fluid to flow from the third supply port directly to the function port  270  and the BOP. The shuttle  248  progressively coins the metal valve seats  244  and  246  in similar fashion as the shuttle  120  described in FIGS. 3-10. Likewise, the shuttle  260  progressively coins the metal valve seats  256  and  258 . 
     FIG. 12 is an alternative embodiment with a four supply design for a low interflow hydraulic shuttle valve  300 . The design in FIG. 12 is identical to the three supply valve  200  shown in FIG. 11 except another supply port and another body section have been added. The four supply valve  300  includes a first body section  202 , a second body section  204  and a third body section  302 . The body sections are aligned and connected by the first alignment pin  220  and a second alignment pin  304 . Zig-zagged passageways  226 ,  227  and  229  are formed in the respective bodies  202 ,  204  and  302  and are interconnected and sealed against the bodies via a first connector  228  and a second connector  306 . The second connector  306  is identical to the connector  228  shown and described in FIG. 11 except connector  228  joins body sections  202  and  204  and connector  306  joins body sections  204  and  302 . The respective body sections  202 ,  204  and  302  are connected by a plurality of nuts  210 ,  212 ,  214  and  216  and bolts  206  and  208 . The valve  300  is mounted via brackets  310  and  312  to a BOP, not shown. 
     The body section  202  includes a first supply port  236  and a second supply port  238  formed in the adapter  240 . The adapter defines a first metal valve seat  244  and the body  202  defines a coaxial second metal valve seat  246 . The shuttle  248  moves from alternative sealing engagement with the first metal valve seat  244  to the second metal valve seat  246  in response to differential fluid pressures in the first supply port  236  or the second supply port  238 . 
     The second adapter  252  defines another metal valve seat  256  and the body portion  204  defines an opposing coaxial metal valve seat  258 . The shuttle  260  moves back and forth into alternative sealing engagement with the metal valve seat  256  or the metal valve seat  258  depending on differential fluid pressures exerted upon the shuttle  260 . A third adapter  314  defines a fourth supply port  316  and another metal valve seat  318 . An opposing coaxial metal valve seat  320  is formed in the body section  302 . A third shuttle  322  moves into alternative sealing engagement with the metal valve seat  318  of the adapter  314  or the metal valve seat  320  of the body  302  depending on differential fluid pressures. 
     FIG. 12 shows the valve  300  with the highest pressure in the first supply port  236  which a) urges the shuttle  248  into sealing engagement with the metal valve seat  244  of the second supply port  230 , b) urges the shuttle  260  into sealing engagement with the metal valve seat  256  of the third supply port  250 , and c) urges the shuttle  322  into sealing engagement with the metal valve seat  318  of the fourth supply port  316 . This allows hydraulic fluid to pass from the first supply port  236  through the zig-zagged passageways  226 ,  227  and  229  of the body portions  202 ,  204  and  302  into the function port  322  and thereafter to the BOP, not shown. 
     In the alternative, a higher differential pressure in the second supply port  238  will cause the shuttle  248  to move into sealing engagement with the metal valve seat  246  thereby allowing fluid to pass from the second supply port  238  through the zig-zagged passageways  226 ,  227  and  229  to the function port  322  and into the BOP, not shown. Higher differential pressures in the third supply port  250  will likewise cause the shuttle  260  to move and engage the metal valve seat  258  and allow fluid to pass from the third supply port  250  through the passageways  226 ,  227  and  229  into the function port  322  and out to the BOP, not shown. If the highest fluid pressure occurs in the fourth supply port  316 , the shuttle  322  will move into sealing engagement with the metal valve seat  320 , thus allowing fluid to flow from the fourth supply port  316  into the function port  322  and thereafter to the BOP, not shown. 
     Using the modular body approach, as shown in FIGS. 11 and 12, it is possible to create low interflow hydraulic shuttle valves with as many supply ports as needed depending on the specific application. 
     While the foregoing is directed to the preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follow.