US3078862A

US3078862A - Valve and well tool utilizing the same

Info

Publication number: US3078862A
Authority: US
Inventors: George P Maly
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1960-01-19
Filing date: 1960-01-19
Publication date: 1963-02-26
Anticipated expiration: 1980-02-26

Description

Feb. 26, 1963 G. P. MALY VALVE AND WELL TOOL UTILIZING THE SAME 3 Sheets-Sheet 1 Filed Jan. 19, 1960 IN V EN TOR. GEORGE MAL Y BY/ 477'ORNEY Feb. 26, 1963 G. P. MALY VALVE AND WELL TOOL UTILIZING THE SAME 5 Sheets-Sheet 2 Filed Jan. 19, 1960 INVENTOR. 765 p M447 BY pin 4 Feb. 26, 1963 e. P. MALY VALVE AND WELL TOOL UTILIZING THE SAME Filed Jan. 19, 1960 3 Sheets-Sheet 3 zs I! L a b2 L (0 23 ll w M 1 /7 A? a g i H M FIG- 9 INVENTOR.

GEORGE P. MALY ATTORNEY! 3,078,862 VALVE AND WELL TQUL UTILIZING THE SAME George P. Maly, Fullerton, Catlin, assignor to Union Gil Uompany of California, Los Angeles, Calili, a corporation of California Filed lien. 19, $60, Ser. N 3,366 7 Claims. (Cl. 137-67) This invention relates to a valve mechanism for controlling the flow of fluids, and in particular relates to a valve which remains in a normally open position when in contact with non-electrolytic fluids but which automatically closes when contacted by electrolytic fluids. In a specific embodiment, this invention relates to the use of the aforementioned valve in combination with a well tool adapted to be inserted into an oil field well bore opposite a production interval to detect and/or prevent flow of oil field water or brine from the water bearing strata into the production tubing.

In oil production, wells are frequently encountered which penetrate both oiland water-producing strata, and as a result the production of oil is accompanied by procluction of water or brine. A not uncommon occurrence is the production of a well eflluent containing as much as 90 percent water. The cost of raising this water to the earths surface, of separating it from the oil, and of disposing it represent economical losses. It is therefore desirable to plug oil the water-producing strata within the well bore and avoid these losses. Although it is possible to prevent Water production by isolating the waterproducing strata with packers and then plugging them with cement, this practice requires accurate location of the water-bearing strata. Most methods presently used to determine the location of water-bearing strata, while satisfactory if the oiland water-producing strata are spaced a substantial distance apart, are not sufiiciently accurate for use where oiland water-producing strata lie close together. Com-eating operations in these instances frequently result in plugging both the oiland water-producing strata.

it is an object of this invention to provide a valve mechanism which is self-actuating to a closed position when contacted with electrolytic or aqueous fluids.

Another object of this invention is to provide a device for accurately determining the location of subterranean water-producing strata which are located adjacent to oilproducing strata.

A further object is to provide a device for selectively sealing off subterranean water-bearing strata which are located adjacent to oil-producing strata.

The first of the aforementioned objectives is attained by my invention which utilizes galvanic corrosion to automatically actuate a valve closure member. The remaining objectives are achieved by the pecific use of my electrolyte sensitive valve in a t e 1 tool.

The valve mechanism of my invention comprises a valve housing having inlet and outlet ports and a spring biased valve closure member normally retained in an open position by an obstructing member such as a link, lug or washer. The obstructing member is composed of a material dissimilar to that of the remaining valve parts and is so selected from the electromotive series of metals as to be anodic to the material used for the remaining valve parts. When the valve is contacted by nonelectrolytic, i.e. non-conducting fluids such as oil, the obstructing member is not corroded and maintains the valve in the open position. However, when aqueous fluids contact the valve the obstructing link or body is corroded until it can no longer overcome the force of the spring and retain the valve closure member in the open position. When this occurs the valve is forced into a closed position. The sensitivity of the valve action or Patented Feb. as, less the time lag between the time when the valve is first contacted by an electrolytic fiuid and closure of the valve can be controlled by judicious choice of the materials employed for the obstructing member and for the remaining valve members. The time lag can also be controlled by the shape, thickness, and spacing of the obstructing member in a manner hereinafter described. By properselection of these varia les it is possible to obtain valve mechanisms which are self-closing within time periods of between a few minutes to several days. In a preferred embodiment, the valve members are constructed from or coated by a non-metallic material, e.g., plastic, rubber, etc., and a selected cathodic material is placed within the valve assembly and grounded to the obstructing member. This type of construction gives more reliable performance and prevents fouling of the sealing surfaces of the valve thereby resulting in a tight seal.

The combination of my valve me-ci anism with a well tool comprises a specific embodiment of the invention suitable to determine the location of subterranean waterproducing strata and/or to selectively seal these strata from production without also sealing adjacent oil producing strata. This device comprises a series of cylindrical members of slightly smaller diameter than the well bore or well casing and a co centrically disposed central longitudinal conduit of smaller diameter than said cylinders. A plurality of fluid-impervious plates are transversely disposed along the length of the elongated conduit, each of said plates being positioned between each of said cylindrical members thereby dividing the annular space between the cylinders and the conduit into a plurality of longitudinally isolated chambers. Fluid passageways are provided within each of these chambers so arranged that a continuous fluid flow passageway exists from the interior of the center cylindrical member to the exterior of each of the outer cylinders. The above described valve mechanism is interspaced in said passageways.

The invention will now be described by reference to the figures of which:

FIGURE 1 illustrates a valve mechanism of my invention employing a corrodible metal link as the obstructing member;

*lGURE 2 illustrates a second valve mechanism of my invention employing a corrodible metal Washer as the obstructing member;

FIGURE 3 illustrates an al ernative sealing mechanism adapted to be inserted in the valve housings of FlG- URE 1;

FIGURE 4 illustrates another alternative sealing mechanism;

FIGURE 5 illustrates an insert composed of nonmetallic material and a selected cathodic metal;

FIGURE 6 illustrates a well tool of my invention within a well bore;

FIGURES 7 and 8 illustrate cross-sectional detailed views of two forms of the device shown in FIGURE 5; and

FIGURE 9 illustrates a valve mechanism of my invention having a reverse action to those previously mentioned.

Referring now to PEGURE 1, there is illustrated one form of my valve mechanism. This valve comprises a first housing member 1 a second housing member 2, secured thereto by any Well known means, e.g., threaded joint, swedged fitting, etc., and sealed by G-ring 5. A port or fluid passageway 35 is rovided in housing member 1 and a similar port 4 is provided in housing member 2. Disposed within the central space of the housing assembly is a spring-biased valve closure member having a spherical end 8 positioned adjacent fluid port 3 and an elongated tail '6 having a hook at its lower end. A compression spring 7 is positioned to exert a force against the lower surface of the closure member 8 so as to seat it tightly against the valve seat in port 3. Spring 7 is normally held in compression by hooking tail 6 of the valve closure member within link 9 which is composed of a selected anodic metal. The assembly of spring 7 and closure member 8 can be held in place within the valve assembly by the base of the spring which fits snugly within housing member 2, as shown.

When in use, fluid passes through the valve assembly via ports 3 and 4. When the fluid is an electrolyte, metal link 9 will corrode until it can no longer retain closure member 8 in its open position. At this point the force of the spring 7 will force the closure member against the valve seat in port 3 and stop the flow of fluids.

In FIGURE 2, there is illustrated a second embodiment of my valve mechanism. This valve, like the one previously described, can comprise housing bodies similar to those of FIGURE 1. However, as illustrated, a perforated cylindrical cap is substituted for the first housing body of FIGURE 1. This perforated cap is securely attached to housing body 16 by any suitable means, e.g., by a lipped edge which fits into a corresponding groove in body 16, as shown, and held securely in place by lock nut 17. A fluid port 18 is provided for fiuid passage through housing 16, and the perforations l9 similarly provide for flow through cap 17. Disposed within the valve body is valve closure member 23 having a frustro-conical lower end with a ball embedded therein, and a hollow upper end within lip 25 extending past its outer cylindrical surface. A compression spring 22 is positioned within the hollowed interior of closure member 20 so as to force this member and its associated ball 21 tightly against the valve seat in port 18. The valve closure member is held in an open position against the force of spring 22 by metal washer 23 and supporting legs 24-. The inner diameter of washer 23 is greater than the diameter of closure member 20 but less than diameter of lip 25 so as to prevent the closure member from moving past its open position. Washer 23 is composed of a selected metal so as to be anodic in the presence of an electrolytic fluid and be corroded thereby.

During use of the device shown in FIGURE 2, fluid will normally pass through perforated cap 17 and open port 13. When, however, an electrolyte flows through the valve, corrosion begins and washer 23 is corroded until it no longer can resist the force exerted by the compression spring 22 and it will then release closure member 20, permitting spring 22 to move ball 21 into a sealing position in port 18.

FIGURE 3 illustrates an alternative sealing means for use in the valve housing of FIGURE 1 adapted to seal both fluids ports 3 and 4. This device comprises two valve closure members 26 similar to the closure member of FIGURE 1 previously described. A compression spring 27 is placed between members 26 and the assembly compressed so that metal link 28 can be placed over their hooked ends to retain them in the contracted positions. Any suitable means can be provided to secure this assembly within the interior chamber of the valve; a protruding lip 29 is illustrated which fits between the abutting edges of housing members 1 and 2. When link 28, which is made of a metal anodic to the metal of the remaining valve parts, is contacted with an electrolytic fluid it will corrode until it can no longer retain members 26 in their compressed position against the force of spring 27 which will then force these members against the valve seats in ports 3 and 4 sealing the valve from further flow.

Referring now to FIGURE 4, there is illustrated another alternative valve closure mechanism suitable for insertion in the valve housings illustrated in FIGURE 1. This valve closure assembly contains two

closure members

30 and 31, each having a ball 32 to seat against the valve seats in both of the fluid ports of the valve assembly and thereby provide more positive sealing of the valve. The

valve closure members

30 and 31 are frustroconical at one end and cylindrical at the other. The cylindrical position is hollowed to receive compression spring 34. The hollowed portions of the

closure bodies

30 and 31 are placed in opposed relationship, and compression spring 34 is placed therebetween within their hollowed interiors. This spring is compressed and the assembly is held in this contracted position by retaining ring 33 which surrounds the valve closure members and firmly attached thereto by suitable means such as threaded joints, swedged or pressed fit, etc. Metal ring 33 is composed of a metal which is anodic to the metal employed in the remainder of the valve so as to be corrodible in the presence of an electrolyte. Surrounding the assembly at opposite ends thereot is perforated cylinder 35 having a crimped edge 36 which engages ring 33. This cylinder fits around the assembly and is provided to prevent the fluid pressure from forcing the balls 32 into a closed position against the valve seats in the fluid ports.

During use of the device illustrated in FIGURE 4, fluid will normally flow into the valve housing through one of the fluid ports, pass through the perforations in the cylinder 35 and then out of the valve assembly through the remaining perforations in cylinder 35 and out the remaining valve port. When an electrolyte flows through the valve and contacts retaining ring 33 it will corrode this ring until it can no longer retain

closure members

30 and 31 in the compressed position against the force of spring 34-. When this occurs, spring 34 will expand and force

closure members

30 and 31 through the perforated cylinder 35 to seat balls 32 tightly against their respective valve seats in the fluid ports.

As previously mentioned, judicious choice of the material for the corrodible obstructing member as well as its shape, size and spacing in the valve permits control of the time lag before the valve closes when contacted with an electrolyte. The choice is based on the electromotive series of metals, reproduced herein as follows with their respective single electrode reduction potentials:

Metal, Reduction potcn- A more complete listing of the electrode potentials and the electromotive series of metals can be found on pages 1213 to 1219 of The Handbook of Chemistry, Ninth Edition, 1956, compiled and edited by Norbert Lange. To be corrodible, the obstructing member must be anodic to the remaining metal parts of the valve. This is achieved by constructing this member from a metal appearing higher in the electromotive series than that employed in the remaining valve parts. The rate of corrosion which detel-mines the time lag of the valve mechanism is directly proportional to the potential difference between the single electrode reduction potentials (electromotive force) of the metals; the greater this difference, the greater the rate of corrosion and, therefore, the shorter the time lag of the valve. When using an iron or steel housing, electromotive forces up to about 1.9 volts are possible. I have constructed a valve useful at pressures as high as 10,000 p.-s.i., similar to that illustrated in FIGURE 2 with a magnesium washer and an aluminum housing having a time lag of only 4 minutes. Valves having time lags up to 200 hours have also been made by use of an aluminum Washer with a steel housing. As mentioned, the time lag is also dependent on the shape, size and spacing of the obstructing member. The shape of the obstructing member influences the time lag since the rate of corrosion is directly dependent on the extent of surface exposed to the electrolyte. Accordingly, members shaped so as to have the greatest wetted perimeter per cross sectional area will have the shortest time lag. The effect of size is apparent; the greater the cross sectional area, the greater in the amount of material to dissolve and, hence, the longer is the time lag. The closer the corrodible member is positioned to the galvanic metal housing the shorter will be the path of current flow and, therefore, the faster will be the corrosion rate and the shorter the time lag. As previously mentioned, a preferred embodiment of my invention is to construct the valve housings and valve closure members of plastic or coat these members and the compression spring with plastic. When this is practiced, it is necessary to place a cathodic metal adjacent and in electrical connection with the corrodible obstructing member. This is suitably accomplished by use of the ring assembly illustrated in FIGURE 5. This ring assembly contains a metal ring 38 sandwiched between plastic rings 37 and 39. The outer diameter of these rings conforms to the inner diameter of the valve housings. The ring assembly is placed within these valve housings and electrical connection between the corrodible obstructing member and cathodic ring 33 is accomplished through the metal valve housing. When the valve housing is of a plastic or hard rubber material, conductive members can be embedded therein to provide conductivity between cathodic metal 33 and the anodic obstructing member. A typical conductive member id is illustrated in FIGURE 5 as a strip or ribbon of metal ill embedded in the lower housing member 2 for use in the 'valve assembly shown in FIGURE 1. The upper portion of contacts metal ring 38 and in turn is electrically grounded to link 9 through spring '7 which contacts the lower portion of metal strip 10. This embodiment permits use of various cathodic metals such as copper, silver, platinum, gold etc., which are not normally suitable for use in the valve housing members but which are desirable because they are strongly cathodic. By this technique, electromotive forces as great as 4 volts can be obtained which will have extremely short time lags before closing when contacted with an electrolyte.

FIGURE 6 illustrates a well tool employing my valve mechanism which is suitable to selectively plug waterbearing strata in a production interval. A tool support 4t) is positioned in casing '41 immediately below the position of formation 42 containing waterand oil-bearing strata. The tool is slipped over the production tubing 53 and is lowered into the casing by means of cable 43 until it rests on tool support 4%. After the tool has been set, each of the fiat packers do is caused to expand radially (by means hereinafter described with regard to FEGURE 7) so as to form a fluid-type seal at its periphery with the inner wall of casing 41. Supported between transverse packers 44 are a series of cylindrical members 45 and central longitudinal conduit 46. This central conduit is of a greater diameter than the production tubing so that when slipped over the production tubing an arm nular space for fluid flow exists between the tubing 53 and the conduit 46. A fluid passageway 54 is provided from the exterior of cylinders 45 through central tubing 46 within each of the longitudinal chambers between packers 44. Valves 4'7 employing my self-sealing meching strata is prevented from mixing with well fluid from other strata by transverse packers dd, and flows through its respective conduit 54 and valve 47 into the annular space between the production tubing and central conduit :6.

When the tool is employed for selective sealing of water producing strata, the production fluids flow into the production tubing from the surrounding annulus through any suitable passageways, e.g., the tubing can be slotted throughout interval 42. In the illustrated embodiment, the fluids flow downwardly to the bottom of the well bore and are there removed to the earths surface through the production tubing. This path of fiuid flow is hereinafter described in greater detail with reference to FEGURES 7 and 8. If the production fluid from any of the aforementioned strata contains brine it will cause the valve obstructing member to corrode in its respective valve 47. This corrosion will ultimately cause the valve for that production stratum to close in the manner previously described and thus seal off that stratum from the production tubing communicating with conduit 46 and thereby shut off production from the brine-producing strata. Use of valve mechanisms having lengthy time lags, 24 hours or more is advantageous since the time delay thus provides an adequate period for equilibrium conditions to be attained in the formation before the valves are actuated.

When the tool is employed as a detecting instrument to determine the location of Water-bearing strata which can thereafter be plugged by any conventional cementing operation, it is positioned Within the well bore in the manner previously described and sufiicient time is allowed to permit the self-closing valves in the well tool to be actuated by the brine from the water-producing strata. The tool is then withdrawn from the bore and the valves examined to determine which have been closed by brine. The water-producing strata are thus located and can be isolated by packers and cemented or plugged in conventional manner, or the tool can be employed in the plugging operation itself by removing the valves which have been closed due to the presence of water in the production fluid and by closing off the valves which were removed from the well bore in the open position, and thereafter relocating the tool within the well bore. Cement or a resinous plugging agent is then forced into and through the well tool via the open ports into the water-producing strata. If desired, the plugging material can be placed in those chambers adjacent the water-producing strata before the tool is relocated in the bore hole, thus simplifying the plugging operation.

Referring now to PZGURE 7, there is illustrated a form of the device of FZGURE 6. The central tubing on surrounding production tubing 73 carries conical wedges or earns 61 having their apexes directly downwardly and being spaced at intervals along its length. Said wedges may be integral with conduit 60, as shown, or may take the form of conical collars afiixed to conduit 6%, as by welding. Resilient sealing means 62 takes the form of relatively thick circular discs having a diameter slightly less than the diameter of perforated well casing 63 in which the device is employed, and being provided with a central hole having a diameter slightly larger than the outside diameter of conduit 6%. Each of sealing means 62 is mounted on conduit it immediately below each of Wedges 61 so that the apex of the latter is in register with the central hole of sealing means 62. Cylindrical shells 64 having a diameter slightly less than that of sealing means 62 extend between the opposed faces of adjacent sealing means 62, and register in peripheral grooves 66 cut in the faces of sealing means 62. Bottom plate 67' is afiixed at the lower end of conduit 60, as by welding, and serves as clamping means to hold the assembly together. The device of FIGURE 6 thus takes the form of a series of isolated fluid-tight cylindrical chambers strung along the length of conduit 60*, each of said chambers being defined by the opposed faces of adjacent sealing means 62, the inner wall of shell 64, and the outer wall of conduit 60. Within each of said chambers is positioned one or more of my electrolyte sensitive valves. These valves are positioned such that the production fluid must pass through them to enter the central conduit 6t These valves 70 can be installed as shown in the uppermost compartment on a conduit 71 communicating through the chamber, or they can be connected directly to the communicating opening in either tubing 69 or in shell 64, as shown in the lower chambers of FIGURE 7. If the valve is connected to the central conduit 60, it is of course apparent that shell 64 must be perforated as shown at 72, and likewise when the valve is connected to shell 64 central conduit 69 must be perforated to complete the fluid passageway.

In employing the device of FIGURE 7, the assembly is lowered into the well bore until bottom plate 67 rests on tool support 75 which has previously been afiixed to the inside of casing 63 at the desired depth. Conduit 60 is then moved downwardly with respect to sealing means 62 and shells 64, said movement being effected either by the force of gravity acting on conduit 60 and/or tubing string to which conduit 60 can be attached at its upper end, or by a positively applied pressure. Said downward movement forces wedges 61 into the center hole of sealing means 62, thereby causing the latter to expand laterally and contact well casing 63 at their peripheries to form fluid-tight seals therewith. The casing is thus divided vertically into a series of chambers, each of which is in communication with the strata traversed by the casing via the perforation therein, and the flow of fluids from the formation is caused to be subdivided by horizontal planes into a number of streams. With valves 70 open, production fluid flows into the central tubing 60 and then into the production tubing. When an electrolyte, i.e., brine, enters from its respective producing strata, it will corrode the obstructing member in the valve through which it passes and ultimately cause this valve to close and seal the strata from production.

Referring now to FIGURE 8, there is there shown a form of device in which hydraulic or pneumatic means are employed to seal off the bore hole into a plurality of chambers. Longitudinal conduit 30 has separators 81 rigidly afiixed along its length in spaced pairs. A cylindrical shell 82 extends between adjacent pairs of separators 81 and forms fluid-tight seals therewith at its upper and lower edges. Sealing means 84 occupies the space between each two separators 81 which together constitute one of said spaced pairs, and takes the form of a flat inflatable hollow disc having relatively thin walls constructed of a resilient material such as rubber. The outer diameter of sealing means 84 in a deflated condition is somewhat less than the inner diameter of well casing 35 in which the tool is to be employed. Each of said sealing means has a center hole through which conduit it} extends and is sealed to conduit 86 at the edges of said hole. Each sealing means thus resembles a tubeless automotive pneu matie tire mounted on conduit 80 between each two separators 81 which form a pair. Hydraulic or pneumatic line 86, which is connected with a source of gas or liquid pressure, not shown, runs substantially parallel to conduit 80 and communicates via ports 87 to the hollow interior of each of sealing means 34. As illustrated, an electrolyte sensitive valve 83 is suitably positioned with the fluid passageway from the exterior of shell 82 to the interior of longitudinal conduit 80. As previously described in reference to FIGURE 7, this valve may be placed on a conduit extending between shell 32 as shown, or it can be attached directly to shell 82 or longitudinal conduit 89. In employing the device of FIGURE 8, it is positioned in casing 85 as previously described, and gas or fluid pressure is applied to line 86 thereby inflating sealing means 84 and causing them to expand laterally to meet and form fluid-tight seals with the inside wall of casing 85 at their peripheries. The production fluids are their free to enter longitudinal conduit for removal at the earths surface until oil field brine is present in the fluids. When this occurs, valve 88 will close in the manner previously described and seal the brine producing strata from production.

As will be apparent to those skilled in the art, various other modifications can be made to my invention without departing from its scope. Thus, a section of the production tubing string can be substituted for central conduit 46 of FIGURE 5 and fluid connection thus directly established into the production tubing. Other transverse packer means then illustrated can be employed to separate the shell portions of my well tool and form the iso' lated chambers, for instance, a packer construction well adapted for use in my well tool comprises the type employing a swellable sealing ring as disclosed in my US. Patent 2,849,070. Various metals other than disclosed can be employed to construct the corridible link and valve housing. If desired, the reverse action can be employed for the valve mechanism, i.e., the valve can be normally closed, but will be spring biased to open when contacted with an electrolyte. A valve having this operation is illustrated in FIGURE 9. The valve housing of this embodiment is identical to that described with regard to FIGURE 2, and as with FIGURE 2, a corrodible washer 23 isemployed as the restraining member. Fluid port 18 is shown to be closed by ball 21 which is attached to valve closure member 13. A spring 12 is positioned between shoulder 14 on member 13 and the base of the valve housing member 16. The valve closure member is held in a closed position against the force of spring 12 by washer 23 and supporting legs 11. The inner diameter of washer 23 is greater than the diameter of closure member 13 but less than the diameter of lip 25 so as to prevent the closure member from moving past its closed position. When an electrolyte flows into the valve chamber (through ports 19) washer 23 will corrode until it no longer can resist the force of spring 12 and it will then release closure member 13 and permit the spring to open the valve. Such a valve would not, however, be suitable for use in my well tool.

Other modes and modifications of my invention can be employed other than herein explained, provided that the apparatus stated by any of the following claims or the equivalent thereof be produced.

I, therefore, particularly point out and distinctly claim as my invention:

1. A valve structure, automatically operative upon the passage of an electrolyte therein, comprising a hollow body member provided with an inlet port and an outlet port; closure means registerable with one of said ports and movable between a closed-port position and an opened-port position; resilient means positioned within said hollow body member to urge said closure means into one of said positions; and a metallic restraining member normally holding said closure means into the other of said position and in electrically conductive relationship with a dissimilar metal than the metal of said restraining member, said dissimilar metal having a single electrode reducing potential more positive than that of said restraining member, said restraining member and said dissimilar metal being positioned Within the fluid passageway of said valve so as to be exposed to contact with liquid passing into said body member.

2. The apparatus of claim 1 wherein said body member comprises a first body portion provided with a plurality of ports and a second body portion secured thereto having a single port, and said closure means is registers.- ble with said single port.

3. The apparatus of claim 1 wherein said hollow body member is said dissimilar metal.

4. The apparatus of claim 1 wherein said hollow body member and said closure means are coated with a non metallic material and an insert of said dissimilar metal is placed within said hollow body member, said insert and said restraining member being electrically grounded to said hollow body member.

5. The apparatus of claim 1 wherein said hollow body member and said closure means are constructed of a non metallic material, an insert of said dissimilar metal is placed within said valve, and an electrical conductor is placed between said insert and said restraining member.

6. The apparatus of claim 1 wherein closure means associated with said first and said second ports, restraining member to hold said closure means away from said first and second ports, and positioning means for holding said closure means, said resilient means and said restraining member at a fixed position within said chamoer.

7. A normally open valve, self operative to a closed position upon passage of an electrolyte therethrough comprising: a valve housing having an interior chamber, an inlet port and an outlet port communicating with said chamber, port closure means disposed within said chamber, said means comprising a port closure member adjacent one of said ports and movable between an open port and a closed port position, a compression spring biased to urge said closure member into a closed port position, a metallic restraining member holding said port closure member in an open port position, said restraining member being in electrically conductive relationship with a dissimilar metal having a single electrode reducing potential more positive than that of said restraining member, said restraining member and said dissimilar metal being positioned Within said interior chamber so as to be exposed for contact with fluid passing through said valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,051,180 Ruzicka Aug. 18, 1936 2,104,519 Hurn Jan, 4, 1938 2,625,166 Lindsay Jan. 13, 1953 2,630,346 Carlson Mar. 3, 1953 2,781,663 Maly et a1 Feb. 19, 1957